UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 8
999 ISm STREET
- SUITE 300
DENVER. CO 80202-2466
J. David Holm, Director Water Quality Control Division Colorado Department of Public Health and ~ n & n n 4300 Cherry Creek Dr. S. Denver, Colorado 80246-1 53 0
Re:
L Approvals Straight Creek (xedimenf ) hnos4uito Creek (metals) $an Miguel River (sedimnf )
V
I
Dear Mr. Holm:
We have completed our review of the total m&um daily loads (TMDLs) as submitted by y w office for the waterbodies listed in the eaclo& to this letter. In accordance with the Clean Water Act (33 U.S.C. 1251 e t seq.), we approvk all aspects of the TMDLs as developed for the water quality limited waterbodies as described Section 303(d)(l). Based on our review, we fee1 the separate TMl?L elements listed in the enclosed review table adequately address the pollutants of concern, takhg into consideration seasonal variation and a margin of safety. Please find enclosed a detail& review of these TMDLs.
Thank you for your submittal. If you have an4 questions concerning this approval, feel free to contact Kathryn Hernandez of my M a t 303012-6101.
Assistant ~ e ~ i o nAdministrator al Office of Emsyhms Protection and Remediation
Enclosure
Colorado Water Quality Control Division
Mosquito Creek
TOTAL MAXIMUM DAILY LOAD ASSESSMENT Mosquito Creek Park County, Colorado TMDL SUMMARY Waterbody Name/Segment Number COSPUS02B: Mosquito Creek, from confluence with South Mosquito Creek to Middle Fork of the South Platte River COSPUS02C: South Mosquito Creek, above Mosquito Creek. Metals: 02b = Zn, Cd, Pb Pollutant/Condition Addressed 02c = Zn, Cd, Fe, Mn South Mosquito Creek and Mosquito Creek from Affected Portion of Segment South Mosquito Creek to the Middle Fork of the South Platte Aquatic life (cold I) Use Classification Recreation (I) Water supply Agriculture Use Protected Waterbody Designation Substantial decreased monthly loads of dissolved Water Quality Target zinc from the Water Tunnel and the London Mine Extension Tunnel into South Mosquito Creek. Specific decreased monthly loads of dissolved cadmium, dissolved manganese and dissolved iron from the Extension Tunnel. Attainment of chronic metals standards in South TMDL Goal Mosquito Creek at it’s confluence with Mosquito Creek and attainment of the Mosquito Creek standards at the confluence with South Mosquito Creek.
EXECUTIVE SUMMARY Section 303(d) of the federal Clean Water Act requires states to identify water bodies or stream segments that are water quality limited on the 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 violating applicable water quality standards and to apportion that allowable quantity among the different pollutant sources. This maximum allowable pollutant quantity is referred to as the Total Maximum Daily Load (TMDL). Metals TMDL
1
06/12/00
Colorado Water Quality Control Division
Mosquito Creek
Mosquito Creek and South Mosquito Creek were included on the 1998 303(d) List as partially supporting and non-supporting respectively due to the existing temporary modifications for cadmium, iron, manganese and zinc standards (WQCC 1998). This document is an assessment of the loading to Mosquito Creek and South Mosquito Creek from the London Mine Extension Tunnel (the “Extension Tunnel”), London Mine Water Tunnel (the “Water Tunnel”), and the non-point source areas contributing to these streams. The water quality in Mosquito and South Mosquito Creeks remain detrimentally affected by the tunnel discharges, primarily by the effluent from the Extension Tunnel, which contributes very high concentrations of zinc to Mosquito Creek. While the Extension Tunnel has roughly one-tenth the flow of the Water Tunnel, the zinc levels in the Extension Tunnel discharge are 100 times the concentration in the Water Tunnel discharge. The background concentrations of zinc upstream of the tunnels are minimal; the background loads upstream are less than 10 percent of the allowable zinc loads in each listed segment. Although cadmium, iron and manganese require removal to attain the stream standards, at least for some months of the year, the amount of removal required for these parameters is significantly less than that required for zinc. It is probable that removal of zinc will also remove these other metals. Zinc is the controlling parameter in this allocation. With respect to the lead standard in segment 2b, the existing load from both tunnels is less than ten percent of the allowable load (and the 85th percentile of the synoptic data is less than the chronic standard). On this basis, it may be appropriate to remove lead from the 303 (d) List for that segment. However, because of the low hardness (36 mg/l) in Segment 2a, the 85th percentile values are 1 to 2 times higher than the standard in this segment. Additional monitoring data may support changes to 303 (d) Listing decisions with respect to lead. The TMDL will be implemented through CDPS discharge permit conditions for metals. The loading is being assigned to the two point sources (the tunnels) as one since metals removal will be required of each of these discharges in order to attain the zinc stream standard. Neither tunnel could be treated separately to attain the water quality standard. In addition complications should be minimized since these point sources have the same discharge permit applicant, London Mine Limited Liability Company. The following table lists the waste load allocation for the tunnels on a monthly basis. Note that this table does not specify whether removal is required for that particular parameter for that particular month or how much of a load reduction is required from the tunnel discharges. In the case of zinc, both tunnels will have to reduce discharge loads to the streams to attain standards.
Metals TMDL
2
06/12/00
Colorado Water Quality Control Division
Mosquito Creek
Table 1
WLA for the Water and Extension Tunnels #/day Month
Cadmium Segment 2c
Iron * Segment 2c
Lead * Segment 2b
Manganese Segment 2c
Zinc Segment 2b
January
0.016
3.6
0.086
0.61
1.7
February
0.015
3.4
0.082
0.57
1.6
March
0.015
3.4
0.082
0.57
1.6
April
0.015
3.4
0.085
0.57
1.7
May
0.018
3.9
0.11
0.66
2.0
June
0.035
7.7
0.27
1.33
5.0
July
0.029
6.5
0.20
1.11
3.8
August
0.027
5.9
0.16
1.01
3.1
September
0.024
5.3
0.14
0.90
2.7
October
0.022
4.8
0.12
0.82
2.3
November
0.020
4.4
0.11
0.74
2.1
December
0.018
4.0
0.1
0.68
1.9
* Values in gray indicate removal not required for that month to attain standard.
I. INTRODUCTION Section 303(d) of the federal Clean Water Act requires states to identify water bodies or stream segments that are water quality limited. Those water quality limited segments currently identified in Colorado are identified in the 1998 303(d) List. Water quality limited segments are those water bodies or stream segments which, for one or more assigned use classifications or standards, the classification or standard is not fully achieved. Once listed, the State is required to quantify the amount of a specific pollutant that a listed water body can assimilate without violating applicable water quality standards and to apportion that allowable quantity among the different pollutant sources. 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 the nonpoint 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. Metals TMDL
3
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Colorado Water Quality Control Division
Mosquito Creek
The Upper South Platte River, segments COSPUS02B (Mosquito Creek) and COSPUS02C (S. Mosquito Creek) were identified on Colorado’s 1998 303(d) list as partially supporting the use classification for Mosquito Creek and as not supporting the use classification for South Mosquito Creek. The water quality in Mosquito and South Mosquito Creeks is being affected by the discharges from the Extension Tunnel into No Name Creek immediately above South Mosquito Creek and from the Water Tunnel into South Mosquito Creek. Although the tunnels contribute loads for cadmium, iron, lead, and manganese, the primary metal contributing mass to the streams is zinc. Both tunnels contribute a significant portion of the load of zinc to Mosquito Creek. Although the Extension Tunnel flow is low compared to the Water Tunnel flow, the concentration of zinc from the Extension Tunnel is so high that it contributes a greater load to Mosquito Creek than the Water Tunnel. See Figure 1 for Mosquito Creek locations, segmentation and sampling station locations. Figure 2 is a chart showing the dissolved zinc concentrations for each sampling date. Note on Figure 2 the extremely high concentrations from the Extension Tunnel (sample location 5988c2) and it’s affect on the next downstream station (sample location 5988d1). Site Description: Mosquito Creek and South Mosquito Creek are located in Park County in central Colorado. See Figure 1. No Name Creek flows into South Mosquito Creek, which flows into Mosquito Creek. Mosquito Creek is tributary to the Middle Fork of the South Platte River approximately 2 miles downstream from Alma and approximately 4 miles upstream of the town of Fairplay. The drainage area encompasses the historical London Mines mining district and receives runoff from a number of rock dumps, mill tailings and abandoned mining sites. Some of these areas were addressed in the mid-1990s by non-point source clean-up activities under Section 319 of the Clean Water Act. See Figure 3 for a map of these project areas. The site is bounded by the continental divide to the west and the Middle Fork of the South Platte to the east. The area elevation ranges from about 14,000 to 10,000 feet. It receives hundreds of inches of snow per year and this makes access to the site complicated in the winter months. The non-attainment areas include South Mosquito Creek below it’s confluence with No Name Creek and Mosquito Creek from the confluence with South Mosquito Creek to the Middle Fork of the S. Platte, segments 2c and 2b of the Upper South Platte River Basin. See Figure 1 for stream classification segmentation. The scope of this TMDL includes these non-attainment areas and includes a review and use of data from the areas upstream of Mosquito Creek and South Mosquito Creek. The South Mosquito Creek watershed (approximately 4 square miles) and the Mosquito Creek watershed (approximately 16 square miles, including S. Mosquito Creek) are part of the Colorado Headwaters Hydrologic Unit Code 10190001.
Metals TMDL
4
06/12/00
Colorado Water Quality Control Division
Mosquito Creek
Discharge Permits, Water Rights and Property Ownership The Water Tunnel discharges effluent pursuant to its Colorado Discharge Permit System (CDPS) discharge permit (CO-0038334) to South Mosquito Creek approximately one mile above South Mosquito Creek’s confluence with Mosquito Creek. The same permittee, London Mine Limited Liability Company, has an application pending for the effluent from the Extension Tunnel (CO-0045209). This application was received in April 1997 after requests by the WQCD in 1996 and 1997 via letters to the Mr. Ben L. Wright. Mr. Wright is the Managing Member of London Mine, LLC. Although the applicant disagreed with the Division’s determination that a permit was appropriate for the Extension Tunnel discharge, they submitted the application “to maintain the cooperation between itself, the Water Quality Control Division, and the Division of Minerals and Geology with the objective of improving the water quality in South Mosquito Creek”. Currently the discharge from the Water Tunnel is piped from a small holding pond to South Mosquito Creek. The discharge point latitude/longitude is 39.16.32/106.08.74 and was obtained from WQCD Monitoring Unit. The permit for the Water Tunnel currently has seasonal metals effluent limitations based on the temporary modifications of water quality standards. The Extension Tunnel water is collected in a small pond at the tunnel portal and piped via a small corrugated plastic pipe to No Name Creek. The discharge point latitude/longitude, obtained from the discharge permit application, is 39.17.30/106.09.15. The discharge into No Name Creek is only several hundred feet above No Name’s confluence with South Mosquito Creek. According to Coors Brewing Company, it is “part owner of water flowing from the London Water Tunnel, together with a right-of-way to facilitate the delivery of the water from the London Water Tunnel to South Mosquito Creek. Rights to the use of other portions of that water are owned by Ben Wright and the Fairplay Fishing Club, a Colorado corporation. Coors does not own any water rights associated with the London Extension Tunnel or any realty in fee, nor does it own or lease any mining claim associated with either the London Extension or Water Tunnels.” In addition they have very clearly stated that “Coors has no role as an owner or operator of the mine”.
II.
WATER QUALITY STANDARDS
There are temporary modifications to the chronic standards for dissolved zinc, dissolved cadmium, total recoverable iron, and dissolved manganese. The temporary modifications to the zinc standard are 220 micrograms per liter in segment 2b and 580 micrograms per liter in segment 2c, with the underlying standards being 110 micrograms per liter and 250 micrograms per liter, respectively. The modification to the dissolved cadmium standard in segment 2c is 1.9 micrograms per liter, with the underlying standard being the Table Value Standard (1.31 micrograms per liter at hardness of 120 mg/l). The modification to the total recoverable iron standard is 1800 ug/l in segment 2c, with the Metals TMDL
5
06/12/00
Colorado Water Quality Control Division
Mosquito Creek
underlying standard of 1000 ug/l. The modification to the dissolved manganese standard in segment 2c is 118 ug/l, with an underlying standard of 50 ug/l. These temporary modifications will expire on December 31, 2000. See Table 2, which presents the water quality classifications and metals standards for Segments 2b and 2c. This information was extracted from the Classifications and Numeric Standards for the Upper South Platte River Basin, Water Quality Control Commission Regulation No. 38, effective date: June 30, 1999 (WQCC 1999A). Segment 2b is 303(b) listed for cadmium, lead, and zinc. Segment 2c is listed for cadmium, iron, manganese and zinc. These five metals are the parameters addressed in this TMDL. Table 2 Summary of Stream Classifications and Water Quality Standards Classifications Designation
Basin: Upper South Platte River
2c
Mainstem of Mosquito Creek from the confluence with South Mosquito Creek to its confluence with the Middle fork of the South Platte River South Mosquito Creek from the source to the confluence with Mosquito Creek.
Temporary Modifications
Expiration date 12/31/00
Stream Segment Description 2b
Numeric Standards (ug/L)
TMDL Metals UP
UP
Aq Life Cold 1 Recreation 1 Water Supply Agriculture
Cd (ac) =TVS(tr) Cd (ch) =TVS Pb (ac/ch) = TVS Zn (ch) = 110 ug/l
Aq Life Cold 1 Recreation 1 Water Supply Agriculture
Cd (ch) =TVS Fe (ch) =300(dis) Fe (ac) =1000(Trec) Mn (ch) =50(dis) Mn (ch) =1000(Trec) Zn (ch) = 250 ug/l
Zn (ch) = 220 ug/l (dis) Cd (ch) = 1.9 ug/l (dis) Fe (Trec) = 1800ug/l Mn (ch) = 118 ug/l (dis) Zn (ch) = 580 ug/l (dis)
The first column in Table 1 is the segment number. The segment is also identified by it’s Waterbody Identification (WBID), COSPUS02b, or “CO = State of Colorado, SP = South Platte River Basin (Major basin), US = Upper South Platte River Basin (Subbasin), 02b = Segment Number”. The segment description follows in the second column. Column 3 describes the Designation, which determines the antidegradation requirements for the segment. Both Segments 2b and 2c are designated Use Protected. This designation means that anti-degradation reviews are not required. The fourth column consists of Use Classifications (Aquatic Life, Recreation, Agriculture, Water Supply). Both these segments are classified for cold water aquatic life class 1, recreation class 1, water supply and agriculture uses. Column 5 contains the metals standards for those parameters on the 303(d) List for these 2 segments. The final column lists the temporary modifications adopted for the segments. The cadmium and lead standards are based on Table Value Standards (TVS). The formulas for these standards are hardness-based. The mean hardness for each segment Metals TMDL
6
06/12/00
Colorado Water Quality Control Division
Mosquito Creek
was used in these calculations. The chronic and acute TVS for these metals, formulas that are hardness-based, are found in the South Platte standards, WQCC Regulation No. 38 (WQCC 1999). III.
PROBLEM IDENTIFICATION
The Extension Tunnel and the Water Tunnel were historically used to support mining activities in the area. According to Mr. Wright, the Water Tunnel has produced water since 1918. However, he also states that there has been no mining at the site since “1989 or before”. In recent years the Water Tunnel has been used primarily as a conduit for the exercise of water rights and the Extension Tunnel has been available for use as an emergency exit and for mine ventilation. Metals laden discharge from the tunnels is impacting South Mosquito Creek and Mosquito Creek below its confluence with South Mosquito Creek. The metals concentrations exceed the levels established to protect aquatic life uses in these streams. The decision to list Segments 2b and 2c on the 1998 303(d) List was based on temporary modifications for metals standards. Clearly the underlying standards for zinc are exceeded in both of these segments. Both tunnels contribute significant loads of zinc to South Mosquito Creek. The Extension Tunnel contributes concentrated zinc levels at a flow that varies from 0.022 cfs (10 gpm) in the wintertime to 0.312 cfs (140 gpm) in July and August. The Water Tunnel flows are considerably higher, ranging from 1.44 cfs (645 gpm) in April to 2.09 cfs (936 gpm) in September. The zinc levels from the Extension Tunnel are 100 times the concentration of zinc from the Water Tunnel. The ambient background load, from Mosquito Creek upstream of South Mosquito Creek, and No Name Creek and South Mosquito Creek upstream of the tunnel discharge points, is less than ten percent of the allowable zinc load. IV.
WATER QUALITY GOALS
The desired endpoint of this TMDL is the attainment of the underlying metals standards for Segments 2b and 2c including the following goals: Goal no.1:
110 ug/l dissolved zinc in segment 2b (evaluated as the 85th percentile of ambient data not to be exceeded more than once in 3 years)
Goal no.2:
1.31 ug/l dissolved cadmium, 50 ug/l dissolved manganese and 300 ug/l dissolved iron in segment 2c (evaluated as the 85th percentile of ambient data not to be exceeded more than once in 3 years)
Post-Implementation monitoring to demonstrate attainment of goals is discussed under Section VII, TMDL Allocation. Metals TMDL
7
06/12/00
Colorado Water Quality Control Division
V.
Mosquito Creek
SOURCE ANALYSIS
The development of this TMDL must include an identification of all potential pollutant sources. The contributing watersheds to Segments 2b and 2c are well defined. Sampling upstream of these two segments shows that the ambient upstream water quality is not a significant contributor to the metal loads in these segments. For a graphical presentation of this for zinc, see Figure 1 for upstream sampling points and Figure 2 for zinc concentrations at the corresponding sampling points. South Mosquito Creek is impacted primarily by the tunnel discharges and those metal loads are carried downstream to impact Lower Mosquito Creek. See more detailed discussion in the following section. VI.
TECHNICAL ANALYSIS
A low flow evaluation, source assessments and mass balance calculations were utilized to determine the maximum allowable metals loads to Segment 2b and 2c to attain standards. This TMDL for metals is developed for the protection of aquatic life for cadmium, lead and zinc and for protection of secondary drinking water standards for iron and manganese. The secondary drinking water standards address aesthetic issues and, since the standards for aesthetics are more restrictive than aquatic life standards for those same parameters, the TMDL was calculated for these more restrictive endpoints. Hydrology: Generally, concentrations of pollutants in surface waters are indirectly related to flow. The higher the stream flow, the lower the concentration and the lower the stream flow, the greater the concentration. Therefore, the low flow condition instream becomes the critical condition for the analysis and for the survival of aquatic life. Flow data for this area is limited. The USGS installed a flow meter at the mouth of Mosquito Creek, just upstream of its confluence with the Middle Fork of the South Platte River in October 1998. Flow regionalization was used to estimate the monthly low flows. This approach is an estimation of the low flows based on calculations from a hydrologically similar, but gauged area. Flow regionalization was used to estimate the low flows of Mosquito Creek upstream of South Mosquito Creek and to estimate the low flows in South Mosquito Creek absent the tunnel flows. The approximations used in the regionalization were: Upper Mosquito Creek area - 6.12 square miles, the South Mosquito Creek area - 4.4 square miles and the total Mosquito Creek drainage - 16.17 square miles. The period of analysis was from 1975 to 1996 and the resultant chronic low flows are listed in Table 3. The results of this low flow analysis were compared to the USGS data from the station at the mouth of Mosquito Creek. Using the assumption of tunnel flows of 1.68 cfs for January and the regionalization-derived estimated low flow for January, the lowest ambient flow month, the result would predict a flow at the mouth of 3.9 cfs. The actual lowest low flow at this location for the period of record (10/98 through 9/99) was 3.8 cfs in January of 1999. The results of regionalization approach are consistent with the available stream flow data. Metals TMDL
8
06/12/00
Colorado Water Quality Control Division
Mosquito Creek
Table 3 Chronic Low Flows for Mosquito Creek and South Mosquito Creek(cfs) 30E3
Annual
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
MC
0.8
0.8
0.8
0.8
0.9
1.3
4.6
2.9
1.9
1.5
1.2
1.0
0.9
SMC
0.6
0.6
0.6
0.6
0.6
0.9
3.3
2.1
1.4
1.1
0.9
0.7
0.7
Because the calculated chronic standards are much more restrictive for the two TVS derived parameters of lead and cadmium (and the acute low flows don’t vary significantly from the chronic low flows) the chronic values dictate the load calculations. Table 4 presents the highest monthly average tunnel flows based on Discharge Monitoring Reports (filed by the permittee) for the Water Tunnel and from information and interpolation of values from the Division of Mineral and Geology for the Extension Tunnel. The tunnel maximum flows lag runoff flows by a few months. The maximum runoff flows normally occur in June. The Extension Tunnel maximum flows occur in July and August and the maximum Water Tunnel flows occur during August and September. See Table 4 for the specific values used and Figure 4 for a graphical presentation of flows. Table 4 Highest Monthly Average Flows from the Tunnels (cfs) Water
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1.66
1.52
1.49
1.44
1.49
1.52
1.75
2.07
2.09
2.03
2.03
1.81
0.022
0.022
0.045
0.089
0.089
0.178
0.312
0.312
0.178
0.133
0.045
0.022
Tunnel Extension Tunnel
Metals TMDL
9
06/12/00
Colorado Water Quality Control Division
Mosquito Creek
Ambient Water Quality: The Monitoring Unit of the WQCD performed 3 synoptic sampling events at 17 locations. Figures 1 shows the sampling locations. The sampling was performed in September of 1998 and 1999 and June of 1999. Personnel from CDPHE’s Hazardous Materials and Waste Management Division (HMWMD) took samples at similar locations in June 1996 as part of a Site Inspection Analytical Results Report (AAR) for the London Mines/Mosquito Creek Basin. In addition, the WQCD had sampled 3 of these locations on a monthly basis starting in January 1999. The data for these 3 stations for the period from January through October 1999 was included in this evaluation. These 12 data sets, in addition to monthly hardness data at USGS station 5988, were used in establishing the stream hardness for each segment and in the evaluation of sources, presented below. Table 5 is a summary of water quality data for the 303 (d) Listed segments. For hardness calculations, the value listed is the mean of all samples within the segment including, for segment 2b, the 16 values from station 5988. The specific metals values listed for segment 2c are from sampling station 5988b1 and those for segment 2b are for sampling station 5988a3. The only detected cadmium value upstream was one sample upstream of the Extension Tunnel in No Name Creek. This sample had a cadmium concentration of 0.4 ug/l, where the applicable chronic standard is 0.51 ug/l. The highest value for upstream dissolved iron is 60 percent of the chronic dissolved iron standard of 300 ug/l. The upstream manganese data are well below the 50 ug/l chronic dissolved standard for this parameter. The data for the upstream segments shows that the 85th percentile ambient zinc concentrations are less than 45 ug/l, the chronic table value standard for the upper segments and thus well below the 110 ug/l standard in South Mosquito Creek. The only exception to the low concentrations upstream when compared to the applicable standard is lead, where the 85th percentile of the data is 2 to 3 times the standard in segment 2a, Upper Mosquito Creek. However, due to the very low hardness (36 mg/l) in these segments the chronic standard for dissolved lead is low in this upper segment, 0.91 ug/l, compared to the chronic dissolved standard for lead in segments 2b and 2c, which are near 5 ug/l. The data for lead shows no contribution from the Water Tunnel and the most significant contribution of lead loads to the drainage to be from the Extension Tunnel.
Metals TMDL
10
06/12/00
Colorado Water Quality Control Division
Mosquito Creek
Table 5 Ambient Water Quality Data Summary (micrograms/liter unless otherwise specified) segment # samples range 50 th%ile 85th%ile 2a 8 Hardness 2b 36 2c 23 upstream of 2b 11 0 0 0 Cd 2b 11 0 – 1.4 0.50 1.10 upstream of 2c 8 0 – 0.4 0 0 2c 12 0 – 3.3 0.70 2.32 Extension Tunnel 4 111-160 155 160 Water Tunnel 4 0-1.4 0.70 1.13 upstream of 2b 11 0 – 180 78 110 Fe 2b 9 34 - 120 60 103 upstream of 2c 8 0 - 39 24 27 2c 10 0 - 180 65 145 Extension Tunnel 4 1060-24000 8250 18600 Water Tunnel 4 0-12 0 6.6 upstream of 2b 11 0-3 0 3 Pb 2b 11 0-5 0 2.00 upstream of 2c 11 0-3 0 0 2c 12 0-8 1.00 6.05 Extension Tunnel 4 0-11 9 11 Water Tunnel 4 0 0 0 upstream of 2b 11 2.7 - 17 8 12 Mn 2b 11 26 – 80 53 65 upstream of 2c 8 0-5 0.8 4 2c 12 11 - 120 57 93 Extension Tunnel 4 1730-3900 3750 3900 Water Tunnel 4 24-53 31 46 upstream of 2b 11 0 - 49 17 28 Zn 2b 9 80 - 760 220 376 upstream of 2c 8 0 - 33 15 26 2c 12 0 - 770 321 615 Extension Tunnel 4 25500-43000 40000 42600 Water Tunnel 4 200-556 425 508 * Hardness values are in milligrams per liter calcium carbonate.
Metals TMDL
11
mean* 36 123 120 -
06/12/00
standard NA NA NA (2a=0.51) 1.33 1.31 NA NA (2a=300) 300 300 NA NA (2a=0.91) 5.22 5.04 NA NA (2a=50) 50 50 NA NA (2a=45) 110 250 NA NA
Colorado Water Quality Control Division
Mosquito Creek
Analysis of the ambient water quality data indicates that the 85th percentile of the data exceeds the segment 2c chronic standards for manganese and cadmium, but does not exceed the iron standards for segment 2c, nor the lead standard for segment 2b. The iron 85th percentile values are less than the chronic dissolved iron standard of 300 ug/l despite the fact that the Extension Tunnel’s average concentration levels are greater than 25 times the standard. The cadmium standard in segment 2c is 1.31 ug/l while the 85th percentile values for cadmium in segment 2c are 2.32 ug/l at the mouth of South Mosquito Creek and 5.43 ug/l directly below the Extension Tunnel outfall (sampling point 5988b2). The lead 85th percentile value for S. Mosquito Creek at the mouth is marginally above the standard here (6.05 ug/l vs. the standard of 5.04 ug/l). The 85th percentile manganese values are 1 to 2 times the chronic dissolved standard of 50 ug/l in segment 2c. Source Assessment: The principal metal loads to Segments 2b and 2c are from the two tunnels. The contribution from upstream sources is minimal for all 5 metals that are subject to this TMDL. See Table 6 for a summary of the load allocations for upstream sources.
Table 6
Load Allocation for upstream sources on Mosquito Creek and South Mosquito Creek #/day Month
Cadmium Segment 2c
Iron Segment 2c
Lead Segment 2b
Manganese Segment 2c
Zinc Segment 2b
January
0.0
0.08
0.0
0.003
0.12
February
0.0
0.08
0.0
0.003
0.12
March
0.0
0.08
0.0
0.003
0.12
April
0.0
0.08
0.0
0.003
0.13
May
0.0
0.12
0.0
0.004
0.19
June
0.0
0.43
0.0
0.014
0.69
July
0.0
0.27
0.0
0.009
0.44
August
0.0
0.18
0.0
0.006
0.29
September
0.0
0.14
0.0
0.005
0.23
October
0.0
0.12
0.0
0.004
0.18
November
0.0
0.09
0.0
0.003
0.15
December
0.0
0.09
0.0
0.003
0.14
Metals TMDL
12
06/12/00
Colorado Water Quality Control Division
Mosquito Creek
For comparison with the allowable loads, the Extension Tunnel and Water Tunnel current loads for each of the 5 metals are listed next to the allowable loads in Tables 7 and 8. These tables present a conservative (i.e. high) estimate of current loads because they are based on assumptions of highest monthly average flows from the tunnels. The current tunnel loads estimates are also based on the 50th percentile values for the concentrations in the tunnel effluent. Using those assumptions, for all parameters except lead, these loads must be reduced in order to meet standards. Iron only requires load reduction from April through October, with significant reductions necessary during July and August. The loads allowable from the tunnels to attain stream standards are also detailed in Section VII, TMDL Allocation.
Table 7 Loads for the Water and Extension Tunnels #/day Cadmium Segment 2c
Month
Zinc Segment 2b
Current
Allowable
Difference
Current
Allowable
Difference
January
0.025
0.016
0.009
8.5
1.7
6.8
February
0.024
0.015
0.009
8.2
1.6
6.6
March
0.043
0.015
0.028
13.1
1.6
11.5
April
0.080
0.015
0.065
22.4
1.7
20.8
May
0.080
0.018
0.062
22.6
2.0
20.6
June
0.154
0.035
0.119
41.9
5.0
36.9
July
0.267
0.029
0.238
71.3
3.8
67.5
August
0.268
0.027
0.242
72.0
3.1
68.9
September
0.157
0.024
0.133
43.2
2.7
40.5
October
0.119
0.022
0.097
33.3
2.3
31.0
November
0.045
0.020
0.026
14.4
2.1
12.3
December
0.025
0.018
0.007
8.9
1.9
7.0
Metals TMDL
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Table 8
Loads for the Water and Extension Tunnels #/day Iron Segment 2c
Month
Lead Segment 2b
Manganese Segment 2c
Current
Allowed
Difference
Current
Allowed
Difference
Current
Allowed
Difference
January
0.98
3.6
NA
0.001
0.086
NA
0.72
0.61
0.11
February
0.98
3.4
NA
0.001
0.082
NA
0.70
0.57
0.13
March
2.00
3.4
NA
0.002
0.082
NA
1.16
0.57
0.59
April
4.0
3.4
0.6
0.004
0.085
NA
2.04
0.57
1.47
May
4.0
3.9
0.1
0.004
0.11
NA
2.05
0.66
1.39
June
7.9
7.6
0.3
0.009
0.27
NA
3.85
1.33
2.52
July
13.9
6.5
7.4
0.15
0.20
NA
6.60
1.11
5.49
August
13.9
5.9
8.0
0.15
0.16
NA
6.65
1.01
5.64
September
7.9
5.3
2.6
0.009
0.14
NA
3.95
0.90
3.05
October
5.9
4.8
1.1
0.006
0.12
NA
3.03
0.82
2.21
November
2.0
4.4
NA
0.002
0.11
NA
1.25
0.74
0.51
December
0.98
4.0
NA
0.001
0.1
NA
0.75
0.68
0.07
Margin of Safety: The MOS used in the TMDL analysis is implicit. It lies in the conservative assumptions used in the calculations and the requirements for additional monitoring and adaptive management in response to treatment or remedial measures to remove dissolved metals from the water column. Conservative assumptions used in the analysis included the use of chronic low flows and the use of the highest monthly average discharge flows. In addition, when the TMDL was to be established for both segments for a parameter, the calculations were performed for both segments and the most restrictive loads were listed in this TMDL. For the “non-controlling” segment, the WLA is more conservative than necessary. The calculations for Lower Mosquito Creek, segment 2b, are conservative in that the mass balance was performed for a point at the upper end of the segment, near sampling station 5988a3. For this segment the calculations were performed using the low flows upstream at that point and did not account for the additional (low) flows available throughout that segment. Metals TMDL
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Post-implementation monitoring at an instream location at the bottom of Segment 2c and one in the upper part of Segment 2b are necessary as part of the MOS to provide assurance that standards are attained. In addition, the treated tunnel effluents shall be monitored to assess the effectiveness of treatment systems/remedial measures. In addition, although not a part of the allocation calculations themselves, conservative assumptions were used in assessing the load removals required. The loads listed are based on assumed tunnel concentrations of the 50th percentile values. This is conservative for parameters with a wide range of values, particularly for iron and, to a lesser extent manganese. Also, a compounding conservative assumption was made by using the highest monthly average discharge flow value from each tunnel for each month of the year. Therefore, it is likely that the removal required, i.e. the “current” and the “difference” columns on Tables 7 and 8, are overstated.
Metals TMDL
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VII.
Mosquito Creek
TMDL ALLOCATION
Allocation Methodology: The required reduction in loads from the tunnels was determined from mass balance calculations for each of the 5 metals for each listed TMDL segment. The monthly TMDL for the stream is based on the Load Allocations listed in Table 6 and the Waste Load Allocations listed in Table 1 and an implicit MOS. The monthly TMDL is equal to the sum of the LA and WLA. For cadmium and lead the LAs were determined to be insignificant. The monthly TMDL for the 5 metals for the controlling segments are presented in Table 9.
Table 9 TMDL for the Water and Extension Tunnels #/day Month
Cadmium Segment 2c
Iron * Segment 2c
Lead * Segment 2b
Manganese Segment 2c
Zinc Segment 2b
January
0.016
3.7
0.086
0.61
1.8
February
0.015
3.5
0.082
0.57
1.7
March
0.015
3.5
0.082
0.57
1.7
April
0.015
3.5
0.085
0.57
1.8
May
0.018
4.0
0.11
0.66
2.3
June
0.035
8.1
0.27
1.34
5.7
July
0.029
6.8
0.20
1.12
4.2
August
0.027
6.1
0.16
1.02
3.4
September
0.024
5.4
0.14
0.91
2.9
October
0.022
4.9
0.12
0.82
2.5
November
0.020
4.5
0.11
0.74
2.3
December
0.018
4.1
0.1
0.68
2.0
*Values in gray indicate removal not required for that month to attain standard. Implementation: The TMDL will be implemented in the form of discharge permit conditions for dissolved metals. Monitoring: In order to insure that the TMDL is adequately protective of the entire segment, and to assist in evaluating improvements in site conditions, monitoring is required. The new permit for the Extension Tunnel and the renewal of the permit for the Water Tunnel should include a monitoring schedule consisting of at least quarterly sampling for pH, total suspended solids, and the dissolved metals: cadmium, iron, lead, manganese, and zinc and total recoverable iron and total recoverable manganese. The sampling locations are identified on Figure 1. At a minimum the sampling should include Metals TMDL
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Mosquito Creek
the tunnel waters, South Mosquito Creek above the confluence with Mosquito Creek and Mosquito Creek below the confluence with South Mosquito Creek. Attainment of standards should be measured at the top of Segment 2b (i.e. in Lower Mosquito Creek at 5988a3) and the bottom of Segment 2c (i.e. in South Mosquito Creek at 5988b1). Attainment should be evaluated at the end of remedial activities at the site and after treatment facilities have been allowed to operate for 3 or 4 years. This allows time for treatment system optimization and for stabilization to occur for (any) other remedial activities. VIII. PUBLIC INVOLVEMENT The public has had the opportunity for involvement since at least 1987 when the these segments were classified to protect aquatic life. The WQCC hearings that have been held over the years regarding these segments have been conducted as a public process. In addition, the compilation of the 303(d) Lists has been a public process. A public meeting was held in Denver on January 25th, 2000 to provide an update on the status of several TMDLs in development including these Mosquito Creek TMDLs. A sign-up list was posted at this meeting for those interested in receiving updates on the TMDL. The interested parties were invited to a public meeting held in conjunction with the Park County Commissioners meeting on April 10th, 2000 in Fairplay. In addition, WQCD Outreach and Assistance personnel and the South Platte Watershed Coordinator have been interacting with the local community on these issues and have kept the Upper South Platte Watershed Protection Association apprised of the TMDL process and the development of these specific TMDLs for the Mosquito Creek area. The draft Mosquito Creek TMDL was public noticed on May 1, 2000. Comments were received on behalf of London Mines LLC on June 2, 2000. A copy of the comments and the response to them are attached.
Metals TMDL
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X.
Mosquito Creek
REFERENCES
WQCC 1998: Colorado Department of Public Health and Environment, Water Quality Control Commission, 1998 303(d) List of Impaired Waters, 1998. WQCC 1997: Colorado Department of Public Health and Environment, Water Quality Control Commission, Classifications and Numeric Standards for South Platte River Basin, Laramie River Basin, Republican River Basin, Smoky Hill River Basin, Regulation No. 38, Amended July 14, 1997. WQCC 1999: Colorado Department of Public Health and Environment, Water Quality Control Commission, The Basic Standards for Methodologies for Surface Water, Regulation No. 31, 5 CCR 1002-31, Amended March 3, 1999. HMWMD 1998: Colorado Department of Public Health and Environment, Hazardous Materials and Waste Management Division, Site inspection Analytical Results report, London Mines/ Mosquito Creek Basin CERCLIS ID #CO0000286203, Park County, Colorado, Prepared by S.V. (Van) Simsiman, April 16, 1998. WQCD 1991: Colorado Department of Public Health and Environment, Water Quality Control Division, Colorado Total Maximum Daily Load and Wasteload Allocation Guidance, Prepared by the WQCD, Groundwater and Standards unit, Revised November 1991. Letter from Ben L. Wright, Jr. to Don Holmer, WQCD August 11, 1993. Letter from Coors Brewing Company, John Schallenkamp to Patricia A. Nelson, WQCD, September 15, 1995. Letter from Cenibark International, Paul N. Seeley to CDPHE - WQCD, September 18, 1995. London Mine LLC (Water Tunnel) discharge permit file, CO-0038334 Park County. London Mine LLC Extension Tunnel discharge permit application CO-0045209 Park County. Section 319 Study of the London Mine Extension Tunnel, prepared for the Division of Minerals and Geology (formerly the Mined Land Reclamation Division) by Cenibark International, June 1997. South Mosquito Creek Nonpoint Source Project Implementation Plan – Colorado Mined Land Reclamation Division, May 29, 1990. London Extension Project Implementation Plan, submitted by Colorado Division of Minerals and Geology, Denver, Colorado April, 1993 Metals TMDL
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Mosquito Creek
Figure 1: Segmentation and Sampling Points
Metals TMDL
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Mosquito Creek Zinc Concentrations
50000
45000
40000
06/26/96
09/09/98
35000
12/09/98
01/12/99
02/25/99 30000
03/23/99
04/21/99 ug/l
05/12/99
06/16/99
25000
07/20/99
09/14/99
10/21/99 20000
15000
10000
5000
5956
5955
5954
5988d2
5988d1
5988c2
5988c1
5988b3
5988b2
5988b1
5988a6
5988a5
5988a4
5988a3
5988a2
5988a1
5988
StnDesc
0
Sampling Station
Figure 2: Zinc Concentrations in the Mosquito Creek Area Metals TMDL 20
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Mosquito Creek
Figure 3: Section 319 – Nonpoint Source Project Areas
Metals TMDL
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Mosquito Creek
Tu n n e l Fl o w s a nd U p s tre a m L o w Fl o w s 5
4.5 H ig h e s t m o n t h ly a v e r a g e t u n n e l flo w s 4
U p p e r M o s q u it o C re e k L o w F lo w s
3.5
3
cfs
S o u t h M o s q u ito C re e k L o w F lo w s 2.5 B o th tu n n e ls to ta l 2
W a t e r tu n n e l 1.5 3
1.5
1
0.5
Ex t e n sio n T u n n e l
Figure 4: Flows Metals TMDL
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M
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M
M o nth
F
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0
Colorado Water Quality Control Division
Mosquito Creek
Appendix A
ACRONYMS
Cd
Fe Mn Pb Zn
cadmium iron manganese lead zinc
CDPHE cfs HMWMD LA TMDL TVS ug/l WLA WQCD #/day
Colorado Department of Public Health and Environment cubic feet per second Hazardous Materials and Waste Management Division Load Allocation Total Maximum Daily Load Table Value Standard micrograms per liter Waste Load Allocation Water Quality Control Division pounds per day
Metals TMDL
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Metals TMDL
Mosquito Creek
24
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Metals TMDL
Mosquito Creek
25
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Metals TMDL
Mosquito Creek
26
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Metals TMDL
Mosquito Creek
27
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