UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8 1595 Wynkwp Street DENVER, CO 80202-1129 Phone 800-227-89'17 http:IEwww.epa.gwlregion08
RECEIVED1 -
SEP 2 2 2QlO
flATER QUALITY COb!T!TROL DlVlSDN
SEP 2 0 2010 Ref: LEPR-EP Mr. Steve Gunderson Director Water Quality Control Division Colorado Department of Public Health and Environment 4300 Cherry Creek Drive South Denver, Colorado 80246- 1530
Re: ~ ~ ~ r o v ~ l s Geneva, reek for Cadmium, Copper, Mnganese
I We have completed our review of the total maximum daily loads (TMDLs) as submitted by your office an Sept 8,201 0 for the waterbody listed in the enclosure to this letter. In accordance with the Clean vater Act (33 U.S.C. 125 1 et. seq.), we approve all aspects of TMDLs as developed for certain pollutants in water quality limited waterbodies as describd in Section 303(d)(l). Based on our review, we feel the separate TMDL elements for the pollutants listed in the enclosed table are adequately addressed, taking into consideration seasonal variation and a margin of dety.
Thank you for submitting these TMDLs for our review and approval. If you have any questions, the most knowledgeable person on my staff is Julie Kinsey and she may be reached at (303) 3 12-7065.
Sincerely,
Carol L. Campbell Assistant Regional Administrator Office of Ecosystems Protection and Remediation
TOTAL MAXIMUM DAILY LOAD ASSESSMENT Geneva Creek Segments COSPUS05a and COSPUS05b Park County, Colorado August 2010
FINAL
TMDL SUMMARY
Waterbody Name/Segment Number
Mainstem of Geneva Creek from the source to the confluence with Scott Gomer Creek / COSPUS05a; Mainstem of Geneva Creek from the confluence with Scott Gomer Creek to the confluence with the North Fork of the South Platte River; all tributaries of Geneva Creek including lakes, reservoirs and wetlands from source to confluence with the North Fork of the South Platte River / COSPUS05b
Pollutant/Condition Addressed
Cd, Cu, Mn, Zn
Affected Portion of Segment
Use Classification/Waterbody Designation Waterbody Antidegradation Designation
Water Quality Target
TMDL Goal
Mainstem of Geneva Creek from the source to the confluence with Scott Gomer Creek; Cd, Cu, Mn, Zn/ Mainstem of Geneva Creek from the confluence with Scott Gomer Creek to the confluence with the North Fork of the South Platte River; all tributaries of Geneva Creek including lakes, reservoirs and wetlands from source to confluence with the North Fork of the South Platte River; Cd. COSPUS05a: Aquatic Life Cold 1, Recreation E, Agriculture; COSPUS05b: Aquatic Life Cold 1, Recreation E, Water Supply and Agriculture reviewable Attainment of site-specific chronic cadmium, copper, manganese, and zinc standards for Segment 5a; Attainment of acute and chronic table value standards for cadmium in Segment 5b. Attainment of site-specific chronic cadmium, copper, mamnganese, and zinc standards for Segment 5a; Attainment of acute and chronic table value standards for cadmium in Segment 5b.
EXECUTIVE SUMMARY Geneva Creek, Segments COSPUS05a and COSPUS05b, were recently added to the 2010 303(d) list as water-quality impaired for dissolved cadmium, as approved by the Colorado Water Quality Control Commission. The adoption of a more stringent aquatic life use-based cadmium standard at the South Platte Rulemaking Hearing in June of 2009 resulted in the assessment of nonattainment of chronic and acute dissolved cadmium standards for Upper South Platte Segment 5b. Segment COSPUS05a of Geneva Creek was also included on the 2010 303(d) list for nonattainment of its site-specific total recoverable cadmium standard and chronic dissolved copper and zinc standards. Through the course of TMDL development, Segment COSPUS05a was also found to be in non-attainment of its chronic dissolved manganese standard. There are no readily FINAL August 2010
2
apparent point source discharges of pollutants, either permitted or un-permitted, to this segment. This TMDL derives load allocations for dissolved cadmium, copper, manganese and zinc and total recoverable cadmium in order to demonstrate the load reductions necessary to attain the currently adopted standards. 1.0 INTRODUCTION Section 303(d) of the federal Clean Water Act requires states to identify water bodies that are water quality impaired. Water quality impaired segments are those water bodies or stream segments that are not fully attaining one or more assigned use classifications or standards. These segments are currently identified on the Colorado 2010 303(d) List. Once listed, the State is required to quantify the amount of a specific pollutant that a listed water body can assimilate without exceeding applicable water quality standards. This maximum allowable pollutant quantity is referred to as the Total Maximum Daily Load ("TMDL"). The TMDL is comprised of the Load Allocation ("LA"), which is that portion of the pollutant load attributed to natural background or non-point sources, the Waste Load Allocation ("WLA"), which is that portion of the pollutant load associated with point source discharges, and a Margin of Safety ("MOS"). The TMDL may also include an allocation reserved to accommodate future growth. The TMDL may be expressed as the sum of the LA, WLA, and MOS. Alternatively, a segment or pollutant may be removed from the list if the applicable standard is attained, if implementation of clean up activities via an alternate means will result in attainment of standards, if the original listing decision is shown to be in error, or if the standards have been changed as the result of a Use Attainability Analysis (“UAA”) or other EPA approved recalculation method. 1.1 Segment Description Geneva Creek rises in Geneva Basin near the Continental Divide in Clear Creek County and flows southeasterly through Park County towards its confluence with the North Fork South Platte River at Grant, Colorado. Geneva Creek has been split into two segments for regulatory purposes. The upper segment (Upper South Platte segment 5a) is from the source of Geneva Creek to the confluence with Scott Gomer Creek, and is roughly 9 miles in length. The lower segment (Upper South Platte segment 5b) is from Scott Gomer Creek to the confluence with the North Fork of the South Platte River, and is roughly 4 miles in length. The upper portion of Geneva Creek, Segment 5a, has been identified as exceeding its total recoverable cadmium, dissolved copper, manganese, and zinc standards. In addition to exceedances in the upper reach, the lower portion, Segment 5b, is impaired relative to instream concentrations of dissolved cadmium. A map of the Geneva Creek watershed is located in Appendix A. The Geneva Creek watershed lies within hydrothermally altered terrain associated with the Montezuma Stock. The Montezuma Stock and associated hydrothermal ore deposits were heavily mined on the western side of the Continental Divide in the Snake River and Peru Creek drainages. Mining on the eastern side of the Continental Divide in areas dominated by Montezuma Stock alteration appears to be minimal (CGS 2000). FINAL August 2010
3
The majority of the Geneva Creek Basin is owned by the U.S. Forest Service as part of the Pike National Forest; therefore it is unlikely that any new discharges will occur in the next twenty years. The Iron Fen area, which is located in the headwaters of Geneva Creek (segment COSPUS05a) and discussed in Section 4.0, is owned by Clear Creek County and is registered as a Colorado State Natural Area with the Department of Natural Resources. There are currently no Colorado Discharge Permit System (CDPS) or National Permit Discharge Elimination System (NPDES) permits that discharge to Geneva Creek or its tributaries. 2.0 WATER QUALITY STANDARDS Waterbodies in Colorado are divided into discrete units or “segments”. The Colorado Basic Standards and Methodologies for Surface Water, Regulation 31, (WQCC 2008a) discusses segmentation of waterbodies in terms of several broad considerations: 31.6(4)(b)…Segments may constitute a specified stretch of a river mainstem, a specific tributary, a specific lake or reservoir, or a generally defined grouping of waters within the basin (e.g., a specific mainstem segment and all tributaries flowing into that mainstem segment. (c) Segments shall generally be delineated according to the points at which the use, physical characteristics or water quality characteristics of a watercourse are determined to change significantly enough to require a change in use classifications and/or water quality standards As noted in paragraph 31.6(4)(c), the use or uses of surface waters are an important consideration with respect to segmentation. In Colorado there are four categories of beneficial use which are recognized. These include Aquatic Life Use, Recreational Use, Agricultural Use and Water Supply Use. A segment may be designated for any or all of these “Use Classifications”: 31.6 Waters shall be classified for the present beneficial uses of the water, or the beneficial uses that may be reasonably expected in the future for which the water is suitable in its present condition or the beneficial uses for which it is to become suitable as a goal. Each assigned use is associated with a series of pollutant specific numeric standards. These pollutants may vary and are relevant to a given Classified Use. Numeric pollutant criteria are identified in sections 31.11 and 31.16 of the Basic Standards and Methodologies for Surface Water. 2.1 Uses and Standards Addressed in this TMDL The uses and numeric standards assigned for Geneva Creek from its source to the confluence with the North Fork of the South Platte River, Segments COSPUS05a and COSPUS05b, are identified in the Classifications and Numeric Standards South Platte River Basin, Laramie River FINAL August 2010
4
Basin, Republican River Basin, Smoky Hill River Basin, Regulation No. 38 (WQCC 2009). Segment 5a has been classified for Aquatic Life Use (Cold 1), Water Supply Use, and Recreation Use (E). This segment is currently in non-attainment of Aquatic Life Use-based cadmium, copper, manganese, and zinc standards. Segment 5b has been classified for Aquatic Life Use (Cold 1), Water Supply Use, Agriculture Use and Recreation Use (E). This segment is currently in non-attainment of Aquatic Life Use-based cadmium standards. Assigned standards associated with other Use designations are either attained and such uses fully supported or a TMDL has been finalized and approved. Table 1 identifies all of the assigned numeric standards for segment COSPUS05a and COSPUS05b. Date (Cycle Year) of Current Approved 303(d) list: 2010 Designated Uses & Impairment WBID Segment Description Status Mainstem of Geneva Creek from the source to the confluence with Scott Gomer Creek
Aquatic Life Cold 1: Impaired Recreation E: Not Impaired Water Supply: Not Impaired
Mainstem of Geneva Creek from the confluence with Scott Gomer COSPUS05b Creek to the confluence with the North Fork of the South Platte River.
Aquatic Life Cold 1: Impaired Recreation E: Not Impaired Water Supply: Not Impaired Agriculture: Not Impaired
COSPUS05a
Table 1. Designated uses and impairment status for Segments 5a and 5b, mainstem of Geneva Creek from its source to the confluence with the North Fork of the South Platte River.
Those standards identified as “TVS” are Table Value Standards. These standards vary with the instream hardness and are Aquatic Life Use-based. The Table Value Standards for cadmium are defined as: Acute (trout) = (1.136672 – [(ln hardness)*(0.041838)] *e(0.9151[ln(hardness)]-3.6236) Chronic = (1.101672 – [(ln hardness)*(0.041838)] *e(0.7998[ln(hardness)]-4.4451) The site-specific standard for total recoverable cadmium for Segment 5a is defined as chronic = 2 g/L. Chronic site-specific dissolved metal standards for Segment 5a are: Cu = 18 g/L; Mn = 530; and Zn = 190 g/L. No acute standards for cadmium, copper, manganese, or zinc have been identified in Segment 5a. Chronic and acute standards are designed to protect against different ecological effects of pollutants (long term exposure to relatively lower pollutant concentrations vs. short term exposure to relatively higher pollutant concentrations). Chronic standards represent the level of pollutants that protect 95 percent of the genera from chronic toxic effects of metals. Chronic standards were therefore used in the Geneva Creek TMDL since they represent a more conservative approach than the acute standards, and moreover, Segment 5a retains only chronic standards for cadmium, copper, manganese, and zinc. By reducing metals concentrations to attain the chronic standards, acute standards will also be attained in Segment 5b. Per Regulation 31, chronic toxic effects include but are not limited to demonstrable abnormalities and adverse effects on survival, growth, or reproduction (WQCC 2009b). FINAL August 2010
5
Segments 5a and 5b are currently in non-attainment of Aquatic Life Use-based cadmium standards. Additionally, Segment 5a is also in non-attainment of Aquatic Life Use-based copper, manganese, and zinc standards. Assigned standards associated with other Use designations are attained and such uses fully supported. Table 2 identifies all of the assigned numeric standards for Segments COSPUS05a and COSPUS05b. An analysis of cadmium, copper, manganese, and zinc loading are included in the TMDL document for Geneva Creek, Segment 5a and an analysis of cadmium loading is included for Segment 5b. Table 2. Water Quality Standards for Upper South Platte River segment 5b (COSPUS05b). Stream Segment Description
Classification
Physical and Biological
Metals1 ug/l
Inorganics mg/l
5a. Mainstem of Geneva Creek from the Aq Life Cold 1 source to the confluence with Scott Recreation E Gomer Creek. Agriculture
T=TVS(CS-I) oC NH3(ac/ch)=TVS D.O.=6.0 mg/l Cl2(ac)=0.019 D.O.(sp)=7.0 mg/l Cl2(ch)=0.011 pH = 3.5-9.0 CN=0.005 E coli=126/100ml S=0.002 B=0.75 NO2=0.05 NO3=100
As(ac)=340 As(ch)=7.6(Trec) Cd(ch)=2 CrIII(ch)=100 CrVI(ch)=25 Cu(ch)=18(dis)
5b. Mainstem of Geneva Creek from the Agriculture confluence with Scott Gomer Creek to Aq Life Cold 1 the confluence with the North Fork of the Recreation E South Platte River; all tributaries of Water Supply Geneva Creek including lakes, reservoirs and wetlands from source to confluence with the North Fork of the South Platte River.
T=TVS(CS-I) oC B=0.75 D.O. = 6.0 mg/l Cl=250 D.O. (sp)=7.0mg/l Cl2(ac)=0.019 pH = 6.5-9.0 Cl2(ch)=0.011 E.Coli=126/100ml CN=0.005 NH3(ac)=TVS NH3(ch)=0.02 NO2=0.05 NO3=10 S=0.002 SO4=WS
Ag(ac)=TVS Hg(ch)=0.01(Tot) Ag(chtr)=TVS Mn(ac)=TVS As(ch)=100(Trec) Mn(ch)=WS(Dis) Cd(actr)=TVS Mn(ch)=TVS Cd(ch)=TVS Ni(ac)=TVS CrIII(ac)=TVS Ni(ch)=TVS CrIII(ch)=TVS Pb(ac)=TVS CrVI(ac)=TVS Pb(ch)=TVS CrVI(ch)=TVS Se(ac)=TVS Cu(ac)=TVS Se(ch)=TVS Cu(ch)=TVS Zn(ac)=TVS Fe(ch)=WS(Dis) Zn(ch)=TVS Fe(ch)=1000(Trec)
1.
“All metals expressed as Trec unless otherwise noted.”
Fe(ch)=1200 Pb(ch)=4 Mn(ch)=530(dis) Hg(ch)=0.05 Ni(ch)=50 Se(ch)=4.6 Ag(ch)=1 Zn(ch)=190(dis)
Table 2. Water Quality Standards for Upper South Platte River Segments 5a and 5b (COSPUS05a and COSPUS05b). Water Quality Criteria for Impaired Designated Uses WBID Impaired Designated Use Applicable Water Quality Criteria and Status Total recoverable Cd (1, 2) / Not Attained Dissolved Phase Cu (1, 2) / Not Attained COSPUS05a Aquatic Life Cold 1 Dissolved Phase Mn (1, 2) / Not Attained Dissolved Phase Zn (1, 2) / Not Attained COSPUS05b Aquatic Life Cold 1
Dissolved Phase Cd (1, 2) / Not Attained
Applicable State or Federal Regulations: (1) Classifications and Numeric Standards for the South Platte River Basin, Republican River Basin, and Smoky Hill River Basin (2) The Basic Standards and Methodologies for Surface Water Table 3. Ambient water quality criteria and status for Segments 5a and 5b, mainstem of Geneva Creek from its source to the confluence with the North Fork of the South Platte River.
FINAL August 2010
6
Currently, there are no acute metal standards adopted for Segment 5a (with the exception of arsenic). On Segment 5b, acute cadmium standards were exceeded on four sampling dates at the sampling site Geneva Creek at Mouth (fourteen percent) of the samples ranging from 1999 through 2007. Acute exceedances below Scott Gomer Creek occur in approximately twentyseven percent of the samples ranging from 2005 through 2007 (three of the eleven sampling dates with corresponding hardness) at the sampling sites Geneva Creek below Scott Gomer Creek and Geneva Creek at Picnic Ground. 2.1.1 Listing History Upper South Platte segment 5a, defined as Geneva Creek from its source to the confluence with Scott Gomer Creek, was initially included on the 1993 303(d) list as partially supporting its aquatic life use-based standards. Ambient metal standards were adopted in the 1990s, and no further listings have been identified until 2010. Upper South Platte segment 5b is defined as the portion of Geneva Creek from the confluence with Scott Gomer Creek to the confluence with the North Fork South Platte River was initially included on the 1998 Section 303(d) List due to non-attainment of Aquatic Life Use-based zinc standards. Copper was subsequently added to the listing in 2002 and was retained until additional water quality monitoring demonstrated attainment of copper standards and copper was removed from the listing in 2008 (WQCC 2008c). Zinc was retained, and a TMDL was completed in 2008. Cadmium was added to the list in 2010. The 1998 and subsequent 303(d) lists rated the segment as a “High” priority for TMDL development. However, the Division had not acted on this listing until 2005 because no significant anthropogenic point sources had been identified in the watershed that could be addressed through regulatory mechanisms (i.e. National Pollutant Discharge Elimination System or Colorado Discharge Permit System permits). The previous TMDL document for COSPUS05b included a TMDL analysis addressing copper as well as zinc. 2.2 PROBLEM IDENTIFICATION Segment 5a cadmium standards are expressed as the total recoverable fraction, and they are assessed as 50th percentile concentrations. Assessment of cadmium in Segment 5a, indicates 50th percentile instream cadmium concentrations of approximately 2.15 g/l which exceeds the chronic cadmium standard of 2.0 g/l. An 85th percentile dissolved copper value of 44.9 g/l exceeds the chronic standard of 18.0 g/l, while an 85th% dissolved manganese concentration of 1118 g/l exceeds the chronic manganese standard of 530 g/l, and an 85th% dissolved zinc concentration of 426 g/l exceeds the chronic zinc standard of 190 g/l. In the case of Segment 5b, Aquatic Life Use-based cadmium standards are expressed as the dissolved fraction. Attainment of chronic dissolved metal standards is determined by comparison of the 85th percentile value of the ranked data against the standard (see Section 303(d) Listing Methodology – 2010 Listing Cycle, WQCC 2009). For this assessment the standard is calculated using the mean hardness value. This TMDL utilizes a dataset comprised of 29 results for sampling performed from March 1999 through September 2007. The 85th FINAL August 2010
7
percentile dissolved cadmium value of 0.48 g/l exceeds the chronic standard of 0.18 g/l based upon a mean hardness value of 31 mg/l (as calcium carbonate). Attainment of acute standards is assessed by comparison of the sample result against the acute standard as calculated using the sample-specific hardness value. Acute cadmium trout standards are exceeded for 4 of the 29 samples which comprise the entire dataset, with two of the most recent samples collected in 2007 exceeding the acute cadmium standard. 2.1 Water Quality Goals and Targets The water quality target and goal for this TMDL is attainment of the Aquatic Life Use-based site-specific total recoverable cadmium, dissolved copper, dissolved manganese, and dissolved zinc standards in Segment 5a and attainment of the current Aquatic Life Use-based table value dissolved cadmium standard in Segment 5b. 2.2 Hydrology Geneva Creek expresses the hydrologic characteristics of a high-altitude, snowmelt-dominated stream, with peak runoff occurring in June. The U.S. Geological Survey operated a hydrologic gage on Geneva Creek near the town of Grant from water-years 1994 through 1997. The drainage area at the USGS gage for Geneva Creek is 74.6 square miles, and the gage is located at 8,760 feet above sea level. Monthly flow information from a hydrologic gage on the North Fork South Platte River minus monthly flows from the operation of the Roberts Tunnel diversion was correlated with flows from Geneva Creek during the years 1994 through 1997 (R2 = 0.94) using Equation 1. Flow values were predicted for the more recent period of record in order to correspond to the sample data. Table 4 and Figure 1 illustrate the annual hydrologic characteristics of Geneva Creek from the period 1995 through 2007. Eq. 1. Geneva Creek flows = (0.000005*(NFSP Flow2)) + (0.2333 * NFSP Flow) – 243.57 Table 4: Annual hydrologic characteristics of Geneva Creek at Grant, CO (USGS gage #06705500), POR = 1994-1997. Estimated flow values from 1998 – 2007. Month 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
25th % Flow (cfs) 368 511 408 63 728 559 1127 590 780 468 359 190 242
5th % Flow (cfs) 272 371 214 17 314 329 761 383 358 364 252 62 102
95th % Flow (cfs) 10548 5480 6643 4633 5629 5277 4238 3102 3864 2230 2700 5783 5431
75th % Flow (cfs) 1954 1660 3062 1498 3190 2931 2487 2157 2578 1293 1178 2112 3051
Median Flow (cfs) 780 697 855 339 1336 755 1653 913 1026 1039 541 717 454
Median Daily Flow, cfs 13 13 17 20 90 191 112 73 30 23 15 15 13
Table 4: Hydrologic characteristics of Geneva Creek at Grant, CO (USGS gage #06705500). FINAL August 2010
8
Geneva Creek at Mouth Annual Flow, cfs 100000 10000 1000 100 10
1 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Figure 1. Annual flows in cubic feet per second for Geneva Creek at Mouth for the period of record 1995 through 2007. Due to the limited data set, and the importance of evaluating both high flow and low flow as possible critical conditions, ambient conditions and loads were characterized on a seasonal flow basis (High flow: May-June and Low flow: July-April) in the TMDL. 2.3 Ambient Water Quality
Segment 5a 5b 5b 5b
Period of Record 2005-2007 1999-2007 2005-2007 2005-2007
N hardness samples 7 29 6 7
No. metal samples 7 29 6 7
Sample Location Geneva Creek above Bruno Gulch Geneva Creek at Mouth Geneva Creek below Scott Gomer Crk Geneva Creek at Picnic Ground
Source River Watch WQCD WQCD WQCD
Table 5. Sources of water quality data for Geneva Creek Segments 5a and 5b. 2.3.1 Segment 5a Cadmium River Watch took 7 water quality samples in Geneva Creek above Bruno Gulch between February 2005 and June 2007 (Table 5). Table 6 illustrates the hardness, total recoverable cadmium concentrations in Geneva Creek, and the chronic cadmium standard. Of the seven samples, three samples demonstrated an exceedance of the chronic standard. Since total recoverable standards are assessed as fiftieth percentile values, Segment 5a remains in nonattainment of its chronic cadmium standard with an annual ambient concentration of 2.15 g/l (Table 6). Annnual reductions of 7% are required in Segment 5a in order to attain chronic cadmium standards. However, if instream concentrations are separated on a seasonal flow basis, both flow seasons attain their chronic cadmium standard. There are no acute cadmium standards for Geneva Creek Segment 5a. FINAL August 2010
9
High Flow (May-June) Low Flow (July-April) Annual
Hardness 43 56 51
Cd-Trec, ug/L 0.97 1.47 2.15
Cd, Std. (ch) 2.0 2.0 2.0
% Reduction (T-rec) 0% 0% 7%
Table 6: Annual total recoverable cadmium concentrations in Geneva Creek Segment 5a with the correlating standard also high and low flow periods. Concentrations are expressed in micrograms per liter. Total recoverable concentrations are expressed as 50th percentiles. Exceedances are shown in bold. 2.3.2 Segment 5a Copper Table 7 illustrates the hardness, dissolved copper concentrations in Geneva Creek, and the chronic copper standard of 18.0 g/l (Table 7). Similar to cadmium, three of the seven samples demonstrated an exceedance of the chronic standard. Since dissolved standards are assessed as eighty-fifth percentile values, Segment 5a remains in non-attainment of its chronic copper standard with an annual ambient concentration of 44.9 g/l (Table 7). Annual reductions of 60% are required in Segment 5a in order to attain chronic copper standards. Furthermore, if instream concentrations are separated on a seasonal flow basis, the low flow season of July through April does not attain its chronic copper standard with a resulting 61% reduction in concentrations. High flow months of May and June provide enough dilution flow for instream concentrations to attain chronic copper standards. There are no acute copper standards for Geneva Creek Segment 5a.
High Flow (May-June) Low Flow (July-April) Annual
Hardness 43 56 51
Cu-D, ug/L 13.8 46.5 44.9
Cu, Std (ch) 18.0 18.0 18.0
% Reduction 0% 61% 60%
Table 7: Annual dissolved copper concentrations in Geneva Creek Segment 5a with the correlating standard also high and low flow periods. Concentrations are expressed in micrograms per liter. Dissolved concentrations are expressed as 85th percentiles. Exceedances are shown in bold. 2.3.3 Segment 5a Manganese Table 8 illustrates the hardness, dissolved manganese concentrations in Geneva Creek, and the chronic manganese standard of 530 g/l (Table 8). Four of the seven samples demonstrated an exceedance of the chronic standard. Since dissolved standards are assessed as eighty-fifth percentile values, Segment 5a remains in non-attainment of its chronic manganese standard with an annual ambient concentration of 1118 g/l (Table 8). Annual reductions of 53% are required in Segment 5a in order to attain chronic manganese standards. Furthermore, if instream concentrations are separated on a seasonal flow basis, the low flow season of July through April FINAL August 2010
10
does not attain its chronic manganese standard (53% reduction). High flow months of May and June provide enough dilution flow for instream concentrations to attain its chronic manganese standard. There are also no acute manganese standards for Geneva Creek Segment 5a.
High Flow (May-June) Low Flow (July-April) Annual
Hardness 43 56 51
Mn-D, ug/L 475 1121 1118
Mn, Std (ch) 530 530 530
% Reduction 0% 53% 53%
Table 8: Annual dissolved manganese concentrations in Geneva Creek Segment 5a with the correlating standard also high and low flow periods. Concentrations are expressed in micrograms per liter. Dissolved concentrations are expressed as 85th percentiles. Exceedances are shown in bold. 2.3.4 Segment 5a Zinc Table 9 illustrates the hardness, dissolved zinc concentrations in Geneva Creek, and the chronic zinc standard of 190 g/l (Table 9). Similar to manganese, four of the seven samples demonstrated an exceedance of the chronic standard. Since dissolved standards are assessed as eighty-fifth percentile values, Segment 5a remains in non-attainment of its chronic zinc standard with an annual ambient concentration of 426 g/l (Table 9). Annual reductions of 55% are required in Segment 5a in order to attain chronic zinc standards. In addition, if instream concentrations are separated on a seasonal flow basis, the low flow season of July through April does not attain its chronic zinc standard (56% reduction). High flow months of May and June provide enough dilution flow for instream concentrations to attain its chronic zinc standard. There are also no acute zinc standards for Geneva Creek Segment 5a.
High Flow (May-June) Low Flow (July-April) Annual
Hardness 43 56 51
Zn-D, ug/L 171 432 426
Zn, Std (ch) 190 190 190
% Reduction 0% 56% 55%
Table 9: Annual dissolved zinc concentrations in Geneva Creek Segment 5a with the correlating standard also high and low flow periods. Concentrations are expressed in micrograms per liter. Dissolved concentrations are expressed as 85th percentiles. Exceedances are shown in bold. 2.3.5 Segment 5b Cadmium The Water Quality Control Division took 29 water quality samples in Geneva Creek at the mouth between March 1999 and September 2007 (Table 5). Of those 29 samples, only 7 were above the detection limit with four samples exceeding both the acute and chronic cadmium standards (Table 10). Based upon the Section 303(d) Listing Methodology – 2010 Listing Cycle, Geneva Creek is considered impaired with respect to the assigned cadmium standards.
FINAL August 2010
11
January February* March April May June July August September October November December
Average hardness, mg/L 32 35 38 36 25 35 25 21 29 31 32 32
Cd-DTable Value Standards, g/L 0.18 0.19 0.20 0.20 0.15 0.19 0.15 0.13 0.17 0.18 0.18 0.18
85th% CdDconcentrations, g/L 0.43 0.74 1.05 0.91 0.00 0.00 0.51 0.00 0.33 0.28 0.34 0.26
% Reductions 58% 74% 81% 78% 0% 0% 71% 0% 48% 36% 47% 29%
Table 10: Monthly dissolved cadmium concentrations in Geneva Creek Segment 5b with the corresponding standard. Exceedances are shown in bold.
Geneva Creek at Mouth 1.60
Dissolved cadmium, ug/L
1.40 1.20 1.00 0.80
0.60 0.40 0.20 0.00 Jan
Feb
Mar
Apr May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Figure 2. Box and whisker plot for dissolved cadmium for Geneva Creek Segment 5b. Boxes represent upper and lower quartiles (25th and 75th) while whiskers represent 5th and 95th percentiles. Red bars indicate median values. 2.4 Source Analysis 2.4.1 Point Sources There are no NPDES or CDPS permitted point source discharges in the Geneva Creek Basin. The majority of the Geneva Creek Basin is owned by the U.S. Forest Service as part of the Pike National Forest; therefore it is unlikely that any new discharges will occur in the next twenty FINAL August 2010
12
years. Topographical maps from the USGS show numerous mining features in the basin at high elevation. Division staff attempted to sample legacy mining features present in the upper Geneva Creek basin in the summer of 2005 and again in the summer of 2010. No discharges, either from draining adits or mine wastes affecting surface drainages, were observed in 2005. Subsequently the Division conducted synoptic sampling of Geneva Creek in May of 2007. Sampling performed above the Scott Gomer Creek confluence indicate some metals loading occurs upstream of this point. Due to closure of Guanella Pass Road for rock slide mitigation and maintenance in the summer of 2010, Division staff were unable to document any legacy mining features. If discharges from legacy mining features were to be identified in Segment 5a in the future, the TMDL document would be reopened for the reassessment of current load allocations. 2.4.2 Non-Point and Natural Sources The headwaters of Geneva Creek are in hydrothermally altered geologic terrain associated with the Montezuma Stock. This type of geologic terrain produces acid rock drainage, which is the naturally occurring degradation of waters by the contact of water with oxidizing sulfide minerals. The most significant natural geochemical feature in the Geneva Creek Basin is the Geneva Creek Iron Fen. An Iron Fen is a unique wetland feature where acidic metal laden groundwater comes to the surface and produces a reddish substrate of precipitated iron minerals on the bed of the wetland. Due to its ecological significance, the property surrounding the Geneva Creek Iron Fen (approximately 100 acres) was purchased by the Clear Creek County Open Space Commission. The Iron Fen is situated in and gives rise to the headwaters of Geneva Creek. More information about the Geneva Creek Iron Fen can be found at the Clear Creek County Open Space Commission’s website (http://www.co.clear-creek.co.us/oswebsite/GenevaCreek.htm). A fen is an area of peat-forming wetlands that receives nutrients usually from upslope mineral soils and groundwater movement. It is typically alkaline due to ground water draining from surrounding calcareous rocks. Fens are different from bogs because bogs are acidic, not alkaline. Most fens have high pH's and have a high mineral content. Furthermore, bogs are rain fed and exist on the Canadian shield (Minnesota, Michigan, Maine, etc.), while fens are fed by ground water. The Geneva Creek Iron Fens are registered as a Colorado State Natural Area. One of eight iron fens in the state, it is an example of both a rare community type and an unusual geologic process. Iron fens are a phenomenon unique to Colorado. There are eight iron fens documented in Colorado, and no other known occurrences in the world. The iron fens, due to the iron substrate, are very low in pH (acid) and are high in minerals. The geologic process forming the iron fen begins with a series of springs flowing over highly fractured, highly mineralized bedrock rich in pyrites producing extremely acidic (pH3), mineral-rich water. This process produces limonite (iron saturated peat) ledges and terraces. The Clear Creek County Open Space Commission acquired management of the Geneva Creek Iron Fen in the spring of 2003. Much of the iron fen is located on two parcels that were former FINAL August 2010
13
mining claims deeded back to the county for open space. After successfully lobbying to have the area preserved, the Geneva Creek Iron Fen was identified as, and adopted into the Colorado Natural Areas Program with Colorado State Parks. Sites qualify as Colorado Natural Areas when they contain at least one unique or high-quality feature of statewide significance. Not only is the Geneva Creek Iron Fen considered one of the best examples of an iron fen in the state, but it also contains Colorado's only known occurrence of Girgensohn sphagnum moss.
Figure 3. Photo of Geneva Creek iron fen attributes. Synoptic sampling performed by the Division documents exceedances of acute and chronic cadmium standards within Geneva Creek below the iron fen. 3.0 TMDL ALLOCATION Total Maximum Daily Loads ("TMDL") A TMDL is comprised of the Load Allocation ("LA"), which is that portion of the pollutant load attributed to natural background or the non-point sources, the Waste Load Allocation ("WLA"), which is that portion of the pollutant load associated with point source discharges, and a Margin of Safety ("MOS"). The TMDL may also include an allocation reserved to accommodate future growth. The TMDL may be expressed as the sum of the LA, WLA and MOS. TMDL = WLA + LA + MOS FINAL August 2010
14
TMDL = Sum of Waste Load Allocations + Sum of Load Allocations + Margin of Safety 3.1 Waste Load Allocations "(WLA") There are no identified waste load allocations for this TMDL. While legacy mining features are present in the upper basin, no discharge associated with these features has been documented. 3.2 Load Allocations ("LA") All other sources that were examined are considered non-point sources (i.e. the Geneva Creek Iron Fen as well as naturally occurring hydrothermally altered terrain) and therefore are accountable to load allocations. All load reductions are required from non-point sources. 3.3 Margin of Safety ("MOS") The MOS used in the TMDL analysis is an explicit ten percent margin of safety. Conservative assumptions used in the analysis include the use of the 85th percentile of the data in establishing ambient conditions, per the 303(d) Assessment Methodology. Mean monthly hardness was also used in the calculation of hardness based TVS. The TMDL equation becomes the following: TMDL = Sum of Load Allocations (LA) LA (lbs/day) = Water Quality Standard, TVS (ug/l) x Flow (cfs) x 0.0054
3.4 TMDL for total recoverable cadmium for Segment 5a A TMDL was calculated for Segment 5a for total recoverable cadmium, with an explicit ten percent margin of safety. Cadmium concentrations were assessed as 50th% values. There are no acute cadmium standards on Segment 5a. Table 11 documents the cadmium TMDL for Geneva Creek Segment 5a. When concentrations are separated on a flow basis, no reductions are necessary to attain cadmium standards. When loads are expressed on an annual basis, a 10% reduction is required in order to attain chronic cadmium standards (Table 11).
Hardness
Cd Std. (ch)
Cd TMDL lbs/day
10% MOS
Cd TMDL with a 10% MOS, lbs/day
226
43
2.0
2.44
0.24
2.20
0.97
1.18
0.0
0%
Low Flow (July-April)
20
56
2.0
0.22
0.02
0.20
1.47
0.16
0.0
0%
Annual
24
51
2.0
0.28
0.03
0.25
2.15
0.28
0.03
10%
Median flow, cfs High Flow (MayJune)
FINAL August 2010
15
CdTrec, ug/L
Current Cd Load (50 th%), lbs/day
Load Reduction (lbs)
% Reduction
Table 11: Total Maximum Daily Load for total recoverable cadmium for Geneva Creek Segment 5a with a 10% Margin of Safety. 3.5 TMDL for dissolved copper for Segment 5a A TMDL was calculated for Segment 5a for dissolved copper, with an explicit ten percent margin of safety. Copper concentrations were assessed as 85th% values. There are no acute copper standards on Segment 5a. Table 12 documents the copper TMDL for Geneva Creek Segment 5a. When concentrations are separated on a flow basis, no reductions are necessary during months of high flow (May and June) to attain chronic copper standards. During periods of lower flow (i.e. July through April), a 65% reduction in the dissolved copper load is required in order to attain chronic copper standards. When loads are expressed on an annual basis, a 64% reduction is required in order to attain chronic copper standards (Table 12).
Hardness
Cu, Std (ch)
Cu TMDL lbs/day
10% MOS
Cu TMDL with a 10% MOS, lbs/day
226
43
18.0
21.97
2.20
Low Flow (July-April)
20
56
18.0
1.99
Annual
24
51
18.0
2.33
Median flow, cfs High Flow (MayJune)
Cu-D, ug/L
Current Cu Load (85th%), lbs/day
Load Reduction (lbs)
% Reduction
19.77
13.8
16.82
0.00
0%
0.20
1.79
46.5
5.13
3.34
65%
0.23
2.10
44.9
5.82
3.72
64%
Table 12: Total Maximum Daily Load for dissolved copper for Geneva Creek Segment 5a with a 10% Margin of Safety 3.6 TMDL for dissolved manganese for Segment 5a A TMDL was calculated for Segment 5a for dissolved manganese, with an explicit ten percent margin of safety. Manganese concentrations were assessed as 85th% values. In addition to cadmium and copper, there are no acute manganese standards on Segment 5a. Table 13 documents the manganese TMDL for Geneva Creek Segment 5a. When concentrations are separated on a flow basis, no reductions are necessary during months of high flow (May and June) to attain chronic manganese standards. During periods of lower flow (i.e. July through April), a 57% reduction in the dissolved manganese load is required in order to attain chronic manganese standards. Similarly, when loads are expressed on an annual basis, a 57% reduction is required in order to attain chronic manganese standards (Table 13).
High Flow (May-June)
FINAL August 2010
Median flow, cfs 226
Hardness
Mn, Std (ch)
Mn TMDL lbs/day
10% MOS
Mn TMDL with a 10% MOS, lbs/day
43
530
646.81
64.7
582.1
16
Mn-D, ug/L
Current Mn Load (85th%), lbs/day
Load Reduction (lbs)
% Reduction
475
580.29
0.00
0%
Low Flow (July-April)
20
56
530
58.46
5.8
52.6
1121
123.59
70.98
57%
Annual
24
51
530
68.69
6.9
61.8
1118
144.89
83.07
57%
Table 13: Total Maximum Daily Load for dissolved manganese for Geneva Creek Segment 5a with a 10% Margin of Safety 3.7 TMDL for dissolved zinc for Segment 5a A TMDL was calculated for Segment 5a for dissolved zinc, with an explicit ten percent margin of safety. Zinc concentrations were assessed as 85th% values. In addition to cadmium, copper, and manganese, there are no acute zinc standards on Segment 5a. Table 14 documents the zinc TMDL for Geneva Creek Segment 5a. Similar to copper and manganese, when concentrations are separated on a flow basis, no reductions are necessary during months of high flow (May and June) to attain chronic zinc standards. During periods of lower flow (i.e. July through April), a 60% reduction in the dissolved zinc load is required in order to attain chronic zinc standards. Similarly, when loads are expressed on an annual basis, a 60% reduction is required in order to attain chronic zinc standards (Table 14).
Hardness
Zn, Std (ch)
Zn TMDL lbs/day
10% MOS
Zn TMDL with a 10% MOS, lbs/day
226
43
190
231.88
23.2
Low Flow (July-April)
20
56
190
20.96
Annual
24
51
190
24.62
Median flow, cfs High Flow (May-June)
Zn-D, ug/L
Current Zn Load (85th%), lbs/day
Load Reduction (lbs)
% Reduction
208.7
171
208.52
0.00
0%
2.1
18.9
432
47.62
28.76
60%
2.5
22.2
426
55.21
33.05
60%
Table 14: Total Maximum Daily Load for dissolved zinc for Geneva Creek Segment 5a with a 10% Margin of Safety
3.8 TMDL for dissolved cadmium, Segment 5b For the dissolved cadmium TMDL, a 10 percent margin of safety was included in the TMDL. Table 15 lists the TMDL for Geneva Creek. The entire TMDL is expressed as a Load Allocation, meaning that all pollutant reduction necessary to attain standards would have to be accomplished through reductions of non-point source pollution. In order to attain chronic cadmium standards, Geneva Creek would require no reduction in cadmium loading in May, June, and August; while an 83 percent cadmium load reduction is required in March (Table 15). The largest loading reductions occur in months of low flow, i.e. January, February, or in the months leading up to spring runoff (rising limb of hydrograph), i.e. March, and April, with the exception of a 74% reduction required in July (Table 15). Comparison of individual sample values, when adjusted by the appropriate monthly loading reductions against the corresponding acute cadmium standards, indicates that acute cadmium standards would be achieved with chronic load reductions. State assessment protocol, as defined FINAL August 2010
17
in the Section 303(d) Listing Methodology – 2010 Listing Cycle, requires individual sample results not to exceed the corresponding acute standard at a frequency greater than one exceedance within a three year period. A single exceedance within the period of record assessed would be considered to demonstrate attainment of the acute standard, however if chronic load reductions were achieved, it would result in attainment of acute standards. The calculated load reductions are therefore protective of both acute and chronic cadmium standards.
Month Jan Feb* Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Median Flow 13 13 17 20 90 191 112 73 30 23 15 15
Hardness, CaCO3, mg/l 32 35 38 36 25 35 25 21 29 31 32 32
Cd TVS Std ug/l 0.18 0.19
0.20 0.20 0.15 0.19
0.15 0.13 0.17 0.18 0.18
0.18
Cd TMDL lbs/day 0.0126 0.0133 0.0184 0.0216 0.0729 0.1960 0.0907 0.0512 0.0275 0.0224 0.0146 0.0146
10% MOS 0.0013 0.0013 0.0018 0.0022 0.0073 0.0196 0.0091 0.0051 0.0028 0.0022 0.0015 0.0015
Cd TMDL with a 10% MOS, lbs/day 0.0114 0.0120 0.0165 0.0194 0.0656 0.1764 0.0816 0.0461 0.0248 0.0201 0.0131 0.0131
Current Cd, ug/l 0.43 0.74 1.05 0.91 0.00 0.00 0.51 0.00 0.33 0.28 0.34 0.26
Current Cd Load, lbs/day 0.030 0.052 0.096 0.098 0.000 0.000 0.308 0.000 0.053 0.035 0.028 0.021
Load Reduction to meet TMDL 0.018 0.040 0.080 0.079 -0.066 -0.176 0.227 -0.046 0.029 0.015 0.014 0.008
Percent Load Reduction 62% 77% 83% 80% 0% 0% 74% 0% 54% 42% 52% 36%
Table 15: Total Maximum Daily Load for dissolved cadmium for Geneva Creek Segment 5b with a 10% Margin of Safety.
4.0 RESTORATION PLANNING AND IMPLEMENTATION PROCESS There is no known restoration planning for the Geneva Creek watershed. Because there are no known discharges associated with legacy mining features in the drainage, regulatory mechanisms (NPDES or CDPS permits) are not an appropriate remedial tool. Additionally, the majority of the basin lies within the Pike National Forest. Therefore it is unlikely that any new discharges will occur in the next twenty years. The Iron Fen area, located outside of the National Forest, is protected as a Colorado State Natural Area. Consequently there is no potential that metals loading arising from this, the predominant source in the basin, will be ameliorated. 5.0 PUBLIC INVOLVEMENT The entire length of Geneva Creek from its source to the confluence with the North Fork of the South Platte River, Segments 5a and 5b, were recently included on the 2010 303(d) list of impaired waters in Colorado for exceeding chronic cadmium standards based upon ambient water quality data. Segment 5a was also included on the 2010 303(d) list for exceeding chronic copper and zinc standards. Through the process of TMDL development, Segment 5a was also identified for exceeding its chronic manganese standard.
FINAL August 2010
18
The development of the 303(d) list is a public process involving solicitation, from the public, of candidate waterbodies, formation of a technical review committee comprised of representatives of both the public and private sector, and a public hearing before the Colorado Water Quality Control Commission. Public notice is provided concerning both the solicitation of impaired waterbodies and the public rulemaking hearing. The TMDL itself is the subject of an independent public process. The TMDL was made available for public review and comment during a 30 day public notice period in April, 2010 and again in May, 2010. Notice was provided in the Colorado Water Quality Information Bulletin, and no comments were received during this period.
6.0 References Matthew A. Sares, Daryl L. Gusey, and John T. Neubert, Abandoned Mines and Naturally Occurring Acid Rock Drainage on National Forest System Lands in Colorado, Colorado Geological Survey, 2000. WQCC 2009. Section 303(d) Listing Methodology – 2010 Listing Cycle. June 2009. WQCC 2008a. Colorado Department of Public Health and Environment, Water Quality Control Commission, The Basic Standards and Methodologies for Surface Water, Regulation No. 31. Amended December 2008. WQCC 2010. Colorado Department of Public Health and Environment, Water Quality Control Commission, Classifications and Numeric Standards South Platte River Basin, Laramie River Basin, Republican River Basin, Smoky Hill River Basin, Regulation No. 38. Amended December 2010, Effective March 2010. WQCC 2010b. Colorado Department of Public Health and Environment, Water Quality Control Commission, 2010, 303(d) List of Impaired Waters, Regulation No. 93. 2010.
FINAL August 2010
19
Appendix A: Map of the Geneva Creek Watershed.
FINAL August 2010
20
