Stormwater runoff from urban areas is a major source of pollution in local waterways and the San Francisco Bay. As rainwater flows from rooftops and pavement, it collects pollutants and carries them to the Bay through storm drains, creeks, and rivers. Green alleys have specially designed features to help slow the flow of runoff and filter pollutants from the water.
Martha Gardens Green Alleys
Three alleys in the Martha Gardens neighborhood of San José were selected for pavement and drainage improvements. Over 35,000 square feet of deteriorated asphalt and bare soil have been replaced with recycled content “green” concrete and permeable paved surface to filter stormwater on site. View the fact sheet.
The specific design features of the Martha Gardens Green Alleys project include:
- Permeable pavement
- Filtration trenches
- Lighter colored surfaces that absorb less sunlight and lower temperatures
- Recycled materials
Water Quality Benefits
- Major source of sediment eliminated
- Pollutants, such as oil and grease from cars, filtered from runoff on site
- Street-sweeping restored
Neighborhood Improvement Benefits
- New pavement with proper drainage
- Reduced runoff to storm sewer
- Cleaner streets and alleys
Protecting Our Watersheds
A watershed is a land area that drains water into a creek, river, lake, or bay. The Guadalupe Watershed is one of the largest watersheds in Santa Clara County and has been identified as a priority watershed due to poor water quality from urban runoff and other pollutants. The Martha Gardens Green Alleys are located near the Guadalupe River that flows through downtown San José and into the South San Francisco Bay. This project showcases a cost-effective stormwater management retrofit that benefits the community and the watershed.
Martha Gardens Green Alleys is a Joint Project of:
- State Water Board – Providing $945,000 of Proposition 84 Stormwater Grant Program funds for project construction.
- City of San José, Department of Public Works – Providing project design and engineering, construction management and inspection, and project acceptance.
- City of San José, Environmental Services Department – Providing grant administration, public education and outreach about the project, and conducting pre- and post-project water quality monitoring.
Funding for this project has been provided in part through an agreement with the State Water Resources Control Board.