I-90 West of George Paving - Warm Mix Asphalt
The Washington State Department of Transportation (WSDOT) paved about 5,000 tons of warm mix asphalt (WMA) as part of their I-90 West of George Pav...
Greenroads Manual
EW-3: Runoff Quality Control
1-3 point
Goal
Improve water quality of stormwater runoff leaving the roadway Right-of-Way (ROW)
Requirements
- Implement a stormwater management plan for the site using stormwater best management practices (BMPs) for water quality treatment. Use low-impact development (LID) BMPs to the maximum extent feasible as determined in Project Requirement PR-8 or by a licensed professional. Do not use detention ponds procured outside of the ROW.
- Demonstrate that these BMPs meet the following quality criteria:
- BMPs reduce sediment loads to total suspended solids (TSS) concentrations of 25 mg/L or less, as an indicator of overall treatment level.
- BMPs conform to all applicable minimum water quality standards for all runoff leaving the ROW set by the governing jurisdiction for contaminants, such as heavy metals, hydrocarbons, pathogens, water temperature and turbidity.
- Compute the 90th percentile average annual rainfall event post-construction runoff volume for two areas: (1) the area of the project ROW and (2) the total tributary area outside the ROW that may generate untreated stormwater which runs into the ROW BMPs (“run-on”), if any. Note that BMPs should be sized appropriately if considering any runoff volumes generated from outside the ROW.
- Treat a percentage of the total computed runoff volume for either area computed as noted in Table EW-3.1.
Documentation
Share
