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[edit] General Description

Please help improve this project page by replacing this text with a description and other factual information about the project. Don't know much about the project? Call your local government and ask for details. The primary purpose of the Upper Las Positas Creek Restoration and Storm Water Management Project is to detain and treat storm water and incidental runoff in order to improve water quality downstream in Las Positas Creek, the Arroyo Burro Estuary, and Arroyo Burro Beach.

The secondary purpose of the project is to reduce peak storm flows in order to facilitate the installation of downstream creek restoration and/or water quality treatment projects. Additional goals are to address runoff from the San Jose Lane neighborhood that can lead to flooding of downstream areas, address runoff and erosion from Adams School, and provide habitat restoration. This will be accomplished through the construction of storm water basins, swales, shallow pools, and planting native vegetation. This project will create jobs, support the green economy, and lead to less pollution.

Extensive water quality monitoring of Las Positas Creek and Arroyo Burro Creek has found concentrations of fecal indicator bacteria that exceed the recreational contact standards. As one of the few large open areas owned by the City, the project site has the potential to serve as a site for detention and treatment facilities for polluted urban and storm water runoff. This facility may reduce downstream pollution in Arroyo Burro Creek and contribute to the City’s long-term efforts to reduce creek pollution and improve ocean water quality at the beach.

[edit] Points in Favor

The final design for the Upper Las Positas Creek Restoration and Storm Water Management Project includes a combination of detention and retention basins, bioswales, pocket wetlands, erosion control, runoff diversion pipes and native plant landscaping. The proposed plans would reduce peak runoff volumes during 100-year storm events by over 50%. During smaller events, i.e. up to 10-year storm events, the proposed plan will retain and treat nearly 100% of the runoff. These scenarios include the diversion of runoff from the San Jose Lane neighborhood onto the golf course. Detention and retention is important because storm water will be treated primarily by the settling of suspended particles and the associated pollutants, including microorganisms and metals. Settling of particles can only occur when the water velocity is sufficiently slow, i.e. as occurs in storm water basins. It is estimated that up to 90% of the suspended load and associated pollutants can be removed during detention or retention. Runoff from smaller storms (~ 2-yr) and nuisance flows will be treated primarily by filtration through vegetated channels known as bioswales. In the upper reaches, bioswales will consist of channels lined by emergent plants, which will slow down the flow for settling of solids and provide some filtration. In the lower reaches, which will see higher flows, the bioswales include rock aeration (step pools that cascade into each other, much like you would see in more natural creek settings) and emergent plants, providing increased opportunity for removal of suspended material. The bioswales are estimated to remove 20-80% of suspended pollutants. Detention and retention are also important because by reducing peak flows off the golf course, lower flows downstream can encourage other projects in the sub-watershed. By retaining such a high proportion of the flow on-site, potential water quality improvement projects downstream will be more feasible since they'll be dealing with less storm water volume. Even lower in the watershed, where the 1400' concrete channel follows Las Positas Road, flows will be reduced by approximately 10% during a 100-year event. At the outflow of Arroyo Burro Creek, the project will reduce flows by 2 - 6%, depending on the size of the storm. Additional project elements include erosion control along the perimeter of the Adams School. At present, storm water runoff from the school is eroding a channel into the edge of the golf course that threatens the stability of the slope there. Furthermore, a carefully considered plant pallet will provide natural landscaping (primarily California natives) that serves biotreatment and habitat functions and improves the aesthetic views. In summary, this project seeks to improve our local water quality for the benefit of recreational users and wildlife, encourage other green projects downstream to move forward, create green jobs that rely on innovative design, and serve as a demonstration project for other similar municipalities and communities.

[edit] Points Against