The Green Alley Project in the City of Fort Bragg will demonstrate low-impact development (LID) concepts by infiltrating urban stormwater now running off City streets and alleys through permeable pavers, open bottom inlets, and bioretention facilities. The goal of the project is to increase the amount of stormwater that can be absorbed in place, and to reduce the pollution from cars that enters Alder Creek and local wetlands with filtration. Infiltrating urban runoff will filter out typical urban pollutants, like motor oil and bacteria, and minimize the amount of pollutants that enter nearby surface waters. Repaving with permeable pavers improved the aesthetics and serviceability of alley conditions while also recharging groundwater and improving the quality of nearby surface waters. This approach is meant to revive the area back to natural conditions before urbanization when native soils absorbed a greater portion of rainfall. The key to the success of the design was good soils and the innovation to install permeable pavers in alleys with low traffic and speeds.
The project serves as an example of the successful utilization of Proposition 84 Stormwater Grant funding. A grant was received from the State Water Resources Control Board for the purposes of demonstrating the beneficial effects of LID on urban receiving waters. The use of LID tools is encouraged by California and other states to improve water quality in local receiving waters while reducing the need for and costs associated with conventional stormwater infrastructure (curb and gutter, stormwater conveyance piping) needed to drain stormwater from hardened urban areas. The hard surfaces common in urban areas (streets and buildings) have inadvertently become barriers to water infiltration, percolation, and groundwater recharge.
Construction was completed in Fall 2015 at the project’s two alleys and five storm drain inlets. Work was performed at the following locations:
Purity Alley (N200E) between Franklin and McPherson streets, running from Redwood Avenue to Alder Street;
South Alley (S100G) between Harrison and Whipple streets, running from Oak Street to Madrone Street;
Two storm drain inlets on Whipple Street;
Two storm drain inlets at the VFD parking lot; and
One storm drain inlet in the alley east of Harold Street and south of Oak Street.