Green Streets For Regulatory Compliance: A City of San Diego BMP Implementation Project
By necessity urban areas, such as the City of San Diego, are filled with impervious surfaces with extensive transportation systems. Roads and travel surfaces are often a significant source of runoff and urban pollution while presenting one of the greatest opportunities for implementation of LID principles, reducing and treating stormwater close to its source. To comply with the MS4 permit by reducing the pollutant load and volume of runoff the City designed and implemented multiple stormwater BMP retrofits in a 20 acre medium density residential watershed. The primary purpose of the project was to implement bioretention areas, treatment planters, and pervious pavement systems within the city controlled rights-of-way to treat the 85th percentile storm for the entire watershed. To fully optimize implementation, a continuous simulation model, SUSTAIN was used to determine the specific size and combination of BMPs best suited to meet the runoff requirements for the bacteria TMDL in Tecolote Creek at the minimum construction cost. An optimization curve was developed to determine the most cost effective design scenario considering the cost of implementation within each classification. BMPs were implemented within the right-of-way using all available space, including opportunities utilizing traffic calming measures retrofitted in accordance with the Street Design Manual, while minimizing impacts to the residential community.
In cooperation with City staff, key management questions were identified that may be answered by monitoring the performance of the BMPs over the near and short terms and a monitoring strategy aimed at collecting important feedback from the installed systems to evaluate conditions and effectiveness is being developed. Because this is the first large-scale LID implementation of its kind in the City, in addition to meeting pollutant load reduction requirements, one of the goals of the project is to provide the City with valuable feedback regarding the design and effectiveness of these BMPs to guide future decision making for LID guidelines and implementation in San Diego and server as a template for future green street projects.
BMP implementation in the 20 acre area began in August. This presentation will build on previous discussions with a brief review of the design process and focus on the construction of 6,250 square feet of pervious concrete and 8,890 square feet of bioretention in the right-of-way. Construction challenges and lessons learned will be highlighted including the importance of early material submittals and potential acceptable material alternatives.