2NDNATURE is leading the design and implementation of a project scale effectiveness evaluation to quantify the water quality benefits of future restoration efforts within the 1 sq mile Upper Truckee Marsh. Planned restoration actions are expected to have significant hydrologic and water quality benefits by reducing annual pollutant loading to Lake Tahoe from the largest drainage in the Basin. The expansive and complex geomorphology and hydrology of the Marsh has required the design and implementation of cost-effective yet reliable data collection techniques. The monitoring will inform the creation of a detailed water budget of the Marsh as a result of contributing inflows, lake levels and antecedent conditions. Creative rising and falling limb water sampling techniques have been developed to sample the changes in sediment loads as a result of marsh interactions and will inform the development of a ‘marsh module’ to append the Stream Load Reduction Tool (SLRT) to quantify the water quality benefits of future Marsh restoration efforts.
Infiltration is one of the primary treatment processes relied upon by Tahoe Basin stormwater treatment BMPs to reduce pollutant loading to Lake Tahoe and is a critical component of all Low Impact Development (LID). Implementers and jurisdictions continue to struggle with optimizing designs and installation of infiltration BMPs to maximize long-term water quality benefits, which must include regular maintenance actions. 2NDNATURE conducted an existing data synthesis and a standardized field evaluation of infiltration Tahoe Basin BMPs to document and evaluate current water quality treatment performance based on BMP design and construction, maintenance schedules, pollutant loading, and geotechnical setting. Laboratory and field controlled studies were conducted to isolate the performance decline and failure mechanisms, and the results have been applied to conceptual engineering solutions to improve the water quality treatment capability and maintenance ease of Tahoe Basin infiltration BMPs. The findings have also been applied to expand the existing TRPA BMP Handbook guidance on the design and maintenance of infiltration BMPs and inform development of a spreadsheet calculator tool designed to complement a well-established BMP sizing calculator.
The primary source of fine sediment particles impairing the clarity of Lake Tahoe is derived from paved roadways due to the application of large volumes of winter road abrasives. Given the need to protect winter driver safety, advance road maintenance strategies are rapidly being developed by Tahoe road maintenance teams. 2NDNATURE is leading a basin wide collaboration between regulators, jurisdictional stormwater representatives, road maintenance personnel, and technical consultants to test the effectiveness of a series of road operation prescriptions to protect stormwater quality. 2N led the experimental design and continues to guide the collaboration among all 7 jurisdictions to test the effectiveness of specific road sanding, plowing and sweeping techniques. Using the Tahoe Road RAM tool developed by 2NDNATURE (www.tahoeroadram.com), the roadway conditions are regularly documented as road practices are implemented. The Road RAM results will be used to quantify the expected road conditions given the combination of road maintenance practices implemented on each test section. The practices being evaluated include reduced annual abrasive application frequency and volumes, the use of more durable abrasives, faster sweeping response following storms, vacuum assisted sweepers, proper sweeper operations, etc. Over the multi-year study, Road RAM observations will be made on each jurisdiction’s subset of roads once to twice a month, and the primary research products will be: the cause and effect linkages between practices and road condition; direct road operations information requirements for each jurisdiction’s pollutant load reduction plans under the Crediting Program; and experimental guidance for continued testing of new techniques into the future.
Natural resource managers continue to struggle with designing restoration effectiveness evaluations that are feasible, cost-effective and reliable. 2NDNATURE developed a clear step-wise process to define, track and evaluate the benefit and effectiveness of stream and meadow restoration efforts. The Framework process integrates the restoration design and expected benefits to improve both planning and post-implementation expectations. The process clearly outlines how to summarize existing (impaired) conditions, how to develop testable restoration project objectives, and how to link objectives to define a valuable restoration project monitoring strategy and actualize the adaptive management process. The Framework has increased consistency in the documentation of the restoration team intentions, improving communication to interested parties many years following the completion of the restoration actions, and directly improving the availability and quality of the data and information available to make long term adaptive management decisions. Local riparian restoration practitioners continue to apply the Framework to define and communicate restoration objectives in a format that guides the evaluation of implemented projects. 2NDNATURE has applied the Framework to develop effectiveness evaluations for restoration efforts in Spooner Meadow and Lake Forest for local partners.
2NDNATURE teamed with EcoNorthwest to provide the Nature Conservancy with a quantification of the potential effectiveness and cost savings of a forest fuels management program in the Upper Mokelumne Watershed. The analysis indicated it is cheaper to manage fuels than incur the cumulative costs of catastrophic wildfires, and the benefits of fuels management to physical, chemical and biological systems within the watershed are significant. 2NDNATURE led the technical group in creating an experimental design that used a myriad of fire behavior and sediment transport models to quantify the avoided cost of fuels treatment. 2NDATURE compiled and analyzed the outputs of the complex fire and sediment models to provide meaningful quantification of how fuels treatments can reduce fire occurrence probability & severity and soil erosion within the watershed. 2NDNATURE developed a process to define the climate adjusted benefits of fuels treatment over a 30 year time frame, for which the team quantified the economic benefits of the predicted changes in fire and erosion behavior within the watershed. The synthesized spatial data provided critical and insightful information to stakeholders determining priority locations for fuels management to reduce the probability and severity of wildfire in the Upper Mokelumne Watershed, as well as similar watersheds throughout California.
2NDNATURE continues to be the stormwater quality expert and is leading a series of focused stormwater research efforts to test, validate and refine empirical assumptions inherent in a number of the technical tools supporting the Lake Tahoe TMDL. The Lake Tahoe TMDL identified the primary pollutant of concern impairing lake clarity as fine sediment particles less than 16 um in diameter (FSP). However, at the onset of our research, little stormwater quality data existed on the fate and transport of FSP on the urban landscape, and so technical tools were developed using best available data and clear hypotheses that can be tested and improved. 2NDNATURE has devised cost-effective yet scientifically defensible techniques to quantify the water quality loading impacts from specific land use conditions and estimate the FSP treatment performance for typical Lake Tahoe stormwater treatment BMPs to refine the Pollutant Load Reduction Model (PLRM). Additional funding has allowed catchment scale sensitivity testing and validation of PLRM estimates by comparing predicted hydrology and pollutant loads to observed loads using high-resolution monitoring methods. The findings will continue to be used to recommend improvements and modifications to existing TMDL tools, and to improve the synergy between PLRM, Road RAM, BMP RAM and the Lake Clarity Crediting Program, such that all tool inputs and outputs are consistent and informative and actualize the adaptive management process towards restoring lake clarity. In addition, the 2NDNATURE data collection, data management and data reporting protocols are being documented in detail and will be used to inform and design the greater long-term regional stormwater monitoring program for the Tahoe Basin. The regional monitoring program will be used to verify that the actions implemented over the upcoming decades are resulting in pollutant load reductions to Lake Tahoe.
Lake Tahoe BMP Monitoring Evaluation Process: Synthesis of Existing Research
Water Quality Performance Evaluation of South Lake Tahoe Dry Basins
Water Quality Evaluations of a Fertilized Turf Surface in the Lake Tahoe Basin (2002-06)
Focused Stormwater Quality Monitoring to Inform PLRM and Road RAM
Pilot Validation of PLRM
Urban Catchment Monitoring to Evaluate Tahoe TMDL Tools