Need for Advanced Stormwater Need for Advanced Stormwater Treatment at Lake TahoeTreatment at Lake Tahoe

John E. Reuter & Dave RobertsTahoe TMDL Research Program

Lake Tahoe: A Changing EcosystemLake Tahoe: A Changing Ecosystem

Significant portions are urbanizedSignificant portions are urbanized Increased resident populationIncreased resident population Millions of touristsMillions of tourists Peak VMT >1,000,000 miles/dayPeak VMT >1,000,000 miles/day Loss of wetland and runoff infiltrationLoss of wetland and runoff infiltration Extensive road networkExtensive road network Land disturbance - soil erosionLand disturbance - soil erosion Air pollutionAir pollution

Unraveling Cause(s) for Unraveling Cause(s) for Declining Water ClarityDeclining Water Clarity

• NutrientsNutrients stimulate algae stimulate algae

• Fine-sedimentsFine-sediments directly directly reduces clarity (1-20 µm)reduces clarity (1-20 µm)

• Progressive accumulation Progressive accumulation leads to long-term declineleads to long-term decline

• Management strategy - P, Management strategy - P, N, sediment controlN, sediment control

• TMDL, EIP & other plans TMDL, EIP & other plans are addressing load are addressing load reductionreduction

TMDL Development PhasesTMDL Development Phases

Phase IPhase I- Determines Current Loading - Determines Current Loading - Determines Basin-wide Load Reduction - Determines Basin-wide Load Reduction

NeedsNeeds

Phase IIPhase II- Identify Load Reduction Possibilities- Identify Load Reduction Possibilities- Allocates Pollutant Load Reductions- Allocates Pollutant Load Reductions- Implementation Plan- Implementation Plan

Phase IIIPhase III-- Implementation and MonitoringImplementation and Monitoring- Adaptive Management framework- Adaptive Management framework- Predetermined Review Periods- Predetermined Review Periods

Tahoe TMDL Phase 2Tahoe TMDL Phase 2

Preliminary finding suggest that in many urban areas at Preliminary finding suggest that in many urban areas at Tahoe, traditional BMPs may not be capable of meeting Tahoe, traditional BMPs may not be capable of meeting the needed levels of pollutant reduction. the needed levels of pollutant reduction.

New approaches/technologies may be required.New approaches/technologies may be required.

Implementers must be given a full range of load Implementers must be given a full range of load reduction options.reduction options.

In 2004 Tahoe Basin one of 14 projects selected nation-In 2004 Tahoe Basin one of 14 projects selected nation-wide to receive A USEPA Targeted Watershed grant.wide to receive A USEPA Targeted Watershed grant.

Tahoe TMDL Phase 2Tahoe TMDL Phase 2 New approaches under consideration at Tahoe:New approaches under consideration at Tahoe:

• • Mitigation of air-borne pollutantsMitigation of air-borne pollutants

• • Hydrologic controls to reduce runoffHydrologic controls to reduce runoff

• • Stream channel erosionStream channel erosion

• • BMP maintenanceBMP maintenance

• • Advanced localized or centralized stormwater treatmentAdvanced localized or centralized stormwater treatment

Collaborative research by Phil Bachand & Assoc., UC Davis, Collaborative research by Phil Bachand & Assoc., UC Davis, Caltrans and CSUS-OWP has been examining use of flocculants Caltrans and CSUS-OWP has been examining use of flocculants and coagulants as a possible means of enhancing treatment and coagulants as a possible means of enhancing treatment either in separate treatment systems or associated with an either in separate treatment systems or associated with an existing BMP.existing BMP.