Perspectives from the Regulated Community Regarding E. coli in Colorado Waters

Transcription

1 Perspectives from the Regulated Community Regarding E. coli in Colorado Waters Prepared by Jim McCarthy, City of Arvada and Jane Clary, Wright Water Engineers, Inc. September 2011 Based on Work Completed for the Water Quality Forum E. coli Work Group Colorado Healthy Rivers Fund

2 Colorado Water Quality Standards Process CWA: Triennial Review Basic Standards: Basin Hearings Water Quality Forum Workgroups

3 The Problem Nationally Top 10 Causes of Impairment in U.S. by # of 303(d) Listings Top 10 Causes of Impairment in Colorado by Stream Miles Affected Source: EPA 2009, based on 2006/ (d) Listings

4 The Problem in Colorado 2008: 22 stream segments listed as impaired 2012 (draft list): approx. 70 stream segments listed as impaired or on M&E for E. coli Looks like problem worsening, but more likely due to change in assessment methodology

5 The Other Part of the Problem Leading to E. coli Work Group Formation: The meaning of these listings in terms of human health risks is unclear. Questions exist regarding: Appropriateness of fecal indicator bacteria used to assess contamination by pathogens Application of marine/great Lakes epidemiological data to inland flowing waters Realistic solutions/practices to bring streams into compliance with standards Despite these questions current regulatory framework requires action, (typically in the form of TMDLs)

6 Overview of White Paper Summarizing Work Group Effort Regulatory Background 2. Colorado Case Studies 3. Sources of Bacteria 4. Monitoring and Assessment of Data 5. Best Management Practices (BMPs) 6. Unresolved Issues Work Group Continues to Meet Quarterly go to Work Groups, then E. coli Work Group

7 Regulatory Background EPA 1986 Criteria 1972 studies to update US Public Health Service studies from1940s/1950s Marine studies (Cabelli) at beaches: New York City, Boston and Lake Pontchartrain. Freshwater studies (Dufour) at beaches: Lake Erie, PA and Keystone Lake, Tulsa Contamination from effluents discharged from single point-sources. Does swimming in sewage-contaminated water carry a health risk for bathers; and, if so, what type of illness? Revised Criteria Expected 2012

8 Current Colorado E. Coli Numeric Standards (Attainment based on Two-Month Geometric Mean) CLASS E (Existing Primary Contact) and CLASS U (Undetermined Use) CLASS P (Potential Primary Contact Use) CLASS N (Not Primary Contact Use) (5 x Class E) 126/100 ml 205/100 ml 630/100 ml

9 What is Considered Primary Contact Recreation? Recreational activities where the ingestion of small quantities of water is likely to occur. Such activities include but are not limited to swimming, rafting, kayaking, tubing, windsurfing, water-skiing, and frequent water play by children.

10 Colorado Case Studies Varying characteristics Urban Agriculture Transitional urban-agriculture National Forest Varying degrees of recreational use Varying degrees of knowledge on sources White Paper Case Studies: South Platte Segment 14 Big Dry Creek Boulder Creek Fountain Creek Elkhead Creek

11 South Platte River Segment 14 First Colorado E. coli TMDL Metro Denver area w/primary contact TMDL: all sources assigned a load in form of 126/100 ml limit Dry Weather MS4 discharges: significant & controllable source of E. coli. Endpoint: attainment of 126/100 ml standard Iterative Implementation Process: 1) control dry weather discharges from MS4s, 2) reevaluate Source: Jon Novick, City and County of Denver

12 Box and Whiskers Plots Showing Annual Changes in E. coli, Segment 14, South Platte River

13 Big Dry Creek Open Space in Westminster, CO

14 Big Dry Creek E. Coli Seasonal Trend Big Dry Creek has a potential primary contact standard = 205/100 ml

15 EPA (2007) High Priority Model Research Processes Affecting Fate and Transport

16 Dry Weather Screening at MS4 Outfalls

17 One Illicit Discharge Identified and Corrected

18

19 Non-point Source Agriculture Land used for cattle grazing Bdc6.0

20 USGS Fountain Creek Study (Stoeckel, Stelzer, Stogner & Mau 2010) USGS-led >$400,000 MST study Contrary to expectations, human sources were NOT indicated as the dominant sources of exceedances Human, cow, dog, cat, elk excluded as dominant sources Sheep, bear, horse probably not dominant sources Birds were the only tested source that matched the data pattern of a dominant source

21 EPA s Current Thinking for 2012 Update Source: Current Thinking On Development of New Criteria, Elizabeth Doyle OST, OW, USEPA, October 6, 2009, Chicago, IL

22 Stormwater BMP Performance Implications for MS4 Permits Implications for MS4 Permit Holders What do we know about structural BMP performance for bacteria? New Technical Memorandum (December 2010: Download from

23 BMP Database Findings Regarding Fecal Indicator Bacteria Most BMP studies report fecal indicator bacteria, not pathogens. Most BMP studies have historically reported fecal coliform; recent studies report E. coli and enterococcus (the currently applicable EPA-recommended criteria). Additional bacteria data have been added to BMP Database since 2010 analysis was completed. Indicator Type Enterococcus E. coli Fecal Coliform Fecal Strep Total Coliform Total Studies Dec Total Studies Jul

24 BR = Bioretention DB = Detention Basin GR = Green Roof GS = Grass Swale MF = Media Filter RP = Retention Pond WB = Wetland Basin

25 DB = Detention Basin GS = Grass Swale MD =Manufactured Device MF =Media Filter RP = Retention Pond

26 Overview of Exceedance Frequency Analysis for Fecal Coliform BMP Category (7-12 studies per category) Detention Basin Grass Swale Manufactured Device Media Filter Retention Pond Primary Contact Benchmark (Geometric Mean) 200 CFU/ 100 ml % Inflow Values Greater Than Threshold % Outflow Values Greater Than Threshold 83% 65% CI: 77% -90% CI: 57% -73% 85% 93% CI: 77% -94% CI: 87% -99% 98% 99% CI: 94% -100% CI: 97% -100% 74% 59% CI: 65% -83% CI: 49% -69% 61% 36% CI: 49% -74% CI: 24% -48% CI = Confidence Interval (95%)

27 What can be realistically controlled? WWTP discharges Illicit discharges/ connections to MS4 Domestic pets Pet waste ordinances Disposal cans Enforcement Agriculture (in some cases) Storm sewer maintenance?

28 Selected Slides from EPA s Current Thinking on Updated Ambient Water Quality Criteria For complete information go to: standards/criteria/health/recreation/index. cfm

29

30

31

32 Meeting Recreational Standards Conclusions Meeting existing EPA and Colorado criteria is extremely difficult - what is an attainable TMDL endpoint? There is not a one-size-fits-all solution. Ongoing research is needed, particularly with regard to natural sources and risks to humans. Sources of bacteria from human sewage should be corrected. Pet ordinances should be enforced and waste receptacles provided in public areas. Realistic solutions need to be developed that recognize natural sources in a variety of settings. Environmental factors affecting bacteria fate and transport must be considered in TMDLs.

33 Questions? Jim McCarthy City of Arvada, Jane Clary Wright Water Engineers,