Brockway Erosion Control Project
Brockway, California
The clarity of Lake Tahoe has deteriorated by 33% since the 1960s, and is currently diminishing at a rate of more than one foot each year. In 1968, a group of scientists led by Dr. Charles Goldman started monitoring lake clarity by lowering a measuring device called a Secchi disk into the lake until it would disappear from view. Initially lake clarity was measured to be more than 30 meters; currently lake clarity is approximately 20 meters.
One of the primary reasons for this decline is soil erosion, caused by the construction of roads and homes and the accelerated storm water runoff that these impervious surfaces create. Fine sediments (less than 20 microns) stay suspended in the water of Lake Tahoe for years in some cases, physically clouding the water. Phosphorous, which is attached to the soil particles contributes to algae growth, which also reduces lake clarity.
The ±128 acre Brockway area of North Lake Tahoe, California abuts the California/Nevada Stateline and is a mostly residential neighborhood linked together by a network of narrow county-owned roads. The area was developed in the early 1900s. Commercial properties used for various motel/hotel lodging and other non-industrial uses exist along the Highway 28 corridor. The Brockway Erosion Control Project (BECP) is part of Placer County’s (County) response to the Tahoe Regional Planning Agency’s (TRPA) ordinance that all stormwater must be treated before discharge to receiving waters (Lake Tahoe) and that all soil must be stabilized. The overall goal is to reduce pollutant loading to Lake Tahoe through sediment source control, improving hydrologic function and treatment.
Every property owner in the Tahoe Basin is legally responsible to comply with the TRPA ordinance. This means that Placer County is responsible for stormwater and soils on County property and in the County Right of Ways (ROW). Primarily, the County is responsible for stormwater generated from paved and unpaved roads, driveway aprons, soils and parking areas in the ROW. The BECP area also contains several open channels and stream environment zones (SEZ) carrying stormwater that require stabilization/improvement.
The Brockway Erosion Control Project (BECP) is part of Placer County’s (County) response to the Tahoe Regional Planning Agency’s (TRPA) ordinance that all stormwater must be treated before discharge to receiving waters (Lake Tahoe) and that all soil must be stabilized. The overall goal is to reduce pollutant loading to Lake Tahoe through sediment source control, improving hydrologic function and treatment.
The project intends to reduce pollutant loading to the receiving water of Lake Tahoe. Infiltration of stormwater flows is the preferred treatment method and is the design emphasis of this project. Infiltration both traps and treats pollutants in the soil matrix and reduces flows that would otherwise contribute to erosion and/or mobilization of pollutants.