Project Location: First Street West Frontage of Depot Park
Project Purpose: Reduce the risk of flooding for homes and businesses along First Street West and improve safety for people traveling along First Street West during storms, while retaining an open drainage channel along Depot Park.
Project Description: First Street West near Depot Park regularly floods during even relatively minor storms. This flooding occurs because the drainage channel along the east side of First Street West near Depot Park is too small to convey stormwater runoff from the large watershed above it, which includes much of the Mountain Cemetery and large portions of Norrbom Road.
During winter storms in 2019, a corrugated metal pipe at the downstream end of this drainage channel collapsed, resulting in a sinkhole in a paved crossing over the drainage channel. Temporary repairs helped keep the drainage flowing through the channel for rest of the rainy season, but the crossing has been indefinitely closed and is no longer needed following changes in solid-waste collection operations at the park.
The project will widen the problematic drainage channel to alleviate flooding and permanently repair the area where the corrugated metal pipe collapsed at the downstream end of the channel. The project will begin with demolition and disposal of existing concrete, asphalt, and Eucalyptus roots that are restricting the channel’s capacity. The drainage channel will then be re-graded and rock slope protection, a boulder weir, a new cast-in-place concrete retaining wall, seed mix, and biodegradable coir mat will be installed to protect the new channel against erosion. On the Depot Park side of the channel, a new concrete pathway and a guardrail along the new retaining wall will be installed to ensure safe access for pedestrians to the park’s picnic areas.
The widened channel will then be revegetated through a grant-funded collaboration between the City of Sonoma, the County of Sonoma, and the Sonoma Ecology Center. This part of the project will include planting native wetland plants in the channel bottom as well as planting new trees and shrubs along the channel bank and upland areas between the channel and the park’s picnic areas.
Quimby Act Funds
Transportation Measure M Funds
Project Status: On-site construction work is scheduled to begin September 14, 2020, with anticipated project completion on November 6, 2020. The revegetation work to be completed by the City of Sonoma, the County of Sonoma, and the Sonoma Ecology Center will begin soon after.