Underwater Installation of Filter Systems for Scour and Erosion Countermeasures, Volume 2: Training Manual (2018)

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A.1 LESSON SCHEDULE UNDERWATER FILTER INSTALLATION WORKSHOP Session Time Topic Part I Session 1 (20) Introduction to the workshop (Learning Outcomes) and Filters - Purpose and Need Session 2 (45) Current Concepts and Practice (Fascines, Geobags, Sandmat, etc.) Session 3 (25) Case Study - Bonner Bridge (North Carolina) (90) Break (30) Break between Parts I and II Part II Session 1 (50) Introduction to Part II (Learning Outcomes) and Underwater Filter Installation Guidance (Findings and Recommendations from 24-42) Session 2 (70) Application Example Group Workshop (Team #1 Assignment and Report) (Team #2 Assignment and Report) (120) (240)

A.2 UNDERWATER FILTER INSTALLATION WORKSHOP PART I LEARNING OUTCOMES 1. Describe the purpose, need, and functions of geotextile and granular filters 2. Identify sources of design guidance for geotextile and granular filters. 3. Discuss experience with and local agency guidance for installing filters underwater. 4. Describe and list several techniques currently used to install filters underwater for typical armoring countermeasures (e.g., riprap, ACBs, etc.). 5. List and discuss the lessons learned from a recent U.S. underwater installation project (Bonner Bridge case study). PART II LEARNING OUTCOMES 6. Describe, evaluate, and list in order of priority (based on local conditions) the recommendations for underwater filter installation from NCHRP Project 24-42. 7. In a Group Workshop setting, develop installation techniques and discuss solutions for a typical underwater filter installation project at a riverine bridge.

A.3 UNDERWATER FILTER INSTALLATION LESSON PLAN Session Title: Underwater Filter Installation Workshop (Part I) Performance-Based Learning Outcomes: At the end of Part I, Participants will be able to: • Describe the purpose, need, and functions of geotextile and granular filters • Identify sources of design guidance for geotextile and granular filters • Discuss experience with and local agency guidance for installing filters underwater • Describe and list several techniques currently used to install filters underwater for typical armoring countermeasures (e.g., riprap, ACBs, etc.) • List and discuss the lessons learned from a recent U.S. underwater installation project (Bonner Bridge case study) Topics: • Purpose and need for filters • Current concepts and practice for underwater filter installation (U.S. and European practice) • Case study - Bonner Bridge installation by North Carolina Department of Transportation (DOT) at a scour critical tidal inlet bridge under emergency conditions Instructional Method: Classroom discussion/presentation consists of 3 Sessions based on PPT presentations, discussion of local agency practice, a case study presentation by the instructor, and group discussion by Participants of lessons learned from the case study. • The first Session of Part I begins with a discussion of the Workshop Schedule and Learning Outcomes, followed by 9 slides highlighting and illustrating the purpose and need for a filter under armoring countermeasures, including granular and geotextile filters: - Emphasize the importance of filters in the overall design of hydraulic countermeasures that use armoring materials, such as: riprap, partially grouted riprap, ACBs, gabions, grout-filled mats, and artificial armor units. - Emphasize that filters are designed to be compatible with the underlying soil, regardless of the type of armor that is placed on top of the filter. - There are two types of filters: (1) Granular (e.g., sand and/or gravel) and (2) Geotextiles. Note that some types of geotextiles are appropriate for use as a filter, while others are not. Material samples passed around the class assist in proper identification. - Identify current guidance from FHWA available to DOTs for filter design.

A.4 • The second Session of Part I begins with an Instructor-led discussion of local agency policy/experience/problems with placing filters underwater. Participants are asked "How would you go about installing a filter underwater and what guidance does your agency provide?" Participants contribute ideas while Instructor develops separate lists for granular filters and geotextile filters on a document camera, whiteboard, or flip chart. • The second Session continues with 25 PPT slides illustrating current concepts and practice in Europe and the U.S. Photos and sketches show fascines, mechanical placement techniques, geotextile bags, Sandmat, tremie, Contractor concepts, etc. • The second Session ends with a Summary Exercise to evaluate Participant comprehension of key outcomes. Participants are given the opportunity to rate current underwater filter installation concepts for applicability and feasibility for local conditions. • The third Session of Part I is a case study presented by the Instructor of Bonner Bridge installation of manufactured A-Jacks™ armor units with underwater filters (geotextile and geobags) by North Carolina DOT under emergency conditions at a tidal inlet on the North Carolina coast in 2003. Instructor presents the background and installation activities using approximately 14 PPT slides. • The third Session ends with Instructor listing on document camera, whiteboard, or flip chart Participant input to the question "What do you think are the key lessons learned by NC DOT from the Bonner Bridge project?" Instructor conducts a Question and Answer refresher on the purpose and need for a filter and summarizes the Learning Outcomes with reference to the flip charts developed during the second and third Sessions of Part I. Time Allotment: 90 Minutes • Introduction and purpose and need for filters (20 minutes) • Current concepts and practice (45 minutes) • Bonner Bridge case study (25 minutes) Evaluation Plan: Participant's attainment of learning outcomes will be evaluated during the lesson by their participation in brainstorming sessions and question and answer knowledge checks. References: FHWA Hydraulic Engineering Circular HEC-23, "Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidance," Third Edition, Volumes 1 and 2, 2009. Holtz, R.D., Christopher, B.R., Berg, R.R.. "Geosynthetic Design and Construction Guidelines," Federal Highway Administration Report No. FHWA- NHI-07-092, Washington, D.C., August 2008. NCHRP Report 568. "Riprap Design Criteria, Recommended Specifications, and Quality Control," Transportation Research Board, 2006.

A.5 References Continued: NCHRP Report 593. "Countermeasures to Protect Bridge Piers from Scour," Transportation Research Board, 2007. NCHRP Report . "Underwater Installation of Filter Systems for Scour and Other Erosion Control Countermeasures," Transportation Research Board. 2018. U.S. Army Corps of Engineers. ""General Design and Construction Considerations for Earth and Rock-Fill Dams," Engineer Manual EM 1110-2- 2300, Appendix B, "Filter Design," Washington, D.C., July 2004.

A.6 LEARNING OUTCOMES (PART I) • Describe the purpose, need, and functions of geotextile and granular filters. • Identify sources of design guidance for geotextile and granular filters. • Describe and list several techniques currently used to install filters underwater for typical armoring countermeasures (e.g., riprap, ACBs, etc.). • List and discuss the lessons learned from a recent U.S. underwater installation project (Bonner Bridge case study). I-1 Key Message: Schedule for the Workshop (Parts I and II) and learning Outcomes for Part I. Background Information: N/A Instructional Method: Part I is comprised of 3 Sessions as shown on the Schedule. At the end of Part I participants should understand the purpose and need for filters and be able to describe some of the current techniques available for underwater installation of granular and geotextile filters. Part I will include: • Discussion • Brainstorming sessions • A case study Session 1 - Instructor led (approximately 20 minutes) based on 10 PPT slides. Notes: Start Session 1.

A.7 TYPES OF FILTERS • Filters can be a geotextile, a layer of granular material, or a combination of both • Granular filters can be composed of multiple layers (e.g., a finer layer next to the soil, and a coarser layer on top of the fine layer) I-2 Key Message: Characteristics of granular and geotextile filters Background Information: HEC-23, Volume 2, Design Guideline 16 Instructional Method: Tell: The general characteristics of granular and geotextile filters. Illustrate: Using the following 3 slides illustrate the characteristics of granular, geotextile, and composite filters (Slides I-3, I-4, I-5). Show: Pass a set of typical geotextile filter samples around the class. Notes: • Note that the woven monofilament and the nonwoven needle punched fabrics have very uniform properties (thickness, thread density and spacing, etc.) and are suitable as a filter. • Note that the spun-bonded fabric has areas of dense fiber spacing and areas of sparse fiber spacing. This fabric is typically used as a separator between layers of different soil types and is not suitable as a filter. • Note that the slit-film (slit-tape) fabric has ribbon-like threads. There are relatively few apertures and they are not uniform in size. This fabric is very inexpensive and is typically used as a silt fence material and is also not suitable as a filter.

A.8 I-3 Key Message: Illustrate granular, geotextile, and composite filters. Background Information: HEC-23, Volume 2, Design Guideline 16 Instructional Method: See Slide I-2 Notes: Some situations may require a composite filter with a granular transition layer under the geotextile.

A.9 I-4 Key Message: Schematic diagram of a typical granular filter beneath riprap. Background Information: HEC-23, Volume 2, Design Guideline 16 Instructional Method: See Slide I-2 Tell: Point out relationship between the riprap armor layer, the underlying granular filter, and the base soil. Notes: N/A

A.10 Geotextile filter beneath armor layer I-5 Key Message: Geotextile filter beneath articulating concrete blocks. Background Information: HEC-23, Volume 2, Design Guideline 16 Instructional Method: See Slide I-2 Tell: Point out relationship between the ACB armor layer and the geotextile filter placed on the prepared surface of the base soil. In some cases, the geotextile can be attached to the ACB matrix. Notes: The next four slides discuss and show hydraulic conditions before, during, and after a flood to illustrate the functions that filters perform.

A.11 FUNCTIONS THAT FILTERS PERFORM • During floods, the flow is very turbulent. • A filter provides a barrier between the turbulence and the fine particles of the native soil. • This prevents the fine soil particles from being winnowed out through the large voids of the riprap and washed away I-6 Key Message: The importance of the filter component of a countermeasure armoring system should not be underestimated. An appropriate filter is the key to successful performance of any countermeasure armoring system. Background Information: HEC-23, Volume 2, Design Guideline 16 Instructional Method: Tell: The general functions that filters perform during low, peak, and flood recession conditions. Illustrate: Using the following 3 slides illustrate seepage gradients and filter functions during low, peak, and flood recession conditions (Slides I-7, I-8, I- 9). Notes: N/A

A.12 I-7 Key Message: Seepage gradients for normal (baseflow) conditions. Background Information: HEC-23, Volume 2, Design Guideline 16 Instructional Method: See Slide I-6 Tell: Normal flow conditions produce very mild seepage gradients. Notes: N/A

A.13 I-8 Key Message: Seepage gradients during flood peak conditions. Background Information: HEC-23, Volume 2, Design Guideline 16 Instructional Method: See Slide I-6 Tell: During flood conditions high water in the channel drives seepage into the stream banks, raising the groundwater level. Notes: N/A

A.14 I-9 Key Message: Seepage gradients after flood recession. Background Information: HEC-23, Volume 2, Design Guideline 16 Instructional Method: See Slide I-6 Tell: • After flood waters recede, high seepage gradients develop as groundwater returns to the channel. • Uplift pressures can develop to damaging levels if filter is not permeable enough. Notes: N/A

A.15 SOURCES OF FILTER DESIGN GUIDANCE • FHWA Hydraulic Engineering Circular HEC-23 "Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidance" Third Edition, Volumes 1 and 2, 2009. • NCHRP Report 568 "Riprap Design Criteria, Recommended Specifications, and Quality Control," 2006. • NCHRP Report 593 "Countermeasures to Protect Bridge Piers from Scour," 2007. • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Holtz, R.D., Christopher, B.R., Berg, R.R., "Geosynthetic Design and Construction Guidelines," Federal Highway Administration Report No. FHWA-NHI-07-092, Washington, D.C., August 2008. • U.S. Army Corps of Engineers, "General Design and Construction Considerations for Earth and Rock-Fill Dams," Engineer Manual EM 1110-2-2300, Appendix B, "Filter Design," Washington, D.C., July 2004. I-10 Key Message: Sources for design guidance for granular and geotextile filters are readily available. Background Information: HEC-23, Volume 2, Design Guideline 16 Instructional Method: Tell: • Filters should have a hydraulic conductivity at least 10 times greater than that of the base soil, so that uplift pressures cannot develop. • Seepage flow can also wash soil particles through the filter, so the aperture size of the filter must be small enough to retain a specified fraction of the soil. Notes: Most references contain worked examples and flow charts for filter design. End Session1.

A.16 INSTALLING FILTERS UNDERWATER – LOCAL EXPERIENCE • What techniques are used locally for installing filters underwater? • What guidance is provided by your agency for the installation of filters underwater? I-11 Key Message: Discussion of local experience and guidance available to Participants for underwater installation of filter systems. Background Information: N/A Instructional Method: Facilitate: Based on the questions on Slide I-11 facilitate a discussion and solicit input on techniques used locally for installation of either granular or geotextile filters underwater (approximately 10 minutes). List: Using the document camera, white board or flip charts develop two lists that summarize Participant experience with underwater filter installation for both granular and geotextile filters. List as follows: • Granular Filter Installation • Geotextile Filter Installation Ask: What references are available to you for underwater installation of filter systems? Ask: Can you cite specific projects that required underwater installation? If so, what problems were encountered with installing the filter and the armor countermeasure? Ask: Has your agency had experience with installation of a composite filter system? Notes: Use the results of this discussion to guide the presentation of currently used techniques for underwater installation in Europe and the U.S. on the slides which follow. Start Session 2.

A.17 INSTALLATION OF FILTER SYSTEMS UNDERWATER - EUROPEAN PRACTICE • Traditional techniques – fascine mattresses • Mechanized devices and equipment • A sandmat • Geotextile containers • Contractor concepts and practice I-12 Key Message: Some traditional techniques for underwater filter installation such as fascines are still in use in Europe. However, in recent years the technology has become increasingly mechanized and sophisticated. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Instructor led discussion (approximately 15 minutes) based on 14 PPT slides. Notes: Introduce the concepts in this session. Techniques recommended for U.S. practice will be covered in more detail in Part II of the Workshop.

A.18 FASCINE MATTRESSES • Used in Europe for 100's of years • Used today in Germany, Netherlands, and UK • Also known as "sinker mat" • Effective but labor intensive I-13 Key Message: 1998 Scanning Review of European practice found that fascines are still considered an effective means of getting a filter underwater in many European countries. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: The next 2 slides show the use of fascine mats in use in Germany in 2001. Tell: • At least 3 countries in Europe still consider fascine mats, a very old, traditional approach for scour protection as an effective means of placing a geotextile filter in deep water. • The fascines consist of a matrix of willow or other natural material woven in long bundles (15 to 20 cm in diameter) to form a matrix which is assembled over a layer of woven geotextile (see Slides I-14 and 1-15). • The geotextile has ties which permit fastening it to the fascine mat. • The fascine mattress or "sinker mat" is floated into position and sunk into place by dropping riprap-size stone on it from a barge. Notes: Show Slides I-14 and I-15 while discussing the sinker mat concept.

A.19 I-14 Key Message: Overall view of fascine mattress being constructed in Germany in 2001. Background Information: NCHRP Report 887 "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-13 Tell: • Fascine mattresses are prefabricated according to the desired geometry on land then they are pulled to the desired position and sunk by dumping the armor material on the mat. • Mattresses require very precise placement, which may be difficult at greater depths. • It is very difficult to place mattresses without gaps so either a certain overlap is necessary or the gap is filled with an erosion resistant material. • With a geotextile filter beneath the mattress, narrow gaps may be acceptable. Notes: Note the geotextile placed on the launching apron prior to assembling the fascine mattress.

A.20 I-15 Key Message: Close up view of fascine mattress being constructed in Germany in 2001. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-13 Tell: The geotextile filter can be seen beneath the fascine. Here an additional brushwood layer is being added for flotation. General query to class: Fascines are still used in Europe. Do you think they would be a practical and cost effective approach in the U.S.? Notes: The Netherlands Centre CUR Report 169 (1995) provides criteria and specifications for constructing fascine mattresses underlain by a geotextile.

A.21 MECHANICAL TECHNIQUES I-16 Key Message: Roller for placing geotextile onto subgrade. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-12 Tell: • In the late 1980s in Germany a system of placing the geotextiles with a big motor driven roller which moves over the subgrade was developed. • In Europe today many geotextiles are placed using mechanical rollers. Notes: See Slide 1-19.

A.22 MECHANICAL TECHNIQUES I-17 Key Message: Flexible revetment with integrated geotextile filter ready to be placed under water with a lifting frame. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-12 Tell: • Because of low specific gravity, geotextiles usually require either pre- weighting or similar restraint when laid alone, particularly when wave or current conditions exist. • It has been found advantageous to pre-attach the geotextile underlay to the underside of a flexible armor panel with the leading valence or skirt temporarily secured to the upper surface, and to then install the combined revetment unit in a single operation. • The leading edge of the skirt may be automatically detached from the upper surface of the panel and temporarily restrained on the slope pending the placing of the next revetment unit Notes: N/A

A.23 THE SANDMAT I-18 Key Message: The sandmat was developed to overcome many problems commonly encountered when placing geotextiles underwater. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-12 Tell: • To overcome the many problems encountered when placing geotextile filters underwater engineers in Germany have developed a product known as a sandmat. • This blanket-like product consists of two nonwoven needle-punched geotextiles with sand in between. • The layers are stitch-bonded or sewn together to form a heavy, filtering geocomposite. The composite blanket exhibits an overall specific gravity ranging from approximately 1.5 to 2.0, so it sinks readily. • This composite geotextile has sufficient stability to be handled even when loaded by currents up to approximately 3.3 ft/s (1 m/s). At the geotextile-base soil interface, a nonwoven fabric should be used because of the higher angle of friction compared to woven geotextiles. This slide shows a close-up photo of sandmat material. • Slide I-19 shows a sandmat blanket being rolled out using conventional geotextile placement equipment.

A.24 Notes: Placing geotextiles under water is problematic for a number of reasons: • Most geotextiles that are used as filters beneath riprap are made of polyethylene or polypropylene. • These materials have specific gravities ranging from 0.90 to 0.96, meaning that they will float unless weighted down or otherwise anchored to the subgrade prior to placement of the armor layer. • Unless the work area is isolated from river currents by a cofferdam, flow velocities create large forces on the geotextile. These forces cause the geotextile to act like a sail, often resulting in wavelike undulations of the fabric (a condition that contractors refer to as "galloping") that are extremely difficult to control. • In mild currents, geotextiles (precut to length) have been placed using a roller assembly, with sandbags to hold the fabric temporarily.

A.25 THE SANDMAT I-19 Key Message: The sandmat was developed to overcome many problems commonly encountered when placing geotextiles underwater. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-18 Tell: This slide shows a roller frame being used to place a geocomposite blanket (sandmat) in the construction yard of Colcrete – Von Essen Inc. The equipment is designed to place the sandmat as a filter for riprap on Germany's extensive inland waterway system. Notes: Slides I-18 and I-19 courtesy of Colcrete – Von Essen Inc.

A.26 GEOTEXTILE CONTAINERS I-20 Key Message: In deep water or in currents greater than 3.3 ft/s (1 m/s), German practice calls for the use of sand-filled geotextile containers. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-12 Tell: • For specific project conditions, geotextile containers can be chosen that combine the resistance against hydraulic loads with the filtration capacity demanded by the application. • Geotextile containers have proven to give sufficient stability against erosive forces in many applications, including wave-attack environments. The size of the geotextile container must be chosen such that the expected hydraulic load will not transport the container during placement. • Once placed, the geotextile containers are overlaid with the final armoring material (e.g., riprap or partially grouted riprap). • This slide shows a 1.0 metric tonne geotextile container being filled with sand in the construction yard of Colcrete – Von Essen Inc. Notes: Slides I-20 and I-21 courtesy of Colcrete – Von Essen Inc.

A.27 GEOTEXTILE CONTAINERS I-21 Key Message: In deep water or in currents greater than 3.3 ft/s (1 m/s), German practice calls for the use of sand-filled geotextile containers. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-20 Tell: • This slide shows the sand-filled geotextile container being handled with an articulated-arm clam grapple. The filled geotextile container in the photograph is a nominal 1-metric-tonne (1,000 kg or 2,200 lb) unit. • The preferred geotextile for these applications is always a non-woven needle punched fabric, with a minimum mass per unit area of 500 g/m2 (15 oz/yd2). • Smaller geotextile containers can be fabricated and handled by one or two people for smaller-sized applications. • To provide flexibility in handling and placement, the geocontainers a filled about 2/3 full with an appropriately designed granular material (sand) meeting the filtration requirements of both the subgrade and the planned armor (such as riprap). Notes: • As a practical minimum, a 200-lb (91 kg) geotextile container covering a surface area of about 6 to 8 square ft (0.56 to 0.74 m2) can be fashioned from nonwoven needle punched geotextile having a minimum mass per unit area of 200 grams per square meter. • The geotextile container is often filled at the job site and the final seam field-stitched with a hand-held machine.

A.28 PLACING GEOTEXTILE CONTAINERS I-22 Key Message: Handling, filling and, closing of geotextile containers at the "Eidersperrwerk" storm surge barrier off the North Sea coast of Germany. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • Large geotextile containers (approximately 1.25 m3 (1.6 yd3) in volume) were placed at Eidersperrwerk storm surge barrier on the Eider estuary using side-dump pontoon barges and divers to ensure the filter attained the desire coverage and thickness. • The elongation capabilities of the fabric and partial filling with sand allowed the containers to adjust to irregularities of the substrate at the site. • For the Eider Estuary project, more than 48,000 geotextile containers were used to repair a 30 meter (100 ft) deep scour hole at the barrier. • An armor layer of 1 to 6-ton stone dumped through more than 20 meters of water and a fascine sinker mat with smaller stones to stabilize the toe completed the installation. • In the upper part the slope was as steep as 1:1. The tidal current had a flow velocity up to 2.5 m/s (8 ft/s), and the final revetment had to sustain flow velocities up to 5 m/s (16 ft/s). Notes: N/A

A.29 PLACING GEOTEXTILE CONTAINERS I-23 Key Message: Installation of scour stabilization by the use of a stone dumping barge/vessel at the "Eidersperrwerk" storm surge barrier off the North Sea coast of Germany. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-22 Tell: • Note the use of the side push dumping barge to place the filled geocontainers. • GPS and divers were used to verify the position and coverage of the geocontainer filter. Notes: N/A

A.30 CONTRACTOR CONCEPTS AND PRACTICE I-24 Key Message: GEOfabrics of the United Kingdom (a geotextile manufacturer) provides installation concepts for installing geotextiles underwater in coastal and river applications. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-12 Tell: • All needle-punched geotextiles will float in seawater and therefore require some form of ballast if they are to be successfully placed below the low-water line. • There are a number of ways of achieving this, and many contractors will have developed their own procedures. In shallow water, where it is possible for a machine to reach the full extent of the site, the geotextile can be rolled onto a steel pole with a buoy attached at one end. • The leading edge is anchored beneath the tracks of an excavator and the roll can then be lowered into place. The pole can be retrieved once the fabric has been weighted with a quantity of stone. Notes: The suggestions presented in Slides I-24 and I-25 are not to endorse any particular product or manufacturer, but are representative of the guidance for underwater installation provided by a geotextile manufacturer.

A.31 CONTRACTOR CONCEPTS AND PRACTICE I-25 Key Message: GEOfabrics of the United Kingdom (a geotextile manufacturer) provides installation concepts for installing geotextiles underwater in coastal and river applications. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-24 Tell: • On larger projects the installation starts as follows: (1) unroll a suitable length of geotextile on level ground away from the installation area, (2) attach one end of a geotextile length to a suitable steel core, (3) attach two lengths of rope to the core and lay the lengths along the fabric, (4) roll the fabric, rebar and ropes onto the core and transport to the installation area. • The installation continues on site with: (5) use suitable methods to locate the exact position of the previous geotextile length to be placed. Divers may be required or it may be possible, in shallow water, to attach floats to the edges of the geotextile. White lines spray painted onto the fabric to identify the correct overlap position may be suitable in some waters. • Finally: (6) the geotextile and core can now be lowered into position by unwinding the ropes as shown in this slide. The steel core can be recovered for future use. On long slopes, it may be more effective to place the roll on the slope shoulder and have the ropes hauled from on board a barge. An initial layer of rock should be placed on the fabric immediately to ballast it. Notes: For speed of installation on larger projects, it is possible to join two widths of geotextile using a prayer seam formed with a portable, sack-closing, sewing machine. Widths up to 12m (40 ft) can be prefabricated prior to installation. Joints with 60% of the geotextile's strength can be fabricated using thicknesses up to 6mm thick. Scrap rebar can be used as sacrificial ballast and lengths can be attached to the geotextile at intervals along its length using cable ties, tying wire or tape.

A.32 INSTALLATION OF FILTER SYSTEMS UNDERWATER - U.S. PRACTICE • Problems with placing granular filters underwater and issues/questions on the use of geotextile filters noted in the 1980's • NCHRP Projects and 1998 Scanning Review of European practice • Development of guidance for using geotextile containers I-26 Key Message: Since the 1980s in the U.S. ongoing efforts and experimentation have been directed toward the more effective use of geotextile filters, particularly for underwater applications. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Instructor led discussion (approximately 10 minutes) based on 10 PPT slides. Tell: Issues related to placing a granular filter in flowing water present significant problems. Problems with the placement of granular filters underwater included achieving positional accuracy, the danger of segregation as the filter material fell through the water column, and obtaining a constant layer thickness for the filter. Ask: Can you think of a possible technique to reduce the impact of these issues? Answer: Use a tremie pipe to release granular filter material closer to the bed (sketch on document camera, white board, or flip chart). Tell: During the 1960s fabric materials were introduced in the U.S. as a revetment filter for U.S. Army Corps of Engineers (USACE) projects, particularly where suitable granular materials were not readily available or were not cost-effective due to transportation, quality control, or manpower constraints. Notes: In the U.S. the initial use of filter fabric for hydraulic applications can be traced to projects placed by "Dutch" engineers in 1956. However, in the ensuing years, filter fabric did not find widespread acceptance in the U.S. engineering community. As late as 1967, there were only two domestic sources of fabric in the U.S.

A.33 USACOE INVESTIGATION OF THE USE OF GEOTEXTILES AS A FILTER FOR REVETMENT APPLICATIONS (1967-1972) Problem areas identified: • Erosion under the fabric - small voids and loose fill areas are generally bridged by filter fabric, providing a site for potential erosion. • Slope failures - A widely reported problem. A typical sign that a failure has occurred was a bulge in the fabric near the bank toe and a depression upslope above the bulge. • Tearing/puncture of the fabric - This problem often lead to loss of large volumes eroded soil through the fabric. • Slippage of revetment material - This type of failure occurred primarily due to poor support at the bank toe or placement of the fabric on a steep slope. I-27 Key Message: As the utility of filter fabric became apparent, the Office, Chief of Engineers, directed the U.S. Army Engineer Waterways Experiment Station to conduct a study to determine the extent and diversity of use of this material by USACOE Divisions and Districts. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-26 Tell: • The findings of the study indicated that although there was wide and varied use of filter fabrics by Corps Districts, a test program was needed to define the engineering properties of the fabrics when used for filter and drainage applications. • Investigation of case histories where a geotextile filter had been used revealed that it was an effective and valuable component of revetment armoring systems. • Cost estimates showed that filter fabric was far cheaper than conventional granular filter layers, and control of filter installations, both underwater and in the dry, was more efficient and cost effective with filter fabric as it assures positive coverage. Notes: At this time (1980s) the USACOE recommended that engineers should continue to investigate the advantages of using certain types of filter fabrics and should challenge the industry to provide better fabrics that will improve the performance of structures.

A.34 1998 SCANNING REVIEW OF EUROPEAN PRACTICE AND NCHRP PROJECTS • European Practice for Bridge Scour and Stream Instability Countermeasures • Sponsored by TRB, NCHRP and FHWA • NCHRP Projects 24-07(1 & 2) to investigate and improve guidance for the installation of pier scour countermeasures I-28 Key Message: Following the Scanning Review NCHRP projects were initiated to improve guidance in the U.S. for countermeasure design, to include use and design of filters and techniques for underwater placement. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-26 Tell: • The Scanning Review found that: (1) In Germany and the Netherlands, a significant investment has been made in the development and testing of geosynthetic materials, and innovative installation techniques have been developed, and (2) The confidence that European hydraulic engineers have in the use of riprap as a permanent scour countermeasure is based in part on their use of innovative techniques for placing an effective filter beneath the riprap in flowing or deep water. • Based on field investigations during NCHRP 24-07(1) it was found that two primary methods of failure were noted for properly sized riprap revetment installations: (1) Instability of the river bed and (2) Failure caused by an inadequate filter • NCHRP 24-07(2) included prototype scale laboratory experiments of the practicality of using geotextile containers to place a filter underwater for riprap pier scour protection (highlighted on the following slides). Notes: The evaluation of the use of geocontainers as a means of placing a filter underwater during NCHRP Project 24-07(2) is highlighted in the following 7 slides. Additional underwater placement techniques currently in use in the U.S. will be illustrated in the case study during Session 3 which follows.

A.35 LABORATORY TESTING OF GEOTEXTILE CONTAINERS FOR UNDERWATER FILTER PLACEMENT • For the geotextile containers testing at prototype scale was, primarily, to demonstrate constructability in flowing water and performance in high velocity flow conditions. • Tests confirmed that geotextile containers can be fabricated locally and that the containers and riprap can be placed in flowing water with standard commercially available equipment (in the U.S.). I-29 Key Message: Laboratory testing confirmed that geotextile containers can be fabricated locally and that the containers and riprap can be placed in flowing water with standard commercially available equipment in the U.S. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-28 Tell: • NCHRP 24-07(2) included prototype scale laboratory experiments of the practicality of using geotextile containers to place a filter underwater for riprap pier scour protection (highlighted on the following slides). Notes: N/A

A.36 LABORATORY SETUP FLOW 9 m PLAN VIEW 6 m 1.5m 0.5m Pier PROFILE Pier Riprap Sand-filled geotextile containers 0.4m 0.5m/s Sand Concrete Concrete I-30 Key Message: Laboratory testing confirmed that geotextile containers can be fabricated locally and that the containers and riprap can be placed in flowing water with standard commercially available equipment in the U.S. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-29 Tell: • The schematic layout for testing sand filled geotextile containers as a filter is shown in this slide. Notes: N/A

A.37 I-31 Key Message: Laboratory testing confirmed that geotextile containers can be fabricated locally and that the containers and riprap can be placed in flowing water with standard commercially available equipment in the U.S. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-29 Tell: • An approach flow 1 ft (0.305 m) deep at approximately 1.5 ft/s (0.5 m/s) was established. A total of 32 geotextile containers were placed around the pier by dropping from a height of about 5 ft (1.5 m) above the water surface. • Installation was facilitated by a backhoe fitted with a special grapple attached to the bucket, which enabled the backhoe to pick up the geotextile container, position it around the pier to a specified location, and release the container. Notes: The geotextile containers measured 4 ft x 1.5 ft x 0.33 ft (1.2 m x 0.5 m x 0.1 m) with a typical volume of 2 ft3 (0.6 m3). Approximately 220 lbs (100 kg) of sand was placed in each bag. Commercial concrete sand meeting appropriate filter criteria was used to fill the geotextile containers which were fabricated locally.

A.38 I-32 Key Message: Laboratory testing confirmed that geotextile containers can be fabricated locally and that the containers and riprap can be placed in flowing water with standard commercially available equipment in the U.S. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-29 Tell: • This slide shows a geotextile container being dropped near the pier; note the grapple plate attachment to the backhoe. Notes: N/A

A.39 I-33 Key Message: Laboratory testing confirmed that geotextile containers can be fabricated locally and that the containers and riprap can be placed in flowing water with standard commercially available equipment in the U.S. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-29 Tell: • This slide shows the geocontainers around a bridge pier after installation in flowing water. • Flow is from lower right to upper left. Notes: N/A

A.40 I-34 Key Message: Laboratory testing confirmed that geotextile containers can be fabricated locally and that the containers and riprap can be placed in flowing water with standard commercially available equipment in the U.S. Background Information: NCHRP Report 887 "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-29 Tell: • This slide shows riprap armor over the geotextile containers. • Flow is from lower right to upper left. Notes: N/A

A.41 I-35 Key Message: Laboratory testing confirmed that geotextile containers can be fabricated locally and that the containers and riprap can be placed in flowing water with standard commercially available equipment in the U.S. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-29 Tell: • This slide shows successful high velocity testing of a geotextile container filter with riprap armor. • Flow is from upper right to lower left. • Geotextile sand containers are strongly recommended as a practical, proven, and effective technique for placing a filter under water for riprap or partially grouted riprap, and gabion and grout-filled mattresses. Notes: The high-velocity test ran for 4 hours, during which time the discharge was steadily increased to the full flow capacity (160 cfs (4.5 m3/s)). At maximum discharge, the approach velocity upstream of the pier reached a maximum of 6.4 ft/s (2 m/s). The estimated local velocity at the pier was approximately 11 ft/s (3.4 m/s).

A.42 SUMMARY EXERCISE Based on your experience and local conditions, rate the following techniques for practicality and adaptability for placing a filter underwater (use a scale of 0 (worst) to 10 (best)). • Granular filter (dump or use tremie pipe) • Fascine sinker mat with geotextile • Mechanical roller or similar device for geotextile • Spreader bar or frame for geotextile attached to flexible armor(e.g., ACBs) • Sandmat-type product • Geotextile containers (geobags) • Crane or barge with rolled geotextile placed on slope I-36 Key Message: Evaluate current technology for local applications in the U.S. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Exercise: • This slide shows the common techniques and concepts for placing filters underwater as discussed in this session. • On the document camera, white board, or flip chart list these techniques and lead a discussion to have Participants reach a consensus as to the applicability and feasibility of applying these techniques locally and indicate a rating from 0 to 10. • 0 would indicate a technique that Participants feel is not applicable or feasible under local conditions. • 10 would indicate a technique that Participants feel is highly applicable and feasible under local conditions. Notes: Allow approximately 10 minutes for this Exercise. The case study in Session 3 which follows will highlight the application of geocontainers and the use of a geotextile filter attached to prefabricated armor units on a scour critical tidal inlet bridge in North Carolina in late 2013. End Session 2.

A.43 LEARNING OUTCOME (PART I, SESSION 3) • Session 3 consists of a case study which will highlight the application of geocontainers and the use of a geotextile filter attached to prefabricated armor units on a scour critical tidal inlet bridge in North Carolina (NCDOT) in late 2013. • At the end of this session you should be able to list and discuss the lessons learned from this recent U.S. underwater filter installation project. I-37 Key Message: Refresher on learning Outcome for Part I, Session 3. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • This third Session of Part I is a case study of the Bonner Bridge installation of manufactured A-Jacks® armor units with an underwater geotextile filter (and the installation of geobags) by North Carolina DOT under emergency conditions at a tidal inlet on the North Carolina coast in 2013. • Instructor led (approximately 15 minutes) based on 13 PPT slides. • We will end this session with a short summary exercise where you will be asked to discuss the question: "What do you think are the key lessons from NCDOT’s experience with the Bonner Bridge project?" • Group discussion (approximately 10 minutes). Notes: This session ends Part I of the presentation/workshop. Start Session 3.

A.44 BONNER BRIDGE OVER OREGON INLET, NC I-38 Key Message: NCDOT determined based on an October 2013 side scan survey that the 2.5 mile long Bonner Bridge over the Oregon Inlet had reached a scour critical condition at one of the mid-span bents. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: Tell: • On Tuesday December 3, 2013, a public news release announced North Carolina Department of Transportation's (NCDOT) closure of NC 12 Herbert C. Bonner Bridge crossing of Oregon Inlet. Inlet dynamics and movement of the 65-ft deep channel coupled with bridge scour jeopardized stability of an interior bent between the navigation span and the southern terminus.

A.45 • In addition, a second element of danger loomed over the only highway connection to the North Carolina Outer Banks. It was possible that a major low pressure system centered over the Midwest would race east, stall off shore, and set up a major nor'easter in the next four or five days. • This case study summarizes the rapid response by NCDOT, with collaboration and cooperation of other agencies and private contractors, which stabilized the scour condition allowing the bridge to be reopened on Sunday, December 15, 2014. Restoring traffic to the Outer Banks was crucial in advance of the holiday influx of tourists headed south to 60 miles of barrier islands, seven historic villages, and the gateway to Oracoke Island. Notes: The weather forecast added an additional factor of urgency to the situation. High winds, heavy seas and extreme tidal exchange from a three day nor'easter is always a concern for Oregon Inlet and the coastal highway which parallels the shoreline along most of the Outer Banks. Although the bridge was closed to traffic, the immediate concern was potential loss of the two spans adjacent to Bent #166 during storm surge created by the nor'easter.

A.46 BONNER BRIDGE OVER OREGON INLET, NC I-39 Key Message: The Bonner Bridge was constructed in 1963 replacing ferry service to Hatteras Island. The coastal geology of the site required the bridge to be founded on friction piles in deep sand. Design life for the bridge was 30 years, but NCDOT's 1992 replacement project was challenged by environmental advocates and continues to be held up by legal appeals in federal court. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9.

A.47 Instructional Method: Tell: • Structural decay and scour have long plagued the bridge. The Bonner Bridge has been identified as scour critical and a comprehensive and aggressive monitoring plan was instituted. Hydrographic surveys and underwater inspection performed monthly and after storm events have been conducted for more than two decades. In 2012 NCDOT initiated monthly side scan sonar monitoring. • The October 2013 survey identified a change in conditions south of the navigation span and monitoring was stepped up to weekly inspection. The November 29th inspection revealed that the bed elevation approached a scour critical condition at Bent #166. Daily monitoring was implemented. On Tuesday December 3, the sonar survey and underwater dive team inspection revealed that the ten- pile cluster at Bent 166 had 9 piles with embedment below scour critical elevation. Three of the piles had less than 4 ft embedment. NCDOT immediately implemented bridge closure in accordance with their monitoring Plan of Action. General query to class: Faced with this problem and the urgent need for corrective action, what options do you think could have been considered by NCDOT? Do you think that NCDOT had any chance of correcting the problem in the three weeks before the Holiday season??? Notes: • Since 1990, NCDOT had spent $56 million on repairs to the Bonner Bridge. • The following 11 slides trace the time line of NCDOT’s response with emphasis on the placement of a geotextile filter and geocontainers in this deep water environment. • In this slide Bent 166 is the first bent to the left (north) of the main piers and navigation channel.

A.48 BONNER BRIDGE Bent #166 I-40 Key Message: NCDOT formulated a three phase strategy for structural countermeasure response. The strategy addressed immediate action to stabilize the scour, intermediate countermeasure installation, and long term integrity of Bent 166. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: Tell: 1. Long term stability involved construction of a crutch bent with installation of longer piles at Bent #166 to provide required embedment. The crutch bent required significant lead time for pile fabrication, precast pile/bent cap, and geotechnical investigation.

A.49 2. The intermediate action would stack three tiers of A-Jacks® prefabricated concrete armor units to form a perimeter around Bent 166. Geotextile containers (sandbags) 3 ft cube and 4 ft cube, would be placed around the perimeter and inside the battered pile cluster to avoid damage to the existing concrete piles. The configuration would also trap sand available in the high sediment transport regime of diurnal tidal exchange. NCDOT contacted suppliers and manufactures for availability and delivery. Geotextiles would require 5-7 days to be delivered. The A-Jacks® components would require 12- 14 days to arrive at the site. 3. The immediate need was a large volume of sand and a delivery system (within 72 hours) to restore a non-scour critical elevation. Notes: • On this slide contours are from a sonar survey and the red indicates the scour critical elevation of the battered piles of Bent #166. • This is a view from the east. The main pier on the north side of the navigation channel can be seen at the left edge of the slide.

A.50 USACOE DREDGE AND FILL AT BENT #166 I-41 Key Message: USACOE dredge and fill provided an immediate (short term) correction for the scour critical problem at Bent #166. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: Tell: • December 5th: NC Governor issues Emergency Declaration which facilitated negotiations with other agencies and contractors. USACE has a contract maintenance dredging project of the navigation channel through the inlet bar. Great Lakes Dredge & Dock is finishing Corps’ work and agrees to contract with NCDOT before moving to their next contract obligation.

A.51 • December 6th: Great Lakes Dredge & Dock begins relocating 2,000 ft of 36-inch diameter discharge line from the beach disposal site to the vicinity of Bent 166. The ALASKA would work around the clock (weather permitting). • December 7th: Dredging (fill) operation begins. • December 8th: Sonar survey indicates dredge material has filled the scour hole above scour critical elevation. Notes: While the dredge and fill operation was a critical first step, cover this topic briefly to allow time for more detailed discussion of underwater filter placement techniques.

A.52 I-42 Key Message: Geotextile container stockpile (4'x4'x4' cubes) at Bonner Bridge. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: Tell: • December 4th: Carolina Bridge Company of Orangeburg, SC was awarded emergency contract. The contractor begins mobilization to drive test piles and install A-Jacks® and geotextile containers. • December 7th: Carolina Bridge Company successfully negotiates with National Park service for a staging area at Oregon Inlet Fishing Center for A-Jacks® assembly and sand bag filling operations. • December 10th: Geotextile containers begin arriving and are filled. Contractor's crane moved to work off the bridge deck at Bent 166. Notes: N/A

A.53 I-43 Key Message: Pallets of 4' A-Jacks® (3 jacks per pallet) at Bonner Bridge assembly area. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2,Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp. 8-9. Instructional Method: Tell: • December 12th: First shipment of A-Jacks® elements arrive at staging area. • December 12th: Divers confirm consolidation of dredge-placed sand at Bent #166. Notes: The next 5 slides show the assembly of the A-Jacks® units, adding the geotextile filter wrap to the assembled units, and the Contractor’s apparatus for placing the units.

A.54 Assembly area Stockpile of assembled A-Jacks® I-44 Key Message: A-Jacks® assembly and stockpile at Bonner Bridge. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2,Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: Tell: • December 15th: NCDOT opens Bonner Bridge to traffic! Access to the Outer Banks and historic villages is open for Holiday season destination travel. December 15th - February 10th: The contractor continues A-Jacks® and geotextile container installation. Weather conditions were favorable immediately after passage of the nor'easter. However, diver safety protocol limited placement of A-Jacks® modules and geotextile containers to periods of slack tide twice a day. Water temperature, visibility, and tidal flow velocity allow for a dive window of only 75 to 90 minutes at slack tide. Notes: N/A

A.55 I-45 Key Message: Stainless steel cable and hardware binding A-Jacks® elements into modules or "logs" for placement. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: See Slide I-44 Notes: For more detail on design and placement of A-Jacks® armor units see FHWA HEC-23, Volume 2, Design Guideline 19.

A.56 I-46 Key Message: A-Jacks® modules placed on barge for transport to bridge. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp. 8-9. Instructional Method: See Slide I-44 Note: Modules are placed on geotextile filter fabric to be fastened to each module prior to placement. Note also the Contractors apparatus for lifting each module into place Notes: For more detail on design and placement of A-Jacks® armor units see FHWA HEC-23, Volume 2, Design Guideline 19.

A.57 I-47 Key Message: Close up of Contractor’s I-beam and cable assembly for lifting and placing A-Jacks® modules. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: See Slide I-44 Note: Tag lines for controlling position of A-Jacks® module. Note also filled geocontainers on barge at lower right of the slide. Notes: N/A

A.58 I-48 Key Message: Geotextile filter applied to the base of each A-Jacks® module. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: See Slide I-44 Note: Close up of geotextile filter wrapped around the base of each A-Jacks® module. Again, note filled geocontainers on barge at lower right of the slide. Notes: Although contractor work continued over the Holiday period, high winds and heavy seas impacted work in the inlet. Unusually cold temperatures interrupted epoxy application in the A-Jacks® assembly process. Upon establishing A-Jacks® perimeter, the area around and between the battered 10 pile group of Bent 166 was protected with geotextile containers (Slides 1- 49 and 1-50).

A.59 I-49 Key Message: With the A-Jacks® perimeter established, 3 ft cube and 4 ft cube sand filled geotextile containers were placed between the Bent #166 piles and within the battered pile cluster. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: Tell: • Upon establishing A-Jacks® perimeter, the area around and between the battered 10 pile group of Bent #166 was protected with geotextile containers. • The schematic in this slide shows the partial placement of 4 ft cube geocontainers around the perimeter of Bent #166 and 3 ft cube geocontainers within the battered piles of the bent. Notes: N/A

A.60 I-50 Key Message: Loading the sand filled geotextile containers from the assembly area to a barge for transport to the bridge site. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. • Henderson, D. 2014. "Scour and the Test of Time: Herbert C. Bonner Bridge Crossing Oregon Inlet, North Carolina," Federal Highway Administration, Hydrologic & Hydraulic News, Vol. 2, Issue 1, April. • Parsons, J. 2013. "Quick Fix Reopens Outer Banks Span," Engineering News Record, December 30, 2013, pp.8-9. Instructional Method: Tell: • February 10th: The last A-Jacks® module was installed and emergency contract for Bonner Bridge was completed. The project was completed ahead of schedule even though weather conditions were not the most accommodating. • The final numbers for work performed were: 78 - 3'x3'x3' geotextile bags 158 - 4'x4'x4' geotextile bags 980 - A-Jacks® elements Cost = $1.79 million (excluding dredge activity estimated at +/- $1 million) Notes: This slide completes the case study presentation. The next slide introduces a summary exercise to complete the learning Outcome established for Session 3 (to list and discuss the lessons learned from this recent U.S. underwater filter installation project).

A.61 SUMMARY EXERCISE Based on this case study and the material presented in Sessions 1 and 2, be prepared to list and discuss the Lessons Learned from this recent underwater filter installation project. I-51 Key Message: "What do you think are the key lessons from NCDOT’s experience with the Bonner Bridge project?" Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Exercise: • On the document camera, white board, or flip chart start a list Lessons Learned and lead a discussion to have Participants provide input to developing the list. • The following are among the observations that Participants should derive from this case study: 1. The Emergency Declaration by the Governor of North Carolina minimized many potential obstacles in contract negotiation and established a dialogue with a host of state agencies (e.g., Marine Fisheries, Division of Water Quality, and Coastal Area Management Commission). 2. Collaboration with Federal agencies (e.g., USACE, U.S. Fish & Wildlife Service, and National Park Service Hatteras National Seashore) was essential to success of the operation. 3. Fastening the geotextile filter to a prefabricated armoring system (e.g., A-Jacks®, ACBS, etc.) provides an effective approach to installing a filter in deep water under adverse conditions. 4. U.S. contractors can mobilize rapidly and provide innovative solutions to difficult and non-standard installation requirements (e.g., implementing the technique of fastening the filter to the base of the A-Jacks® modules and developing the I-Beam and cable lifting assembly for placing the modules). 5. The use of divers to assist in placing the A-Jacks® modules and geocontainers was essential to proper placement and appropriate coverage (but also limited installation operations to periods when the divers could operate safely). 6. While in this case the geocontainers were not used as a filter, the project demonstrated that geotextile containers are available in the U.S. and can be placed in deep water with equipment and skills available to U.S. contractors if the need arises.

A.62 • As time allows make the following points (see the Henderson 2014 article referenced above): 1. One of the key components of timely response action was effective NCDOT internal coordination including establishing chains of command and communication. 2. During the spring and summer of 2013 the North Carolina FHWA Division promoted and facilitated a Table Top Exercise for implementation of an emergency plan of action for Bonner Bridge closure. 3. Based on experience gained and the open dialogue and observations made during the Table Top Exercise, there was a clear and concise determination of authority, decision making, and cross lines of communication which created a positive climate for managing internal roles and external influences of social, media, and political pressures (Henderson 2014). Notes: Allow approximately 10 minutes for this Exercise. See Slides 1-52 and 1-53 for listing of possible responses.

A.63 SUMMARY OF LESSONS LEARNED • Fastening the geotextile filter to a prefabricated armoring system provides an effective approach to installing a filter in deep water under adverse conditions. • U.S. contractors can mobilize rapidly and provide innovative solutions to difficult and non-standard installation requirements. • The use of divers to assist in placing the A-Jacks® modules and geocontainers was essential to proper placement and appropriate coverage. • The project demonstrated that geotextile containers are available in the U.S. and can be placed in deep water with equipment and skills available to U.S. contractors if the need arises. I-52 Key Message: Possible responses to the question "What do you think are the key lessons from NCDOT’s experience with the Bonner Bridge project?" Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-51 Notes: N/A

A.64 ADDITIONAL LESSONS LEARNED • Establishing NCDOT internal coordination including chains of command and communication was a key to success. • Advanced planning and drills promoted by the NC FHWA Division facilitated implementation of the emergency plan of action. • Experience gained and open dialogue and observations during the drills established clear and concise lines of communication. • This created a positive climate for managing internal roles and external influences of social, media, and political pressures. I-53 Key Message: Additional responses to the question "What do you think are the key lessons from NCDOT’s experience with the Bonner Bridge project?" Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: See Slide I-51 Notes: This ends Session 3 and Part 1 of the Workshop.

A.65

A.66 UNDERWATER FILTER INSTALLATION LESSON PLAN Session Title: Underwater Filter Installation Workshop (Part II) Performance- Based Learning Outcomes: At the end of Part II, Participants will be able to: • Describe, evaluate, and list in order of priority (based on local conditions) the recommendations for underwater filter installation from NCHRP Project 24-42. • In a Group Workshop setting, develop installation techniques and discuss solutions for a typical underwater filter installation project at a riverine bridge. Topics: • Recommendations for underwater filter installation from NCHRP Project 24-42 • Group Workshop on installation techniques and solutions for a typical underwater filter installation project at a riverine bridge Instructional Method: After Introduction of Part II Learning Outcomes classroom discussion/ presentation consists of 2 Sessions. Session 1 is instructor-led based on PPT slides to discuss recommendations from NCHRP Project 24-42 for underwater filter installation including a variety of techniques for both granular and geotextile filters. Session 1 begins with an overview of lessons learned from diver assisted testing of installation techniques for both granular and geotextile filters in the prototype-scale flume at Colorado State University (CSU). Session 1 continues with a summary of underwater installation guidance from the NCHRP 24-42 Final Report (Chapter 4). • The first Session of Part II (50 minutes) begins with a discussion of the Schedule and Learning Outcomes, followed by 10 PPT slides and video clips showing testing results and lessons learned from diver assisted installation of granular and geotextile filters in a laboratory setting (20 minutes). The Session continues with 11 PPT slides highlighting and illustrating the recommendations and conclusions on installation guidance resulting from NCHRP Project 24-42. The session ends with a summary exercise to evaluate recommended technologies for local applications in the U.S. (30 minutes). Session 2 is introduced by the instructor with PPT slides following which Participants will work from Workshop handout sheets to develop solutions to typical underwater installation problems at a riverine bridge. • The second Session of Part II is a Group Workshop (70 minutes) during which Participants will develop installation techniques and discuss solutions for a typical underwater filter installation project at a riverine bridge. The Workshop is introduced and conducted with the following steps: 1. Organize the Participants into two Groups – Group(s) #1 and Group(s) #2 such that each group consists of no more than 6 Participants, i.e., for a large number of Participants there will be several groups assigned the Group #1 workshop problem and several groups assigned the Group # 2 problem.

A.67 UNDERWATER FILTER INSTALLATION LESSON PLAN 2. Instructor introduces the objectives of the workshop assignments which are to evaluate and develop techniques and approaches for installing an appropriate filter and overlying riprap armor for a scour critical bridge on the Snake River in Idaho. 3. Instructor provides an overview and reconnaissance of the workshop problem area and bridge using 6 PPT slides. 4. Hand out the workshop problem sheets for Group(s) # 1 and # 2 and discuss group assignments using the document camera. Assignments are similar but Group(s) #1 are to develop a plan and approach to install a granular filter underwater with an overlying riprap armor. Group(s) #2 are to develop a plan and approach to install a geotextile filter underwater with an overlying riprap armor. 5. Briefly go over the given data which include: • Low flow (Fall) construction season hydraulics (discharge, velocity, and flow depth). • Design flow (Spring) discharge, velocity, and flow depth. • Low flow and design flow conditions for Group(s) #1 are lower than these conditions for Group(s) # 2. The Group(s) # 1 low flow and design conditions are in a range that make the installation of a granular filter feasible and yield a slightly smaller riprap size. The Group(s) #2 low flow and design conditions are in a range that would mandate the installation of a geotextile filter and yield a slightly larger riprap size. • Each set of handout sheets contains a CAD plan and profile of the bridge and bridge piers drawn to scale; the characteristics of the substrate (bed) material; the size, gradation, and thickness of an appropriate granular filter (for Group(s) #1); the specifications for an appropriate geotextile filter (for Group(s) #2); and the size, gradation, and thickness of the riprap required for the flow conditions given to each group. Assumptions: Participants are told to assume that cost of installation is not a concern and that any specialized equipment and personnel needed to support their conceptual installation procedure(s) are readily available. In addition, the abutments are not an issue for this problem. Allow approximately 10 minutes for Steps 1 – 5. 6. Each Group’s assignment is identical. By analysis and discussion each group is to develop answers to the following requirements (outlined and with space for notes provided on the workshop sheets): (1) Develop a conceptual plan for the underwater installation of an appropriate filter (as assigned) and the overlying riprap armor.

A.68 UNDERWATER FILTER INSTALLATION LESSON PLAN (2) Identify and list equipment needs (no cost limit) to support the installation concept. (3) Identify and list specialized personnel skills (no cost limit) to support the installation concept. (4) Describe, step by step, the procedures for filter installation underwater. (5) Describe, step by step, the procedures for underwater installation of the armor layer. (6) Identify procedures to verify that the installation meets established specifications. 7. Be prepared to discuss the group’s solutions to the installation problem. Allow approximately 30 minutes for Steps 6 and 7. 8. Instructor select a Group #1 team to present their approach. Other Group #1 teams critique/discuss the approach presented. 9. Instructor select a Group #2 team to present their approach. Other Group #2 teams critique/discuss the approach presented. Allow approximately 10 minutes for each group’s presentation and discussion (20 minutes total). 10. Instructor provide a brief overview with 11 PPT slides of the actual Idaho DOT A-Jacks® installation at this bridge on the Snake River in late 2002. 11. Instructor wrap up the discussion and make any final points on underwater filter installation, as appropriate. Allow approximately 10 minutes for Steps 10 and 11. Time Allotment 120 Minutes • Introduction and discussion of recommendations from NCHRP Project 24-42 (50 minutes) • Group Workshop during which Participants will develop installation techniques and discuss solutions for a typical underwater filter installation project at a riverine bridge (70 minutes) Evaluation Plan: Participant’s attainment of learning outcomes will be evaluated by their presentations and discussion of the Group #1 and Group #2 Workshop solutions. Learning outcomes will be reinforced by the instructor during the Workshop wrap up.

A.69 UNDERWATER FILTER INSTALLATION LESSON PLAN References: FHWA Hydraulic Engineering Circular HEC-23 “Bridge Scour and Stream Instability Countermeasures: Experience, Selection, and Design Guidance” Third Edition, Volumes 1 and 2, 2009. NCHRP Report 568 “Riprap Design Criteria, Recommended Specifications, and Quality Control,” Transportation Research Board, 2006. NCHRP Report 593 “Countermeasures to Protect Bridge Piers from Scour,” Transportation Research Board, 2007. NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” Transportation Research Board, 2018.

A.70 LEARNING OUTCOMES (PART II) • Describe, evaluate, and list in order of priority (based on local conditions) the recommendations for underwater filter installation from NCHRP 24- 42. • In a Group Workshop setting, develop installation techniques and discuss solutions for a typical underwater filter installation project at a riverine bridge. II-1 Key Message: Schedule for the Workshop (Part II) and Learning Outcomes. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Part II is comprised of 2 sessions as shown on the Schedule. At the end of Session 1 Participants should be able to describe, evaluate, and list recommendations for granular and geotextile filter underwater installation techniques in relation to local conditions in their state/region. The first 20 minutes of Session I are Instructor led based on 10 PPT slides and video clips showing testing results and lessons learned from diver assisted installation of selected granular and geotextile filters in a laboratory setting. Session 1 continues with a discussion of recommendations from NCHRP 24- 42 for underwater filter installation techniques for both granular and geotextile filters using 11 PPT slides (approximately 20 minutes). Session 1 concludes with a Group Exercise to list and prioritize recommendations from NCHRP 24-42 considering practicality and local conditions (10 minutes). Notes: N/A Start Session 1.

A.71 LABORATORY TESTING OF FILTER INSTALLATION Diver assisted installation of granular and geotextile filters in prototype scale laboratory flume. • Geotextile filters: -Buoyant, non-woven geotextile sheets unrolled in direction of flow. -Negatively buoyant composite sheets unrolled in direction of flow. • Composite filters - Empty geobags placed on bed adjacent to pier and filled with typical filter gravel using sand pump and flexible tremie hose. • Granular filters – Filter mixture placed with rigid tremie pipe at various elevations above the bed to investigate dispersion and segregation issues. II-2 Key Message: Summary of diver assisted laboratory testing of filter installation. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • Alternative filter materials were considered, particularly for cases where access for construction equipment is limited (eg. beneath bridge deck with limited clearance). • Certified divers assisted with the placement of both granular and geotextile filter materials in flowing water to demonstrate proof-of- concept installation techniques. • The following slides illustrate the testing facility and diver operations during testing. Notes: For additional views of the testing facility see Slides I-30 through I-35 which show testing of pre-filled geotextile containers as a filter under a previous NCHRP project.

A.72 LABORATORY TESTING FACILITY II-3 Key Message: Views of the testing facility and divers in the water. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • The testing facility at CSU is 180 feet long, 20 feet wide, and 8 feet deep. A 4 feet long by 1.5 feet wide bridge pier was installed in the center section of the flume bed which consisted of a 30 feet long by 8 feet deep sediment recess filled with 0.8mm uniform concrete masonry sand to act as riverbed sediment during the testing. • Two steady flow rates were established at a depth of 4 feet during testing. The first flow rate was held at 50 ft3/s, resulting in an approach velocity of about 0.6 ft/s along the flume centerline. The second flow rate was 200 ft3/s resulting in a centerline approach velocity in excess of 3.5 ft/s upstream of the pier. • The dive team consisted of two scuba divers and a topside line handler who managed the tether ropes. Underwater communications were via comm lines in the tether ropes. • The photo on the left shows a flume test at a 4-foot depth and 200 ft3/s with an approach velocity of about 3.5 ft/s. The flow is from right to left in this photo. Note the bow wave around the nose of the pier. • The photo on the right is looking upstream toward the flume inlet box and shows tethered divers preparing to place geotextile filters during a 200 ft3/s test at a 4-foot depth. Notes: N/A

A.73 BUOYANT vs. SELF-SINKING FILTER FABRICS II-4 Key Message: Successful installation of buoyant and self-sinking filter fabrics at 0.6 ft/s velocity. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • Both buoyant and self-sinking panels of nonwoven needle-punched geotextiles were placed around the pier, first at a flow rate of 50 ft3/s (0.6 feet per second) and again at a flow rate of 200 ft3/s (3.5 feet per second). • A standard 8-ounce per square yard polypropylene geotextile (Mirafi 180N) was used as the buoyant fabric. • A 6 mm thick double-sided drainage composite (CETCO Aquadrain G25) with HDPE geonet core was used as the self-sinking fabric; it was made negatively buoyant by affixing metal strips at 4-foot intervals along its length to achieve a handling capability comparable to the sandmat commonly used in Europe (see Slides I-18 and I-19). • The photo on the left shows rolls of the self-sinking geotextile filter ready for installation. The photo on the right shows successful installation by divers of the buoyant and self-sinking geotextile filters at a velocity of 0.6 ft/s. One gallon sand-filled Ziploc bags and 9” riprap stones were used to temporarily weigh down the fabrics while they were being unrolled at the pier in the direction of flow. Notes: N/A

A.74 BUOYANT vs. SELF-SINKING FILTER FABRICS II-5 Key Message: Problematic installation of buoyant and self-sinking filter fabrics at 3.5 feet per second velocity. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: See Slide II-4 Tell: • As shown in the photo on the left, during the 200 ft3/s test the turbulence around the pier created significant difficulty for placing the buoyant geotextile. The divers reported that the geotextile was “sailing” and “twisting” in the current, and that the rocks and sandbags could not effectively hold it down. The divers used heavier pieces of concrete rubble to weigh the fabric down. The installation of the buoyant fabric was unsatisfactory during the 200 ft3/s (3.5 ft/s velocity) test. • The divers reported that the self-sinking drainage composite was easier to handle because it was stiffer and easier to unroll and control, although the resulting placement was still not ideal (see photo on the right). Notes: N/A

A.75 COMPOSITE (GEOBAG) FILTER FILLED WITH FLEXIBLE TREMIE UNDERWATER II-6 Key Message: Diver installation of a composite filter consisting of empty geobags placed at the pier and filled with granular filter material using a flexible tremie hose. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • Placing granular material under water is relatively easy to accomplish with a standard solids handling pump (also known as a trash pump) and a flexible tremie pipe or hose. • Even with limited access or clearance beneath a bridge deck there is no impediment to placing and filling a geobag filter. A solids handling pump can be used to suction up a slurry of gravel and water with up to about 40% solids by volume, and deliver it to divers working under water at the site of filter placement. • For this test a solids handling pump and 40-hp engine was used. The pump had 4-inch diameter suction and discharge capacity, but both suction and discharge hoses were reduced to 2-inch diameter for ease of handling by the divers. A submerged wooden bin containing pea gravel was used as the material source for the suction hose. • The photo on the left shows a nonwoven needle-punched geobag with fill port. The photo on the right shows divers filling the in-place geobag with pea gravel underwater using a 2-inch diameter flexible tremie hose. Show: • At this point show and narrate a video clip (approximately 3 minutes) of diver operations in the laboratory flume and filling of the in-place geobags under water. Notes: N/A

A.76 COMPOSITE (GEOBAG) FILTER FILLED WITH FLEXIBLE TREMIE UNDERWATER II-7 Key Message: Diver installation of loose pea gravel and filling of in place empty geobags at the pier and filled using a flexible tremie hose. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • The photo on the left shows a diver placing loose pea gravel around a pier at 50 ft3/s flow rate (0.6 feet per second). Note gravel exiting the tremie hose. • For this test, the tremie hose approach was successful in placing loose material adjacent to the pier, as well as for underwater filling of 3-foot by 3-foot square geobags having an integral fill port. The photo on the right shows the filled geobags in place adjacent to the pier. • During the 200 ft3/s tests at 3.5 feet per second, the loose pea gravel was partially disrupted by the turbulence around the pier; however, the divers were able to fill the geobags successfully, even at the higher flow rate. Notes: N/A

A.77 DISPERSION AND SEGREGATION ISSUES WITH PLACING GRANULAR FILTER MATERIAL IN FLOWING WATER • When placed in flowing water, granular filter materials will disperse and segregate unless placed directly on the bed. • To quantify the effect of dispersion while dropping granular filter material through the water column, a well-graded mixture of sand and pea gravel was placed at various heights above the bed in 4 feet of flowing water using a 2-inch diameter rigid tremie pipe. II-8 Key Message: Investigation of dispersion and segregation issues when attempting to place granular filter material in flowing water. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • Tests were run at 50 ft3/s and 80 ft3/s - At 50 ft3/s, the average velocity was 0.6 ft/s and the critical particle size was dc = 0.02 mm - At 80 ft3/s, the average velocity was 1.0 ft/s and the critical particle size was dc = 0.11 mm Notes: N/A

A.78 DISPERSION AND SEGREGATION ISSUES WITH PLACING GRANULAR FILTER MATERIAL IN FLOWING WATER II-9 Key Message: Investigation of dispersion and segregation issues when attempting to place granular filter material in flowing water. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • As shown in the photo on the left, for each flow rate, a 5-gallon bucket of granular filter material was emptied into a funnel connected to the top of the tremie pipe. The lower end of the tremie was positioned at the following locations in the flow: -At the water surface (4.0 ft. above the bed) -At 80% flow depth (3.2 ft. above the bed) -At 60% flow depth (2.4 ft. above the bed) -At 20% flow depth (0.8 ft. above the bed) -Directly on the bed • This resulted in the filter material falling through the water column and landing on the bed in five discrete piles for each of the two flow rates, as shown in the photo on the right. • Samples from each pile were taken and analyzed for particle size gradation and compared to a sample from the stockpile. The grain size distribution curves for the test at 1.0 foot per second are provided in the next slide. Notes: N/A

A.79 DISPERSION AND SEGREGATION ISSUES WITH PLACING GRANULAR FILTER MATERIAL IN FLOWING WATER II-10 Key Message: Variations in resulting in place grain size distributions when placed with a rigid tremie pipe at various elevations above the bed (approach velocity of 1.0 ft/s). Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • The gradation curves clearly show the effect of dispersion as a function of both velocity and height of the tremie pipe above the bed. Placing the tremie pipe on or near the bed resulted in less dispersion compared to locating the end of the pipe higher up in the water column. In addition, Test 1 at a lower flow velocity resulted in less dispersion than Test 2. • These tests clearly show that the granular material released higher off the bed results in a filter placement that is increasingly coarser and more uniform compared to the original stockpile. • It is important to utilize uniformly-sized filter gradations and not allow loose dumping from the water surface. • Achieving a “design” granular filter gradation in flowing water is difficult unless the tremie is placed essentially on the bed at the desired filter location. Flow velocity at the time of placement should be no greater than 0.5 times Vcrit, where Vcrit is the critical velocity associated with the d50 particle size of the granular filter. Notes: N/A

A.80 LESSONS LEARNED FROM UNDERWATER TESTING OF FILTER INSTALLATION TECHNIQUES • The practical limit for buoyant geotextile placement by divers was roughly 2.5 ft/s. Placing a self-sinking fabric was barely manageable at an approach velocity of approximately 3.5 ft/s. • Underwater filling of standard 3- by 3-foot square geobags with integral fill port, with pea gravel filter material, was found to be rapid and efficient, even at an approach velocity of 3.5 ft/s. • Dispersion and segregation of granular filter materials was investigated using a rigid 2-inch diameter tremie pipe. The filter material landing on the bed became increasingly coarser and more uniform with increasing height of placement. • The difficulty in achieving a “design” granular filter gradation in flowing water was the result of the finer particles being winnowed out and swept downstream as the material fell through the water column. II-11 Key Message: Appraisal of underwater installation testing results. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • Prior to filling, the geobags were unrolled in the downstream direction with the fill port on the upstream side. One diver held the bag in place against the pier while the other filled it using the flexible tremie hose. The divers noted that with this approach, “the bags almost filled themselves,” even during the high-flow test. Given the rate of gravel delivery from the solids-handling pump, each bag could be filled in about 3 minutes.

A.81 • It should be noted that safety precautions were taken during all phases of the installation demonstration tests. Divers were tethered at all times, and maintained constant communication with the topside line handler. Also, care was taken to ensure that the divers were never located directly downstream of the filter materials during placement, so that potential tangling or entrapment by loose geosynthetic fabrics caught in the turbulence was minimized. Notes: Session 1 continues with an instructor led discussion of additional guidelines and recommendations from NCHRP 24-42 for both granular and geotextile filters.

A.82 GUIDELINES FOR PLACING GRANULAR FILTERS UNDERWATER – INSTALLATION • Underwater installation of granular filters can be performed by clamshell bucket or tremie, with the filter material being released on or very near the bed. • The tremie method of placement can employ a rigid pipe from the surface or a flexible hose through which the filter material is pumped in a water slurry to divers at the end of the hose. • Dumping loose granular filter aggregates into the water column will lead to segregation and dispersion of the filter particles, even in relatively quiescent water. • The resulting dumped material will be coarser and more uniform than the original stockpile material and may not meet “design” filter requirements. II-12 Key Message: Summary of guidelines for placing granular filters underwater - Installation Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • A successful demonstration of the flexible tremie hose technique is described in detail in Chapter 3 of the NCHRP 24-42 Final Report. • In flowing water, granular filters must be placed on or near the bed, and only when local flow velocities are less than about 0.5 times Vcrit, where Vcrit is the critical velocity for incipient motion of the d50 (median) particle size of the filter material. Notes: N/A

A.83 GUIDELINES FOR PLACING GRANULAR FILTERS UNDERWATER – INSPECTION AND MAINTENANCE • Immediately after placing the granular filter, and before the armor layer is installed, the filter should be inspected for adequate thickness and areal coverage. • If the granular filter layer is not thick enough, or is spotty in places, additional material must be added before placing the armor. • Once the armor layer is placed on the filter, there is no maintenance required unless the armor layer is damaged. • If inspection of the armor reveals that it has been displaced or is missing, the underlying granular filter is likely gone as well and must be replaced prior to repairing and restoring the armor layer. II-13 Key Message: Summary of guidelines for placing granular filters underwater – Inspection and Maintenance. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • In the U.S. when bridge inspections include underwater components, regular inspections must be made at intervals not to exceed 5 years. At many bridges, more frequent underwater inspections may be required in a bridge-specific Plan of Action; for example, inspection of underwater bridge components and scour countermeasures may be required after significant flood events. Notes: N/A

A.84 GUIDELINES FOR PLACING GRANULAR FILTERS UNDERWATER – QUALITY ASSURANCE Quality assurance measures for the design and installation of granular filters underwater include: 1. Filter design per established procedures (e.g. FHWA HEC-23). 2. Filter extent, thickness, and termination details per established procedures (e.g. FHWA HEC–23). 3. Material properties should be specified in accordance with test methods and allowable values from established sources (e.g. FHWA HEC-23). 4. Aggregate gradation should be specified in accordance with standard classes from established sources (e.g. ASTM C33). II-14 Key Message: Summary of guidelines for placing granular filters underwater – QA. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. • For construction projects, the quality assurance program focuses on the procedures used to ensure that the design meets quality standards. This includes design calculations, construction plans and detail drawings, and specifications for required material properties Instructional Method: Tell: • Testing - Mineral aggregates used for granular filters should be hard, dense, durable, and generally of good quality. The recommended tests and frequency of testing for granular filter material are similar to those for rock used as riprap. Detailed guidance is provided in FHWA HEC-23. • Specifications - Standard gradations of aggregate are preferred over custom gradations because of cost. ASTM C33/C33M, "Standard Specification for Concrete Aggregates," provide 15 standard size classes of aggregates. Notes: N/A

A.85 GUIDELINES FOR PLACING GRANULAR FILTERS UNDERWATER – QUALITY CONTROL Quality control measures for the design and installation of granular filters underwater include: 1. Check that contractor's submittals for material quality testing and size gradation conform with project specifications. 2. Spot-check random truckloads for proper gradation of granular material delivered to the job site. 3. Local velocity of flow at the job site should be determined. Loose granular material must not be placed if velocity exceeds 0.5 Vcrit . 4. Inspection of the filter placement extent, thickness, and termination details should be performed to determine conformance with the design plans and detail drawings, generally by divers for underwater placement. II-15 Key Message: Summary of guidelines for placing granular filters underwater – QC. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. • During construction, quality control procedures ensure that the materials at the job site meet the design standards, including material testing requirements, and that they have been installed in accordance with the design intent. Instructional Method: Tell: • Spot checks may be made by random sampling and sieve analysis, or by a visual examination and comparison with a control sample in a bag or jar.

A.86 • Vcrit is the velocity for the threshold of motion for the d50 (median) size particle of the filter gradation. • The use of divers should be performed with all applicable dive safety precautions, including tethers, underwater and topside communications, and buffer distance from equipment and machinery. Notes: N/A

A.87 GUIDELINES FOR PLACING GEOTEXTILE FILTERS UNDERWATER – INSTALLATION OF GEOTEXTILE SHEETS • In general, the geotextiles should be placed so that they are free of folds and wrinkles and lie in intimate contact with the subgrade. • Individual sheets should be overlapped a minimum of 12 inches and temporarily weighed down before the armor is placed. • Buoyant geotextile fabrics can be placed by divers in currents of up to about 2.5 ft/s. • Self-sinking geotextile sheets such as a sandmat are both stiffer and heavier, and can be placed by divers in flows up to about 3.5 ft/s. II-16 Key Message: Summary of guidelines for placing geotextile filters underwater – Installation of geotextile sheets. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • Unrolling the geotextile sheet in the direction of flow facilitates placement. Notes: N/A

A.88 GUIDELINES FOR PLACING GEOTEXTILE FILTERS UNDERWATER – INSTALLATION OF GEOBAGS • Geotextile filters can also be installed as bags filled with sand or gravel filter material. • Geotextile containers can be filled prior to placement, sewn shut, and dropped through the water column. • Alternatively, empty geobags can be placed by divers and filled in-place with a flexible tremie hose. II-17 Key Message: Summary of guidelines for placing geotextile as filters underwater – Installation of geotextile composites (geotextile containers or geobags containing granular filter material). Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • Installation of pre-filled geotextile containers may be limited by site access and overhead clearance when installed near a bridge, although contractors have demonstrated a high degree of ingenuity in developing specialized handling equipment to facilitate installation. • Installation of empty geobags by divers and filled in-place underwater resolves access and clearance problems, but may be limited in practice by flow velocity issues (3.5 ft/s or less) and other hazards to diving operations. • Successful installation of large geotextile containers 1.25 m3 (1.6 yd3) in water depths approaching 30 m (100 ft) and flow velocities of 2.5 m/s (8 ft/s) has been reported in European practice. Notes: N/A

A.89 GUIDELINES FOR PLACING GEOTEXTILE FILTERS UNDERWATER – INSPECTION AND MAINTENANCE • Immediately after placing the geotextile filter, and before the armor layer is installed, the filter should be inspected for sufficient areal coverage and overlaps. • When geotextile containers or geobags are used, they must be inspected to ensure that appropriate overlap has been achieved and no voids or bare spots exist in the filter layer. • Once the armor layer is placed on the filter, there is no maintenance required unless the armor layer is damaged. • If inspection of the armor reveals that it has been displaced or is missing, or the geotextile filter is exposed, the geotextile filter must be replaced prior to repairing and restoring the armor layer. II-18 Key Message Summary of guidelines for placing geotextile filters underwater - Inspection and Maintenance. Background Information: NCHRP Report ____ "Underwater Installation of Filter Systems for Scour and Other Erosion Control Countermeasures," 2018. Instructional Method: Tell: • In the U.S. when bridge inspections include underwater components, regular inspections must be made at intervals not to exceed 5 years. At many bridges, more frequent underwater inspections may be required in a bridge-specific Plan of Action; for example, inspection of underwater bridge components and scour countermeasures may be required after significant flood events. Notes: N/A

A.90 GUIDELINES FOR PLACING GEOTEXTILE FILTERS UNDERWATER – QUALITY ASSURANCE Quality assurance measures for the design and installation of geotextile filters underwater include: 1. Filter design methods per established procedures (e.g. FHWA HEC-23). 2. Filter extent and termination details per established procedures (e.g. FHWA HEC–23). 3. Geotextile material properties should be specified in accordance with test methods and allowable values from established sources (e.g. ASTM and AASHTO M 288). 4. Geotextiles should be specified in accordance with AASHTO M288 for Permanent Erosion Control applications. Recommended specification language is provided in Appendix C of the NCHRP 24-42 Final Report. II-19 Key Message: Summary of guidelines for placing granular filters underwater – QA. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. • For construction projects, the quality assurance program focuses on the procedures used to ensure that the design meets quality standards. This includes design calculations, construction plans and detail drawings, and specifications for required material properties. Instructional Method: Tell: • Testing - Recommended standard tests and the allowable values for geotextile properties are provided by ASTM and AASHTO M 288.

A.91 • Specifications - The recommended specification for geotextiles is AASHTO M288. It covers six geotextile applications and provides materials specifications and construction/installation guidelines for geotextiles in highway applications. It is not a design guideline. • It is the engineer's responsibility to choose a geotextile for the application that takes into consideration site-specific soil and water conditions. When site conditions are unknown, engineers can refer to AASHTO M288 Survivability Default Classes for guidance. • Survivability is divided into three classes: Class (1) being the most severe and Class (3) being the least severe. Each class is then subdivided according to elongation. This offers a choice of non- woven geotextiles or woven geotextiles for each class. For certain applications hydraulic properties are included in AASHTO M288. Notes: Example specification language for geotextiles used in Permanent Erosion Control applications is provided in Appendix C of the NCHRP 24-42 Final Report (from Holtz, Christopher and Berg 2008).

A.92 GUIDELINES FOR PLACING GEOTEXTILE FILTERS UNDERWATER – QUALITY CONTROL Quality control measures for the design and installation of geotextile filters underwater include: 1. Check contractor's submittals for material quality testing in conformance with project specifications. 2. Check product labels on rolls of geotextile delivered to the jobsite. 3. Local velocity of flow at the job site should be determined. Placement of standard geotextiles can be performed by divers, but there are practical limits for safe and effective operations. 4. Inspection of the filter placement for sufficient areal coverage and overlaps should be performed to determine conformance with the design plans and detail drawings, generally by divers for underwater situations. II-20 Key Message: Summary of guidelines for placing granular filters underwater – QC. Background Information: • NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. • During construction, quality control procedures ensure that the materials at the job site meet the design standards, including material testing requirements, and that they have been installed in accordance with the design intent. Instructional Method: Tell: • Placement of standard geotextiles can be performed by divers in flow velocities up to 2.5 feet per second; self-sinking geotextiles can be placed in velocities up to 3.5 feet per second. • When geotextile containers or geobags are used, they must be inspected to ensure that appropriate overlap has been achieved and no voids or bare spots exist in the filter layer.

A.93 • The use of divers should be performed with all applicable dive safety precautions, including tethers, underwater and topside communications, and buffer distance from equipment and machinery. Notes: N/A

A.94 CONCLUSIONS FROM NCHRP PROJECT 24-42 • A survey of practitioners across the U.S. revealed that some underwater installation practices in other countries are still new and largely untried in the U.S. • The use of self-sinking geotextile composite fabrics (e.g., a sandmat) is one such practice. Another example is the use of a flexible tremie hose to deliver a slurry of coarse granular filter material to divers for placement underwater (e.g., for filling in-place geobags). II-21 Key Message: Conclusions from NCHRP project 24-42. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Tell: • NCHRP Project 24-42 resulted in a synthesis of the state of the practice for installing filter systems underwater for bridge scour and other erosion control countermeasures. Materials, equipment, and placement techniques developed in Europe, the U.S., and other countries are described in detail in the Final Report. • For both granular and geotextile filters, recommended design procedures, specification items, material testing requirements, installation alternatives, and QA/QC checklist items are provided in the NCHRP 24-42 Final Report. In addition, filter selection guidance is provided based on site-specific conditions which include flow depth, flow velocity, access for construction equipment, and overhead clearance. • Geotextile filters can be installed as bags filled with sand or gravel. The geobags can be filled prior to placement, sewn shut, and dropped through the water column. Alternatively, empty geobags can be placed by divers and filled in place with a flexible tremie hose. Both approaches are commonly used in Europe, but are relatively unknown in the U.S. Wider use of the geobag or geocontainer approaches would constitute a significant advance in the state of practice for placing filters in flowing water in the U.S. Notes: N/A

A.95 CONCLUSIONS FROM NCHRP PROJECT 24-42 • Practitioners in the U.S. indicated that underwater inspection of a filter installation is not usually required prior to placing the armor layer on top. This is an undesirable practice that must be rectified. • The current state of the practice provides a variety of filter material types and placement techniques to accommodate most underwater filter requirements. There should be very few instances where a filter cannot be placed as an integral part of a properly designed and installed scour or erosion control countermeasure. II-22 Key Message: Conclusions from NCHRP project 24-42. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: See Slide II-21. Notes: Session 1 concludes with a Group Exercise to list and prioritize recommendations from NCHRP 24-42 considering practicality and local conditions (10 minutes).

A.96 SUMMARY EXERCISE Based on your experience and local conditions, rate the following techniques for practicality and adaptability for placing a filter underwater. Use a scale of 0 (worst) to 10 (best). • Granular filter (use rigid or flexible tremie pipe) • Mechanical roller or similar device for placing geotextile • Crane or barge with rolled geotextile placed on slope • Spreader bar or frame for geotextile attached to flexible armor (e.g. ACBs) • Buoyant geotextile sheets placed by divers • Self-sinking geotextile sheets (sandmat-type product) • Geotextile containers filled prior to placement • Geobags placed by divers and filled in place with flexible tremie II-23 Key Message: Evaluate recommended technology for local applications in the U.S. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures,” 2018. Instructional Method: Exercise: • This slide shows the recommended techniques and concepts for placing filters underwater as discussed during this workshop. • On the document camera, white board, or flip chart list these techniques and lead a discussion to have Participants reach a consensus as to the applicability and feasibility of applying these techniques locally and indicate a rating from 0 to 10. • 0 would indicate a technique that Participants feel is not applicable or feasible under local conditions. 10 would indicate a technique that Participants feel is highly applicable and feasible under local conditions. Notes: Allow approximately 10 minutes for this Exercise. End Session 1.

A.97 LEARNING OUTCOMES (PART II, SESSION 2) • Session 2 consists of a Group Workshop to develop installation techniques and discuss solutions for a typical underwater filter installation project at a riverine bridge. • The Workshop includes presentation and discussion of individual group solutions. II-24 Key Message: Refresher on Learning Outcome for Part II, Session 2. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • The second Session of Part II is a Group Workshop (70 minutes) during which teams will develop installation techniques and discuss solutions for a typical underwater filter installation project at a riverine bridge. • The objective of the workshop is to develop installation techniques given the design specifications for both the filter and the riprap armor. Notes: This session ends Part II of the presentation/workshop. Start Session 2.

A.98 TEAM ORGANIZATION FOR SESSION 2 • You will work as teams from a DOT Hydraulics Section to develop installation techniques for underwater filter and riprap armor installation at a typical riverine bridge. • Group(s) #1 have the task of developing installation techniques for a granular filter with riprap armor. • Group(s) #2 have the task of developing installation techniques for a geotextile filter with riprap armor. II-25 Key Message: Organization of the teams (Groups) for the workshop. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • A Workshop Handout will provide all the design and specification data required. The Group assignments will require developing installation techniques for the filter/armor combination assigned. • Based on site conditions (substrate and hydraulics) appropriate granular (Group #1) and geotextile (Group #2) filters have been designed. Both low flow (construction season) and design flow (Q50) hydraulic conditions have been determined and are provided in the Handout. • Bridge geometry is provided in the Handout. Notes: After a brief overview (reconnaissance) Handouts will be distributed and data and specific assigned tasks will be discussed. This introduction to the Workshop should take no more than 10 minutes.

A.99 ASSIGNED TASKS 1. Develop a conceptual plan for underwater installation of the assigned filter and riprap armor 2. Identify and list equipment needs to support the installation concept. 3. Identify and list specialized personnel skills to support the installation concept. 4. Describe, step by step, the procedures for filter installation underwater. 5. Describe, step by step, the procedures for installation of the armor layer underwater. 6. Identify procedures to verify that installation meets established specifications. 7. Be prepared to discuss the group’s solutions to the installation problem. II-26 Key Message: Team Workshop assignment tasks. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • Group 1 will work with different hydraulic conditions and site constraints compared to Group 2. • Both groups have the same overall objectives, which are to develop a plan for properly installing a filter and riprap armor system around three bridge piers. • Each group will have 10 minutes to present its solution and answer questions from the other class participants. Notes: After a brief overview (reconnaissance) Handouts will be distributed and data and specific assigned tasks will be discussed.

A.100 SITE LOCATION MAP II-27 Key Message: Map of Ferry Butte Road bridge site. Background Information: Map from USGS website. Instructional Method: Tell: • The project site is an actual bridge located in southeastern Idaho over the Snake River. • Note: Some characteristics and conditions at this bridge have been altered for instructional purposes. Notes: After a brief overview (reconnaissance) Handouts will be distributed and data and specific assigned tasks will be discussed.

A.101 AERIAL PHOTOGRAPH II-28 Key Message: Aerial photograph of bridge site. Background Information: Photograph from Google Earth. River is about 300 feet wide at the bridge. Instructional Method: Tell: • The bridge has been determined to be scour critical during flood events. Notes: After a brief overview (reconnaissance) Handouts will be distributed and data and specific assigned tasks will be discussed.

A.102 BRIDGE (flow is from left to right) II-29 Key Message: Detailed view of bridge site. Background Information: Photograph by Idaho Transportation Department (ITD) shows how a bed bathymetric survey was conducted with a portable truck-mounted sonar system. In this photo, a velocity probe is being lowered into the water on the upstream side of the bridge. Instructional Method: Tell: • The three piers are long, wall-type piers that are 2 ft. wide and 34 ft. in length. • The piers are aligned with the flow. • The piers are founded on shallow spread footings which can become undermined by scour during flood events. Notes: After a brief overview (reconnaissance) Handouts will be distributed and data and specific assigned tasks will be discussed.

A.103 BRIDGE PLAN AND PROFILE II-30 Key Message: Bridge plan and profile. Background Information: Bridge plans from ITD were used to develop the scour countermeasure design. Instructional Method: Tell: • The piers are skewed at 60 degrees from the bridge deck centerline. Notes: After a brief overview (reconnaissance) Handouts will be distributed and data and specific assigned tasks will be discussed.

A.104 DIVE TEAM ON SITE II-31 Key Message: DOT dive team on site. Background Information: A dive team was used to determine the condition of the piers, type of bed material, and debris/obstructions prior to the countermeasure design. Instructional Method: Tell: Prior to countermeasure design, a dive team determined: • The condition of the piers. • The type and size of bed material (sand and gravel). • The debris and obstructions at the base of the piers (logs, old tires, etc.) Notes: After a brief overview (reconnaissance) Handouts will be distributed and data and specific assigned tasks will be discussed.

A.105 CONDITIONS AT BASE OF PIERS II-32 Key Message: Stream bed conditions at typical bridge pier. Background Information: Photograph by ITD shows logs and other debris at the base of the piers. Instructional Method: Tell: • Logs, old tires, shopping carts and other debris must be removed prior to construction. • Subgrade preparation will include excavation because the riprap countermeasure cannot be mounded on the streambed. Notes: After a brief overview (reconnaissance), Handouts will be distributed and data and specific assigned tasks will be discussed.

A.106 WORKSHOP HANDOUT • Group 1 will develop a plan to install a granular filter beneath a riprap armor layer. • Group 2 will develop a plan to install a geotextile filter beneath a riprap armor layer. • Each group will have a different set of hydraulic conditions and site constraints to contend with. • Instructor(s) will be available to explain site conditions and answer questions as the participants develop their plans (30 minutes). II-33 Key Message: Workshop Handout Background Information: NA Instructional Method: Tell: • The three piers are long, wall-type piers that are 2 ft. wide and 34 ft. in length. • The piers are aligned with the flow. The piers are founded on shallow spread footings which can become undermined by scour during flood events. Show: Use the document camera to briefly show what is in the Handout. Then have the teams start work on the Workshop. Notes: The Handouts are now distributed. After 30 minutes have the Group #1 and Group #2 solutions presented by their designated spokesperson. Presenters are allocated 10 minutes for each discussion, including time for comments and questions from the other groups. After the group presentations, wrap up the Workshop with a brief overview of the ITD’s constraints and solutions using the following 11 slides (10 minutes).

A.107 IDAHO TRANSPORTATION DEPARTMENT’S APPROACH • A-Jacks® armor systems with underlying geotextile filters were installed by ITD on two bridges on the Snake River. • News Release: “Pocatello – A process used to prevent erosion from the base of bridge piers will be used for the first time in Idaho to control “scouring” on two eastern Idaho bridges that were severely damaged in the 1997 Snake River Flood.” II-34 Key Message: The ITD’s solution Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • In late 2002 early 2003 the A-Jacks® armor system with an underlying geotextile filter was installed by ITD on two bridges on the Snake River in eastern Idaho. • Installations were completed at the Ferry Butte Bridge and the West Shelley Bridge. • The installation at the Ferry Butte Road bridge will be illustrated. Notes: The following slides summarize constraints that led to this approach and provide an overview of the installation as a summary to the Workshop (10 minutes).

A.108 SELECTION OF THE SCOUR COUNTERMEASURE • Idaho Department of Natural Resources (DNR) rejected the ITD proposal to fill the scour holes with clean washed gravel prior to placing a countermeasure. • A-Jacks® could be installed in modules with geotextile filter attached. • Scour holes were so deep that multiple layers of A- Jacks® were required at some piers. • The A-Jacks® units are designed to capture sediment and begin refilling the eroded riverbed around the piers. II-35 Key Message: ITD reasons for selecting the A-Jacks® approach. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • Idaho DNR disapproval of the ITD plan to refill scour holes with clean washed gravel ruled out consideration of placing a granular filter. • Flow velocity at Ferry Butte was low with water depth of about 9 feet but at West Shelley flow velocity exceeded 6 fps and flow depth was up to 15 ft. • Pier #2 at Ferry Butte had severe undulating riverbed conditions and exposed footing. • ITD was seeking an opportunity to try a new approach (other than riprap) for pier scour countermeasure installations. • A-Jacks® system offered the opportunity to attach the geotextile filter to the A-Jacks® modules and install filter and armor as a unit. Notes: Note for Instructor: ITD did not specify or require a filter but Contractor requested that geotextile be attached to the A-Jacks® modules prior to placement.

A.109 ITD SITE PREPARATION • Woody debris removed from scour protection zones. • Boulders projecting 400 mm (16 inches) above streambed removed from scour protection zones. • Scour holes to be filled with clean gravel (disapproved by DNR). • All A-Jacks® modules be connected together and secured to the pier structure to prevent modules from being displaced. II-36 Key Message: ITD site preparation specifications. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • ITD’s first objective on arriving on site of Ferry Butte was to investigate conditions of the river bed in the vicinity of pier structures using divers. The dive equipment included an underwater video camera. • Based on dive inspection, specifications were developed for site preparation. Notes: Attaching a scour countermeasure to a bridge pier is not recommended in FHWA’s HEC -23.

A.110 ASSEMBLY OF THE A-JACKS® II-37 Key Message: Preparation and assembly of the A-Jacks®. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • Skids were used to fabricate the 6 x 6 A-Jacks® modules to provide easy transport of each module assembly. After assembling the A- Jacks® into modules they were then secured tightly by using 0.25 in. corrosion resistant steel cables and copper clamps. The modules were then ready for delivery to the bridge site. • At the bridge site placement depths at the piers ranged from 2 ft. to about 9 ft. and river velocity was low. Notes: NA

A.111 CONTRACTOR’S LIFTING FRAME FOR THE A-JACKS® II-38 Key Message: Contractor’s lifting frame for the A-Jacks®. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • Contractor designed a lifting frame to handle each of the 6 x 6 A- Jacks® modules Notes: NA

A.112 APPLYING THE GEOTEXTILE TO THE A-JACKS® II-39 Key Message: Adding the geotextile filter to the A-Jacks®. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • Each of the 6 x 6 A-Jacks® modules was lifted to apply the geotextile filter on site. Notes: NA

A.113 HANDLING DEVICE TO PLACE THE A-JACKS® II-40 Key Message: Contractor designed handling device to place the A-Jacks® underwater. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • Contractor designed a specialized handling device to place each module. Notes: NA

A.114 PLACING THE A-JACKS® AT FERRY BUTTE BRIDGE II-41 Key Message: Overview of placing operation for A-Jacks® modules at the Ferry Butte Bridge. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • This slide shows the crane and assembled module at the bridge site. • Assembly at the pier started downstream and progressed upstream to facilitate handling of the modules and ensure good fit-ups between modules. • It was found essential to support the installation with divers and a pontoon boat for proper and safe placement of the modules. Notes: The next slide shows the divers and pontoon boat used to assist module placement.

A.115 DIVERS ASSISTING PLACING THE A-JACKS® II-42 Key Message: Divers assisting placing the A-Jacks® modules at the Ferry Butte Bridge. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: See slide II-41. Notes: NA

A.116 ITD REQUIREMENTS AND SPECIFICATIONS • Fit modules as close as possible between one another and to pier structure. • Manufacturer requested that geotextile be applied to modules prior to placement. • Contractor shall provide divers to verify fit-ups and acceptability of placed modules. • Remove any broken A-Jacks® from river. • Provide connections between all modules. • Contractor shall provide direct evidence to ITD for final acceptance of all A-Jacks® placed. II-43 Key Message: ITD requirements for the contractor. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: Review the bullets on Slide II-43. Notes: Note to Instructor: The geotextile was a manufacturer’s requirement, not ITD’s.

A.117 DIVER VERIFICATION OF FINAL INSTALLATION II-44 Key Message: Divers inspecting placement of the A-Jacks® modules at the Ferry Butte Bridge. Background Information: NCHRP Report 887. "Guidance for Underwater Installation of Filter Systems for Scour and Other Erosion Countermeasures," 2018. Instructional Method: Tell: • This slide shows a diver inspecting and providing video documentation of the installed A-Jacks® modules at the Ferry Butte Bridge. • Site visit to the ferry Butte Bridge in 2013 revealed that the A-Jacks® were completely covered by aggradation of stream bed material and inspector needed to probe through 1.5 ft. of sand and gravel to find the top of the A-Jacks®. • Any questions on the IDT installation? • Any questions on the Workshop? • Any final comments or observations? Notes: This completes Part II, Session 2 and the Workshop.

HO1.1 Group #1 Handout Underwater Filter Installation Workshop 1. Problem Statement The Ferry Butte Bridge crosses the Snake River between Blackfoot, ID and the American Falls Reservoir in southeastern Idaho. The bridge carries Ferry Butte Road, a local two-lane paved road. After a flood last year, scour was noted at the piers of this bridge and a study was initiated to determine appropriate measures to protect this bridge from further scour. Your supervisor (the Instructor) is familiar with the history of this bridge crossing and has assembled relevant historical information and data necessary for developing several alternative scenarios for installing appropriate countermeasures. He has divided the DOT Hydraulics Section into two teams and has directed that each team explore a specific countermeasure alternative and develop installation techniques to support that alternative. An application to the State DNR to cofferdam the bridge reach and install countermeasures “in the dry” was denied because of fish passage concerns and the potential for serious ecological impacts. Consequently, the countermeasures must be installed in flowing water, but construction timing will permit installation during the low flow season. Your team (Group #1) has been assigned the task of determining the feasibility of and developing an installation plan for the underwater installation of riprap armor over a granular filter to protect the bridge piers. The other team (Group #2) will investigate the feasibility of installing a geotextile filter under a riprap armor to protect the bridge piers. The alternative approaches will be presented and evaluated in a meeting of the full Hydraulics Section with input from the Geotechnical Section and the Structural Bridge Design Section. 2. Background and Pertinent Data Based on office and field reconnaissance all relevant data has been assembled. Figure 1 provides a regional map of the Ferry Butte reach of the Snake River. Figure 2 shows a Google Earth™ aerial view of the bridge reach and Figure 3 provides a view of the bridge (looking upstream) taken during the site reconnaissance. Research of the bridge data files has provided a CAD drawing (Figure 4) of the bridge plan and profile. During the field reconnaissance, the DOT dive team was on site (Figure 5) and provided underwater photography of the bed conditions at a typical pier of the Ferry Butte Bridge (Figure 6).

HO1.2 Ferry Butte Rd Bridge N0 3 6 miles Blackfoot American Falls Reservoir Project site Figure 1. Snake River project site in southeastern Idaho (image courtesy USGS). Bridge N 0 1000 2000 feet Flow direction Figure 2. Ferry Butte Road Bridge near Blackfoot, ID (image courtesy Google Earth).

HO1.3 Figure 3. Ferry Butte Road Bridge. Flow is from left to right. (courtesy ITD) Limits of riprap (typ.) Figure 4. Ferry Butte Road Bridge plan and profile. (base drawing courtesy ITD)

HO1.4 Figure 5. Dive team on site at Ferry Butte Road Bridge. (courtesy ITD) Figure 6. Typical river bed conditions at base of piers, Ferry Butte Road Bridge. (courtesy ITD)

HO1.5 Research of the bridge data files also produced pertinent hydraulic data, bridge geometry, and bed material characteristics from a previous Bridge Hydraulics Report (BHR). (Note: Characteristics and conditions at this bridge have been altered for instructional purposes.) The relevant information for this project is provided below: Low flow (construction season) hydraulic information: Low flow Qconstr = 1,050 ft3/s Section average velocity Vavg = 3.2 ft/s Local velocity at piers Vconstr = 3.2 x 1.5 = 4.8 ft/s Low flow depth yconstr = 4.7 ft Design flow (50-yr flood event) hydraulic information: Design flow Q50 = 17,200 ft3/s Section average velocity V50 = 6.5 ft/s Design velocity at piers Vdes = 6.5 x 1.5 = 9.8 ft/s Design flow depth y50 = 9.2 ft 100-yr pier scour depth ys = 6.1 feet 100-yr contraction scour and long-term degradation = 2.8 feet Bed material characteristics: • Description – Sandy gravel; logs and debris around base of piers • Bed material gradation: D85 = 12.7 mm (0.5 in.) D50 = 7.0 mm (0.3 in.) D15 = 2.3 mm (0.1 in.) • Bed material hydraulic conductivity: Kbed = 0.062 cm/s Bridge geometry: • Bridge length between abutments = 480 ft with 4 spans @ 120 ft /span (simply supported) • Round nose wall piers on spread footers, Width = 2 ft, Length = 34 ft (aligned with the flow) • Piers at 60 degrees skew to bridge centerline • Clearance at low flow from water surface to bridge low chord = 14.3 ft • Clearance at 50-yr design flow from water surface to bridge low chord = 9.8 ft

HO1.6 Based on bed material characteristics, typical construction season flows, and 50-year flood design flow, you estimate that the following granular filter requirements and riprap sizing will be required: Granular filter requirements (to be placed at low flow): • Filter gradation: D85 = 21 mm ( 0.8 in.) D50 = 18 mm ( 0.7 in.) D15 = 7 mm ( 0.3 in.) Note: This gradation corresponds to ASTM C33 No. 57 coarse aggregate • Filter hydraulic conductivity: Kfilter = 7.4 cm/s • Filter layer thickness: T ≥ 6” x 1.5 (factor for placement under water) = 9” (0.75 ft) • Incipient motion velocity for D15 of the granular filter: Vcrit = 5.4 ft/s Riprap armor layer requirements (for 50-yr design discharge): • Riprap gradation: D85 = 305 mm ( 12 in.) D50 = 230 mm ( 9 in.) D15 = 150 mm ( 6 in.) Note: This gradation corresponds to HEC-23 Class II riprap • Riprap layer thickness: T ≥ 3 x 9” x 1.5 (factor for placement under water) = 40” (3.3 ft) • Riprap is readily available from a local quarry which can produce angular, well-graded stone. Subgrade preparation for filter and riprap installation: The spread footings at the piers are 6.5 to 9 feet below the present riverbed elevation, but will become exposed and undermined due to scour during flood events. Mounding the riprap on top of the riverbed is not acceptable for many reasons; therefore, the bed must be excavated such that the top of the riprap is flush with the ambient riverbed elevation. The depth of excavation is dictated by the riprap layer thickness (3 x D50 x 1.5) because the contraction scour plus long- term degradation at this site is less than the riprap layer thickness. The DNR will permit excavation, provided that turbidity curtains are installed downstream of the work area. Logs and other debris at the base of the piers will be removed prior to excavation.

HO1.7 3. Group 1 Assignment Based on the information provided above, your team assignment for the next 30 minutes is to evaluate the feasibility of protecting the Ferry Butte bridge piers with a granular filter/riprap armor countermeasure and develop underwater installation techniques to support this alternative. Working as a team you should, as a minimum, consider the following installation factors: 1. Develop a conceptual plan for the underwater installation of an appropriate filter (as assigned) and the overlying riprap armor. 2. Identify and list equipment needs (no constraints on cost or availability) to support the installation concept. 3. Identify and list specialized personnel skills (no constraints on cost or availability) to support the installation concept.

HO1.8 4. Describe, step by step, the procedures for filter installation underwater (provide sketches of your approach, as necessary). 5. Describe, step by step, the procedures for underwater installation of the armor layer (provide sketches of your approach, as necessary). 6. Identify procedures to verify that the installation meets established specifications. 7. After 30 minutes a designated spokesperson from your team should be prepared to present your team’s observations, analysis, and approach to installing your assigned underwater filter/armor pier protection countermeasure at a typical pier of the Ferry Butte Road Bridge. The document camera will be available to support your presentation. Be brief and use sketches, as necessary. You will have 5-6 minutes to present your installation approach. Other Group #1 teams will have 4-5 minutes to ask questions and critique your approach.

HO2.1 Group #2 Handout Underwater Filter Installation Workshop 1. Problem Statement The Ferry Butte Bridge crosses the Snake River between Blackfoot, ID and the American Falls Reservoir in southeastern Idaho. The bridge carries Ferry Butte Road, a local two-lane paved road. After a flood last year, scour was noted at the piers of this bridge and a study was initiated to determine appropriate measures to protect this bridge from further scour. Your supervisor (the Instructor) is familiar with the history of this bridge crossing and has assembled relevant historical information and data necessary for developing several alternative scenarios for installing appropriate countermeasures. He has divided the DOT Hydraulics Section into two teams and has directed that each team explore a specific countermeasure alternative and develop installation techniques to support that alternative. An application to the State DNR to cofferdam the bridge reach and install countermeasures “in the dry” was denied because of fish passage concerns and the potential for serious ecological impacts. Consequently, the countermeasures must be installed in flowing water, but construction timing will permit installation during the low flow season. Your team (Group #2) has been assigned the task of determining the feasibility of and developing an installation plan for the underwater installation of riprap armor over a geotextile filter to protect the bridge piers. The other team (Group #1) will investigate the feasibility of installing a granular filter under a riprap armor to protect the bridge piers. The alternative approaches will be presented and evaluated in a meeting of the full Hydraulics Section with input from the Geotechnical Section and the Structural Bridge Design Section. 2. Background and Pertinent Data Based on office and field reconnaissance all relevant data has been assembled. Figure 1 provides a regional map of the Ferry Butte reach of the Snake River. Figure 2 shows a Google Earth™ aerial view of the bridge reach and Figure 3 provides a view of the bridge (looking upstream) taken during the site reconnaissance. Research of the bridge data files has provided a CAD drawing (Figure 4) of the bridge plan and profile. During the field reconnaissance, the DOT dive team was on site (Figure 5) and provided underwater photography of the bed conditions at a typical pier of the Ferry Butte Bridge (Figure 6).

HO2.2 Ferry Butte Rd Bridge N0 3 6 miles Blackfoot American Falls Reservoir Project site Figure 1. Snake River project site in southeastern Idaho (image courtesy USGS). Bridge N 0 1000 2000 feet Flow direction Figure 2. Ferry Butte Road Bridge near Blackfoot, ID (image courtesy Google Earth).

HO2.3 Figure 3. Ferry Butte Road Bridge. Flow is from left to right. (courtesy ITD) Limits of riprap (typ.) Figure 4. Ferry Butte Road Bridge plan and profile. (base drawing courtesy ITD)

HO2.4 Figure 5. Dive team on site at Ferry Butte Road Bridge. (courtesy ITD) Figure 6. Typical river bed conditions at base of piers, Ferry Butte Road Bridge. (courtesy ITD)

HO2.5 Research of the bridge data files also produced pertinent hydraulic data, bridge geometry, and bed material characteristics from a previous BHR. (Note: Characteristics and conditions at this bridge have been altered for instructional purposes.) The relevant information for this project is provided below: Low flow (construction season) hydraulic information: Low flow Qconstr = 1,400 ft3/s Section average velocity Vavg = 3.7 ft/s Local velocity at piers Vconstr = 3.7 x 1.5 = 5.6 ft/s Low flow depth yconstr = 5.4 ft Design flow (50-yr flood event) hydraulic information: Design flow Q50 = 21,600 ft3/s Section average velocity V50 = 8.1 ft/s Design velocity at piers Vdes = 8.1 x 1.5 = 12.2 ft/s Design flow depth y50 = 9.2 ft 100-yr pier scour depth ys = 6.1 feet 100-yr contraction scour and long-term degradation = 2.8 feet Bed material characteristics: • Description – Sandy gravel; logs and debris around base of piers • Bed material gradation: D85 = 12.7 mm (0.5 in.) D50 = 7.0 mm (0.3 in.) D15 = 2.3 mm (0.1 in.) • Bed material hydraulic conductivity: Kbed = 0.062 cm/s Bridge geometry: • Bridge length between abutments = 480 ft with 4 spans @ 120 ft /span (simply supported) • Round nose wall piers on spread footers, Width = 2 ft, Length = 34 ft (aligned with the flow) • Piers at 60 degrees skew to bridge centerline • Clearance at low flow from water surface to bridge low chord = 10.3 ft • Clearance at 50-yr design flow from water surface to bridge low chord = 6.5 ft

HO2.6 Based on bed material characteristics, typical construction season flows, and 50-year flood design flow, you estimate that the following geotextile filter requirements and riprap sizing will be required: Geotextile filter requirements (to be placed at low flow): Using the base soil (bed material) information, particle retention criterion, hydraulic conductivity criterion, and considering the requirement to minimize long-term clogging potential, a nonwoven needle-punched fabric is selected as the geotextile filter. After investigating a number of alternatives, a suitable fabric designated “NWN-1200x” is selected. This fabric has the requisite mechanical and hydraulic characteristics for the Snake River site conditions. The fabric has the following physical characteristics: Mechanical Properties Test Method Unit Minimum Average Roll Value Weight ASTM D5261 oz/yd2 (g/m2) 12.0 (407) Thickness ASTM D5199 mils (mm) 130 (3.3) Grab Tensile Strength ASTM D4632 lbs (N) 320 (1424) Grab Tensile Elongation ASTM D4632 % 50 Trapezoid Tear Strength ASTM D4533 lbs (N) 125 (556) CBR Puncture Strength ASTM D6241 lbs (N) 900 (4005) Apparent Opening Size (AOS)1 ASTM D4751 U.S. Sieve (mm) 100 (0.15) Permittivity ASTM D4491 sec-1 0.9 Permeability ASTM D4491 cm/sec 0.3 Flow Rate ASTM D4491 gal/min/ft2 (l/min/m2) 65 (2648) UV Resistance (at 500 hours) ASTM D4355 % strength retained 80 1 ASTM D4751: AOS is a Maximum Opening Diameter Value Physical Properties Unit Typical Value Roll Dimensions (width x length) ft (m) 15 x 300 (4.5 x 91) Roll Area yd2 (m2) 500 (418) Estimated Roll Weight lb (kg) 424 (192) Note: The fabric has a specific gravity of 0.92; therefore, it will float in water. Also note that each roll weighs more than 400 lbs. Riprap armor layer requirements (for 50-yr design discharge): • Riprap gradation: D85 = 530 mm ( 21 in.) D50 = 380 mm ( 15 in.) D15 = 300 mm ( 12 in.) Note: This gradation corresponds to HEC-23 Class IV riprap • Riprap layer thickness: T ≥ 3 x 15” x 1.5 (factor for placement under water) = 67” (5.6 ft) • Riprap is readily available from a local quarry which can produce angular, properly-graded stone.

HO2.7 Subgrade preparation for filter and riprap installation: The spread footings at the piers are 6.5 to 9 feet below the present riverbed elevation, but will become exposed and undermined due to scour during flood events. Mounding the riprap on top of the riverbed is not acceptable for many reasons; therefore, the bed must be excavated such that the top of the riprap is flush with the ambient riverbed elevation. The depth of excavation is dictated by the riprap layer thickness (3 x D50 x 1.5) because the contraction scour plus long- term degradation at this site is less than the riprap layer thickness. The DNR will permit excavation, provided that turbidity curtains are installed downstream of the work area. Logs and other debris at the base of the piers will be removed prior to excavation. 3. Group 2 Assignment Based on the information provided above, your team assignment for the next 30 minutes is to evaluate the feasibility of protecting the Ferry Butte bridge piers with a geotextile filter/riprap armor countermeasure and develop underwater installation techniques to support this alternative. Working as a team you should, as a minimum, consider the following installation factors: 1. Develop a conceptual plan for the underwater installation of an appropriate filter (as assigned) and the overlying riprap armor. 2. Identify and list equipment needs (no constraints on cost or availability) to support the installation concept. 3. Identify and list specialized personnel skills (no constraints on cost or availability) to support the installation concept.

HO2.8 4. Describe, step by step, the procedures for filter installation underwater (provide sketches of your approach, as necessary). 5. Describe, step by step, the procedures for underwater installation of the armor layer (provide sketches of your approach, as necessary). 6. Identify procedures to verify that the installation meets established specifications.

HO2.9 7. After 30 minutes a designated spokesperson from your team should be prepared to present your team’s observations, analysis, and approach to installing your assigned underwater filter/armor pier protection countermeasure at a typical pier of the Ferry Butte Road Bridge. The document camera will be available to support your presentation. Be brief and use sketches, as necessary. You will have 5-6 minutes to present your installation approach. Other Group #2 teams will have 4-5 minutes to ask questions and critique your approach.