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 NutrientsID
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?