Lake Van Norden Special-Status Plant Survey Lake Van Norden Dam Spillway Modification Project Nevada County, California
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Lake Van Norden Special-status Plant Survey Lake Van Norden Dam Spillway Modification Project Nevada County, California August 2015 Prepared for: John Svahn Stewardship Director Truckee Donner Land Trust 10069 West River Street Truckee, CA Prepared by: C.S. Ecological Surveys and Assessments 11331 Star Pine Road Truckee, CA 96161 C.S. Ecological surveys and Assessments Lake Van Norden Special-status Plant Survey Executive Summary This report presents the results of the focused botanical survey for vascular special-status plants at the proposed Lake Van Norden Dam Spillway Modification Project (proposed project). A complete pedestrian survey of the approximately 160 acre botanical survey area was conducted on June 16th and 17th 2015. The survey generally complied with the botanical survey guidelines of the California Department of Fish and Game (CDFG), the California Native Plant Society (CNPS), the U.S. Fish and Wildlife Service (USFWS), and the Bureau of Land Management (BLM), but differed from these protocols in that a survey of the aquatic habitat was also conducted. The aquatic survey followed guidelines outlined in Aquatic Plant Sampling Protocols: Publication No. 01-03-017 produced by the Washington State Department of Ecology (Parsons 2001). Pre-field research was conducted to select special-status plant species with potential to be found within the survey area. The list of potentially occurring special-status plants was derived from several sources including the California Natural Diversity Database, the CNPS On-line Inventory, and the California Consortium of Herbaria. Twenty-three special-status plant species, including nineteen vascular plants and four non-vascular plants (one liverwort and three mosses) were determined to have potential to occur within the survey area based on habitat preferences and known distribution. No federal or state-listed plant taxa were observed. One rare plant species was documented within the survey area: ribbon leaf pond weed (Potamogeton epihydrus), CRPR 2B.3. The number of occurrences and the approximate number of individuals observed is described in this report, and a map depicting the location of the occurrences is provided. A total of 184 taxa of vascular plants, one liverwort and four algae were identified in the survey area during the June survey. Of the vascular plant taxa observed, 171 are native, 9 are naturalized, and 4 are considered invasive or noxious weeds in California. Fourteen of the twenty-three special-status plants considered for occurrence within the survey area were determined to be absent based on the survey results. One of these three species, ribbon leaf pond weed, was found during the surveys and the remaining eight species are considered unlikely to occur, but could not be definitively ruled out due to their life cycle or because they are non-vascular plants. Habitat for non-vascular plants within the survey area was surveyed for noted but non-vascular plants were not identified or collected for identification during the survey. This was due to the low likelihood of occurrence and because the actions of this project will not impact potential habitat for these species. C.S. Ecological surveys and Assessments Lake Van Norden Special-status Plant Survey Page i Table of Contents 1 Introduction .......................................................................................................................................... 1 1.1 Project description ........................................................................................................................ 1 1.2 Project location and survey area .................................................................................................. 1 1.3 Project setting ................................................................................ Error! Bookmark not defined. 1.3.1 Environmental setting and climate ....................................................................................... 1 1.3.2 Vegetation communities ....................................................................................................... 4 2 Methods ................................................................................................................................................ 7 2.1 Pre-field research .......................................................................................................................... 7 2.2 Reference site visits .................................................................................................................... 13 2.3 Botanical surveys ........................................................................................................................ 14 3 Results ................................................................................................................................................. 14 3.1 Rare plant species observed ....................................................................................................... 14 3.2 Special-status plant taxa not observed, but with potential to occur ......................................... 17 3.3 Invasive non-native plant species and non-local species ........................................................... 19 4 Summary ............................................................................................................................................. 21 4.1 Ribbon leaf pond weed ............................................................................................................... 21 4.2 Other rare plants ......................................................................................................................... 22 5 References .......................................................................................................................................... 23 Figures Figure 1. Project vicinity map ........................................................................................................................ 2 Figure 2. Survey area map ............................................................................................................................ 3 Figure 3. Vegetation Map ............................................................................................................................. 6 Figure 4. Special-status plant locations ...................................................................................................... 16 Tables Table 1. Vegetation alliance and cover type acreages within the SMS survey area ..................................... 4 Table 2. Special-status plants considered for occurrence. ........................................................................... 9 Table 3. Special-status plant reference sites visited ................................................................................... 13 Table 4. Invasive non-native plant species observed. ................................................................................ 20 Appendices Appendix A List of observed species Appendix B List of Special-status plants retrieved from CNDDB and CCH databases Appendix C Botanical survey tracks Appendix D Representative photographs C.S. Ecological surveys and Assessments Lake Van Norden Special-status Plant Survey Page ii 1 Introduction 1.1 Project description The Truckee Donner Land Trust (TDLT) proposes the Lake Van Norden Dam Spillway Modification Project (proposed project). The proposed project involves constructing a 5-foot notch in the existing spillway or the complete removal of the Lake Van Norden dam at the existing spillway to reduce the volume of water retained behind the dam to less than 5-acre feet to comply with the regulatory requirements of the California Department of Water Resources' Division of Safety of Dams (DSOD) and the State Water Resources Control Board (SWRCB), and other safety standards. The proposed project is located in Nevada County, California. The survey was conducted prior to dewatering of the reservoir that was directed by the Cal dept of water resources and authorized by the CDFW in October 2015. 1.2 Project location and survey area 1.2.1 Environmental setting and climate The project area, Lake Van Norden and the surrounding meadow are located just west of the Sierra Crest at approximately 6,770 feet elevation. The Project area includes Lake Van Norden, the portions of Castle Creek and the South Yuba River that are affected by the dam and the adjacent wetlands bordering Lake Van Norden. Lake Van Norden is actually a reservoir that was first dammed in the late 1800’s or early 1900’s historical records are not clear on when the first significant dam was constructed but it is likely that flow in the South Yuba River has been altered since the 1850’s. An official earthen dam was constructed by the Pacific Gas and Electric Company (PG&E) in the early 1900’s which impounded 5,800 acre-feet of water at the peak of the summer season (Lindstrom 2014). In 1976 the dam was found to be “unsound” and was notched by PG&E such that from 1977 to present the capacity of the reservoir is around 175 acre-feet (Balance Hydrologic 2014). Mean annual precipitation at the project site is 67 inches (Balance 2014). The majority of this precipitation is in the form of winter and spring snow. This snowmelt supplies runoff to the rivers and creeks and supports shallow ground water that flows down gradient towards the Project area and is the main source of water that supports the wetland meadow and riparian vegetation within and around the Project area.