Upper Truckee Marsh Sewer Facility Protection
The South Tahoe Public Utility District (District) proposes to implement an Adaptive Management Plan (AMP) to protect its existing force and gravity sewer mains along with its Bellevue Pump Station facility in the City of South Lake Tahoe, California. The sewer facilities are located on property owned by the California Tahoe Conservancy (CTC) at the north margin of the Upper Truckee Marsh.
The goal of the project is to protect the sewer infrastructure from flooding and reduce the risk of sewage discharges through the implementation of the AMP. The AMP is a set of measures that would be implemented and monitored over time that would encourage channel formation in a more favorable location, raise the easement area slightly and increase its hydraulic roughness to make it more resistant to any future channel avulsions, and potentially improve flood conveyance and sediment transport. WBS was involved with revegetation and monitoring, including the installation of propagated marsh mat.
As part of the AMP for this project, WBS completed its first year of post construction vegetation monitoring and oversaw the installation of an additional 600 sq. ft. of marsh mat. This year’s work included the deepening and widening of several pilot and braided channels on both the east and west sides of the marsh. This work, in addition to the successful revegetation efforts, has resulted in an almost complete re-direction of Trout Creek, away from the sewer line, and back into the main channel.
Update November 2016:
As part of the Adaptive Management Plan for this project, WBS completed its third year of post construction vegetation monitoring in 2016. In 2015 work included 600 sq. ft. of additional marsh mat hummocks and wetland plug plantings as well as the deepening and widening of several pilot and braided channels on both the east and west sides of the marsh. Work in 2016 included additional marsh mats with willows and wetland plugs.
Update December 2020:
Surveyed in 2020 after a four-year hiatus, it appeared that the biotechnical treatments were largely successful as designed. Coir mats and logs, along with plug plantings, were very effective in achieving the desired results. Five and six years after installation the mats and logs were well vegetated and difficult to locate. Roughness created by the coir mats contributed to sedimentation by coarse particles, also raising the channel bed elevation.
