Tahoe Resource Conservation District

Archives: July 2018

MTS Diver assist suction removal

Elk Point Marina Aquatic Invasive Plant Control Project

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Elk Point Country Club Homeowners pitch in to tackle aquatic invasive plant infestation on East Shore

Tahoe Resource Conservation District is pleased to announce the development of a partnership with Elk Point Marina Homeowners’ Association. In Fall of 2016, Tahoe RCD presented a project proposal to the Elk Point Country Club Homeowners’ Association Board to address the aquatic invasive plant infestation at Elk Point Marina on Tahoe’s East Shore. The homeowners were eager to learn how they could assist. To start, their Marina Manager attended Eyes on the Lake Training provided by the League to Save Lake Tahoe. In this training, their staff learned how to identify native and non-native aquatic invasive plant species in the marina and how to monitor their presence.

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In 2017, Nevada Division of State Lands provided funding for Tahoe Resource Conservation District’s contracted divers to survey the Nevada shoreline from Stateline to Zephyr Point for the aquatic invasive plants Eurasian watermilfoil (Myriophyllum spicatum) and curly-leaf pondweed (Potamogeton crispus). The divers found Eurasian watermilfoil occupying shoreline just to the north and south of the Marina. These detections demonstrated the need for a comprehensive control strategy for Elk Point Marina to eliminate this source of invasive plants from the East Shore.

In 2018, the Elk Point Country Club HOA made a commitment to eliminate invasive plants in the Marina by providing a 25% match to the funds that Nevada Division of State Lands provided for the project. In June, divers installed 65 bottom barriers in the marina that will remain in place for the duration of the summer. In July, the League to Save Lake Tahoe provided an Eyes on the Lake 

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training for homeowners and discussed best management practices to deter the growth of plants in the Marina once the project has reached completion. These practices include daily skimming of the Marina for any detected plant fragments, an annual Eyes on the Lake survey conducted by marina staff, and annual diver surveys. Tahoe RCD extends its sincere thanks to Nevada Division of State Lands, Elk Point Country Club Homeowners’ Association, and the League to Save Lake Tahoe for their collaboration on this project and their commitment to this partnership.


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Could Repaving Roads Be a Water Quality BMP?

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In partnership with El Dorado County and Texas Southern University, the Tahoe Resource Conservation District (Tahoe RCD) is monitoring stormwater runoff from Elk’s Club Drive to quantify the amount of fine sediment that comes from the road itself. Samples are taken of the runoff water and sent to the laboratory for source apportionment analysis. This lab test uses microscopic markers to determine what portion of the fine sediment in the runoff comes from native soil (road shoulder erosion), traction abrasives (road sand), and asphalt (the road itself). 

Elks Club road cracked with potholes

Elks Club road cracked with potholes.

Currently, Elk’s Club Drive is in poor condition. It is covered in cracks and potholes. Not only is a degraded road bad for public safety, it is difficult to recover road sand and other material through road sweeping. Road sediment is a large portion of the fine sediment that ends up in Lake Tahoe, reducing its famed clarity. Early results show that up to 30% of this fine sediment includes asphalt (aggregate and binder). El Dorado County will be repaving Elk’s Club Drive this summer. After it is repaved, the Tahoe RCD will continue to monitor the runoff from the road for an additional year. If data shows that repaving roads contributes to improved water quality (less sediment), then improved pavement condition could be recognized as a water quality Best Management Practice (BMP). This would not only be identified for garnering credits for the Lake Tahoe TMDL Clarity Crediting Program (https://clarity.laketahoeinfo.org/), but also potentially opening up water quality improvement funds for road maintenance. New roads would be beneficial for public safety, vehicle maintenance costs, aesthetic appeal, driving pleasure, road maintenance and sweeping operations, long term durability, snow removal operations, stormwater quality, and lake clarity. 

Runoff flowing over road surface.

Runoff flowing over road surface.

 

Measuring the runoff flow and volume.

Measuring the runoff flow and volume, and collecting water samples to take back to the laboratory for further analysis.

A washoff simulation was conducted in April to analyze runoff under controlled conditions. Over 5,000 gallons of water were released on Elk’s Club Drive and sampled at the terminal location. In a rainstorm, water runs off the road shoulder contributing native soil in runoff. In a snowstorm, there is likely to be high concentrations of road sand on the road and in runoff. The controlled simulation excluded native soil and road sand from the procedure, and focused runoff on the road surface only.  Early results show peak turbidities (cloudiness) occurring with peak flows, indicating that sediment is being continually supplied by the road and suggesting that the road itself is eroding. The sediment in the samples will be subjected to the source apportionment analysis to confirm if this hypothesis is correct. Though the data is not yet in, the Tahoe RCD and El Dorado County are hopeful that, in the future, investments in new roads will be viewed as a win-win for the community and the lake.

Early results show cloudiness of water (measured in NTU) coincides with the runoff flow peaks.

Early results show cloudiness of water (measured in NTU) coincides with the runoff flow peaks.