UNITED STATES ENVIRONME~TALPROTECTION AGENCY REG1 N 8 1595 Wynk op Street DENVER, CO 80202-1129

i

Phone 800- 27-8917

Ref: 8EPR-EP Steven H. Gunderson, Director Water Quality Control Division Colorado Department of Public Health and Environmpt 4300 Cherry Creek Drive South Denver, Colorado 80246-1 530

Re:

TdOSPUSI p Approval PZu#e rrscherichia (Emcola L

4 South coii

River, Segment I4

Dear Mr. Gundersan:

t

We have completed our review of the total m 'mum daily load (TMDL) as submitted by your office for the waterbody listed in the enclosure this letter. h accordance with the Clean Water Act (33 U.S,C. 125 1 et. seg.), we approve all ts of the TMDL as developed for the water quality limited waterbody as described in Section 303(d)(l). Based on our review, we have determined that the separate elements of the TMDLs listed in the enclosed table adequately address the pollutants of concern as given in the tabIe, taking into consideration seasonal .variationand a margin of safety.

)

Thank you for submitting this TMDL for questions, the most knowledgeable person on (303) 5 12-6846.

I

and approval. If you have any Ruppel and can be reached at

L i {b.? Lf1 Rushin

.>

Administrator Office of Ecosystems Protection [andRemediation

Enclosures

FINAL

TMDL – E. coli COSPUS14

TOTAL MAXIMUM DAILY LOAD ASSESSMENT

Escherichia coli South Platte River, Segment 14 Bowles Avenue to the Burlington Ditch Diversion Arapahoe and Denver Counties, Colorado

TMDL SUMMARY COSPUS14: Mainstem of the South Platte River from Bowles Avenue to the Burlington Ditch Headgate. Escherichia coli (E. coli) (protection of recreational uses) all Water Supply, Agriculture Aquatic life Warm 1, Recreation 1a Reviewable Attainment of E. coli standard throughout segment. Protection of public health and recreational uses

Waterbody Name/Segment Number Pollutant/Condition Addressed Affected Portion of Segment Use Classification/Waterbody Designation Waterbody Antidegradation Designation Water Quality Target TMDL Goal

I.

EXECUTIVE SUMMARY

Segment 14 of the Upper South Platte River Basin in Colorado is the mainstem of the South Platte River from Bowles Avenue in Arapahoe County to the Burlington Ditch Diversion in the City and County of Denver. Approximately 30% of the segment is in Arapahoe County, with the remainder in the City and County of Denver. Segment 14 has been on the State’s 303(d) list of water quality impaired waterbodies since 1998 for fecal coliform and/or Escherichia coli (“E. coli”). Fecal coliform and E. coli are indicators of the possible presence of pathogenic organisms that may cause illness in those who come in contact with or ingest contaminated waters. Segment 14 periodically exceeds current pathogen standards. The goal of this Total Maximum Daily Load (“TMDL”) assessment is the protection of recreational uses and public health. The organismal contributions of E. coli in segment 14 are presently unconfirmed, i.e. wildlife, human, or domestic animal sources. However, more is known about how E. coli is conveyed to the South Platte River. Significant contributions of E. coli are conveyed to segment 14 through urban stormwater collection systems during storm events and dry weather conditions. Sanitary sewer seepage, cross connections, wildlife, and pets are all known sources of E. coli to storm 1

FINAL

TMDL – E. coli COSPUS14

sewer systems and expected contributors to segment 14. E. coli levels are measured as a density-based unit, i.e. a number of bacteria colony forming units (“cfu”) per 100 milliliters (“ml”) of water. E. coli sources are not additive due to death, reproduction, and diurnal fluctuations. Also, South Platte River flows in segment 14 fluctuate on a non-seasonal basis due to intensive water management. Therefore, the Colorado Water Quality Control Division (“Division”) has adopted a density based approach for this TMDL assessment, which allocates pollutant loads to sources based upon the E. coli water quality standard. An example of the density-based TMDL allocations are shown in Table 1. Table 1. Density-Based Pollutant Load and Wasteload Allocations by source. Pollutant Source E. coli TMDL CDPS permitted discharges 126 cfu/100ml Wildlife 126 cfu/100ml Humans and animal pets in riparian zone 126 cfu/100ml Tributaries to Segment 14 126 cfu/100ml

II.

INTRODUCTION

Section 303(d) of the federal Clean Water Act (“CWA”) requires States to periodically submit to the U. S. Environmental Protection Agency (“EPA”) a list of water bodies that are water quality impaired. Water quality impaired segments are those water bodies that, for one or more assigned use classifications or standards, the classification or standard is not fully achieved. This list of water bodies is referred to as the “303(d) List”. In Colorado, the agency responsible for developing the 303(d) List is the Water Quality Control Division (“WQCD”). The List is adopted by the Water Quality Control Commission (“WQCC”) as Regulation No. 93. The WQCC adopted the current 303(d) List in March of 2006. This TMDL was assigned a high priority by the WQCC. The assigned priority is due to the documented non-attainment of a human health based water quality standard. Completion of this TMDL is consistent with the priority assigned by the WQCC. South Platte River Segment 14, designated as COSPUS14, is located in Arapahoe and Denver Counties, within the Upper South Platte Watershed. Approximately 4.3 stream miles of segment 14 lie within Arapahoe County, and approximately 11 stream miles lie within the City and County of Denver. III.

WATER QUALITY STANDARDS

The U.S. Environmental Protection Agency (“EPA”) published the current national water quality criteria for bacteria in surface water in 1986 (Ambient Water Quality Criteria for Bacteria, 1986 (EPA440/5-84-002)). The criteria is based upon “currently accepted illness rates”, which are “an estimated 8 illnesses per 1,000 swimmers at fresh water beaches”. That rate of illness was calculated using the fecal coliform indicator group at the maximum geometric mean of 200 cfu per 100 ml of water. In the 1986 criteria document, EPA made a transition from fecal coliform

2

FINAL

TMDL – E. coli COSPUS14

to E. coli at the same illness rate, which is a maximum geometric mean of 126 cfu per 100 ml of water. Segment 14 was designated as a Recreation Class 1 use with the corresponding standard of 200 cfu per 100 ml fecal coliform in 1982. In 1998, the segment was identified on the State’s 303(d) List of Impaired Waterbodies as impaired by fecal coliform. In 2000 the WQCC adopted a dual fecal coliform/E. coli standard for segment 14, and in 2004 removed the fecal coliform standard. Segment 14 remains in non-attainment of the E. coli standard. The 303(d) List listing for segment 14 was modified in 2002 to include both fecal coliform and E. coli, and further revised in 2004 to specify E. coli only. Recreational use of the South Platte River occurs frequently. Municipalities have built amenities to attract visitors to the South Platte corridor. Such amenities include a walking and biking trail along the entire length of the segment 14, numerous golf courses and parks adjacent to the river, and a kayak chute at Confluence Park in Denver. Also, during the summer, a non-profit youth program, called River Reach Youth Initiative, conducts raft trips on the South Platte River through Denver.

IV.

PROBLEM IDENTIFICATION

Substantial monitoring of fecal coliform and E. coli has occurred on segment 14 since the 1998 listing. Several agencies and entities have performed monitoring on segment 14, including Denver Department of Environmental Health (“DEH”), U.S. Geological Survey (“USGS”), Denver Water Board, Littleton/Englewood Wastewater Treatment Facility, South Platte Coalition for Urban River Evaluation (“SPCURE”), Urban Drainage and Flood Control District (“UDFCD”), and the WQCD. E. coli levels in segment 14 are not spatially or temporally consistent, which makes it difficult to show a consistent pattern or location of E. coli loading or significant die-off. In general, E. coli levels in segment 14 are higher in the summer than other months. E. coli also typically has a diurnal pattern with E. coli levels generally highest in the early morning due to ultraviolet radiation from sunlight causing genetic mutation in E. coli (Burkhardt, 2000). As a result of the mutation, individual organisms are not able to reproduce. Table 2 shows E. coli data collected by DEH in 2004. Table 3 shows historical South Platte River E. coli concentrations collected by the WQCD, Denver Water, DEH, and the Littleton and Englewood Wastewater Treatment Facility. The data in Table 2 and 3 is considered to be data collected during dry weather periods. There is a slight, but not dominant, tendency for E. coli concentrations to be greatest during the rising phase of a storm hydrograph and for the concentrations to decline as the hydrograph recedes (igs.indiana.edu). The USGS and UDFCD conducted storm event sampling in South Platte River segment 14 from 1998 to 2001 at two locations (USGS, 2005). All samples taken in segment 14 during storm events exceeded the E. coli water quality standard. The Colorado Water Quality Control Act” (CCR 61.8(11)(a)(i)) regulation controls stormwater discharge. The regulation states that the MS4 operator must “develop, implement, and enforce a stormwater 3

FINAL

TMDL – E. coli COSPUS14

management program designed to reduce the discharge of pollutants from the MS4 to the Maximum Extent Practicable (MEP), to protect water quality, and to satisfy the appropriate water quality requirements. In short, the permittee must develop programs that meet the requirements of the six minimum measures (public education and outreach, public participation/involvement, illicit discharge detection and elimination, construction site stormwater runoff control, post-construction stormwater management, and pollution prevention/good housekeeping for municipal operations) and protect state waters from pollution, contamination, and/or degradation. Table 2. Denver Environmental Health 2004 E. coli sampling on segment 14. Sample Location E. coli c.f.u./100ml* South Platte near Dartmouth (above L/E WWTF) 164 South Platte near Evans 154 South Platte above Lakewood Gulch 184 South Platte above Cherry Creek 125 South Platte near 31st 325 South Platte near 49th 639 * Geometric Mean

No. Samples 24 24 12 12 12 12

Table 3. Historic E. coli data for segment 14. Sample Location WQCD 000156 S Platte at 19th Street Denver Water S Platte at Florida Ave. DEH S Platte at Colfax DEH S Platte at 25th DEH S Platte at 38th WQCD 5701 S Platte abv Cherry Creek WQCD 5185 S Platte at 20th Street Viaduct WQCD 5170 S Platte upstrm Burlington Ditch WQCD 5175 S Platte at 49th Denver Water S Platte blw Cherry Creek Littleton and Englewood Wastewater Treatment Facility upstream of outfall * Geometric Mean

V.

E. coli No. c.f.u./100ml* Samples 323 48 305 15 170 32 88 78 559 31 968 2 274 3 654 3 1014 3 513 15 247

73

Time Period 2001-2006 1999-2003 1998-2002 1998-2002 1998-2002 1998-1999 1998-1999 1998 -1999 1998-1999 1999-2003 1998-2003

WATER-QUALITY GOAL AND TARGET

The goal of this Total Maximum Daily Load assessment is to protect public health through attainment of the E. coli water quality standard throughout segment 14. To achieve this goal, the Division is proposing a density based allocation approach to this TMDL that will encompass non-point and point sources of E. coli. The ambient water-quality standard is reflective of the entire stream segment as a whole; therefore any point sampled on Segment 14 should meet the E. coli standard of 126 cfu/100 ml. Attainment of the numeric target will be determined by the calculation of a 30-day geometric mean for the end-of-pipe dry weather discharge, which 4

FINAL

TMDL – E. coli COSPUS14

incorporates periodic acute exceedances into the calculation. The limit will not be based on an acute exceedance.

VI.

ANALYSIS OF POLLUTANT SOURCES

Tributaries and Non-Point E. coli Sources Table 4 shows historic E. coli data on tributaries to segment 14. Non-point sources of E. coli to segment 14 include wildlife, humans, and domesticated animals. Because there is currently no information available to the Division to differentiate between sources of non-point E. coli or even between non-point source vs. point source E. coli, the Division can not make those distinctions. Table 4: Historic E. coli data on tributaries to segment 14 Tributary E. coli * No. samples Time Period Bear Creek 393 51 2000-2004 Cherry Creek at mouth 109 216 2001-2005 Goldsmith Gulch 48 10 1999-2003 Harvard Gulch 99 9 1999-2003 Lakewood Gulch 78 11 1998-2003 Niver Gulch 67 3 1998-1999 Sanderson Gulch 70 7 1999-2003 Weir Gulch 47 7 1999-2003 West Harvard Creek 109 9 1999-2003 Westerly Creek 165 80 2001-2005 *Geometric Mean

Agency Littleton/Englewood WWTF DEH DEH DEH DEH, WQCD WQCD DEH DEH DEH DEH

CDPS Process Water Permits CDPS process water permits include construction dewatering, groundwater remediation, mining, minimal industrial discharges, water and wastewater treatment, and other permits not falling into the above categories. There are numerous CDPS process water permits that discharge directly to segment 14 or to a stormwater collection system that drains to segment 14. The CDPS Regulation (WQCC Regulation No. 61) requires the Division to develop permit limitations for any discharged pollutant that causes or contributes to, or that has the reasonable potential to cause or contribute to, an exceedance of water quality standards. The Division has developed a guidance (Determination of the Requirement to Include Water Quality StandardsBased Limits in CDPS Permits Based on Reasonable Potential, Procedural Guidance, February 2003) to determine a discharge’s “reasonable potential” to cause or contribute to an exceedance of water quality standards. There is only one CDPS process water permit that discharges to segment 14 that has been determined to have reasonable potential to discharge E. coli at a level that may cause or contribute to an exceedance of the E. coli water quality standard, which is the Cities of Littleton 5

FINAL

TMDL – E. coli COSPUS14

and Englewood Wastewater Treatment Facility (CDPS permit CO-0032999). The design capacity of the Littleton and Englewood Wastewater Treatment Facility is 36.3 million gallons per day (MGD) for hydraulic flow (30-day average). The facility currently has pathogen effluent limits for fecal coliform, which are: 30-day average of 245 c.f.u./100ml; 7-day average maximum concentration of 490 c.f.u./100ml. Currently, the facility discharges at levels significantly below the permitted effluent limits. CDPS Municipal Separate Storm Sewer System Permits Under Colorado’s Municipal Separate Storm Sewer (“MS4”) program, municipalities are authorized to discharge stormwater, discharges authorized under separate CDPS process water permits, and other allowable non-stormwater discharges from their stormwater collection system. There are five MS4 permittees that discharge directly to segment 14, listed in Table 6. Allowable non-stormwater discharges, include: landscape irrigation lawn watering diverted stream flows irrigation return flow rising ground waters uncontaminated ground water infiltration uncontaminated pumped ground water springs flows from riparian habitats and wetlands water line flushing discharges from potable water sources foundation drains air conditioning condensation water from crawl space pumps footing drains individual residential car washing dechlorinated swimming pool discharges street wash water discharges or flows from fire fighting activities Under the MS4 permit, municipalities must implement a program to detect and eliminate other non-stormwater discharges into their drainage or collection system. At present, the only water quality data from stormwater outfalls along the South Platte has been collected by Denver Environmental Health (“DEH”). DEH has collected dry weather outfall data since 2002. Dry weather discharge data from DEH from urban stormwater outfalls shows high levels of E. coli in several drains (2002, 2003, and 2004 Water Quality Assessment Report, City and County of Denver, Volume I: Rivers). The loading of E. coli from dry weather flows from stormwater outfalls is considered to be a significant and controllable source through Best Management Practices (BMPs) of E. coli to segment 14. Therefore, municipalities and facilities with a CDPS MS4 permit are assigned a wasteload allocation under this TMDL. 6

FINAL

TMDL – E. coli COSPUS14

Table 5 lists the CDPS Municipal Separate Storm Sewer (“MS4”) permittees that discharge directly to segment 14. Table 5: CDPS MS4 permittees that discharge to segment 14. CDPS Permit Permit Holder COR-090048 Arapahoe Community College COR-080010 Arapahoe County COR-090080 Auraria Higher Education Center COS-000001 City and County of Denver COR-090056 City of Englewood COR-090055 City of Littleton COR-090082 City of Sheridan COR-090090 Colorado Rockies Baseball Club COR-090081 Denver Health & Hospital Authority COR-090086 Denver Public Schools COR-090067 Littleton Public Schools COR-090098 Metropolitan Football Stadium District COR-090023 Regional Transportation District COR-090075 University of Colorado Health Sciences Center

Permit Renewal March 9, 2008 March 9, 2008 March 9, 2008 April 30, 2008 March 9, 2008 March 9, 2008 March 9, 2008 March 9, 2008 March 9, 2008 March 9, 2008 March 9, 2008 March 9, 2008 March 9, 2008 March 9, 2008

Other Sources There are other sources of E. coli to segment 14 that are considered to be natural (nonanthropogenic in nature) or non-point source pollution. These sources, which include runoff not captured by a stormwater collection system, wildlife, domestic pets, horses, livestock, and humans, are considered a part of the load allocation for this TMDL. VII.

TMDL ALLOCATION

Allocation Methodology Traditional TMDL assessments utilize a mass per time accounting of pollutant sources. However, E. coli sources are not additive like other pollutant sources due to natural processes in the stream. Also, flows in segment 14 fluctuate on a non-seasonal basis due to the intensive water management of the South Platte system. Therefore, developing traditional mass-based load allocations for segment 14 is not possible. For this TMDL, the WQCD has used density-based load allocations. Density-based load allocations do not add up to equal a TMDL as a mass per time, such as pounds per day. Rather the load allocations assign targets for known and potential sources as density. To achieve the water quality goals of a density-based TMDL, each source must meet its density-based load or wasteload allocation. Tables 6 and 7 present the density-based pathogen load and wasteload allocations proposed for segment 14.

7

FINAL

TMDL – E. coli COSPUS14

Table 6. Density-Based Load Allocations (LA) by pollutant source. Pollutant Source E. coli Density Urban runoff 126 cfu/100ml Wildlife 126 cfu/100ml Humans and animal pets in riparian zone 126 cfu/100ml Tributaries to Segment 14 126 cfu/100ml Table 7. Density-Based Wasteload Allocations (WLA) by discharge. Pollutant Source E. coli Density CDPS MS4 permitted discharges to segment 14. 126 cfu/100ml Cities of Littleton and Englewood Wastewater Treatment Facility (CO-0032999) 126 cfu/100ml Examples of Load Reductions E. coli levels instream oscillate with natural die off and diurnal fluctuations. Also, flows in segment 14 fluctuate dramatically on a non-seasonal basis due to water deliveries. Thus it is difficult to determine a load reduction that is a fixed number. Table 8 shows examples of load reduction at specific sampling locations, and should not be considered as regulatory load reductions. Table 8: Examples of load reduction at specific sampling locations. Station Location E. coli* No. of Load Samples Allocation cfu/100 ml South Platte at 19th St. in Denver 325 84 126 (WQCD #00156) South Platte above L/E outfall 247 73 126 South Platte below Cherry Creek 513 15 126 (Denver Water) South Platte at 38th (DEH) 559 31 126 South Platte at Colfax (DEH) 170 32 126 South Platte at Florida (Denver 305 15 126 Water) South Platte near Dartmouth 164 24 126 (above L/E WWTF) South Platte near Evans 154 24 126 South Platte above Lakewood 184 12 126 Gulch South Platte above Cherry Creek 125 12 126 South Platte near 31st 325 12 126 South Platte near 49th 639 12 126 * Geometric Mean

8

Load Reduction cfu/100 ml

Percent Load Reduction

199

61%

121

49%

387

75%

432 44

77% 26%

179

59%

38

23%

28

18%

58

32%

0 199 513

0% 61% 80%

FINAL

TMDL – E. coli COSPUS14

Margin of Safety A Margin of Safety (“MOS”) can be either implicit or explicit. Implicit MOS’s are incorporated into the TMDL analysis thorough conservative assumptions, and explicit MOS’s can be expressed in the TMDL as a portion of the loadings. This TMDL uses an implicit MOS because all flows will not cause or contribute to an exceedance of the standard when implementation is complete. Implementation Implementation of this TMDL will be an iterative process involving the CDPS permittees that discharge to segment 14 and other non-point source pollution programs. The first iteration of this TMDL will be to address CDPS MS4 permitted outfalls that have dry weather flows with elevated E. coli levels. A reevaluation of the TMDL by the Division will occur once all dry weather flows from stormwater collection systems that drain to segment 14 with elevated E. coli are considered to be controlled through Best Management Practices (BMPs). Following is an “adaptive implementation” plan that was established for this TMDL in a coordinated effort with the Permits unit. Permitting Approaches: For process water permits, the approach would be fairly straightforward in that all numeric water quality based effluent limits for E. coli would be equal to the water quality standard, or 126 cfu/100 ml. The approach for the MS4 sources is more complex. To comply with Regulation 61, the WQCD cannot issue a permit that allows discharges that cause or have the potential to cause an exceedance of a numeric water quality standard unless the permit contains effluent limitations and a schedule of compliance specifying treatment requirements. Therefore, the WQCD must issue permits that contain effluent limits for those MS4s with illicit dry weather discharges identified as being in excess of the TMDL allocations. However, Regulation 61 allows the effluent limit to consist of Best Management Practices (BMPs) to ensure protection of the water quality standard when numeric effluent limits are infeasible, or when practices are reasonably necessary to achieve effluent limits or standards. BMP effluent limits may be included in the MS4 permits, instead of numeric effluent limits, if it can be shown that numeric limits are infeasible. EPA’s policy recognizes that because storm water discharges are due to storm events that are highly variable in frequency and duration and are not easily characterized, only in rare cases will it be feasible or appropriate to establish numeric limits for municipal discharges (EPA memo, 2002). The WQCD may provide dischargers the opportunity to provide evidence that numeric limits are infeasible and request the WQCD to apply BMP effluent limits to control or abate the discharge. If BMP effluent limits are used in MS4 permits, WQCD staff recommends that the Division convey to MS4s that in accordance with our regulations, the Division intends to require in their permits that BMPs be implemented to identify and remove illicit discharges to the MS4 to ensure that dry weather discharges do not potentially contribute to an exceedance of the water quality standard. The basis for determining the potential to contribute to an exceedance of the water quality standard would be outfall data that exceeds the density based TMDL. An appropriate compliance schedule allowing up to 10 years to meet this requirement could be allowed. MS4s 9

FINAL

TMDL – E. coli COSPUS14

in the segment would be required to collect dry-weather based outfall-monitoring data to determine if dry weather discharges exist that could exceed the density based TMDL. For Denver, data already exist that demonstrate the need to apply an effluent limit for E. coli. The BMP effluent limits could be inserted in the permit through two approaches: a) Requiring that BMPs be implemented to the extent necessary for the water quality standard to be met at the outfall. This approach would essentially function as a numeric effluent limit and places the burden on the MS4 to ensure that BMPs are successful in protecting water quality standards. b) Requiring BMPs to be implemented that the WQCD has determined would result in the water quality standard being met at the outfall. The WQCD would require that the permittee submit proposed BMPs, along with evidence that the BMPs would result in protection of the water quality standard. In this case, the permittee would not be out of compliance if the BMPs were implemented but failed to meet the standard. The Division would have the burden of determining the adequacy of measures proposed by the MS4s to attain the TMDL and water quality standard. If dischargers believe that attainment of the underlying standard within a 10 year compliance schedule is infeasible, then it may appropriate for them to request a temporary modification from the WQCC. The WQCC could weigh the evidence to determine the infeasibility of attaining the standard and could establish an appropriate timeframe for attainment. It may also be appropriate for the WQCD to request a temporary modification if we believe that control of point sources would not be adequate to attain the underlying standard within a 10 year compliance schedule for the MS4 permits. Denver’s MS4 permit expires April 30, 2008. The MS4 general permit for the Phase II MS4s expires on March 10, 2008. The WQCD will work with the MS4s immediately to begin assessment of their discharges and address known issues prior to their next permit term. TMDL Endpoint The endpoint of this TMDL will be attainment of the E. coli water quality standard using the WQCC’s approved 303(d) Listing Methodology. Post-Implementation Monitoring The Division will continue to work with stakeholders, such as Denver Environmental Health, South Platte CURE, and UDFCD to maintain and improve the current level of sampling on the segment. A compliance schedule in the MS4 permit may allow up to 5 years to meet the E. coli requirement of 126 cfu/100 ml. MS4s in the segment would be required to collect dry-weather based outfall-monitoring data to determine if dry weather discharges exist that could exceed the density based TMDL.

VIII. PUBLIC INVOLVEMENT

10

FINAL

TMDL – E. coli COSPUS14

The Division met with the City and County of Denver, South Platte CURE, Denver Regional Council of Governments, and the Colorado Water Quality Forum in the winter and spring of 2006. This TMDL was noticed for public comment on July 1, 2006. Public comments received will be summarized below as well as the WQCD response to those comments. IX.

REFERENCES

Burkhardt, W., III, K. R. Calci, W. D. Watkins, S. R. Rippey, and S. J. Chirtel. 2000. Inactivation of indicator microorganisms in estuarine waters. Water Res. 34:2207-2214 Colorado Department of Public Health and Environment (2004). Guidance on Data Requirements and Data Interpretation Methods Used in Stream Standards and Classification Proceedings. Water Quality Control Division, August. Colorado Department of Public Health and Environment (2006). Regulation 93 - Section 303(D) List Water-Quality-Limited Segments Requiring TMDLs. Water Quality Control Commission, effective April 30, 2006. Colorado Department of Public Health and Environment (2005). Regulation 31- Basic Standards and Methodologies for Surface Water. Water Quality Control Commission, effective 12/31/05. Colorado Department of Public Health and Environment (2002). Regulation 38 - Classification and Numeric Standards for South Platte River Basin; Laramie River Basin; Republican River Basin; Smoky Hill River Basin. Water Quality Control Commission, effective 1/30/02. Colorado Department of Public Health and Environment (2005). Section 303(d) Listing Methodology, 2006 Listing Cycle. Water Quality Control Division, May. Colorado Department of Public Health and Environment (2003). Determination of the Requirement to Include Water Quality Standards-Based Limits in CDPS Permits Based on Reasonable Potential, Procedural Guidance, February. Denver Department of Environmental Health (2005). 2004 Water Quality Assessment Report, City and County of Denver, Volume I: Rivers. August. Denver Department of Environmental Health (2005). 2003 Water Quality Assessment Report, City and County of Denver, Volume I: Rivers. February. Denver Department of Environmental Health (2004). 2002 Water Quality Assessment Report, City and County of Denver, Volume I: Rivers. June. Fujioka, R. S., H. H. Hashimoto, E. B. Siwak, and R. H. F. Young. 1981. Effect of sunlight on survival of indicator bacteria in seawater. Appl. Environ. Microbiol. 41:690-696 http://igs.indiana.edu/survey/projects/greatmarsh/index.cfm Sinton, L. W., R. K. Finlay, and P. A. Lynch. 1999. Sunlight inactivation of fecal bacteriophages 11

FINAL

TMDL – E. coli COSPUS14

in sewage-polluted seawater. Appl. Environ. Microbiol. 65:3605-3613 Sinton, L. W., C. H. Hall, P. A. Lynch, and R. J. Davies-Colley. 2002. Sunlight inactivation of fecal indicator bacteria and bacteriophages from waste stabilization pond effluent in fresh and saline waters. Appl. Environ. Microbiol. 68:1122-1131 U.S. Geological Survey (2005). Summary and Evaluation of the Quality of Stormwater in Denver, Colorado, Water Years 1998-2001. By Clifford R. Bossong, Michael R. Stevens, John T. Doerfer, and Ben R. Glass.

12

FINAL

TMDL – E. coli COSPUS14

X. RESPONSES TO COMMENTS RECEIVED CONCERNING JUNE 2006 PUBLIC NOTICE DRAFT Issue: Use of E. coli as an environmental indicator Several commenters objected to the use of E. coli as an indicator of environmental pathogens and the density based approach of this TMDL. The Northern Colorado Alliance of Stormwater Coordinators noted “E. coli as an indicator is based on unsubstantiated science.” The City of Littleton commented that “there are some uncertainties in the current state of the science and data concerning E. coli and the density based approach for the TMDL.” Division Response: The Division believes that the data supporting the water quality criteria were obtained through substantiated science. A series of research studies conducted by EPA examining the relationship between swimming-associated illness and the microbiological quality of the waters used by recreationists were the basis for the E. coli water-quality standard of 126 cfu/100 ml (EPA, 1986). Most disease-causing microbes exist at very low levels and are difficult and expensive to detect. E. coli is found in much higher concentrations than most pathogens in fecal material, easy to detect, and includes a 24-hour turnaround in analyses. Indicator organisms, such as E. coli, have been used for more than a century to help identify where fecal contamination has occurred, and therefore, where diseasecausing microbes may be present. These organisms generally do not cause illness directly; however, they have characteristics that make them good indicators that fecal contamination has occurred and that harmful pathogens may be in the water (http://www.epa.gov/waterscience/beaches/bacteria-rule-questions.htm). Therefore, until a new or revised criteria is developed, the Division will continue to use E. coli as an indicator of environmental pathogens. The WQCC adopted E. coli standards based upon the federal criteria at a July 2000 rulemaking. The E. coli standards were subsequently assigned by the WQCC to waterbodies within the South Platte River Basin in 2004. It is also appropriate to note that segment 14 initially appeared on the 1998 section 303(d) List based upon non-attainment of the then assigned fecal coliform standard. Regardless of questions concerning the adequacy of the current, enforceable standard, it is apparent that water quality within the segment has long been in exceedance of human health-based pathogen standards. Issue: Implementation of the TMDL Several comments addressed implementation of the TMDL. The Northern Colorado Alliance of Stormwater Coordinators noted that “ There will be substantial cost and resources required to implement a program that currently does not adequately specify the desired product of the effort, nor adequately define the best 13

FINAL

TMDL – E. coli COSPUS14

method to attain it in Colorado” Comments submitted by Littleton/Englewood state: “The “Implementation” section of the TMDL should be modified to specifically state that implementation of the TMDL based limits in CDPS Permits shall be in accordance with the applicable requirements of Regulation No. 61; and that nothing in the TMDL is intended or shall be deemed to require an averaging period for TMDL-based effluent limits different from the applicable averaging period specified by Regulation No. 61.” The South Platte Coalition for Urban River Evaluation commented that “We recommend the Division include a phased implementation plan in the TMDL that includes investigation of recommended BMPs and BMP effectiveness.” The City of Englewood noted that the addition of the statement “and implement source identification procedures to establish appropriate BMPs to reach attainment of the E. coli water-quality standard” should be included in the implementation section. Comments submitted by the City of Littleton state: “The “Implementation” paragraph should contain a statement that the density based limit of 126 cfu/100 ml sets a goal, but its effectiveness in improving overall water quality is yet to be determined.” Denver Environmental Health commented that “an adaptive implementation approach, such as a phased TMDL, be selected,… and that the approach be BMP-based as opposed to a numeric-based approach.” Division Response: The Division concurs with the idea of the “adaptive implementation” of the TMDL. A staged plan will be established for this TMDL in a coordinated effort with the Permits unit. BMP effluent limits will be included in the MS4 permits for dry weather discharge, instead of numeric effluent limits, if it can be shown that numeric limits are infeasible. EPA’s policy recognizes that because storm water discharges are due to storm events that are highly variable in frequency and duration and are not easily characterized, only in rare cases will it be feasible or appropriate to establish numeric limits for municipal discharges (EPA memo, 2002). The WQCD will provide dischargers the opportunity to provide evidence that numeric limits are infeasible and request the WQCD to apply BMP effluent limits to control or abate the discharge. An additional section will be added to the “Implementation” Section of the TMDL which outlines the implementation approach and is included below: Permitting Approaches: For process water permits (i.e. domestic wastewater or industrial discharges), the approach would be fairly straightforward in that all numeric water quality based effluent limits for E. coli would be equal to the water quality standard, or 126 cfu/100 ml. The approach for the MS4 sources is more complex. To comply with Regulation 61, the WQCD cannot issue a permit that allows discharges that cause or have the potential to 14

FINAL

TMDL – E. coli COSPUS14

cause an exceedance of a numeric water quality standard unless the permit contains effluent limitations and a schedule of compliance specifying treatment requirements. Therefore, the WQCD must issue permits that contain effluent limits for those MS4s with illicit dry weather discharges identified as being in excess of the TMDL allocations. However, Regulation 61 allows the effluent limit to consist of Best Management Practices (BMPs) to ensure protection of the water quality standard when numeric effluent limits are infeasible, or when practices are reasonably necessary to achieve effluent limits or standards. BMP effluent limits may be included in the MS4 permits for dry weather discharge, instead of numeric effluent limits, if it can be shown that numeric limits are infeasible. EPA’s policy recognizes that because storm water discharges are due to storm events that are highly variable in frequency and duration and are not easily characterized, only in rare cases will it be feasible or appropriate to establish numeric limits for municipal discharges (EPA memo, 2002). The WQCD may provide dischargers the opportunity to provide evidence that numeric limits are infeasible and request the WQCD to apply BMP effluent limits to control or abate the discharge. If BMP effluent limits are used in MS4 permits, WQCD staff recommends that MS4s, in accordance with our regulations, require permits to implement BMPs to identify and remove illicit discharges to the MS4 to ensure that dry weather discharges do not potentially contribute to an exceedance of the water quality standard. The basis for determining the potential to contribute to an exceedance of the water quality standard would be outfall data that exceeds the density based TMDL. A compliance schedule allowing up to 5 years to meet this requirement could be allowed. MS4s in the segment would be required to collect dry-weather based outfall-monitoring data to determine if dry weather discharges exist that could exceed the density based TMDL. For Denver, data already exist that demonstrate the need to apply an effluent limit for E. coli. The BMP effluent limits could be inserted in the permit through two approaches: a) Requiring that BMPs be implemented to the extent necessary for the water quality standard to be met at the outfall. This approach would essentially function as a numeric effluent limit and places the burden on the MS4 to ensure that BMPs are successful in protecting water quality standards. b) Requiring BMPs to be implemented that the WQCD has determined would result in the water quality standard being met at the outfall. The WQCD would require that the permittee submit proposed BMPs, along with evidence that the BMPs would result in protection of the water quality standard. In this case, the permittee would not be out of compliance if the BMPs were implemented but failed to meet the standard. The Division would have the burden of determining the adequacy of measures proposed by the MS4s to attain the TMDL and water quality standard. If dischargers believe that attainment of the underlying standard during the 5-year term is infeasible, then it may appropriate for them to request a temporary modification or alternate E. coli standard from the WQCC. The WQCC could weigh the evidence to determine the infeasibility of attaining the standard and could establish an appropriate timeframe for attainment. It may also be appropriate for the WQCD to request a 15

FINAL

TMDL – E. coli COSPUS14

temporary modification if we believe that control of point sources would not be adequate during the 5-year term to attain the underlying standard. Denver’s MS4 permit expires April 30, 2008. The MS4 general permit for the Phase II MS4s expires on March 10, 2008. Thus, Denver and any other MS4 that is found to be contributing to an exceedance will have two years to develop an implementation plan on attaining the E. coli standard for dry-weather discharges or eliminate the dry-weather discharges, including a schedule. The WQCD could also work with the MS4s immediately to begin assessment of their discharges and address known issues prior to their next permit term. Issue: Dry Weather Discharge The Division received comments from various sources indicating concerns on the focus of dry weather discharge as opposed to storm events. The Northern Colorado Alliance of Stormwater Coordinators commented “the proposal is to begin working with dry weather only; will this change?” The City of Englewood noted that “reference to “storm events” should be deleted as dry weather illicit discharges are the focus of this TMDL.” Division response: With respect to focus on dry weather discharge, this will be the primary focus of the implementation and monitoring plan proposed by the WQCD. Storm events are covered in the individual MS4 permits. The Division feels, however, that “storm events” should be included in the problem identification section, since in urban watersheds, more than 60% of the annual load of all contaminants is transported during storm events (Curriero and Rose, 2001). Periods of heavy rainfall, runoff, and subsequent turbidity load have been correlated with increased illness in communities (Curriero and Rose, 2001). Therefore it is important to include in reference to the E. coli exceedances in the South Platte Segment 14 and subsequent inclusion on the 303(d) list. The TMDL focuses on dry weather discharge, however, it is important to mention storm events and their contribution to elevated E. coli concentrations. Issue: Monitoring Plan Concerns raised by the Northern Colorado Alliance of Stormwater Coordinators included the need for a monitoring plan as a component of the TMDLs. They stated the need for the development of a “well-coordinated monitoring program and the water quality modeling tools needed to make sound scientific decisions”. Division response: A monitoring plan is not a required element of the TMDL. A monitoring plan may be

16

FINAL

TMDL – E. coli COSPUS14

included, however, and is often identified as an element of an implicit Margin of Safety. Additional monitoring and data analysis will be performed as part of the “adaptive implementation” plan of this TMDL. A compliance schedule allowing up to 5 years to meet the E. coli standard of 126 cfu/100 ml could be allowed. MS4s in the segment would be required to collect dry-weather based outfall-monitoring data to determine if dry weather discharges exist that exceed the density based TMDL. Per the memo from the EPA entitled “Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on those WLAs”, “The NPDES permit must require the monitoring necessary to assure compliance with permit limitations, although the permitting authority has the discretion under EPA’s regulations to decide the frequency of such monitoring” (40 CFR § 122.44(i)). Issue: Point of Compliance Denver Environmental Health‟s comments note, “No supporting science, data, or modeling, is presented that would indicate that by meeting the allocations required of the TMDL that Segment 14 will come into compliance with the stream standard.” The Northern Colorado Alliance of Stormwater Coordinators asked the question “Where is the point of compliance? Is it the E. coli levels found within the stream or is it the levels at the end of the outfall? If the point of compliance is located at the end of the outfall, would only major outfalls be included or would all outfalls?” Similarly, “What happens if stream segments never meet the stream standards set?” Division response: The Division believes that with respect to the point of compliance, the ambient waterquality standard is applicable to the entire stream segment as a whole; therefore any point sampled on Segment 14 should meet the E. coli standard of 126 cfu/100 ml. However, if stakeholders identify the specific point of compliance as the outfall, and it is demonstrated that the outfalls are in compliance with the stream standard while the stream still does not meet 126 cfu/100 mL, then the remaining (that which results in nonattainment) load shall be considered a non-point source. Similarly, MS4 permits and Regulation No. 61 state that each individual outfall should meet the E. coli requirement of 126 cfu/100 ml. The Division believes that should the segment continue to not meet the stream standards for E. coli, an alternate E. coli standard, or Use Attainability Analysis (UAA) may be required. A UAA is defined in Regulation 31 as "an assessment of the factors affecting the attainment of aquatic life uses or other beneficial uses, which may include physical, chemical, biological, and economic factors." 5 CCR. §1002-31, §31.5 (30). A UAA is required in order to justify the omission of an aquatic life class 1 or 2 classification or a recreation class 1 classification 31.6(3)(a)(iii). A UAA is also one of the methods that can be used to support adoption of a site specific criteria-based standard that differs from the table value standard. §31.7(1)(b)(iii). EPA Region VIII prepared guidance for Use Attainability Analyses for Aquatic Life Uses 17

FINAL

TMDL – E. coli COSPUS14

to respond to a number of policy and technical questions commonly associated with UAAs. It is intended to ensure that the analysis addresses appropriate issues. Fundamentally, the guidance asks: What are the stressors limiting the use; and are those stressors controllable? The Division has expanded that direction to focus on the following questions. • What level of aquatic life is currently being achieved in the water body? • What are the causes of any impairment in the use? • What level of aquatic life could potentially be attained based on the physical and biological characteristics of the water body if the controllable sources were not present (i.e. how does the water body compare to a non-impacted reference site)? • What barriers, both technical and regulatory, are there to achieving the “potentially attainable” level of aquatic life? • What improvement in the level of aquatic life is feasible? ISSUE: Load Allocation The South Platte Coalition for Urban River Evaluation commented that “ …the load allocations should be defined as 30-day geometric means.” Division response: The Division agrees that the load allocations for E. coli will be calculated as a 30-day geometric mean, in accordance with current MS4 permits and Regulation No. 61.

ISSUE: Analysis of Pollutant Sources and Allocation Comments received from Denver Environmental Health noted that “The TMDL does not provide sufficient data regarding the identification of E. coli sources and lacks an analysis on their respective contribution to river impairment.” “Moreover, the TMDL does not address loading from other sources other than stormwater outfalls associated with Denver‟s MS4 permit and does not address the link between mitigation of E. coli sources, stream flow, or the effects of other water quality parameters and resulting changes in stream water quality.“ Division response: The Division believes that the TMDL significantly addresses the sources of E. coli on Segment 14. In the memo entitled “Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on those WLAs” from EPA in 2002, it states that “It may be reasonable to quantify the allocations through estimates or extrapolations, based either on knowledge of land use patterns and associated literature values for pollutant loadings or on actual, albeit limited, loading information. EPA recognizes that these allocations might be fairly rudimentary because of data limitations.” Furthermore, “EPA also recognizes that the available data and information usually are not detailed enough to 18

FINAL

TMDL – E. coli COSPUS14

determine waste load allocations for the NPDES-regulated storm water discharges on an outfall-specific basis. In this situation, EPA recommends expressing the wasteload allocation in the TMDL as a single number for all NPDES-regulated storm water discharges…” Issue: Margin of Safety Denver Environmental Health commented that “The margin of safety discussion is unclear.” Division response: The Division would like to clarify that the “conservative assumptions” in the margin of safety refer to the use of a 30-day geometric mean to calculate E. coli levels as opposed to using either acute exceedances, 7-day averages, or arithmetic means.

General Comments “Section 6, last paragraph on page 7, should include domesticated animals. Horses are a likely sources of E. coli.” Horses and the term livestock were included as sources of E. coli. “Section VII, Table 8, on page 8 should contain the word “theoretical” in the title.” The term “theoretical” in the load reduction table refers to load reductions that would be required at the current time to attain the water-quality, recreation based standard for E. coli of 126 cfu/100ml. The definition of “theoretical” implies that the load reduction numbers are purely speculative, “existing only in theory; hypothetical”. These load reduction numbers were calculated directly from data analysis of the E. coli data provided by Denver Environmental Health, and they refer to the percentage of load reduction necessary to meet the 126 cfu/100 ml standard. Variability of density-based load allocations is implicit in the Margin of Safety incorporated into this TMDL. “Section VII Public Involvement and Section VIII References, as shown on page 9, are numbered incorrectly.” This numbering has been corrected. “Data to support the statement „E. coli also typically has a diurnal pattern…‟ has not been collected for Segment 14 and no reference to a peer reviewed work is provided.” These citations and references have been added.

19

FINAL

TMDL – E. coli COSPUS14

20