The Upper Talmont subdivision was developed approximately thirty years ago on a terrace overlooking the west shore of Lake Tahoe in the Ward Creek watershed. The entire subdivision is located on steep slopes, necessitating large cut and fill operations to construct the subdivision roads. The Ward Creek watershed is one of the three largest contributors of fine sediment to Lake Tahoe, along with the Blackwood Creek and Upper Truckee River watersheds.
Drainage infrastructure in the subdivision has eroded badly in many areas and formed deeply incised gullies that convey storm water and fine sediment to Lake Tahoe. Due to the steepness of the subdivision, the best opportunity to improve water quality is to collect and convey stormwater to less steep areas where infiltration of the runoff can be obtained. The Conservancy and the U.S. Forest Service Lake Tahoe Basin Management Unit (LTBMU) own several parcels within the project area, providing publically owned land where storm water can be collected, infiltrated, or treated. Sediment source control opportunities such as stabilization of cut and fill slopes and conveyance channels are possible.
A multi-agency Technical Advisory Committee participated in the review and evaluation of alternatives for this project. The majority of stormwater from the Upper Talmont subdivision collects on the south side of the neighborhood. The Conservancy owns several parcels in the vicinity upon which a large storm water detention and infiltration basin and associated storm drain are being installed to address storm water runoff from the subdivision. Overflow from this basin is being conveyed to Ward Creek through rock-lined channels and storm drain constructed on easements purchased for the project. Stormwater conveyance paths within the subdivision will be stabilized with rock and vegetation to control sources of sediment. Additional source control will be achieved by stabilizing eroding slopes with vegetation and rock. Where possible, high velocity flows will be attenuated by diversion structures, coupled with smaller infiltration areas constructed on Conservancy and LTBMU parcels located throughout the neighborhood.
Construction of Phase 1, which includes the large basin, was completed in 2010. Post construction monitoring will be completed in 2012. Engineered construction documents are currently being developed for Phase 2. Contingent upon funding availability, construction of Phase 2 is scheduled to begin in 2012.