Grass Valley—a disadvantaged community that was established in the 1850s during the Gold Rush—is located in the Sierra Nevada Foothills northeast of Sacramento. Steady and ongoing development has created large tracts of impervious surface in the town and surrounding region, and many of the area’s creeks have been locked in concrete and funneled into underground culverts and pipes.
This continues to greatly alter the area’s natural hydrology, impacting the function of remaining natural systems and putting pressure on the City’s stormwater infrastructure. Every year, winter storms bring heavy rain and instead of soaking into unpaved land, stormwater runs off of hard surfaces like rooftops, parking lots, roads, and sidewalks, and is channelized into storm drains concentrating and intensifying in volume so that it erodes stream banks, causes local flooding, and carries pollutants such as bacteria and heavy metals into local waterways. The local waterway, Wolf Creek, and its tributaries are part of the Bear River watershed and provide drinking water to Southern Nevada County and Placer County. The State Water Resources Control Board has now listed 23 miles of Wolf Creek and its associated tributaries (including Peabody Creek) as impaired under Section 303(d) of the Clean Water Act and put an applicable TMDL schedule for fecal coliform in place. Additionally, a significant number of Grass Valley’s residents are at risk from flooding.
Updates to the Grass Valley’s aging stormwater and drainage infrastructure have not been able to keep pace with the City’s expansion, and many needed repairs have been too costly for this disadvantaged community since there is no established funding mechanism to pay for drainage improvements. In addition, conventional methods for addressing the community’s issues, including engineered “solutions,” are costly, require expensive maintenance over time, and are only partially effective in solving water quality and flooding problems.
This project includes five primary cost-effective elements that will abate flooding, reduce erosive peak flows in the watershed, and reduce water quality impacts:
1) Floodplain restoration on two high-priority sites that will slow and spread peak flows reducing flood potential and improving infiltration;
2) Stormwater source control management through downspout disconnection, rain barrels, and contractor training and installation of pervious pavement; and
3) Watershed assessment to determine additional high-priority areas that contribute to pollutant loads and flooding and areas that would be good candidates for installation of green infrastructure stormwater management elements.
4) Modeling to improve flood management and update antiquated FEMA flood maps to more accurately document flood risk.
5) The project includes initial implementation of these elements, but it also lays the ground work for expanding green infrastructure throughout Grass Valley and the CABY region by training local contractors to pour pervious pavement and creating education materials local residents can use to manage stormwater runoff on their property.
All aspects of this project will help rainwater to reach pervious surfaces so that it can infiltrate into the ground, rather than sluicing across pavement, picking up pollutants, and building into ever bigger volumes. The project includes floodplain restoration to help abate erosive peak flows and flooding and a source control program that will expand disconnection of rainwater downspouts onto landscaped areas, the use of rain barrels, and installation of pervious pavement.
Thus, this project will reduce the risk of flood flows, minimize erosion and sedimentation, reduce pollutant loads, and over time, provide capital cost savings to a disadvantaged community.
Current Status (December 2016):
The project team has made substantial progress on all elements of the project. Design and permitting are close to completion.
Floodplain Restoration: We have conducted an assessment of baseline conditions and modeling at the floodplain restoration site, which has informed development of conceptual restoration design alternatives. It has also allowed for updated mapping of the flood inundation zone that will be used to update FEMA flood maps. AR in collaboration the Sierra Native Alliance removed invasive plants at the site and will be planting native plants at the site in December.
Stormwater Source Control Management: Solicitation and evaluation of bids for permeable pavement installation have been completed and we have obtained approval from the Grass Valley City Council and awarded the project to a qualified contractor. The Notice of Award and Notice to Proceed have been issued to the successful contractor. American Rivers in collaboration with Wolf Creek Community Alliance has also conducted water quality monitoring and GIS analyses in an effort to identify local pollutant sources, as well as additional priority sites for stormwater source control measures.
Green Infrastructure: American Rivers has developed stormwater source control outreach materials and distributed them at local events, including farmers’ and winter markets. American Rivers has also advertized, organized and held permeable pavement contractor training including classroom and test-pore components.
Lead Agency: American Rivers
Contact: Julie Fair, Associate Director California Conservation 530-478-0206 x206 firstname.lastname@example.org
Measurable Physical Benefits: Flood Control, Water Quality