PUBLIC HEALTH ASSESSMENT
DEL NORTE, RIO GRANDE COUNTY, COLORADO
Explanation of Environmental Contaminant Data Tables
ATSDR selected the contaminants in the data tables for further evaluation based on thosecontaminants (predominantly metals) being released to surface water at the Summitville Minesite and any metals that were above federal drinking water standards in private wells.ATSDR uses comparison values--contaminant concentrations in specific media consideredprotective of public health--to select contaminants for further evaluation. ATSDR and otheragencies have developed the comparison values to provide guidelines for estimating contaminantconcentrations in media that are not likely to cause adverse health effects, given a standard dailyingestion rate and standard body weight.
The comparison values in Tables 1 and 2 are primarily the drinking water standards, such as themaximum contaminant levels (MCLs), established by EPA. MCLs are limits on chemicalconcentrations in drinking water that EPA considers protective of public health (considering theavailability and cost-effectiveness of water treatment technology) over a lifetime (70 years) at anexposure rate of 2 liters of water per day (for an adult). Maximum contaminant level goals(MCLGs) are EPA drinking water health goals set at levels at which no known or anticipatedadverse health effects would be experienced by exposed persons. MCLs are EPA regulationsthat can be enforced; MCLGs are goals that are not enforceable. EPA also has lifetime healthadvisories (LTHAs) for drinking water. If ATSDR or EPA comparison values are not available,ATSDR may refer to other agencies' standards as applicable.
|= Maximum Contaminant Level|
|= Maximum Contaminant Level Goal|
|= parts per billion|
|= parts per million|
|= the number of times a concentration exceeded the standard value compared to the number of times it was analyzed.|
|Stations Progressively Downstream* [Figures 1 and 2]|
|Parameter||Represents:||WF-5.5||WF-0.0||AR-45.4||AR-34.5||AR-31||Federaldrinkingwater standard (ppm)|
|Avg.||0.015||0.014||.003||0.016||0.002||0.015 EPAaction level|
|* Signs are posted warning people not to drink contaminated river water. These river segments are not classified fordrinking water use but for agricultural and recreational uses.|
** The cyanide drinking water comparison value is for free cyanide (HCN or CN). Only some of the total or WADcyanide concentrations would be free cyanide. Most of the cyanide in these concentrations would be in the form of metalcyanide complexes.
The metals concentrations are total recoverable concentrations.
WAD = Weak Acid Dissociable
See Figures 1 and 2 for locations
OFF-SITE DOMESTIC WATER
(ppb) or pH range
|6.6 - 8.5|
6.6 - 8.8
|15 EPA action level||****|
|NA = Not Analyzed|
*Spring - March through June CSU results
Fall 1 - October through November CSU results
Fall 2 - Resampling in November by State of Colorado
** Detection limit of 10 ppb is above comparison value of 5 ppb, 1 sample out of 75 samples (1/75) exceeded 10 ppb.
|COMPLETED EXPOSURE PATHWAY AT THE SUMMITVILLE MINE SITE|
|Pathway Name||Point of Exposure||Route of Exposure||Exposed Population||Time of Exposure||Contaminant||Estimated ExposedPopulation|
|Air||Heap Leach Pad||Inhalation|
Responses to Comments Received During the Public Comment Period for the SummitvilleMine site.
The public comment period for the public health assessment (PHA) for the SummitvilleMine site was April 18 through May 23, 1997. The PHA is available at threerepositories: the Del Norte Public Library in Del Norte, Conejos County Agricultural andSoil Conservation Service in La Jara, and the Environmental Protection Agency (EPA)Superfund Records Center in Denver. The Summitville technical assistance grant (TAG)coordinator received copies of the PHA for distribution to a local citizens group. Comments from this group and their technical advisor and our responses to thosecomments follow. Repetitive comments were omitted, and some comments have beencondensed. However, anyone can request the original letters from the Agency for ToxicSubstances and Disease Registry (ATSDR) through the Freedom of Information Actprocess. ATSDR also received comments from the Colorado Department of PublicHealth and Environment and has made changes to the public health assessment based onthese comments. Those comments are not included here, but they are available, alongwith any other comments, from ATSDR through the Freedom of Information Act process.
COMMENT: Why haven't the Federal Secondary Drinking Water Standards been used inevaluating drinking water quality? It is very important that water tastes good and thatthere are no foul odors or colors.
RESPONSE: Our focus was to determine whether the contaminants in groundwatercould cause adverse human health effects. We used the primary drinking water standards(primarily the maximum contaminant levels [MCLs]) because they are enforceable, health-based standards. Secondary maximum contaminant levels (SMCLs) represent reasonablegoals for drinking water quality but are not enforceable. They are guidelines for odor,color, taste, and other aesthetic qualities.
Some of the metals in private wells influenced by Alamosa River water (For example:aluminum, iron, and manganese) exceed SMCLs established by the EPA.(1) The SMCL foraluminum is a range of 0.05 to 0.2 parts per million (ppm). The SMCL for manganese is0.05 ppm. Excess manganese produces a brownish color in laundered goods and affectsthe taste of beverages. Concentrations exceeding the SMCL may cause dark brown orblack stains on plumbing fixtures and may coat distribution pipes. Iron will also produce abrownish color in laundered clothing, and it stains plumbing fixtures with a characteristicrust color. Iron can be tasted at 1 ppm and has a bitter, astringent taste.
Copper concentrations in 1993 private well data are below 1 ppm, the concentration statesusually establish as an SMCL. Copper at concentrations exceeding 2 ppm usually causessignificant staining and unpleasant tastes. Many people can taste copper at 1 ppm. Theoptimum range for pH is around neutral or 7, 6.5 to 8.5.
Residents whose wells are or could be influenced by Alamosa River water downstream ofthe Summitville Mine site should contact The Colorado Department of Public Health andEnvironment (CDPHE), Water Quality Control Commission, if they are concerned aboutor notice changes in water quality.
COMMENT: According to ATSDR, three main sources- the heap leach pad, frenchdrain, and Reynolds Adit "and other associated acid drainages"- have releasedcontamination from the site. Do those other associated acid drainages include the Cropsyfoot print? How about seeps and springs from plugging? Uncontrolled pollution thatflows from the Cropsy footprint negates pollution control efforts in other parts of the minesite.
RESPONSE: Yes, the other acid drainages include all of the ones mentioned. Pluggingthe adits has substantially reduced the volume of water being released from the site and,therefore, the metal loading to streams. Although the uncontrolled pollution from theCropsy footprint contributes to metal loading of streams, it does not negate the reductionin metal loading that results from plugging.
COMMENT: There is possibly premature judgement on groundwater quality since therewill undoubtedly be a time delay before contaminated water that has been released into theAlamosa River has had a chance to reach the groundwater unless there is directcontamination from surface water sources.
RESPONSE: ATSDR has suggested continued monitoring of surface water for use as anindicator of the potential for groundwater contamination. We have added in this versionof the PHA a recommendation for a private well sampling program to confirm 1995results and assure residents that their drinking water is safe. We have recommendedsampling private wells during surface water sampling.
COMMENT: In the document it has been recommended that surface water continue to bemonitored in order to assess the impacts on the groundwater without saying anywhere inthe document that groundwater should also continue to be monitored. It would be ratherdifficult to assess the impacts on groundwater without continuing to monitor thegroundwater as well.
RESPONSE: We have recommended a phased approached that suggests that surfacewater be used as an indicator. However, the best of all worlds would be to have privatewells tested during surface water sampling. Since conditions may change (irrigationditches may be lined, lessening the volume of water entering wells; the soil's capacity toretain metals may change, etc.), we have recommended further sampling to confirm thatprivate wells are not being influenced.
COMMENT: There are a number of errors in the document such as saying that the NorthWaste Dump was moved when it was not and also leaving the impression that moving thewaste dumps and plugging the adits has taken care of the problems.
RESPONSE: We have omitted the North Waste Dump from our list of waste piles thathave been moved. Moving the waste dumps and plugging the adits are part of EPA'sremedy for the site. The remedial actions have not been completed; there are still somewastes that will be relocated to the mine pit area, and there will be further revegetation(personal communication with the EPA Remedial Project Manager on June 12, 1997). Some water from the Cropsy footprint is still being treated, and remedial efforts arecontinuing. Plugging the adits has reduced metal loading to surface water.
COMMENT: In reaching its conclusion that the Summitville site represents no apparentpublic health hazard, the PHA relies on data primarily obtained in 1993....PHA should beupdated to include the 1994-96 data. Maybe some of the conclusions would change.
RESPONSE: The PHA did include surface water data through November 1995, andconclusions reflected those data. The document contains repeated mentions of the yearssupporting data were collected. This version of the PHA includes information on the1995 studies on ducks and sheep.
COMMENT: Although ATSDR considers Summitville to present no apparent publichealth hazard, further sampling of heavy metals in surface water is recommended. Whatare the metals? A specific list would be nice. And how about pH?
RESPONSE: The metals listed in Tables 1 and 2 are the primary ones coming fromSummitville drainages. We recommend that future analyses of environmental mediaaddress those metals and the pH of the media. Other metals could also be analyzeddepending on the purpose of the investigation.
COMMENT: Drinking water wells along the river should be tested regularly. Crop,livestock and soil studies should also be continued, although ATSDR might argue thatthese don't apply directly to human health.
RESPONSE: The most recent private well sampling, completed in June 1995, did notshow any metals exceeding drinking water standards except in one control well notinfluenced by Alamosa River water. ATSDR didn't recommend continued routinemonitoring because previous testing during years when metal loading was high didn'tindicate that wells were being influenced. However, we have added a recommendationthat private wells be tested again to confirm the 1995 private well data. The PHA statesour support for continuing studies on metal uptake by crops and metals in soils as well asfor surface water analyses. Livestock studies are continuing.
COMMENT: Did adit plugging really "reduce" acid mine drainage from the site?...
RESPONSE: The volume of water being released from the site has been substantiallyreduced, therefore reducing the loading of metals to the Alamosa River. However, theconcentrations of metals, as you pointed out, have not necessarily decreased. Theconcentrations will tend to increase during low flow conditions.
COMMENT: There's a contradiction on page 5 as to whether Jasper is 17 or 7 milesdownstream from the mine.
RESPONSE: The 17 miles is the distance to Terrace Reservoir, and the 7 miles is thedistance to Jasper, the nearest community. The document has been changed to clarify thedistances.
COMMENT: ATSDR incorrectly assumes that the Alamosa River between Stunnercampground and Terrace does not sustain agricultural crops or livestock.
RESPONSE: This statement has been deleted.
COMMENT: What specific drainages are being referred to when ATSDR states "Fish insome Colorado drainages include brook trout, etc ?" Also, which specific stream reacheswould it be difficult to get fish to return to even if acid mine drainage from Summitvillewas eliminated?
RESPONSE: In the first question, ATSDR was not referring not to specific drainages butto fish found in Colorado rivers and streams in general. If drainage from Summitville wereeliminated, it might be difficult to reestablish fish in the Alamosa River downstream of themine site from Wightman Fork to a location above its confluence with Fern Creek becauseof drainage from Bitter, Alum and Iron Creeks. However, the Use AttainabilityAssessment (UAA) and future modeling efforts may help us determine which riversegments would likely experience reestablishment of fish and when.
COMMENT: The statement is made that EPA's remedial actions have reduced theamount of metals and "other contaminants" entering surface waters. This may not be truefor the metals. And how about hydrogen (H+) ions? What are those "other"contaminants?
RESPONSE: As explained in an earlier response, the volume of water being releasedfrom the site has been substantially reduced, therefore reducing the loading of metals andhydrogen ions to the Alamosa River. The other contaminants that we were referring toincluded cyanide and cyanide compounds.
COMMENT: ATSDR states "EPA continues to dewater and detoxify the heap leachpad." They've discontinued this.
RESPONSE: Noted. We have deleted this statement.
COMMENT: In discussing actions taken at the mine, there's no mention of theincomplete job and lingering pollution problems at the Cropsy footprint. Uncontrolledacid mine drainage from Cropsy cancels out gains made elsewhere at Summitville. EPAapparently does not consider the Cropsy footprint a part of the mine site (see Appendix B,UAA). If ATSDR bought into this scam, then many of the assumptions stated in this PHAare erroneous.
RESPONSE: Water from the drainage ditch at the base of the former Cropsy waste pile isrouted to Cropsy Creek and isn't treated. Although the majority of acid-generatingmaterial has been removed, some residual flushing of mineral salts occurs. This flushingadds to the metal loading coming from the Summitville Mine site. This year, as part ofthe remedial effort, EPA is going to apply lime to the Cropsy valley followed by top soiland grass seed (personal communication with the EPA Remedial Project Manager,6/20/97). This remedial measure may help to lessen the metal loading coming from thissource.
COMMENT: What's the vegetative cap the PHA refers to on top of the mine pit?
RESPONSE: Although some test vegetation plots have been established, revegetationwill take years. Therefore, we have eliminated this statement.
COMMENT: The first paragraph under the subsection "River Water" is confusing.
RESPONSE: We have rewritten the paragraph to make it more readable.
COMMENT: Drinking water standards are discussed, but not exceedances of agriculturaluse standards. These exceedances could impact human health, too.
RESPONSE: The Colorado Surface Water Agricultural Use Standards are standards forsurface waters that are suitable or intended to become suitable for irrigation of cropsusually grown in Colorado and that are not hazardous as drinking water for livestock.(2) Based on July 1995 irrigation water samples, the only metals exceeding the agriculturaluse standards are copper and manganese. Both of these metals may be mobile in TerraceReservoir irrigated fields. Therefore, future environmental studies should consider bothmetals. Although a human health impact is unlikely, there should be evaluation ofadditional information on the metals' effects on livestock because livestock are more likelythan humans to experience exposure to metals from multiple sources. Some livestock, forinstance, drink water directly from the Alamosa River and eat feed containing elevatedmetals. The section on livestock contains information on situations in whichconcentrations exceed maximum tolerable levels for metals in feed and on the availableinformation on metals in crops.
COMMENT: ATSDR assumes most fields receiving irrigation water from the AlamosaRiver are alkaline. ....Though this might be true for other parts of the San Luis Valley, it'snot necessarily so for the Alamosa River watershed.
RESPONSE: Noted. The statement has been deleted.
COMMENT: Hydrogen (H+) ions are not mentioned as a contaminant from theSummitville Mine in the second paragraph on page 17.
RESPONSE: Reference to acidic waters has been added to the paragraph. Acid minedrainage is mentioned throughout the document.
COMMENT: ATSDR assumes remedial actions have improved downstream waterquality and therefore shallow wells are safe.
RESPONSE: We have added a recommendation to continue remediation at the mine siteand for additional sampling of private wells.
COMMENT: Livestock were eliminated as an exposure pathway. This may bepremature. How about human consumption of big game animals that drink from the riverand/or consume plants that receive water from the river? This potential exposure pathwayis not discussed.
RESPONSE: In this version of the PHA, we have changed the eliminated exposurepathways of fish and livestock to potential exposure pathways. Big game animals, such asdeer, may be exposed to metals in the environment at locations such as the area nearTerrace Reservoir. No exposure data on large game animals near Summitville Mine wereavailable for our review. However, our analysis would run similar to that presented forlivestock, which we have identified as a potential exposure pathway.
COMMENT: In the last paragraph of the report, ATSDR says it supports continuingstudies on metal uptake in crops. How about livestock? How about soils?
RESPONSE: The PHA emphasizes crops because they are a more direct pathway forhuman exposure. The PHA contains evaluations of livestock and soils pathways, judgingthem unlikely to have negative impacts on human health. However, we have addedstatements supporting studies in most environmental media impacted by the SummitvilleMine.
1. Sheldon, T.B. Interpreting Drinking Water Quality Analysis, What Do the Numbers Mean? RutgersCooperative Extension, The State University of New Jersey, Rutgers. E185.
2. Erdman JA, Smith KS. Impact of the Summitville Mine on irrigation water, agricultural soils, and alfalfain the southwestern San Luis Valley, CO. United States Geological Survey open file report 93-616. 1993.