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A.1 Survey of Practice: National Cooperative Highway Research Project 24-42: "Underwater Installation of Filter Systems for Scour and Other Erosion Control Countermeasures" Introduction: Current technical guidance on scour and erosion control countermeasure design includes recommendations for either a granular or geotextile filter beneath the countermeasure. However, there is little guidance on actual installation techniques for placing the filter under water when temporary dewatering of the site cannot be performed. The objective of NCHRP Project 24-42 is to develop specific guidance for use by design, construction, and maintenance personnel on the function of filters and their installation, particularly when filter placement must be performed under water. This survey should take about 10 minutes to complete. It is intended to solicit information on the current state of practice with regard to filter design and underwater placement. Your participation is very important to the successful development of future guidelines on this topic. 1. Contact Information: Your name: ______________________________________ Title: ______________________________________ Agency name: ____________________________________ Phone: __________________________________________ email: ___________________________________________ 2. Type of agency (select only one): o Federal Government o State Government o Local Government o Construction Contractor o Engineering/Design Consultant o Other (please describe): ________________________________ 3. Location:
A.2 PLEASE ANSWER THE FOLLOWING QUESTIONS USING THE RESPONSE THAT BEST REPRESENTS TYPICAL PRACTICES OF YOUR AGENCY: PART A - FILTER DESIGN: The following set of questions is related to filter design practices typically used by your agency for bridge scour protection and other erosion control projects: 4. Does your agency require filters beneath the armor layer where the countermeasure must be placed under water? o Always o Usually o Sometimes o Rarely o Never 5. If you answered "Never" to Question 4, please indicate the reasons why you donât use filters (select all that apply): o Donât need a filter beneath the armor o Too costly to place under water o Too difficult to place under water o Too difficult to obtain environmental permitting o Other (please explain): ________________________________________ Note: If you answered "Never" to Question 4, you may now skip to the end of this survey and click "Submit". Thank you for your time. 6. What types of scour or erosion control applications are most often encountered by your agency where filter placement must occur under water? (select all that apply): o Lateral stream stability / bank protection o Vertical stability / streambed armoring o Rock spurs, dikes, groins etc. o Bridge abutment scour
A.3 o Bridge pier scour o Vertical walls or bulkheads o Other (please describe): __________________________________________________ 7. When selecting a filter material for placement under water, which of the following materials is typically preferred? o Geotextile fabric o Granular layer o Geotextile, granular, or both (i.e., composite filter) depending on site-specific conditions o Other (please identify): __________________________________________________ 8. When designing and specifying a filter, which guidance document does your agency typically use? o FHWA Hydraulic Engineering Circular No. 23 (HEC-23), Lagasse et al., 2009. o NCHRP Report 568, "Riprap Design Criteria, Recommended Specifications, and Quality Control," Lagasse et al., 2006. o FHWA HI-07-092, "Geosynthetic Design and Construction Guidelines," Holtz, Christopher and Berg, 2008. o "Designing with Geosynthetics," Koerner, R.M., 1998. o U.S. Army Corps of Engineers EM-1110-2-1901, Appendix D, "Filter Design," 1993. o Agency-specific, in-house guidance document or design manual (please identify): ______________________________________________________________________ o Other (please identify): ___________________________________________________ PART B - FILTER PLACEMENT: The following set of questions is related to filter placement methods typically used by your agency for bridge scour protection and other erosion control projects, when placement must be performed under water: 9. When placing a geotextile filter under water, which practices do your agency typically employ? (select all that apply):
A.4 o Dive crew placing and temporarily pinning or weighting the geotextile (e.g., with sandbags) prior to placement of the armor system o Floating the geotextile on the water surface and subsequently sinking it with weights o Dumping sand-filled geocontainers (geobags) from the bank, bridge, or barge o Redirecting current to decrease velocity in vicinity of work area o Hand placed and pinned by workers wading in shallow water o Attaching or wrapping the geotextile filter to a frame or to the countermeasure material o Anchors, chain falls. or large pipe to hold geotextile in place o Other (please describe): _________________________________________________ 10. When placing a granular filter layer under water, which practices does your agency typically employ? (select all that apply): o Dumping granular material from the bank, bridge, or barge with a clamshell, bucket or front-end loader o Large diameter tremie pipe or tube o Redirecting current to decrease velocity in vicinity of work area o Other (please describe): _________________________________________________ 11. After the filter is placed under water, does your agency require inspection (typically by diver) prior to placing the armor layer? o Yes o No o I donât know 12. In your opinion, assuming that you will be placing an armor system under water, what is the biggest impediment to the successful placement of a filter prior to placing the armor? (choose only one): o Velocity of flow o Depth of water o Visibility under water (i.e., inability to place and inspect)
A.5 o Construction access o Constructability issues o Environmental concerns/permitting o Lack of knowledge of importance of filter by construction personnel o Other (please describe): __________________________________________________ 13. Do you have any inspection information or other performance assessment data that may be useful to this project? (If you answer "yes," you will receive a follow-up contact from our research team). o Yes o No 14. Please list any agency reports (especially case histories), construction specifications, or other publications that are relevant to the underwater placement of filters. Any other comments, observations or insights that you feel will help the Research Team in conducting NCHRP Project 24-42 will also be greatly appreciated: __________________________________________________________________________ __________________________________________________________________________ Thank you very much for your time in completing this survey.
