Need for Advanced Stormwater Treatment at Lake Tahoe John E. Reuter & Dave Roberts Tahoe TMDL Research Program

Lake Tahoe: A Changing Ecosystem  Significant portions are urbanized  Increased resident population  Millions of tourists  Peak VMT >1,000,000 miles/day  Loss of wetland and runoff infiltration  Extensive road network  Land disturbance - soil erosion  Air pollution

Unraveling Cause(s) for Declining Water Clarity Nutrients stimulate algae Nutrients stimulate algae Fine-sediments directly reduces clarity (1-20 µm) Fine-sediments directly reduces clarity (1-20 µm) Progressive accumulation leads to long-term decline Progressive accumulation leads to long-term decline Management strategy - P, N, sediment control Management strategy - P, N, sediment control TMDL, EIP & other plans are addressing load reduction TMDL, EIP & other plans are addressing load reduction

TMDL Development Phases Phase I - Determines Current Loading - Determines Basin-wide Load Reduction Needs Phase II - Identify Load Reduction Possibilities - Allocates Pollutant Load Reductions - Implementation Plan Phase III - Implementation and Monitoring - Adaptive Management framework - Predetermined Review Periods

Tahoe TMDL Phase 2  Preliminary finding suggest that in many urban areas at Tahoe, traditional BMPs may not be capable of meeting the needed levels of pollutant reduction.  New approaches/technologies may be required.  Implementers must be given a full range of load reduction options.  In 2004 Tahoe Basin one of 14 projects selected nation- wide to receive A USEPA Targeted Watershed grant.

Tahoe TMDL Phase 2  New approaches under consideration at Tahoe: Mitigation of air-borne pollutants Mitigation of air-borne pollutants Hydrologic controls to reduce runoff Hydrologic controls to reduce runoff Stream channel erosion Stream channel erosion BMP maintenance BMP maintenance Advanced localized or centralized stormwater treatment Advanced localized or centralized stormwater treatment  Collaborative research by Phil Bachand & Assoc., UC Davis, Caltrans and CSUS-OWP has been examining use of flocculants and coagulants as a possible means of enhancing treatment either in separate treatment systems or associated with an existing BMP.