Dominant Land Use:
This catchment is comprised of medium density single-family residential neighborhoods crisscrossed with secondary roads.
Percentage of Impervious Surface:
39% of the catchment is impervious.
City of South Lake Tahoe
The Pasadena monitoring site is located at the northern most end of Pasadena Avenue in the City of South Lake Tahoe. A 36-inch pipe emerges from the side of the steep slope at the end of Pasadena Avenue and conveys runoff directly to Lake Tahoe. There are two monitoring stations at this site, the first at the inflow to a series of two parallel Contech Stormfilter vaults (“Stormfilter”) and the second at the outflow from the vaults. Monitoring at the first station will determine runoff volumes and pollutant loads exiting the small-scale infiltration BMPs dispersed within the catchment (see description of environmental improvement project below) and entering the Stormfilter. Monitoring at the second station will determine runoff volumes and pollutant loads exiting the Stormfilter, and characterize the catchment outfall. Effluent pollutant loads will be compared to influent pollutant loads to assess how well the Stormfilter reduces pollutant loads. Monitoring data can also be used to confirm whether maintenance, such as filter replacement, improves load reduction performance in the Stormfilter.
An environmental improvement project completed in 2010 made several improvements in the catchment, including the installation of 9,694 square feet of permeable pavement on the shoulders of six blocks of residential streets and 3,891 linear feet of perforated storm drain pipes to increase in-situ infiltration wherever feasible throughout the project area. Due to the gentle slope in the area, erosion control measures such as rock-lined channels and stabilization of slopes were not as important here. The perforated storm drain pipes include approximately 2,750 linear feet of main line 18-inch and 24-inch perforated pipes under roadways, and smaller diameter perforated pipes connecting drain inlets and sediment traps to back-of-curb infiltration areas. The permeable pavement was an attempt to maximize infiltration and stabilize road shoulders while providing parking and unimpeded snow removal on a stable surface, a challenge that California jurisdictions have been struggling with in their project designs for more than twenty years. A pre-treatment Vortechnics storm vault and the Stormfilter were installed at the end of the catchment. The Stormfilter is designed to treat up to 2.2 cubic feet per second (cfs) of runoff. The first vault is designed for low-flow conditions and contains twenty-five 27-inch tall filter cartridges. The second vault is designed to handle larger flows and contains thirty-two 27-inch tall filter cartridges. The Stormfilter is designed to capture pollutants but not reduce runoff volumes.
This outfall was the former Regan Beach TMDL monitoring site, one of 19 sites in the Tahoe Basin equipped with auto-samplers and monitored during 2003 and 2004 by the University of California, Davis, Tahoe Environmental Research Center (UCD TERC) and the Desert Research Institute (DRI) as part of the Lake Tahoe TMDL research effort. Data collected at this site was used to establish Event Mean Concentrations for residential land-use categories that ultimately populated the Pollutant Load Reduction Model (PLRM). In addition, this catchment was monitored for flow and turbidity by 2NDNATURE from March 2012 to February 2013. The data collected by the Tahoe RCD is continuing the long-term data set for this site and can be used to evaluate how effective the environmental improvement project was at reducing runoff volumes and pollutant loads to Lake Tahoe.