Presentation on theme: "Cahaba River Watershed"— Presentation transcript:
1Cahaba River Watershed Nutrient TMDLfor theCahaba River WatershedA joint proposalbyADEM and EPA Region 4Chris JohnsonWater Quality BranchOctober 13, 2005
2Outline Overview of Nutrient Impacts to the Cahaba River Summary of the Cahaba River Nutrient TMDLNutrient Target DevelopmentApplication of Target to Cahaba RiverTMDL Results and NPDES Permit RequirementsTMDL Implementation StrategyPublic Participation ProcessFuture Activities
4Segment Location (Downstream to Upstream) §303(d) Listed SegmentsWaterbody NameMilesDesignated UsesCauses of ImpairmentSources§303(d) ListSegment Location (Downstream to Upstream)Cahaba River (Segment 01)17.4Fish & WildlifeNutrients, SiltationUrban runoff / storm sewers, municipal1998Buck Creek to US Hwy 280Cahaba River (Segment 02)*36.9Outstanding AL Water, Public Water Supply, Fish & WildlifeSiltation and Other Habitat AlterationUrban runoff / storm sewersUS Hwy 280 to I-59Cahaba River (Segment 03)26.5Outstanding AL Water, Fish & WildlifeNutrients, Siltation, Pathogen, and Other Habitat AlterationMunicipal, urban runoff / storm sewers, land development1996 (Nutrients only); 1998 (all other causes added)Shades Creek to Buck CreekCahaba River (Segment 04)24.0Outstanding AL Water and SwimmingNutrients, Siltation, and Other Habitat Alteration1998 (Nutrients and Other Habitat Alteration Only); 2002 (Siltation added)AL Hwy 82 to Shades Creek* Segment 02 is not currently listed as being impaired for nutrients on Alabama’s §303(d) List, howeverdue to observed impacts in recent studies it is considered part of the TMDL.
5§303(d) Segments *Currently Listed for Nutrients IDMilesSegment Location (Downstream to Upstream)0117.4Buck Creek to US Hwy 2800326.5Shades Creek to Buck Creek0424.0AL Hwy 82 to Shades CreekS1 is 17.4 milesS2 is 36.9 milesS3 is 26.5 milesS4 is 24 miles
6Nutrient Impacts – What Are They? Aquatic life use is impaired by excessive nutrients:Confirmed by ADEM, EPA, & Jefferson County dataImpairment to overall community, not just T&E speciesUS I-59 downstream to AL Hwy 82Nuisance algal blooms (excess periphyton growth)Dissolved oxygen violationsLarge daily swings in dissolved oxygenUndesirable shifts in the native species of plants and animals
7Continuous Dissolved Oxygen Data Collected during2 stations in Cahaba (downstream of urban areas and municipal facilities):S1 = Bibb County Hwy 24S2 = Shelby County Hwy 52Rainfall and Solar Radiation from Birmingham AirportFlows from USGS gage at Helena (same location as S2)
8Bibb County Highway 24 (S1) Station also known as Piper BridgeDownstream of Shades CreekWide and flatNo canopyS1
9Shelby County Highway 52 (S2) Downstream of Buck CreekHighly entrenchedCanopy presentS2S1
12Nutrient Impacts – When and Where Do These Impacts Occur? Downstream of urban point and nonpoint sourcesDuring periods of low flow, low velocity, and high temperatureAreas where the river is wide, water is shallow, tree canopy is open and light is readily available
14Why Do We Need Nutrient Targets? Numeric Nutrient Criteria for Rivers and Streams Not Currently EstablishedNeed Quantifiable Endpoints to Evaluate Condition of Waterbody in Regards to Meeting its Designated Use(s)Necessary for TMDL Development
15Key Aspects of Nutrient Target Development Consistent with EPA Guidance and RecommendationsUses a Reference Condition ApproachScientifically DefensibleUses Total Phosphorus (TP) as the Controlling NutrientFully Supports Designated UsesLong-Term Monitoring Plan is Essential
16Key Aspects of Nutrient Target Development (cont’d) ADEM and EPA Region 4 have compiled extensive resources to determine the nutrient targetConducted field studies by EPA Region 4 and contract scientistsReviewed and synthesized all information in consultation with national expert in stream nutrient-algae relationships (Jan Stevenson, PhD)EPA Region 4 ConclusionRecommended range of 20 to 40 µg/L total phosphorus should prevent filamentous algae growth and be protective of designated uses.
17ADEM’s Nutrient Target Approach for the Cahaba River Select Set of Least-Impacted Reference Streams based on the following:ADEM Reference Station with Sufficient DataSame Level III Ecoregion (Ridge & Valley)Mixed Land UseLow Levels of Measured PeriphytonHealthy Habitat, Macroinvertebrates, and Fish CommunitiesCalculate the 75th percentile of growing season dataFor Ecoregion 67, Target = 35µg/L of TP
18Level III Ecoregions*Upper Cahaba River is located in Ecoregion 67
21Application of Nutrient Target Spatial – 3 locations chosen to monitor instream conditionsRoper Road (St. Clair County Road 10)Bain’s Bridge (Old Montgomery Highway)Shelby County Highway 52Temporal – growing season median (multiple years) should not exceed TP target at these predetermined evaluation pointsGrowing season defined as April – OctoberStudy Period Evaluated growing seasons
22Application of Target to Cahaba River: 1999-2000 TP Concentrations
25Cahaba River Analysis Physical characteristics GeometryTributary inflow locationsInstream longitudinal data trendsPoint source assessmentDMR records, WWTP Nutrient DatabaseNonpoint source assessmentCorrelation of GIS landuse to instream data
26Modeling System LSPC watershed model Utilizes precipitation to make hydrologic predictionsEPD-RIV1 hydrodynamic and WQ modelKinematic wave transportEutrophication kinetics but not periphytonCahaba Spreadsheet ModelCustom mass balance frameworkPredict instream TPEvaluate point and nonpoint sourcesEvaluate permit limits
27TMDL Implementation Strategy Phase I: NPDES permit revisions required by 2010*Majors (≥1.0 MGD) – monthly avg. limit not to exceed TP = 0.40 mg/LMinors (<1.0 MGD) – monthly avg. limit not to exceed TP = 2.0 mg/LPhase II: NPDES permit revisions required by 2015*Majors (≥1.0 MGD) – monthly avg. limit not to exceed TP = 0.20 mg/LMinors (<1.0 MGD) – monthly avg. limit not to exceed TP =0.50 mg/LUrban areas achieve 25% reduction in TP ( baseline)Phase III: NPDES permit revisions required by 2020*:Majors (≥1.0 MGD) – monthly avg. limit not to exceed TP = mg/LMinors (<1.0 MGD) – monthly avg. limit not to exceed TP = 0.30 mg/LUrban Areas achieve 65% reduction in TP ( baseline)Cahaba River meets instream target of 35 µg/L at evaluation points*based on assumed TMDL approval date of 2005
29Comparison of WWTP Effluent TP and Proposed TP Limits
30Implementation Strategy to Reduce TP Loads Reducing WWTP loads:NDPES permits for reduced effluent TP concentrationsReducing MS4/urban loads:NDPES MS4 permittees are expected to meet a 65% reduction using a BMP approachReducing nonpoint source loads:CWP and UCCLand use planning considerations for watershed protection
31Public Participation Process Collaborative effort between ADEM, EPA Region 4 and Cahaba Stakeholders.Draft TMDL Report was public noticed on October 11, 2004.45 day public comment period which was extended another 60 days.Extensive public comments have been submitted to ADEM.Currently in the process of compiling and responding to public comments.TMDL will be finalized in consideration of all comments received.
32Future Activities Follow-up monitoring plan Nutrient SamplingHabitat, Macroinvertebrate, and Fish SamplingDiurnal Dissolved Oxygen StudiesPeriphyton EvaluationsFurther Ecoregion Reference Site InvestigationsEcoregion 67 and Hatchet Creek StudiesContinued Reference Site InvestigationsDevelop an effects-based targetCahaba River & Hatchet Creek SamplingAdaptive Management may suggest re-evaluation of TP target as new data and information becomes available.