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From page 49... ... 49 C H A P T E R 4 This chapter describes a focused menu of primary VRAs that has been developed to provide the user with options for achieving surface runoff volume reduction in the urban highway environment. Section 4.1 begins with identification of stormwater control measures (SCMs) Read the entire page →
From page 50... ... 50 Volume Reduction of Highway Runoff in Urban Areas The International BMP Database (www.BMPdatabase.org) included 533 studies as of March 2013, of which more than 25% (142 studies) Read the entire page →
From page 51... ... Volume Reduction Approaches 51 4.1.2 Relative Frequency of Application of SCMs by State DOTs In a survey of DOT representatives conducted in 2012 (Venner et al., 2013) , respondents from all 50 states plus Puerto Rico and the District of Columbia provided rankings of the relative frequency of various SCM types. Read the entire page →
From page 52... ... 52 Volume Reduction of Highway Runoff in Urban Areas 4.1.3 Recent Research and Emerging Concepts in Volume Reduction Approaches for Urban Highways This section highlights several areas of recent research related to volume reduction and volume reduction approaches to identify new and emerging concepts that may be applicable in achieving volume reduction. International BMP Database Volume Reduction Technical Report The International BMP Database contains over 530 BMP studies, a portion of which include data that relate to the volumetric performance of stormwater controls. Read the entire page →
From page 53... ... Volume Reduction Approaches 53 of precipitation event size and facility design parameters. Table 9 provides a summary of bioretention volume reduction performance, including studies divided into those without and with underdrains. Read the entire page →
From page 54... ... 54 Volume Reduction of Highway Runoff in Urban Areas Figure 8. Examples of ODOT bioretention installations. Read the entire page →
From page 55... ... Volume Reduction Approaches 55 bioretention with internal water storage (i.e., elevated underdrain) as a preferred approach for maximizing volume reduction when infiltration rates are measureable but are not adequate to support a full infiltration design without underdrains. Read the entire page →
From page 56... ... 56 Volume Reduction of Highway Runoff in Urban Areas Mark Maurer, April 18, 2013) Read the entire page →
From page 57... ... Volume Reduction Approaches 57 permeable surfaces within high-volume roadways with heavy loadings (Maine DOT, 2010; see also Appendix F, which is part of NCHRP Web-Only Document 209) Read the entire page →
From page 58... ... 58 Volume Reduction of Highway Runoff in Urban Areas Development of Technical Guidance for Retain On-Site Requirements The introduction of "retain on-site" requirements in non-DOT environments -- for example, EISA legislation as well as various MS4 permits (see Section 3.1.1) -- has introduced new considerations and challenges into the project design process in these areas. Read the entire page →
From page 59... ... Volume Reduction Approaches 59 Research in Active Real-time Controls Most current efforts in the field of stormwater engineering are focused on analyzing and developing designs that passively achieve target goals (e.g., peak attenuation, volume reduction, water balance, pollutant removal targets) ; however, passive systems rarely represent optimal solutions. Read the entire page →
From page 60... ... 60 Volume Reduction of Highway Runoff in Urban Areas Opportunities to increase infiltration discharge rates potentially include: • Piping pretreated discharge to deeper wells below compacted fills, • Directional drilling to convey pretreated runoff to areas with better infiltration, • Breaking up lower-permeability materials using ripping or blasting, and • Using plant palettes with high ET rates (and capable of withstanding drought) Read the entire page →
From page 61... ... Volume Reduction Approaches 61 introduces site planning approaches that are integral to reducing runoff volumes and providing opportunities to incorporate VRAs. This chapter and the accompanying fact sheets in Appendix A are intended to help the user answer the following questions: • What is the menu of volume reduction approaches available for my project? Read the entire page →
From page 62... ... 62 Volume Reduction of Highway Runoff in Urban Areas VRA 01 – Vegetated Conveyance This category includes engineered vegetated swales and other vegetated drainage features that serve the purpose of conveying stormwater runoff and can also provide significant reduction of stormwater runoff volume. Variations on this approach include an amended soil or stone storage layer to increase storage capacity and promote infiltration. Read the entire page →
From page 63... ... Volume Reduction Approaches 63 VRA 07 – Infiltration Trench This category of VRA consists of a stone-filled trench that provides subsurface storage of stormwater runoff and allows water to infiltrate through the bottom and walls of the trench into subsoils. Pretreatment for infiltration trenches is commonly provided via a vegetated conveyance such as swales or filter strips. Read the entire page →
From page 64... ... 64 Volume Reduction of Highway Runoff in Urban Areas media filters with permeable bottoms, and other controls not specifically identified as VRAs. Site-specific design information or monitoring data can be used to help estimate the potential incidental volume losses that may occur. Read the entire page →
From page 65... ... Volume Reduction Approaches 65 Hydrologically referenced discharge is a recent concept that has not seen extensive application in addressing volume reduction requirements; however, it may be an important concept for balancing volume reduction goals with physical constraints such as shallow groundwater, low soil infiltration rates, and sensitive water balance conditions. In these cases, infiltration could have negative consequences. Read the entire page →
From page 66... ... 66 Volume Reduction of Highway Runoff in Urban Areas to reduce the runoff volume from the site and potentially achieve other benefits. The following sections provide guidance on planning principles, with specific emphasis on how these can be incorporated into urban roadway designs. Read the entire page →
From page 67... ... Volume Reduction Approaches 67 could be conducted, and if results were favorable, opportunity areas could begin to be identified for placement of VRAs such as bioretention areas, infiltration basins, and infiltration galleries. Working around critical infrastructure such as the light-rail tunnel, various utilities, and other constraints, project designers could attempt to reserve opportunity areas for VRA features. Read the entire page →
From page 68... ... 68 Volume Reduction of Highway Runoff in Urban Areas Limit Footprint of Disturbance Limiting the footprint of disturbance is a general principle that can potentially be incorporated into the grading design of some roadway projects as well as the construction-phase plans for equipment access and stockpiling of materials. During grading design, footprints of disturbance can be limited by attempting to leave areas at their natural grade, without cut or fill, when possible. Read the entire page →
From page 69... ... Volume Reduction Approaches 69 4.3 Summary of VRA Attributes and Considerations Each VRA has a distinct set of attributes and considerations that are inherent in its design and function. Fact sheets provided in Attachment A provide an extended summary of each of the primary VRAs. Read the entire page →
From page 70... ... 70 Volume Reduction of Highway Runoff in Urban Areas 4.3.1 Summary of Relative Volume Reduction Mechanisms and Potential Water Balance Issues by VRA The amount of volume reduction achieved by a VRA, as well as the proportional split between deeper infiltration and ET that occurs in a VRA, is a function of the underlying infiltration rate of site soils, soil moisture-retention properties, plant root depths, rainfall intensity, and facility design characteristics, specifically the footprint and the depth of the BMP. When shallow BMPs with larger surface areas are used, the level of ET tends to increase due to the additional retained moisture content in the top layer of soils in closer contact with the atmosphere (Strecker and Poresky, 2009) Read the entire page →
From page 71... ... Volume Reduction Approaches 71 areas should have a relatively long flow path perpendicular to the roadway. VRAs such as infiltration basins are inherently larger and involved ponding of water within an impoundment such that they are practical only where there is a larger contiguous space with a relatively flat profile. Read the entire page →
From page 72... ... 72 Volume Reduction of Highway Runoff in Urban Areas • Major increases in sizing tend to be required to improve volume reduction performance from 40% to 80% capture, suggesting that partial volume reduction is likely to be significantly more practicable in space-constrained highway environments. • Soil infiltration rates were most sensitive in the performance of shallow-flow VRAs and least sensitive for VRAs with deeper ponding depths. Read the entire page →
From page 73... ... Volume Reduction Approaches 73 environment and the inherent unit processes provided by these VRAs (see Table 11) can be used to provide a relative assessment of potential geotechnical issues associated with different types of VRAs (Table 14) Read the entire page →
From page 74... ... Category of VRA Characteristic Properties Example Opportunities and Constraints Related to Geotechnical Issues1 Opportunities Constraints Direct infiltration into roadway subgrade Example: VRA 04• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • – Permeable Shoulders VRA 09 – Infiltration Gallery Broad footprint; may only receive direct rainfall or equivalent Road subgrade has important structural considerations, particularly for flexible pavement design Broad footprint may allow infiltration in relatively dense soils Standard roadway designs typically account for wetting of subgrade Rigid pavement design (i.e., concrete) less sensitive to strength of subgrade Utilities in the right-of-way (ROW) Read the entire page →
From page 75... ... Volume Reduction Approaches 75 Risk Factor Discussion Lower Risk Indicators Higher Risk Indicators Footprint/tributary area ratio The relative footprint of the system influences the pollutant loading per unit area and the potential for natural assimilative capacity to be overwhelmed. Systems with broader, shallower footprint such as dispersion Systems with deeper profiles and smaller footprints, such as infiltration trenches Strata at which infiltration occurs When infiltration occurs below the strata of organic soil or closer to the groundwater table, there tends to be less assimilative capacity. Read the entire page →
From page 76... ... 76 Volume Reduction of Highway Runoff in Urban Areas 4.3.5 Summary of Safety Considerations by VRA A number of key safety considerations that may relate to the siting and design of VRAs include: • Limitations on grading and structures within the "clear zone" along the road shoulders to allow errant vehicle recovery and reduce collision hazards, • Vegetation management to maintain line-of-site requirements as well as to eliminate collision hazards within the clear zone, • Adequate supplemental drainage, as needed to avoid flooding of travel lanes, and • Lane closures to facilitate low-speed maintenance activities within the right-of-way. Based on its respective location within the highway environment and its inherent design attributes, each VRA has a different suite of factors that should be considered in design. Read the entire page →
From page 77... ... Volume Reduction Approaches 77 Routine Maintenance Activities VR A 01 – V eg et at ed C on ve ya nc e VR A 02 – D is pe rs io n VR A 03 – M ed ia F ilt er D ra in VR A 04 – Pe rm ea bl e Sh ou ld er s VR A 05 – Bi or et en tio n w /o U nd er dr ai ns VR A 06 – Bi or et en tio n w ith U nd er dr ai ns VR A 07 – In fil tra tio n Tr en ch VR A 08 – In fil tra tio n Ba si n VR A 09 – In fil tra tio n G al le ry Mowing Maintain level spreading functions Landscaping and weeding Routine woody vegetation management Sediment removal/management Vacuum sweeping Trash and debris removal Erosion repair Rodent hole or beaver dam repair Fence or access repair Key: Primary maintenance activity; Minor maintenance activity; may not apply in some cases or may be limited; Not usually applicable. Table 18. Read the entire page →
From page 78... ... 78 Volume Reduction of Highway Runoff in Urban Areas and corrective maintenance activities, respectively, that may apply to each of the primary VRAs. These tables were developed based on review of guidance manuals and interviews with DOT maintenance staff. Read the entire page →
From page 79... ... Volume Reduction Approaches 79 are proposed. Therefore, the cost of vegetating a VRA would only be the incremental cost of the proposed VRA vegetation versus the baseline vegetation or stabilization plans had the VRA not been used. Read the entire page →
From page 80... ... 80 Volume Reduction of Highway Runoff in Urban Areas Replacement cost. This is the cost to install a new VRA at the end of the current VRA's life span or substantially reconstruct the VRA. Read the entire page →
From page 81... ... Volume Reduction Approaches 81 Project-scale and unit costs. Larger projects with fewer, large-scale VRAs can potentially be built at lower costs than smaller-scale projects or those that have many distributed controls. Read the entire page →
From page 82... ... 82 Volume Reduction of Highway Runoff in Urban Areas VRA Capital Costs – New Roadway or Major Redevelopment1 Capital Costs – Retrofits or Minor Redevelopment O&M and Replacement/ Reconstruction Costs Effective Life Span 2 VRA 01 Vegetated Conveyance Low to Moderate Can typically be easily incorporated into grading plans for non–ultra-urban settings Provides conveyance function that can offset pipes and structures Low to Moderate Modifications to existing swales to improve volume reduction may be inexpensive. Can add significant cost if regrading and rerouting must be done to accommodate VRA Low to Moderate Requires more frequent maintenance of debris removal and vegetation upkeep than typical vegetated or concrete ditch without water quality functions Erosion/scour must be addressed. Read the entire page →
From page 83... ... Volume Reduction Approaches 83 VRA Capital Costs – New Roadway or Major Redevelopment1 Capital Costs – Retrofits or Minor Redevelopment O&M and Replacement/ Reconstruction Costs Effective Life Span 2 VRA 08 Infiltration Basin Moderate Assumes no acquisition costs for land Assumes potential additional excavation and infrastructure to convey water to centralized location Basins can offset pipes or reduce size of downstream conveyance. High Cost depends on cost of rerouting flows to specific areas. Read the entire page →
From page 84... ... 84 Volume Reduction of Highway Runoff in Urban Areas • Geosyntec Consultants et al. Read the entire page →
From page 85... ... Volume Reduction Approaches 85 State Year Published Publication Title AZ 2009 ADOT Post-Construction Best Management Practices Manual For Highway Design and Construction http://www.azdot.gov/Inside_ADOT/OES/Water_Quality/Stormwater/PDF/adot_post_con struction_bmp_manual.pdf 1993 Highway Drainage Design Manual – Hydrology, http://www.azdot.gov/Highways/Roadway_Engineering/Drainage_Design/PDF/ADOTHig hwayDrainageDesignManual_Hydrology.pdf 2007 Highway Drainage Design Manual – Hydraulics, http://www.azdot.gov/Highways/Roadway_Engineering/Drainage_Design/PDF/ADOTHig hwayDrainageDesignManual_Hydraulics.pdf CA 2010 Caltrans Storm Water Quality Handbooks – Project Planning and Design Guide, http://www.dot.ca.gov/hq/oppd/stormwtr/ppdg/swdr2012/PPDG-May-2012.pdf 2012 Caltrans Highway Design Manual, http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm GA 2001 Georgia Stormwater Management Manual Volume 2, http://documents.atlantaregional.com/gastormwater/GSMMVol2.pdf MA 2004 Storm Water Handbook For Highways and Bridges, http://www.mhd.state.ma.us/downloads/projDev/2009/MHD_Stormwater_Handbook.pdf 2006 Massachusetts Project Development & Design Guide, http://www.mhd.state.ma.us/default.asp? pgid=content/designguide&sid=about MD 2000 2000 Maryland Stormwater Design Manual – Volumes I and II, http://www.mde.state.md.us/programs/Water/StormwaterManagementProgram/SoilErosi onandSedimentControl/Documents/MD%20SWM%20Volume%201.pdf MN 2000 MnDOT Drainage Manual, http://www.dot.state.mn.us/bridge/hydraulics/drainagemanual/ 2009 Stormwater Maintenance BMP Resource Guide http://www.lrrb.org/media/reports/2009RIC12.pdf NJ 2004 New Jersey Stormwater Best Management Practices Manual, http://nj.gov/dep/stormwater/bmp_manual2.htm NV 2006 Storm Water Quality Manuals – Planning and Design Guide, http://www.nevadadot.com/uploadedFiles/NDOT/About_NDOT/NDOT_Divisions/Engine ering/Hydraulics/2006_PlanningAndDesignGuide.pdf NY 2010 New York State Stormwater Management Design Manual, http://www.dec.ny.gov/chemical/29072.html, http://www.dec.ny.gov/docs/water_pdf/swdm2010entire.pdf OH 2012 Location & Design Manual, Volume 2 Drainage Design, http://www.dot.state.oh.us/Divisions/Engineering/Hydraulic/LandD/Pages/TableofConten ts.aspx OR 2011 Hydraulics Manual, ftp://ftp.odot.state.or.us/techserv/geoenvironmental/Hydraulics/Hydraulics Manual/Table_of_Contents_rev_Nav.pdf PA 2010 PennDOT Drainage Manual, ftp://ftp.dot.state.pa.us/public/bureaus/design/PUB584/ RI 2010 Rhode Island Stormwater Design and Installation Standards Manual, http://www.dem.state.ri.us/programs/benviron/water/permits/ripdes/stwater/t4guide/desm an.htm SD 2011 Drainage Manual, http://sddot.com/business/design/forms/drainage/default.aspx TX 2011 Hydraulic Design Manual, http://onlinemanuals.txdot.gov/txdotmanuals/hyd/hyd.pdf WA 2011 Highway Runoff Manual, http://www.wsdot.wa.gov/publications/manuals/fulltext/m3116/Chapter5.pdf (updates expected in 2014) Read the entire page →

From page 49...

... 49 C H A P T E R 4 This chapter describes a focused menu of primary VRAs that has been developed to provide the user with options for achieving surface runoff volume reduction in the urban highway environment. Section 4.1 begins with identification of stormwater control measures (SCMs)