Guidelines for Evaluating and Selecting Modifications to Existing Roadway Drainage Infrastructure to Improve Water Quality in Ultra-Urban Areas (2012) / Chapter Skim
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Pages 124-160
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124 This section describes seven case studies of ultra-urban BMP retrofits and retrofit pilot testing as listed in Table 10.1. The case studies illustrate how some DOTs are meeting the challenges of ultra-urban retrofits, as well as the range of regulatory requirements and objectives that can drive the projects.
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125 urban commuter corridor with an ADT of 122,000. Land use adjacent to the highway is a mixture of residential and commercial uses.
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126 NMFS, Oregon Department of Environmental Quality, the FHWA, USFWS, USEPA, and the Oregon Department of Fish and Wildlife. The products of the SWAT effort included triggers for stormwater treatment, water quality and flow control design storms, definition of the "contributing impervious area" targeted for treatment by a project, and a general ranking of stormwater BMPs.
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127 media, or through load reduction achieved in infiltration systems. Candidate BMPs The stormwater performance standard developed through the multi-agency SWAT effort required the use of a designated "preferred BMP" to satisfy the regulatory and treatment objectives.
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128 – Compost-amended soils in the swale bottom to allow as much infiltration as practicable – A perforated pipe underdrain system constructed below the amended soils to route filtered flow to natural streams – Retaining walls of approximately 21,000 ft2 to fit the bioswales to the existing embankment and avoid encroaching on an existing county road – Substantial grading and the relocation and/or retrofit of existing utility poles to accommodate bioswale widths • Standard media filter drain (bioslope) : The preliminary design of the standard MFD included the following treatment components and requirements from the WSDOT and ODOT design manuals (See Section 4.7.3 and Figure 4.12)
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129 major goal of LID, whereby inlets and conveyance pipes are not used in the drainage system, allowing some infiltration. This design also addresses maintenance department concerns about vegetation management.
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130 extensively with maintenance staff and roadway designers in an effort to identify crucial design and operational constraints. This coordination allowed design of BMPs that were compatible with highway safety requirements regarding obstacles in the clear zone and that do not overly burden maintenance staff.
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131 ments (e.g., hydromodification control)
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132 Design Constraints The primary BMP design constraint was the city's policy to utilize infiltration BMPs to the extent feasible. WSDOT coordinated with the city to locate and design BMPs that could achieve the city's policy for LID practices.
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133 ceded with a pretreatment sedimentation manhole (Figure 10.7)
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134 expected to result in overall treatment performance that meets and exceeds the minimum basic treatment requirements in the HRM. • West end BMP design.
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135 Figure 10.9. WSDOT Manette Bridge replacement, west end BMP layout.
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136 minimum basic treatment requirements, which are based on an 80% TSS removal standard. In addition, the infiltration system will substantially reduce stormwater discharges from the east end of the bridge and will achieve project objectives for LID.
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137 Pre-Project Stormwater Treatment Existing treatment controls (swales, ponds, media filter drains) provide water quality treatment for a small portion of the existing highway area.
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138 receiving waters are considered critical habitat for Chinook salmon and Bull trout, which are federal-listed endangered species. Regulatory Requirements Enhanced treatment was required for the project in accordance with procedures in the WSDOT HRM (WSDOT, 2008a)
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139 drains. A design objective was to retain pre-project drainage patterns and conveyances to the extent feasible.
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140 and Benson Road is a BMP opportunity area where two modified MFDs and a flow control basin are to be located (Figure 10.14)
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141 Discussion and Lessons Learned WSDOT engineers were faced with developing a challenging BMP plan for a highway-widening project in a heavily used suburban commuter corridor. The challenges included (1)
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142 where feasible to provide treatment of new and existing highway sections. – Used a combination of BMPs to fit site constraints.
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143 Poplar Street bridge to the new Mississippi River bridge, and modifying the existing Tri-Level I-55/I-64/I-70 Interchange to accommodate connections from the existing interstate routes to the I-70 connection (Figure 10.17)
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Figure 10.18. IDOT Mississippi bridge, Bowman Avenue pump station location.
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145 includes the I-70 area east of the railroad tracks, I-64, I-55, and the new or re-aligned ramps. The added impervious area results in approximately 1.64 ac-ft of detention storage volume required for the 100-year storm event.
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146 Avenue to the west, and Portland Avenue to the east. The segment lies in a heavily urbanized area within and between Minneapolis and Richfield, Minnesota (Figure 10.21)
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147 • Cultural resources, including historically significant sites and buildings; • Construction impacts; • Right-of-way; • Parks; and • Visual/aesthetics. After reviewing comments received on the EA/EAW published in July 2004, MnDOT determined that all state requirements for environmental review of the I-35W/Highway 62 reconstruction project had been met, and the FHWA approved a "Revised Record of Decision." Step 2: Define Retrofit Objective Treatment Objective The regulatory compliance objective was to address sediment loading and floatable debris.
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148 need some type of treatment prior to discharging stormwater into five water bodies. One of the practices for treatment is a partnership with the cities of Minneapolis and Richfield to build lined regional ponds and ring treatment systems upstream of the existing water bodies.
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149 oils, and fuels -- from stormwater runoff during frequent wet weather events. The structures must be capable of 80% removal of TSS on an annual average basis based on the gradation analyses.
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150 designed in cooperation with the City of Minneapolis to capture and treat city and highway stormwater runoff. These ponds were named Powell and Lake Mead.
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151 nance requirements. Routine maintenance practices for the grit chamber design are anticipated to include litter pickup and vacuuming the sediment when the chamber is filled.
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152 Information regarding this project was provided by Brett Troyer (brett.troyer@state.mn.us)
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153 ited to TSS, bacteria, metals such as copper and zinc, PCBs, and oil and grease. Regulatory Requirements The primary stormwater regulatory requirements are focused on compliance with the current Phase I NPDES permit, the existing long-term control plan to eliminate combined sewer overflows, and the upcoming wasteload allocations for the TMDL implementation plan that is currently being developed.
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154 Soils The existing soils in the area are fill and are heavily compacted urban soils and clay loams. There is little capacity for rapid soil infiltration in these areas.
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155 Figure 10.30. DDOT interchange retrofit project, bioretention grading plan.
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156 10.7 Maryland State Highway Administration Concrete V-Ditch Conversion Pilot Study Project Scope Background The Maryland SHA manages approximately 14,500 lanemiles of highway throughout the state and owns approximately 25,000 acres of impervious area. The State of Maryland Department of the Environment (MDE)
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157 Receiving Waters and Issues of Concern The preservation and restoration of the Chesapeake Bay and its tributaries are the primary water quality concerns in the region. Major urban centers of concern to Maryland SHA are the Washington DC and Baltimore metropolitan areas.
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158 Design Constraints This project has limited design constraints; because of the lack of utilities and wide median, many of the design constraints found in narrower ROWs are not present. Construction access and maintenance of traffic issues were also minimal.
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159 subgrade. Table 10.3 lists the design parameters for the direct runoff from the concrete channel, the design from the current stormwater manual standards, and the enhanced swale.
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160 conventional design; additional monitoring was needed to obtain statistically significant verification of the water quality benefits. The study also needed to demonstrate construction and maintenance requirements in order to make sure the new design elements could be integrated into the Environmental Management System and the SHA design manuals and standards.
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