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Cahaba River Watershed

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Presentation on theme: "Cahaba River Watershed"— Presentation transcript:

1 Cahaba River Watershed
Nutrient TMDL for the Cahaba River Watershed A joint proposal by ADEM and EPA Region 4 Chris Johnson Water Quality Branch October 13, 2005

2 Outline Overview of Nutrient Impacts to the Cahaba River
Summary of the Cahaba River Nutrient TMDL Nutrient Target Development Application of Target to Cahaba River TMDL Results and NPDES Permit Requirements TMDL Implementation Strategy Public Participation Process Future Activities

3 Nutrient Impacts to the Cahaba River

4 Segment Location (Downstream to Upstream)
§303(d) Listed Segments Waterbody Name Miles Designated Uses Causes of Impairment Sources §303(d) List Segment Location (Downstream to Upstream) Cahaba River (Segment 01) 17.4 Fish & Wildlife Nutrients, Siltation Urban runoff / storm sewers, municipal 1998 Buck Creek to US Hwy 280 Cahaba River (Segment 02)* 36.9 Outstanding AL Water, Public Water Supply, Fish & Wildlife Siltation and Other Habitat Alteration Urban runoff / storm sewers US Hwy 280 to I-59 Cahaba River (Segment 03) 26.5 Outstanding AL Water, Fish & Wildlife Nutrients, Siltation, Pathogen, and Other Habitat Alteration Municipal, urban runoff / storm sewers, land development 1996 (Nutrients only); 1998 (all other causes added) Shades Creek to Buck Creek Cahaba River (Segment 04) 24.0 Outstanding AL Water and Swimming Nutrients, Siltation, and Other Habitat Alteration 1998 (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, however due to observed impacts in recent studies it is considered part of the TMDL.

5 §303(d) Segments *Currently Listed for Nutrients
ID Miles Segment Location (Downstream to Upstream) 01 17.4 Buck Creek to US Hwy 280 03 26.5 Shades Creek to Buck Creek 04 24.0 AL Hwy 82 to Shades Creek S1 is 17.4 miles S2 is 36.9 miles S3 is 26.5 miles S4 is 24 miles

6 Nutrient Impacts – What Are They?
Aquatic life use is impaired by excessive nutrients: Confirmed by ADEM, EPA, & Jefferson County data Impairment to overall community, not just T&E species US I-59 downstream to AL Hwy 82 Nuisance algal blooms (excess periphyton growth) Dissolved oxygen violations Large daily swings in dissolved oxygen Undesirable shifts in the native species of plants and animals

7 Continuous Dissolved Oxygen Data
Collected during 2 stations in Cahaba (downstream of urban areas and municipal facilities): S1 = Bibb County Hwy 24 S2 = Shelby County Hwy 52 Rainfall and Solar Radiation from Birmingham Airport Flows from USGS gage at Helena (same location as S2)

8 Bibb County Highway 24 (S1)
Station also known as Piper Bridge Downstream of Shades Creek Wide and flat No canopy S1

9 Shelby County Highway 52 (S2)
Downstream of Buck Creek Highly entrenched Canopy present S2 S1

10 Cahaba River S1 versus S2 (1999)

11 Cahaba River S1 versus S2 (Jul – Aug, 1999)

12 Nutrient Impacts – When and Where Do These Impacts Occur?
Downstream of urban point and nonpoint sources During periods of low flow, low velocity, and high temperature Areas where the river is wide, water is shallow, tree canopy is open and light is readily available

13 Overview of the Cahaba River Nutrient TMDL

14 Why Do We Need Nutrient Targets?
Numeric Nutrient Criteria for Rivers and Streams Not Currently Established Need Quantifiable Endpoints to Evaluate Condition of Waterbody in Regards to Meeting its Designated Use(s) Necessary for TMDL Development

15 Key Aspects of Nutrient Target Development
Consistent with EPA Guidance and Recommendations Uses a Reference Condition Approach Scientifically Defensible Uses Total Phosphorus (TP) as the Controlling Nutrient Fully Supports Designated Uses Long-Term Monitoring Plan is Essential

16 Key Aspects of Nutrient Target Development (cont’d)
ADEM and EPA Region 4 have compiled extensive resources to determine the nutrient target Conducted field studies by EPA Region 4 and contract scientists Reviewed and synthesized all information in consultation with national expert in stream nutrient-algae relationships (Jan Stevenson, PhD) EPA Region 4 Conclusion Recommended range of 20 to 40 µg/L total phosphorus should prevent filamentous algae growth and be protective of designated uses.

17 ADEM’s Nutrient Target Approach for the Cahaba River
Select Set of Least-Impacted Reference Streams based on the following: ADEM Reference Station with Sufficient Data Same Level III Ecoregion (Ridge & Valley) Mixed Land Use Low Levels of Measured Periphyton Healthy Habitat, Macroinvertebrates, and Fish Communities Calculate the 75th percentile of growing season data For Ecoregion 67, Target = 35µg/L of TP

18 Level III Ecoregions *Upper Cahaba River is located in Ecoregion 67

19 ADEM Reference Stations in Ecoregion 67

20 Ecoregion Reference Site Data
µg/L Target

21 Application of Nutrient Target
Spatial – 3 locations chosen to monitor instream conditions Roper Road (St. Clair County Road 10) Bain’s Bridge (Old Montgomery Highway) Shelby County Highway 52 Temporal – growing season median (multiple years) should not exceed TP target at these predetermined evaluation points Growing season defined as April – October Study Period Evaluated growing seasons

22 Application of Target to Cahaba River: 1999-2000 TP Concentrations

23 Instream Evaluation Points

24 Instream Evaluation Points

25 Cahaba River Analysis Physical characteristics
Geometry Tributary inflow locations Instream longitudinal data trends Point source assessment DMR records, WWTP Nutrient Database Nonpoint source assessment Correlation of GIS landuse to instream data

26 Modeling System LSPC watershed model
Utilizes precipitation to make hydrologic predictions EPD-RIV1 hydrodynamic and WQ model Kinematic wave transport Eutrophication kinetics but not periphyton Cahaba Spreadsheet Model Custom mass balance framework Predict instream TP Evaluate point and nonpoint sources Evaluate permit limits

27 TMDL Implementation Strategy
Phase I: NPDES permit revisions required by 2010* Majors (≥1.0 MGD) – monthly avg. limit not to exceed TP = 0.40 mg/L Minors (<1.0 MGD) – monthly avg. limit not to exceed TP = 2.0 mg/L Phase II: NPDES permit revisions required by 2015* Majors (≥1.0 MGD) – monthly avg. limit not to exceed TP = 0.20 mg/L Minors (<1.0 MGD) – monthly avg. limit not to exceed TP =0.50 mg/L Urban 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/L Minors (<1.0 MGD) – monthly avg. limit not to exceed TP = 0.30 mg/L Urban 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

28 Point Sources in Cahaba River Basin

29 Comparison of WWTP Effluent TP and Proposed TP Limits

30 Implementation Strategy to Reduce TP Loads
Reducing WWTP loads: NDPES permits for reduced effluent TP concentrations Reducing MS4/urban loads: NDPES MS4 permittees are expected to meet a 65% reduction using a BMP approach Reducing nonpoint source loads: CWP and UCC Land use planning considerations for watershed protection

31 Public 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.

32 Future Activities Follow-up monitoring plan
Nutrient Sampling Habitat, Macroinvertebrate, and Fish Sampling Diurnal Dissolved Oxygen Studies Periphyton Evaluations Further Ecoregion Reference Site Investigations Ecoregion 67 and Hatchet Creek Studies Continued Reference Site Investigations Develop an effects-based target Cahaba River & Hatchet Creek Sampling Adaptive Management may suggest re-evaluation of TP target as new data and information becomes available.


34 The Cahaba Lily Blooms from early May to late June
Hatchet Creek Cahaba River

35 Questions?

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