TOTAL MAXIMUM DAILY LOAD ASSESSMENT East Mancos River, San Juan and Dolores River Basin Segment COSJLP04a Montezuma County, Colorado TMDL SUMMARY
Waterbody Name/Segment Number
Mainstem of the Mancos River, including all wetlands, tributaries, lakes, and reservoirs, from the source of the East, West and Middle Forks to Hwy 160, except for the specific listing in segment 4b. Segment ID: COSJLP04a
Pollutant/Condition Addressed
Cu, Mn
Affected Portion of Segment
East Mancos River
Use Classification/Waterbody Designation
Aquatic Life Cold Water 1 Nov.1 to April 30: Recreation N May 1 to Oct. 31: Recreation E Water Supply Agriculture
Waterbody Antidegradation Designation
Reviewable
Water Quality Target
Copper (dissolved) Acute = e(0.9422(ln(hardness))-1.7408) Chronic = e(0.8545(ln(hardness))-1.7428)
Water Quality Goal
Manganese (dissolved) = 50 µg/l Attainment of the acute and chronic Aquatic Life Use-based dissolved copper and Water Supply Use-based dissolved manganese water quality standards in the East Mancos River.
EXECUTIVE SUMMARY The East Mancos River, segment COSJLP04a, was identified as water-quality impaired for dissolved copper on the 2002 and subsequent 303(d) lists, as approved by the Colorado Water Quality Control Commission. Segment COSJLP04a was recently identified for impairment in regards to Water Supply Use-based dissolved manganese, and was subsequently listed on the 2012 303(d) list. The sources of pollutants in this watershed are mixed. There are apparent
FINAL DRAFT
Total Maximum Daily Load Assessment for East Mancos River segment 4a
unpermitted point source discharges of pollutants to the East Mancos River from and historic mine activity in the area, in addition to natural non-point sources. Natural hydrothermal alteration in conjunction with historic mining activity (either inactive or abandoned) has contributed to the elevated levels of copper and manganese in the East Mancos River (CGS, 2000). This TMDL derives allocations for dissolved copper and manganese to demonstrate the load reductions necessary to attain the currently adopted standards. The East Mancos River is classified as abandoned mine lands through EPA nomenclature, and a Comprehensive Environmental Response, Compensation and Liability Action (CERCLA ID CO0012947186) and site assessment has been performed to characterize, or assess, the abandoned mine lands in the East Mancos River drainage. I.
INTRODUCTION
Section 303(d) of the federal Clean Water Act (―CWA‖) requires States to periodically submit to the U. S. Environmental Protection Agency (―EPA‖) a list of water bodies that are water quality impaired. Water quality limited segments are those water bodies that, for one or more assigned use classifications or standards, the classification or standard is not fully achieved. This list of water bodies is referred to as the ―303(d) List‖. In Colorado, the agency responsible for developing the 303(d) List is the Water Quality Control Division (―WQCD‖). The 303(d) List is adopted by the Water Quality Control Commission (―WQCC‖) as Regulation Number 93. The WQCC adopted the current 303(d) List in March of 2012. For water bodies and streams on the 303(d) list, a Total Maximum Daily Load (TMDL) is developed to determine the maximum amount of a pollutant that a water body may receive and still maintain water quality standards. The TMDL is the sum of the Waste Load Allocation (WLA), which is the load from point source discharge, Load Allocation (LA), which is the load attributed to natural background and/or non-point sources, and a Margin of Safety (MOS) (Equation 1). (Equation 1)
TMDL = WLA + LA + MOS
Alternatively, if a TMDL is not developed, a segment or pollutant may be removed from the list if the applicable standard is attained, 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 method. Current Approved 303(d) List: 2012 WBID Segment Description COSJLP04a East Mancos River
Designated Uses & Impairment Status Aquatic Life Cold Water 1 / Impaired Nov.1 to April 30: Recreation N / Not Impaired May 1 to Oct. 31: Recreation E / Not Impaired Water Supply / Impaired Agriculture / Not Impaired Table 1.1. Designated uses and impairment status for the East Mancos River.
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
Water Quality Criteria for Impaired Designated Uses WBID Impaired Designated Use Applicable Water Quality Criteria and Status
COSJLP04a
Aquatic Life Cold 1
Dissolved Phase Cu (1) / Not Attained
COSJLP04a
Water supply
Dissolved Phase Mn (1) / Not Attained
Applicable State or Federal Regulations: (1) Classifications and Numeric Standards for the San Juan and Dolores River Basins.
Table 1.2. Ambient water quality criteria and status for the 303(d) listed East Mancos River segment. II.
GEOGRAPHICAL EXTENT
2.1 Segment Description East Mancos River Segment 4a is located in the southwestern portion of Montezuma County, in southwestern Colorado. The East Mancos River watershed, as measured from the USGS gauging station #09369000 located near the confluence of the East Fork and Middle Fork of the Mancos River, drains an area of approximately 11.9 square miles northeast of the town of Mancos. The entire segment is water quality impaired, and is currently listed on the 2012 303(d) List for dissolved copper and manganese. The source of dissolved copper is predominately from a sub-economic copper deposit referred to as the ―Allard Stock‖ (DRMS, 2009), but also includes sources from historic mining activity. The source of dissolved manganese can be attributed to ore mining in addition to natural sources. However, the mining activity for this region did not likely focus on copper or manganese products, and the presence of these particular metals is a by-product of the historic mining activity undertaken to extract other metals. The watershed contains several historic mines, including the Red Arrow/Outwest (Permit # COR 040158), Gold Dollar, Florence W., Thunder, Silver Falls, Lady Stafford, Kimball, Georgia Girl, Doyle Group and additional unnamed, inactive, or abandoned mine workings. Area land ownership is a combination of Federal (USDA Forest Service) and private interests. Topography in the study area is extremely rugged and ranges in altitude from 7380 feet above mean sea level (amsl) near the confluence with the Middle Fork to a high of approximately 13,220 feet amsl near Spiller Peak at the top of the watershed. Thus, the vertical relief of the watershed is 5,840 feet. The East Mancos River watershed is located on the western edge of the La Plata mining district in Southwestern Colorado. Topography of the watershed is composed of high mountain peaks dissected by deeply incised drainages, talus slopes, and sheer rock faces. Slopes below timberline (11,000 to 11,500 ft amsl) are made up of Mountain White Oak (Scrub oak), dwarf maple, western chokecherry, and western serviceberry (HMWMD 2005). The upper watershed is composed of aspen, Douglas and white fir, Englemann and blue spruce, and western pine. Portions of the watershed above timberline, with vegetation, contain a mixture of grasses, sedges, dwarf willows, and low shrubs (HMWMD 2005). Year round access to the mine sites is difficult and is largely dependent on the amount of precipitation and the rate of snowmelt.
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
2.2 Geology The La Plata Mountains were carved from a domal uplift of sedimentary rocks intruded by numerous stocks, dikes, and sills of igneous rock. Sedimentary formations exposed within the La Plata Mining District include the Upper-cretaceous aged Mancos shale and Dakota sandstone that overlays the Upper Jurassic aged formations inclusive of the Morrison shale, Junction Creek sandstone, Wanakah formation, and the Entrada sandstone. The Upper Jurassic formations are, in turn, underlain by the Jurassic-aged Dolores formation consisting of 500 to 750 feet of soft redbed sand and mudstones with some limestone conglomerates. Several hundred feet of Cambrian, Devonian, and Mississippian strata as well as pre-Cambrian granite and hornblendes underlie these sandstone formations. These sandstone formations are, in turn, overlain by large deposits of Upper Cretaceous and Tertiary rocks that formed part of the dome but are now eroded (DRMS, 2005).
Figure 1.0. East Mancos River watershed with major mine areas highlighted.
The most pronounced feature of the La Plata Mining District is a domal uplift of sedimentary beds measuring fifteen miles in diameter. A well-defined, horseshoe shaped hinge fold that opens toward the south outlines the dome. Rocks within the fold are altered and are thoroughly silicified. The sedimentary rocks present outside the fold are unaltered and several strong faults have uplifted the rocks near the center of the dome. During the formation of the
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
dome, numerous short, discontinuous faults of small displacement formed. After intrusion of the nonporphyritic stocks many of these faults reopened and subsequently became the location of the ore deposits. The La Plata mining district is most well known for its veins and replacement deposits of gold-bearing and silver-bearing telluride ores, from which the greater part of production has come. The district contains a wide variety of differing deposits within a small area. The most economically important are native gold and various telluride materials, particularly those of gold and silver. Significant quantities of sulfide minerals are present in the rocks of the headwaters of the Mancos and East Mancos Rivers. Measurable quantities of acid drainage are generated as the East Mancos River flows over outcrops of these mineralized volcanic rocks, and a significant amount of acid rock drainage develops (USFS, 1991). Within the East Mancos basin, specifically at alpine elevations, a lack of base cations from weathering-resistant metamorphic and igneous rocks exists. The result is a rapid depression in pH and increase in iron and sulfide concentrations as surface waters interact with these features (Meyer, 1993 as cited in Cheney, 1995). Groundwater in the area occurs primarily in fractures and voids in the sedimentary rocks as well as fractures in the underlying materials. Alluvial deposits in the East Mancos River drainage are typically saturated but are fairly thin and discontinuous. Recharge to the glacial and underlying materials is chiefly from snowmelt and rainfall infiltration with the greatest amount of recharge occurring in late spring and early summer during the snowmelt season. During late summer and fall, intense rainstorms can be sources of recharge, and thus, large sources of metals. 2.3 Discharge Permits and Property Ownership One mining operation is currently permitted in the East Mancos River watershed. The Red Arrow/Outwest Mine (COR 040158) is currently permitted for stormwater discharge associated with metal mining operations. No actual discharge has been reported at this location for several years. There are currently no other Colorado Discharge Permit System (CDPS) or National Permit Discharge Elimination System (NPDES) permits that discharge to the East Mancos River. Ownership of the land in the East Mancos River watershed is a combination of Federal (USDA Forest Service) and private interests. Gold mining operations have historically occurred in the East Mancos River drainage. Mines in the drainage include the Red Arrow/Outwest, Gold Dollar, Red Arrow Extension, Florence W., Thunder, Silver Falls, Lady Stafford, Kimball, Georgia Girl, and Doyle Group. III.
WATER QUALITY STANDARDS
The Colorado Basic Standards and Methodologies for Surface Water, Regulation 31, identifies standards applicable to all surface waters statewide (WQCC, 2012b). The pollutants of concern for this TMDL are dissolved copper and dissolved manganese. The specific numeric standards assigned to the listed stream segments are contained in Regulation 34, the Classifications and Numeric Standards for the San Juan River and Dolores River Basins (WQCC, 2012c). The relevant standards for the East Mancos River Segment 4a addressed in this document are the Aquatic Life Use-based table value standards for Cu, which vary based on hardness, and
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
the Water Supply standards for Mn. The highest hardness values and therefore more lenient Cu standards occur during low flow, which helps to offset the lack of dilution available at these times. The manganese water supply standard is set at a fixed value of 50 µg/l; therefore, it does not vary under different hardness and flow regimes.. The stream segment addressed here is use classified as Aquatic Life Cold Water 1 Recreation N: Nov.1 to April 30, Recreation E: May 1 to Oct. 31, Water Supply and Agriculture. The elevated levels of dissolved copper and manganese exceed the Aquatic Life Use standards and Water Supply Use standards, respectively, while other uses are supported. 3.1 Water Quality Goals and Targets The Colorado Basic Standards and Methodologies for Surface Water, Regulation 31, identifies standards potentially applicable for any surface water statewide (WQCC, 2012). The WQCC assigns specific numeric standards to a given water body based upon that water‘s designated uses. The segmentation of waters in the San Juan basin, and the relevant assigned numeric standards, is detailed in Classifications and Numeric Standards for San Juan River and Dolores River Basisn, Regulation 34 (WQCC, 2012). Typically the assigned standard is unchanged from the Table Value Standard (TVS) identified in the Basic Standards and Methodologies for Surface Water. That is the case for this assessment. The pollutants of concern for the East Mancos River watershed include copper and manganese. Aquatic Life Use-based criteria for copper are expressed as the dissolved fraction of those metals. Aquatic Life Use-based standards are two part, and include both acute and chronic criteria. 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). Acute standards are intended to protect against outright mortality. Chronic standards represent the level of pollutants that protect 95 percent of the genera from chronic toxic effects of metals. Chronic toxic effects include, but are not limited to, demonstrable abnormalities and adverse effects on survival, growth, or reproduction (WQCC 2006). Water Supply Use-based criteria may be expressed as either dissolved or total fractions and individual criteria may be applied on either a long-term, chronic, or short-term, acute basis. Water Supply Use-based manganese standards are expressed as the dissolved fraction and are applied as chronic standards. Per the Section 303(d) Listing Methodology, 2012 Listing Cycle (WQCD 2011), attainment of Aquatic Life Use-based and Water Supply Use-based metals standards, when expressed as the dissolved fraction, is determined by comparison of the 85th percentile value of the ranked data against the standard. Additionally, most Aquatic Life Use-based metal standards, including the copper standard included in this TMDL assessment, are hardness based. Because the toxicity of these metals is ameliorated at higher hardness values, the calculated standard increases as hardness is increased. The water quality target and goal for this TMDL is attainment of the current dissolved copper and dissolved manganese water quality standards in the East Mancos River, thereby improving water quality to ensure that it is safe and protective of all its assigned uses. The following table lists the water quality standards for the East Mancos River Segment 4a from the Water Quality Control Commission‘s Regulation No. 34.
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
Water quality standards for the East Mancos River Segment 4a (COSJLP04a) Stream Segment Description
Classification
Metals (µg/l)
4a: Mainstem of the Mancos River, including all wetlands, tributaries, lakes, and reservoirs, from the source of the East, West and Middle Forks to Hwy 160, except for the specific listing in segment 4b.
Aquatic Life Cold 1 Recreation E: May Recreation N: Nov. Water Supply Agriculture
Cu: Acute = e(0.9422(ln(hardness))-1.7408) Chronic = e(0.8545(ln(hardness))-1.7428) Mn = 50 µg/l
Table 3.1. Water quality standards for the East Mancos River Segment 4a (COSJLP04a). 3.2 Hydrology Data from the weather station at Mancos, Colorado indicates that the watershed is arid to semi-arid. Most of the moisture is from winter snowfall, although intense rainstorms during late summer and fall (e.g., August) can contribute a fair amount to precipitation totals, and in turn, higher monthly streamflow totals and copper concentrations in the fall. Climate data for the Mancos Weather Station, the nearest weather station in the watershed, for the period of August 1948 through June 2007 is summarized as follows: Average annual precipitation: 16.4 in. (416 mm.) Month of highest precipitation: August (1.84 in. (47 mm.)) Month of lowest precipitation: June (0.58 in. (15 mm.)) Average annual snowfall: 47.1 in. (120 cm.) Average annual temperature: 47.1º F (8.4º C) Month of highest average temperature: July (84.7º F (29.3º C)) Month of lowest average temperature: December (14.6º F (-9.7º C)) (Source: http://www.wrcc.dri.edu/summary/climsmco.html) The East Mancos River originates in Rush Basin on the western slope of Spiller Peak. From its origin, the East Mancos River flows approximately 11 miles west of Spiller Peak to its confluence with the Middle Mancos River. The Mancos River flows an additional 1.5 miles to the confluence with the West Mancos River approximately 1.5 miles upstream of the town of Mancos. The drainage area of the East Mancos River as measured at USGS gage #09369000 (East Mancos River near Mancos, CO) is 11.9 square miles, and is located at approximately 7,475 feet above sea level. The hydrograph of the East Mancos River near Mancos, Colorado is typical of higher elevation mountain streams. High flows typically occur from April through July, coinciding with spring runoff followed by a tapered flow decrease in August (Table 3.2, Figure 2). Figures 2 and 3 and Table 3.2 illustrate the hydrologic characteristics of the East Mancos River near Mancos, Colorado.
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
Hydrologic characteristics of the East Mancos River near Mancos, CO (USGS gage # 09369000)
Month
Mean Flow (cfs)
25th Percentile Flow (cfs)
Median Flow (cfs)
75th Percentile (cfs)
1E3 Acute Flow (cfs)
30E3 Chronic Flow (cfs)
January
1.7
1.5
1.6
1.8
1.5
1.6
February
1.7
1.5
1.6
1.9
1.6
1.5
March
2.6
1.8
2.2
3.1
1.5
1.5
April
6.5
2.8
4.1
7.4
1.5
1.5
May
19.3
5.7
12.4
24.9
1.5
1.5
June
8.1
3.4
4.4
8.2
1.6
1.6
July
3.6
3.0
3.4
4.0
1.5
1.6
August
3.4
2.9
3.2
3.6
1.7
1.7
September
3.1
2.2
2.8
3.8
1.6
1.7
October
2.5
1.7
2.0
2.6
1.6
1.8
November
1.9
1.6
1.8
1.9
1.7
1.8
December
1.7
1.5
1.7
1.8
1.8
1.6
Table 3.2. Hydrologic characteristics of the East Mancos River near Mancos, CO (COSJLP04a).
Historically, USGS operated flow gage #09369000 (East Mancos River near Mancos, CO) from April 1937 through September 1951. In order to better approximate current flow conditions in the East Mancos River, a regression analysis was performed using USGS gage #09370000 (Mancos River near Mancos, CO) and USGS gage #09369000 for the overlapping time period of April 1937 through September 1938 (R2 = 0.92). To ensure that the flow record represents the typical flow of the area, this analysis was done for the time period recorded from both stations. This time period, or period of record, only occurred from April 1937 to September 1938. However, the regression analysis, using the two (2) stations, should model an accurate representation of stream flow for this watershed. The regression analysis was applied to the Mancos River (#09370000) data from October 1998 to September 2009 to provide a current flow model. The resulting equation was used to predict current flows in the East Mancos River (Equation 1). Eq.1: East Mancos flows = -0.000001x3 + 0.0008x2 + 0.078x + 1.3245 The two USGS gages are within approximately 1.5 miles of each other. USGS #09369000, East Mancos River near Mancos, CO is located just upstream of the confluence with Middle Mancos River. At present, USGS no longer operates either gage, but the Division of Water Resources (DWR) currently operates a similar gage (MANMANCO) approximately 0.25 miles downstream from USGS #09370000 (Mancos River near Mancos), which was not used explicitly since it is unclear whether the Middle Mancos contributes to the flow measurement. Median monthly flows were approximately between 1.6 and 12.4 cubic feet per second (cfs), based on predicted flows (Table 3.2). Acute and chronic low flows were calculated using USEPA DFLOW software.
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
For this region of Colorado, an increase in flow for the months of March through June is expected to coincide with spring runoff. Review of State of Colorado records indicate permitted diversions occur at several points along the East Mancos River for irrigation use. The diversion uses are not constant and vary month to month, and year to year. The diversion uses occur from April to September, with typical activity occurring from May through July. The diverted irrigation flow ranges from 0.1 to 12.3 cfs. Considering the average flow in the East Mancos River, this amount of diverted flow is considerable. Predicted East Mancos River 14.0 12.0
Median Flow, cfs
10.0 8.0 6.0 4.0 2.0 0.0 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Figure 2.0. Predicted monthly median flows from the East Mancos River (POR = 1998 – 2009).
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
Flow, cfs
100
10
1 Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Month
Figure 3.0. Box and whisker plot of monthly flow percentiles on the East Mancos River near Mancos, CO. Values are plotted on a logarithmic scale and refer to 5th, 25th, 75th and 95th percentile flow values. X refers to monthly median values.
3.3 Ambient Water Quality To identify exceedances of the assigned water–quality standards, the eighty-fifth percentile concentrations of metals were calculated using the most current available data from the Colorado Department of Public Health and Environment (CDPHE). The sampling site was located on the East Fork of the Mancos River at Road 44. The metals concentrations (in addition to acute and chronic standards) are expressed as "dissolved" concentrations in micrograms per liter (µg/L). Technically, the term "dissolved" metals refers to the portion of metals from samples that were filtered through a 0.45-micrometer filter before analysis. Water quality data have been collected by the Colorado Department of Public Health and Environment (CDPHE) in the East Mancos River near the confluence with the Middle Mancos River since 1998. Samples from the East Mancos River taken at, or near, this location on sixtytwo (62) occasions between 1998 and 2010 indicated impairment and resulted in the 303(d) listings for Cu and Mn in 2002 and 2012, respectively. Sampling was performed by WQCD and the Division of Wildlife – Riverwatch program. Ambient concentrations and table-value standards of dissolved copper are expressed in Table 3.3 and dissolved manganese is expressed in Table 3.4. Segment 4a of the East Mancos River is in attainment of the dissolved copper standard in the month of October. Exceedances of the standard occur in the remaining months of the year. Attainment of the dissolved manganese standard occurs in May and December. While the ambient concentrations listed in Tables 3.3 and 3.4 represent data collected from 1998 to 2010, a steady average increase from 2007 to 2010 occurs for manganese. This recent average increase coincides with the recent addition of manganese to the 303(d) list for this segment.
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
Ambient water quality data (dissolved copper)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Avg. Hardness
Cu-D, TVS (g/L)
85th % Cu-D (g/L)
Difference
% Reduction
179 177 139 98 68 117 139 141 135 160 158 169
14.7 14.6 11.9 8.8 6.4 10.3 11.9 12.0 11.6 13.4 13.2 14.0
37 23 29 37 23 36 20 26 68 11 18 22
22.7 8.7 17.3 28.6 16.2 25.3 8.1 13.7 56.2 -2.7 5.0 7.9
61% 37% 59% 77% 72% 71% 41% 53% 83% 0% 27% 36%
Table 3.3. Ambient water quality data for COSJLP04a (dissolved copper), the East Fork Mancos River above the confluence with the Mancos River (concentrations are given as 85th %). Exceedances are highlighted in bold. This table represents the chronic standards. Note that additional reductions are required for March and June according to acute standards. The acute standards, and associated reductions, are addressed later in this assessment.
Ambient water quality data (dissolved manganese)
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mn-D, TVS (g/L)
85th % Mn-D (g/L)
Difference
% Reduction
50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0
57 65 86 66 39 104 71 220 211 101 58 43
6.6 14.6 35.6 15.7 -10.7 53.6 20.7 170.1 160.5 51.2 8.0 -7.0
12% 23% 42% 24% 0% 52% 29% 77% 76% 51% 14% 0%
Table 3.4. Ambient water quality data for COSJLP04a (dissolved manganese), the East Fork Mancos River above the confluence with the Mancos River (concentrations are given as 85th %). Exceedances are highlighted in bold.
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
The East Fork of the Mancos River was sampled for dissolved copper twenty-five (25) times by CDPHE between October 1998 and May 2010, and thirty-one (31) times by DOWRiverwatch. The sample sites include WQCD #9720 (East Fork Mancos River at 44 Road) and DOW-Riverwatch #4129 (East Fork Mancos River above the confluence with Mancos). Seven out of the twenty-five dates (CDPHE) sampled exceeded both the chronic and acute dissolved copper standards. Five of the seven exceedances occurred in April or May, during snowmelt. The remaining two exceedances occurred in June 1999 and August 2001 and could be attributed to extended snowmelt or high precipitation events. For the DOW-Riverwatch data set, twentyfive out of the thirty-one dates (DOW-Riverwatch) exceeded the chronic dissolved copper standards and twenty-three out of the thirty one dates exceeded the acute dissolved copper standards. The dissolved manganese sampling for the East Fork of the Mancos River includes additional data from WQCD site #9723 (East Mancos River at Forest Road 567 Above Mine). The East Fork Mancos was sampled for dissolved manganese twenty-five (25) times at WQCD #9720, five (5) times at WQCD #9723, and thirty-two (32) times at DOW-Riverwatch #4129. Two out of the twenty-five dates sampled at WQCD #9720 exceeded the standard. Five out of the five dates sampled at WQCD #9723 exceeded the standard, with ambient values ranging from 83 µg/l to 540 µg/l. Nineteen out of the thirty-two dates sampled at DOW-Riverwatch #4129 exceeded the standard.
IV.
PROBLEM IDENTIFICATION
4.1 Background Anecdotal information was provided to HMWMD by the U.S. Forest Service and the Colorado Division of Wildlife and indicated that past activities at the Gold Dollar Mine may have resulted in a serious degradation of water quality in the East Mancos River. Excavation activities in the streambed in the mid-1980‘s may have resulted in an ongoing release of low pH water and elevated copper concentrations in the river. This release reportedly resulted in a largescale fish kill in the East Mancos River with the ongoing release of elevated metals since the date of the incident (HMWMD, 2005). Mine wastes may generate three major types of pollutants including acid drainage, concentrations of heavy metals, and sediments derived from the erosion of tailings and waste rock piles. Mine drainage composition is a function of ore deposit geology, climate, and mining methods used (Plumlee, et al. 1993). Factors controlling pH and dissolved metal concentrations include the acid buffering capacity of the host rock, and the availability of water and oxygen, coupled with the abundance and availability of sulfide minerals for weathering (HMWMD 2005). Figures 4.1 and 4.2 illustrate the current water quality levels and the relationship to the current standards. Note that, for copper, the acute and chronic standards are dependent, and vary, on hardness. The manganese standard is set at 50 µg/l, as determined by the WQCC.
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
Figure 4.1. Observed dissolved copper concentrations with underlying acute and chronic standards.
Figure 4.2. Observed dissolved manganese concentrations with underlying water supply standard.
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
Ore bearing veins on the East Mancos River are characterized by the presence of acidgenerating reactive sulfides in the form of pyrites and chalcopyrites (Cheney, 1995). Site reconnaissance activities conducted by CDPHE Hazardous Materials and Waste Management Division in July 2003 did not identify specific draining adits in the lower and middle reaches of the East Mancos River, although there were numerous indicators of surface water contamination in the form of discolored water and the accumulation of a whitish precipitate in the streambed (HMWMD 2005). Additionally, during the 2003 site visit, CDPHE staff were not able to identify a specific source for the contamination near the Red Arrow Mine site, nor were there obvious tailings or waste rock piles present in the drainage near the mine site. However, there were still obvious indicators of surface water contamination in the drainage area above the mine site. The presence of precipitate and discolored water upstream of the Red Arrow Mine site is indicative of the presence of additional loading sources in the upper reach of the East Mancos River. Additional reconnaissance performed in July 2005 did not indicate the presence of waste rock piles immediately adjacent to the East Mancos River. There were waste rock piles present on the hill slopes surrounding the drainage; however, these piles were well removed from the creek bed and were not subject to continual inundation and did not appear to be actively eroding into nearby waters (HMWMD 2005). Hazardous Materials and Waste Management Division performed a sampling event on July 27 and 29, 2004 of the East Mancos River. HMWMD noted the presence of large iron bog deposits near the headwaters of the East Mancos River. The streambed was cemented with a ferricrete/iron precipitate in the vicinity and for an undetermined distance downstream of these deposits (HMWMD, 2005). Surface water samples were collected from the headwaters of the East Mancos River to the confluence with the Middle Fork of the Mancos River (Table 4.10). In general, metals concentrations are highest in the upper reaches of the watershed and attenuate as they travel downstream. As demonstrated in Table 4.11, the highest concentrations of dissolved copper are seen at site EMR-SW-01 (headwaters of the East Mancos River). Analysis from surface water samples collected from the Middle Fork of the Mancos River indicate that water quality impairments are limited to the East Fork of the Mancos River, with no apparent water quality degradation occurring in the Middle Fork. Groundwater samples had slightly elevated concentrations of copper (Table 4.11). Acid discharge from mine adits and acidic/metal containing runoff from waste piles is available to shallow groundwater proximal to the mine workings. In addition, the ore materials in the area may have an acid generating potential and may facilitate inorganic contaminant migration via metals mobilization (HMWMD, 2005).
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
Sample Type
Sample No. EMR-SW-01
EMR-SW-02
EMR-SW-03
EMR-SW-04 Surface Water EMR-SW-05
EMR-SW-06
EMR-SW-07
EMR-SW-08
Ground Water
EMR-GW-01
EMR-AS-01 Adit Samples EMR-AS-02
Location Upstream surface water sample collected from East Mancos River upstreaam of mining influences. Surface water sample collected from East Mancos River below northern-most outfall from Rush Basin immediately upstream of the Doyle Group mines Downstream surface water sample collected from East Mancos River below PPE for the Georgia Girl, Kimball, and Lady Stafford mines. Downstream surface water sample collected from East Mancos River below PPE for the Silver Falls Mine Downstream surface water sample collected from East Mancos River below the PPE for the Gold Dollar Mine Downstream surface water sample collected from East Mancos River below the PPE for the Gold Dollar Mine Downstream surface water sample collected from East Mancos River below the PPE for the Billings and Charlene mines Downstream surface water sample collected from East Mancos River below PPE for the Red Arrow Extension Mine Sample from existing domestic well located approximately 0.25 mile upgradient of the confluence with East and Middle Mancos Rivers Adit discharge sample collected at Red Arrow Mine portal Adit discharge sample collected at Gold Dollar Mine portal
Rationale Characterize upstream conditions on East Mancos River
Document upstream conditions in the East Mancos River upstream of historic mining sites
Document an observed release by chemical analysis of mining-related contaminants to fisheries and wetlands associated with East Mancos River Document an observed release by chemical analysis of mining-related contaminants to fisheries and wetlands associated with East Mancos River Document an observed release by chemical analysis of mining-related contaminants to fisheries and wetlands associated with East Mancos River Characterize upstream conditions on East Mancos River
Document upstream conditions in the East Mancos River upstream of historic mining sites Document an observed release by chemical analysis of mining-related contaminants to fisheries and wetlands associated with East Mancos River Evaluate ground water conditions and check for impacts from mining-related activities.
Sample to characterize adit discharge at ground surface, if present Sample to characterize adit discharge at ground surface, if present
Table 4.10. Water sampling sites (surface water and ground water) on East Mancos River taken by HMWMD on June 27 and 29, 2004.
15
Total Maximum Daily Load Assessment for East Mancos River segment 4a
Adit samples were taken from both the Red Arrow and Gold Dollar mines. Samples from the Red Arrow Mine discharge were in attainment of chronic stream standards, with concentrations of 7.0 g/L of copper and 4.2 g/L of manganese (Table 4.11). Adit samples from below the Gold Dollar Mine indicated elevated metals concentrations, with concentrations of 99.7 g/L for dissolved copper, and 1170 g/L for dissolved manganese (Table 4.11), which exceed standards for both constituents.
Date
pH
Hardness
Cu-D µg/l
Mn-D µg/l
EMR-SW-01 EMR-SW-02 EMR-SW-03 EMR-SW-04 EMR-SW-05 EMR-SW-06 EMR-SW-07 EMR-SW-08 EMR-GW-01 EMR-AS-01
7/27/2004 7/27/2004 7/27/2004 7/27/2004 7/27/2004 7/27/2004 7/27/2004 7/27/2004 7/29/2004 7/29/2004
4.2 5.95 3.81 3.76 5.74 6.18 6.47 6.72
21 3 20 41 70 71 88 28 140 237
2990.0 12.1 2330.0 2150.0 1090.0 1050.0 139.0 20.1 141.0 7.0
1660.0 1.2 1270.0 856.0 544.0 519.0 284.0 77.8 62.2 4.2
EMR-AS-02
7/29/2004
204
99.7
1170.0
Site
Average
5.4
83.7
911.7
586.2
Median
5.8
69.9
141.0
519.0
Min
3.8
2.8
7.0
1.2
Max
6.7
236.7
2990.0
1660.0
85th %
6.5
171.7
2240.0
1220.0
Table 4.11. Surface water dissolved metals concentrations in the East Fork of the Mancos River, taken on July 27 and 29, 2004. The bolded items represent the sample locations related to mining influence. All cases exceed standards, except EMR-AS-01 (Cu and Mn), and EMR-SW-02 (Mn only). Samples were taken from below the Silver Falls and Gold Dollar mines in May and October of 2009. Samples from below the Silver Falls Mine exceeded chronic stream standards, with concentrations above 200 g/L of copper (Table 4.12). Samples from below the Silver Falls and Gold Dollar mines indicated higher copper and manganese concentrations, with concentrations above 1000 g/L (Table 4.13). The data shown in tables 4.11, 4.12, and 4.13 are to illustrate that specific sampling incidents took place to determine attainment or impairment for the East Mancos River. The specific data in these tables do not generate the impairment on their own, but are included in the overall data to calculate the TMDL and load reductions. These sampling locations and dates are from the HMWMD site assessment previously mentioned (2005). Figure 5 depicts a portion of the East Mancos River watershed and the locations of the mines listed in this assessment. The figure illustrates the proximity of the listed mines to each other.
16
Total Maximum Daily Load Assessment for East Mancos River segment 4a
Date
pH
Hardness
Cu-D µg/l
Mn-D µg/l
DMR-AS-02 DM
5/20/2009
6.59
195
0*
763
DUP-01 DM
5/20/2009
--
44
42.6
104
EG DM EMR-SW-04 DM EMR-SW-04a DM EMR-SW-05 DM
5/20/2009 5/20/2009 5/20/2009 5/20/2009
7.15 5.83 5.86 6.82
40 29 29 44
0* 272 278 44.4
15.5 146 150 104
EMR-SW-06 DM
5/20/2009
7.00
43
47.3
95.6
FC DM
5/20/2009
7.83
79
0*
0*
GDC DM
5/20/2009
7.86
102
0*
0*
7.29 6.91 7.00 5.83 7.86 6.01**
39 64 44 29 195 94
0* 137 47.3 42.6 278 274
0* 197 104 15.5 763 211
Site
GRC DM 5/20/2009 Average Median Min Max 85th % *Refers to below detection limit **Refers to 15th %
Table 4.12. Surface water dissolved metals concentrations in the East Fork of the Mancos River, taken on May 20, 2009. Aside from cases of ―non-detect,‖ all cases exceed standards, except Mn compliance for EG-DM.
Site
Date
pH
Hardness
Cu-D µg/l
Mn-D µg/l
85
1850
1110 11.7 1100 1120 837 779
DUP-01 DM
10/1/2009
EG DM EMR-SW-04 DM EMR-SW-04a DM EMR-SW-05 DM EMR-SW-06 DM
10/1/2009 10/1/2009 10/1/2009 10/1/2009 10/1/2009
6.9 4.53 4.56 4.71 4.72
120 85 85 104 106
3.71 1840 1870 1420 1230
FC DM
10/1/2009
7.50
173
0*
GRC DM 10/1/2009 Average Median Min Max 85th % *Refers to below detection limit **Refers to 15th %
7.59 5.79 4.72 4.53 7.59 4.56
167 116 105 85 173 165
0* 1369 1630 3.71 1870 1855
20.9 711 837 11.7 1120 1111
Table 4.13. Surface water dissolved metals concentrations in the East Fork of the Mancos River, taken on October 1, 2009. Aside from cases of ―non-detect,‖ all cases exceed standards, except EG DM (Cu and Mn) and GRC DM (Mn only).
17
Total Maximum Daily Load Assessment for East Mancos River segment 4a
Figure 5.0. Primary abandoned mine sites in the East Mancos River Watershed.
18
Total Maximum Daily Load Assessment for East Mancos River segment 4a
4.2 Source Analysis Point Sources The largest stream load is found below the Gold Dollar Mine in the East Mancos River watershed (i.e., 29.4 pounds of copper per day), followed by the Silver Falls Mine (i.e., 22.8 pounds per day of copper) (Table 4.20). The upstream contribution of copper is not insignificant, contributing approximately 15.4% to the total stream load (Table 4.20, Figure 5). The estimated contributions of the individual point sources may be increased during periods of snowmelt or flushing precipitation events.
Site Name Upstream Site Georgia Girl, Kimball, Lady Stafford Silver Falls Mine Gold Dollar Mine Billings and Charlene Mines Red Arrow Mine Extension Sum of Upstream Load
Summary of samples to establish contributions to East Mancos and load allocation Median Mn Flow, Mn Load % Cu Load Drainage cfs ug/l lbs/day contribution Cu ug/l lbs/day East Mancos River 0.76 1660 6.8 14.8 2990 12.3 East Mancos River East Mancos River East Mancos River East Mancos River East Mancos River East Mancos River
% contribution 15.4
0.9
1270
6.0
13.0
2330
10.9
13.8
2.0
856
9.1
19.7
2150
22.8
28.6
5.1
532
14.6
31.9
1070
29.4
37.0
4.9
284
7.5
16.4
139
3.7
4.6
4.5
78
1.9
4.1
20
0.5
0.6
45.9
100
79.6
100
Table 4.20. Point source contributions of copper and manganese to the East Mancos River watershed. Upstream site (EMR-SW-01) info, or other site details, can also be found in Table 4.10. Figure 6.0 illustrates a graphical representation of the contributions from the mine sites. The distribution, based on copper, was used to establish the load allocations. The copper contribution matrix was used, instead of manganese, since it represented a more conservative approach to allocation. Reference Table 4.20 to compare percent contributions for copper and manganese.
19
Total Maximum Daily Load Assessment for East Mancos River segment 4a
Percent Contribution of Mine Sites to Stream Load Billings and Charlene Mines 4.6% 0.6%
Red Arrow Mine Extension 15.4% Upstream Site
Georgia Girl, Kimball and Lady Stafford Mines
Gold Dollar Mine 37.0%
13.8%
Silver Falls Mine 28.6%
Figure 6.0. Percent source contributions of copper to the East Mancos River watershed from abandoned mine sites. 5.0 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 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. TMDL = WLA + LA + MOS TMDL = Sum of Waste Load Allocations + Sum of Load Allocations + Margin of Safety Waste Load Allocations "(WLA") One mining operation (Red Arrow/Outwest COR 040158) is currently permitted in the East Mancos River watershed. There are however, non-permitted point sources (i.e., abandoned mines) to the East Mancos River that will require waste load reductions. Load Allocations ("LA") The upstream site is considered background, or a non-point source, and is therefore accountable to a load allocation.
20
Total Maximum Daily Load Assessment for East Mancos River segment 4a
Margin of Safety ("MOS") The MOS used in the TMDL analysis is both implicit and explicit and resides in the conservative assumptions utilized in the calculations, management response to removal of the source materials, and post-remediation water quality monitoring that will be performed. A MOS of 10% was included in the calculation of the TMDL for COSJLP04a. The conservative assumptions used in the analysis include the use of the 85th percentile of the data in establishing ambient conditions. TMDL load reductions are based on reductions necessary to meet eighty-fifth percentile copper and manganese concentrations. This will tend to overestimate the loading reductions. The TMDL is calculated using monthly median flows (estimated from USGS gage stations #09369000 and #09370000 as described in section III above), multiplied by the existing stream standard and a conversion factor (0.0054) to approximate a load in pounds/day. This load is reduced by 10% to reflect the margin of safety (MOS). The resulting load is allocated between background nonpoint source for the Load Allocation and the discrete and diffuse sources throughout the East Mancos watershed for the Waste Load Allocations. 5.1 TMDL FOR DISSOLVED COPPER Attainment of the TMDL is based on the sampling point on the East Mancos River just above the confluence with the Middle Fork. The average copper load reduction for the East Mancos River (COSJLP04a) based on chronic standards would be approximately 63%. The highest load reductions occur in the higher flow months of April through June, with reductions ranging between 74% and 79% up to the highest reduction of 91%. Load reductions drop to as low as 35% in November and 42% in December. Note that no load reductions are necessary for October. To attain water quality standards for the East Mancos River, both acute and chronic standards must be addressed. For Tables 5.11, 5.12, and 5.13, the majority of both water quality standards are attained when meeting the chronic standards. However, March and June require additional reductions to meet both the acute and chronic standards. Load allocations were allocated to both point and non-point sources. Table 5.12 illustrates the load provided to non-point sources based on natural background calculated from the sampling site upstream of any mining related influences. Waste load allocations were given to the remaining point sources (i.e., abandoned mine sites) on the basis of their contribution to the dissolved copper load in the East Mancos River. The Gold Dollar Mine was given the greatest waste load allocation at 37% of the remaining TMDL with the Silver Falls Mine receiving 28.6% of the allocation. Waste load allocation 1 (WLA 1) refers to the allowable load from the Georgia Girl, Kimball and Lady Stafford Mines; WLA 2 refers to the allowable load from the Silver Falls Mine; WLA 3 refers to the allowable load from the Gold Dollar Mine; and WLA 4 combines the remaining abandoned mine sources. Non-point sources and background were given approximately 15% of the allowable load (Table 5.12).
21
Total Maximum Daily Load Assessment for East Mancos River segment 4a
TMDL for dissolved copper for COSJLP04a with a 10% Margin of Safety
Month
Median Flow (cfs)
Hardness, CaCO3, mg/L
Cu-D TVS, ug/L
Cu TMDL lbs/day
Cu TMDL lbs/day with 10% MOS
January
1.6
179
14.7
0.131
0.118
37.4
0.333
0.215
65
February
1.6
177
14.6
0.130
0.117
23.3
0.208
0.091
44
March
2.2
80
10.9
0.128
0.116
33.9
0.400
0.284
71
April
4.1
98
8.8
0.195
0.175
37.4
0.831
0.655
79
May
12.4
68
6.4
0.430
0.387
22.7
1.512
1.125
74
June
4.4
24
3.5
0.082
0.074
34.4
0.809
0.735
91
July
3.4
139
11.9
0.219
0.197
20.0
0.368
0.171
46
August
3.2
141
12.0
0.207
0.186
25.7
0.444
0.258
58
September
2.8
135
11.6
0.174
0.156
67.8
1.016
0.859
85
October
2.0
160
13.4
0.146
0.131
10.7
0.117
-0.015
0
November
1.8
158
13.2
0.127
0.114
18.2
0.175
0.061
35
December
1.7
169
14.0
0.128
0.115
21.9
0.200
0.085
42
Ambient Cu, ug/L
Ambient Cu Load lbs/day
Load Reduction
Percent Load reduction
Table 5.11. TMDL for dissolved copper for COSJLP04a with a 10% Margin of Safety. Italicized items are percent reduction based on attainment of acute standard. All standards are met with the listed load reductions. A current permit is issued for the Red Arrow/OutWest mine for ‗Stormwater Discharges Related to Metal Mining.‘ Since the permit does not address a specific discharge related to mining activity, and the possibility of future mining exists, a reserve capacity was included in the TMDL in order to reserve allocations for future permitted discharges to this segment. Specifically, the WLA 5 allocation (Table 5.12) is assigned for the existing permit and any future point sources. Because the mine has not reported mining related discharges for several years, the Division did not assign it an individual allocation; however, if any mining activity is initiated which would discharge to the East Mancos River segment, this TMDL shall undergo revision to provide individual WLAs for specific dischargers/permittees.
22
Total Maximum Daily Load Assessment for East Mancos River segment 4a
Copper TMDL allocations for East Mancos River
Month January February March April May June July August September October November December
TMDL lbs/day
10% MOS
LA lbs/day (Background)
WLA 1 lbs/day
WLA 2 lbs/day
WLA 3 lbs/day
WLA 4 lbs/day
Future Growth WLA 5 lbs/day
0.131
0.0131
0.0161
0.0145
0.0300
0.0388
0.0054
0.0131
0.130
0.0130
0.0160
0.0144
0.0298
0.0385
0.0054
0.0130
0.128
0.0128
0.0158
0.0142
0.0294
0.0380
0.0053
0.0128
0.195
0.0195
0.0240
0.0215
0.0446
0.0577
0.0081
0.0195
0.430
0.0430
0.0530
0.0475
0.0984
0.1273
0.0179
0.0430
0.082
0.0082
0.0102
0.0091
0.0189
0.0244
0.0034
0.0082
0.219
0.0219
0.0270
0.0242
0.0501
0.0648
0.0091
0.0219
0.207
0.0207
0.0255
0.0228
0.0473
0.0612
0.0086
0.0207
0.174
0.0174
0.0214
0.0192
0.0397
0.0514
0.0072
0.0174
0.146
0.0146
0.0180
0.0161
0.0334
0.0432
0.0061
0.0146
0.127
0.0127
0.0157
0.0140
0.0291
0.0376
0.0053
0.0127
0.128
0.0128
0.0158
0.0141
0.0293
0.0379
0.0053
0.0128
Table 5.12. Waste load and load allocations for dissolved copper for COSJLP04a with a 10% Margin of Safety. Copper load reductions for COSJLP04a
Month
Cu Load Reduction lbs/day
Cu Load Reduction lbs/day (Background)
Cu Load reduction for WLA 1 lbs/day
Cu Load reduction for WLA 2 lbs/day
Cu Load reduction for WLA 3 lbs/day
Cu Load reduction for WLA 4 lbs/day
January
0.215
0.0331
0.0297
0.0615
0.0795
0.0112
February
0.091
0.0140
0.0125
0.0259
0.0335
0.0047
March
0.284
0.0438
0.0392
0.0813
0.1051
0.0148
April
0.655
0.1009
0.0905
0.1875
0.2425
0.0341
May
1.125
0.1732
0.1552
0.3217
0.4162
0.0585
June
0.735
0.1132
0.1015
0.2103
0.2720
0.0382
July
0.171
0.0263
0.0236
0.0489
0.0633
0.0089
August
0.258
0.0397
0.0356
0.0737
0.0954
0.0134
September
0.859
0.1323
0.1186
0.2458
0.3179
0.0447
October
0.000
0.0000
0.0000
0.0000
0.0000
0.0000
November
0.061
0.0094
0.0084
0.0174
0.0225
0.0032
December
0.085
0.0131
0.0117
0.0243
0.0315
0.0044
Table 5.13. Dissolved copper load reductions from abandoned mine sources in pounds per day for COSJLP04a. No load reductions necessary for October (see Table 5.11).
23
Total Maximum Daily Load Assessment for East Mancos River segment 4a
5.2 TMDL FOR DISSOLVED MANGANESE Attainment of the TMDL is based on sampling along several points of the East Mancos River. The average manganese load reduction in the months that are out of attainment (JanuaryApril and June-November) for the East Mancos River (COSJLP04a) would be approximately 46%. The highest load reductions occur in the latter half of the year, with reductions ranging between 56% and 80%. Load reductions drop to as low as 20% in January and 22% in November. The months of August and September require the highest reductions, 80% and 79% respectively, most likely due to summer precipitation events. Note that no load reductions are necessary for May and December. Load allocations were allocated to both point and non-point sources. Table 5.22 illustrates the load provided to non-point sources based on natural background calculated from the sampling site upstream of any mining related influences. Waste load allocations were given to the remaining point sources (i.e., abandoned mine sites) on the basis of their contribution to the dissolved manganese load in the East Mancos River (reference section 5.1). The Gold Dollar Mine was given the greatest waste load allocation at 31.9% of the TMDL, with the Silver Falls Mine receiving 19.7% of the allocation. Wasteload allocation 1 (WLA 1) refers to the allowable load from the Georgia Girl, Kimball and Lady Stafford Mines; WLA 2 refers to the allowable load from the Silver Falls Mine; WLA 3 refers to the allowable load from the Gold Dollar Mine; and WLA 4 combines the remaining abandoned mine sources. Non-point sources and background were given approximately 15% of the allowable load (Table 5.22). A current permit is issued for the Red Arrow/OutWest mine for ‗Stormwater Discharges Related to Metal Mining.‘ Since the permit does not address a specific discharge related to mining activity, and the possibility of future mining exists, a reserve capacity was included in the TMDL in order to reserve allocations for future permitted discharges to this segment. Specifically, the WLA 5 allocation (Table 5.22) is assigned for the existing permit and any future point sources. Because the mine has not reported mining related discharges for several years, the Division did not assign it an individual allocation; however, if any mining activity is initiated which would discharge to the East Mancos River segment, this TMDL shall undergo revision to provide individual WLAs for specific dischargers/permittees.
24
Total Maximum Daily Load Assessment for East Mancos River segment 4a
TMDL for dissolved manganese for COSJLP04a with a 10% Margin of Safety
Month
Median Flow (cfs)
Hardness, CaCO3, mg/L
Mn-D TVS, ug/L
Mn TMDL lbs/day
Mn TMDL lbs/day with 10% MOS
January
1.6
179
50.0
0.445
0.401
56.6
0.504
0.103
20%
February
1.6
177
50.0
0.445
0.401
64.6
0.576
0.175
30%
March
2.2
80
50.0
0.590
0.531
85.6
1.009
0.479
47%
April
4.1
98
50.0
1.111
1.000
65.7
1.459
0.460
32%
May
12.4
68
50.0
3.337
3.003
39.3
2.625
-0.379
0%
June
4.4
24
50.0
1.177
1.059
103.6
2.437
1.378
57%
July
3.4
139
50.0
0.923
0.830
70.7
1.304
0.474
36%
August
3.2
141
50.0
0.863
0.777
220.1
3.800
3.023
80%
September
2.8
135
50.0
0.749
0.674
210.5
3.153
2.479
79%
October
2.0
160
50.0
0.545
0.490
101.2
1.102
0.612
56%
November
1.8
158
50.0
0.481
0.433
58.0
0.558
0.125
22%
December
1.7
169
50.0
0.457
0.411
43.0
0.393
-0.018
0%
Ambient Mn, ug/L
Ambient Mn Load lbs/day
Load Reduction
Percent Load reduction
Table 5.21. TMDL for dissolved manganese for COSJLP04a with a 10% Margin of Safety.
Manganese TMDL allocations for East Mancos River
Month
TMDL lbs/day
10% MOS
LA lbs/day (Background)
WLA 1 lbs/day
WLA 2 lbs/day
WLA 3 lbs/day
WLA 4 lbs/day
Future Growth WLA 5 lbs/day
January
0.445
0.045
0.053
0.046
0.070
0.114
0.073
0.045
February
0.445
0.045
0.053
0.046
0.070
0.114
0.073
0.045
March
0.590
0.059
0.070
0.061
0.093
0.150
0.097
0.059
April
1.111
0.111
0.132
0.116
0.175
0.283
0.182
0.111
May
3.337
0.334
0.396
0.347
0.527
0.852
0.547
0.334
June
1.177
0.118
0.140
0.122
0.186
0.300
0.193
0.118
July
0.923
0.092
0.110
0.096
0.146
0.235
0.151
0.092
August
0.863
0.086
0.103
0.090
0.136
0.220
0.142
0.086
September
0.749
0.075
0.089
0.078
0.118
0.191
0.123
0.075
October
0.545
0.054
0.065
0.057
0.086
0.139
0.089
0.054
November
0.481
0.048
0.057
0.050
0.076
0.123
0.079
0.048
December
0.457
0.046
0.054
0.048
0.072
0.117
0.075
0.046
Table 5.22. Waste load and load allocations for dissolved manganese for COSJLP04a with a 10% Margin of Safety.
25
Total Maximum Daily Load Assessment for East Mancos River segment 4a
Manganese load reductions for COSJLP04a
Month
Mn Load Reduction lbs/day
Mn Load Reduction lbs/day (Background)
Mn Load reduction for WLA 1 lbs/day
Mn Load reduction for WLA 2 lbs/day
Mn Load reduction for WLA 3 lbs/day
Mn Load reduction for WLA 4 lbs/day
January
0.103
0.015
0.013
0.020
0.033
0.021
February
0.175
0.026
0.023
0.035
0.056
0.036
March
0.479
0.071
0.062
0.095
0.153
0.098
April
0.460
0.068
0.060
0.091
0.147
0.094
May
0.000
0.000
0.000
0.000
0.000
0.000
June
1.378
0.205
0.179
0.272
0.440
0.283
July
0.474
0.070
0.062
0.094
0.151
0.097
August
3.023
0.449
0.393
0.597
0.964
0.620
September
2.479
0.368
0.322
0.489
0.791
0.508
October
0.612
0.091
0.080
0.121
0.195
0.126
November
0.125
0.019
0.016
0.025
0.040
0.026
December
0.000
0.000
0.000
0.000
0.000
0.000
Table 5.23. Dissolved manganese load reductions from abandoned mine sources in pounds per day for COSJLP04a. No load reductions necessary for May and December (see table 5.21). 6.0 RESTORATION PLANNING AND IMPLEMENTATION PROCESS The Mancos River Watershed Project was created in 2006 with the vision of a healthy and sustainable watershed from the source to the San Juan River. The mission of the Mancos River Watershed Stakeholders is to engage in a collaborative process with representation from diverse stakeholders to protect, manage, and enhance the quality and health of the watershed (http://www.sustainablemancos.com/watershed_project). The Mancos River Watershed is an 800 square mile watershed that originates in the San Juan National Forest and travels via the Mancos River through private land, the Town of Mancos, Mesa Verde National Park, the Ute Mountain Ute Indian Reservation and drains into the San Juan River at the border of New Mexico within the Navajo Nation. The Watershed Project was spearheaded in 2006 by the Mancos Conservation District. There are four phases to Watershed Project development: 1) assessment, 2) planning, 3) implementation, and 4) monitoring. Currently, the group is in the planning phase, working with a diverse group of stakeholders in a collaborative effort to create and write a watershed plan. While the Mancos River Watershed Project (MRWP) is in its planning phase, studies and ground work are being implemented in an ongoing effort to bring the group closer to accomplishing its goals. The MRWP Program Director (Lea Cody, Chester Anderson, or Ann Oliver) acts as primary grant writer to fund shovel-ready projects, assessments, and general operations. Completed projects include: •A Rapid Watershed Assessment in partnership with the Natural Resources Conservation Service •Monthly water quality monitoring through Colorado Riverwatch •Riparian corridor assessment of 17 reaches of the river and its major tributaries
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Total Maximum Daily Load Assessment for East Mancos River segment 4a
•Sixty acres of Tamarisk and Russian Olive eradication •Two in-stream aquatic habitat/bank stabilization enhancement projects •Fencing of livestock off riparian corridors •Compilation and analysis of all studies to date of the East Mancos River •Completion of a Mancos Source Water Protection Plan with the Colorado Rural Water Association •Landowner survey of resource concerns •Two tours, one of the Lower Basin of the Mancos River Watershed and one of the Middle Basin; for stakeholders, regional conservation district members, and local elected officials/representatives •The MRWP has succeeded in bringing historically clashing interests like agriculturists, the Ute Mountain Ute Tribe, forest service staff, landowners, Mesa Verde National Park, land conservancy representatives, miners, real estate agents and concerned citizens to the table for a collaborative watershed planning process. Monitoring In order to ensure that the TMDL is adequately protective of the segment, monitoring of the East Mancos River, in addition to the mainstem Mancos River above and below the confluence with the East Fork, is required. A more in-depth characterization of the abandoned mine source contribution would also be beneficial to the remediation of the East Mancos River watershed. Additional remediation of the East Mancos River is required. Conclusion The goal of this TMDL is the attainment of the Aquatic Life Use based standard for copper, and Water Supply standard for manganese, within COSJLP04a, the East Mancos River. This TMDL assessment addresses all uses, and they are met with the proposed load reductions. An average annual loading reduction of approximately 63% is necessary to reach the copper TMDL, and 46% for manganese. 7.0 PUBLIC INVOLVEMENT There has been a strong public participation in protecting and enhancing the water quality of the Mancos River watershed. The Mancos River Stakeholders Group, U.S. Environmental Protection Agency (Region 8), U.S. Forest Service (USFS), Colorado Division of Wildlife River Watch, the Colorado Division of Reclamation, Mining and Safety, and the Colorado Department of Public Health and Environment (CDPHE) have been actively involved in better understanding the water quality issues of the Mancos River watershed in order to better deal with the legacy of historical mining. The public has had an opportunity to be involved in the Water Quality Control Commission (WQCC) hearings. Opportunities have also been available through the 303(d) listing process which also has a public notice period for public involvement. A draft of these TMDLs was provided for public review and comment in April 2012. No comments were received at that time. These TMDLs were, however, revised per comments subsequently provided by USEPA. Public participation will continue to promote future restoration of the watershed, as new remediation possibilities are explored.
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9.0 REFERENCES Besser and Leib,1999. Modeling frequency of occurrence of toxic concentrations of zinc and copper in the upper Animas River, in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program—Proceedings of the Technical Meeting, Charleston, S.C., March 8-12, 1999, v. 1, Contamination from Hardrock Mining: U.S. Geological Survey Water-Resources Investigations Report 99-4018A, p. 75-81. Besser J.M., Brumbaugh, W.G., May, T.W., Church, S.E., and Kimball, B.A., 2001, Bioavailability of metals in stream food webs and hazards to brook trout (Salvelinus fontinalis) in the upper Animas River watershed, Colorado: Archive of Environmental Contamination and Toxicology, v. 40, p. 48-59. Cheney, Joni, 1995. Neutralization of a Naturally Generated Acidic Plume by Instream and Watershed Processes. Colorado State University. Colorado Division of Mining Reclamation and Safety (CDRMS) 2007. Colorado Abandoned Mine Land Program Non-Point Source and Water Quality Control Projects. December 2007 Update. Eckel, P.A. 1949. Ore Deposits of the La Plata Mountains. USGS Water-Supply Paper 2205. Hazardous Materials and Waste Management Division (HMWMD), Colorado Department of Public Health and Environment, 2005. Combined Assessment – Site Inspection Draft Analytical Results Report, East Fork of Mancos River, Montezuma County, Colorado. Kimball, B.A., Bencala, K.E., and Broshears, R.E., 1994, Geochemical processes in the context of hydrologic transport: Reactions of metals in St. Kevin Gulch, Colorado, in, Dutton, A., ed., Toxic Substances in the Hydrologic Sciences: Minneapolis, Minn., American Institute of Hydrology, p. 80-94. Meyer, W.A. 1993. Natural Geochemical Processes of Acid Rock Drainage: East Mancos River, La Plata Mountains, Colorado. Masters of Science Thesis, Northern Arizona University, Flagstaff, AZ. USDA Forest Service, 1991. Acid Rock Drainage and Water Quality in the East Mancos River, San Juan National Forest. Final Report for Cost-Share Agreement #110213179103. WQCC 2012a. Colorado Department of Public Health and Environment, Water Quality Control Commission, 2012, 303(d) List of Impaired Waters, 2012. WQCC 2012b. Colorado Department of Public Health and Environment, Water Quality Control Commission, The Basic Standards and Methodologies for Surface Water, Regulation No. 31. Amended June, 2011, Effective January 1st, 2012.
FINAL DRAFT
Total Maximum Daily Load Assessment for East Mancos River segment 4a
WQCC 2012c. Colorado Department of Public Health and Environment, Water Quality Control Commission, Classifications and Numeric Standards San Juan and Dolores River Basins, Regulation No. 34. Amended June 2011, Effective January 1st, 2012. Colorado Division of Mining, Reclamation, and Safety, East Mancos River, powerpoint presentation, 2009. http://www.wrcc.dri.edu/summary/climsmco.html. Western Regional Climate Center.
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