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PETITIONED PUBLIC HEALTH ASSESSMENT

CRIPPLE CREEK AND VICTOR GOLD MINING
CRIPPLE CREEK, TELLER COUNTY, COLORADO


APPENDIX A: SITE MAP

Intro Map
Figure 1. Intro Map


APPENDIX B: QUALITY ASSURANCE AND ATSDR METHODOLOGY

Quality Assurance

In preparing this report, ATSDR relied on the information provided in the referenced documentsand by contacts with the Colorado Department of Public Health and Environment, communitymembers, and CC&V. ATSDR assumes that adequate quality assurance and control measureswere taken during chain-of-custody, laboratory procedures, and data reporting. The validity of theanalyses and conclusions drawn in this document are determined by the availability and reliabilityof the information.

Human Exposure Pathway Evaluation and the use of ATSDR Comparison Values

ATSDR assesses a site by evaluating the level of exposure in potential or completed exposurepathways. An exposure pathway is the way chemicals may enter a person's body to cause a healtheffect. It includes all the steps between the release of a chemical and the population exposed: (1) achemical release source, (2) chemical movement, (3) a place where people can come into contactwith the chemical, (4) a route of human exposure, and (5) a population that could be exposed. Inthis assessment, ATSDR evaluates chemicals in the air that people living in nearby residences mayconsume or come into contact with.

Data evaluators use comparison values (CVs), which are screening tools used to evaluateenvironmental data that is relevant to the exposure pathways. Comparison values areconcentrations of contaminants that are considered to be safe levels of exposure. Comparison valuesused in this document include ATSDR's environmental media evaluation guide (EMEG) andcancer risk evaluation guide (CREG). Comparison values are derived from available healthguidelines, such as ATSDR's minimal risk levels and EPA's cancer slope factor.

The derivation of a comparison value uses conservative exposure assumptions, resulting in valuesthat are much lower than exposure concentrations observed to cause adverse health effects; thus,insuring the comparison values are protective of public health in essentially all exposure situations.That is, if the concentrations in the exposure medium are less than the CV, the exposures are not ofhealth concern and no further analysis of the pathway is required. However, while concentrationsbelow the comparison value are not expected to lead to any observable health effect, it should notbe inferred that a concentration greater than the comparison value will necessarily lead to adverseeffects. Depending on site-specific environmental exposure factors (for example, duration ofexposure) and activities of people that result in exposure (time spent in area of contamination),exposure to levels above the comparison value may or may not lead to a health effect. Therefore,ATSDR's comparison values are not used to predict the occurrence of adverse health effects.

The comparison values used in this evaluation are defined as follows: The CREG is a concentrationat which excess cancer risk is not likely to exceed one case of cancer in a million persons exposedover a lifetime. The CREG is a very conservative CV that is used to estimate cancer risk. Exposureto a concentration equal to or less than the CREG is defined as an insignificant risk and is anacceptable level of exposure over a lifetime. The risk from exposure is not considered as asignificant risk unless the exposure concentration is approximately 10 times the CREG andexposure occurs over several years. The EMEG is a concentration at which daily exposure for alifetime is unlikely to result in adverse noncancerous effects.

Selecting Contaminants of Concern

Contaminants of concern (COCs) are the site-specific chemical substances that the health assessorselects for further evaluation of potential health effects. Identifying contaminants of concern is aprocess that requires the assessor to examine contaminant concentrations at the site, the quality ofenvironmental sampling data, and the potential for human exposure. A thorough review of each ofthese issues is required to accurately select COCs in the site-specific human exposure pathway. Thefollowing text describes the selection process.

In the first step of the COC selection process, the maximum contaminant concentrations arecompared directly to health comparison values. ATSDR considers site-specific exposure factors toensure selection of appropriate health comparison values. If the maximum concentration reportedfor a chemical was less than the health comparison value, ATSDR concluded that exposure to thatchemical was not of public health concern; therefore, no further data review was required for thatchemical. However, if the maximum concentration was greater than the health comparison value,the chemical was selected for additional data review. In addition, any chemicals detected that didnot have relevant health comparison values were also selected for additional data review.

Comparison values have not been developed for some contaminants, and, based on new scientificinformation other comparison values may be determined to be inappropriate for the specific type ofexposure. In those cases, the contaminants are included as contaminants of concern if currentscientific information indicates exposure to those contaminants may be of public health concern.

The next step of the process requires a more in-depth review of data for each of the contaminantsselected. Factors used in the selection of the COCs included the number of samples with detectionsabove the minimum detection limit, the number of samples with detections above an acute or chronic health comparison value, and the potential for exposure at the monitoring location.


APPENDIX C: ATSDR HYDROGEN CYANIDE MODELING

ATSDR used the Industrial Source Complex, Version 3 Short Term Model (ISC3ST) to estimatethe air transport of HCN from the heap leach areas to locations people may live or visit. TheISC3ST model was run via a commercial interface called BREEZE ISC SUITE (Version 3.2.2)made by Trinity Consultants, Inc.

ATSDR used 1993 meteorological data collected onsite by the CC&V; the Colorado Air PollutionControl Division concurs that 1993 data are representative of a dataset.

The emissions data are based on the HCN emission rates were collected by CC&V in 1999(Reference to Schmidt 1999-Leach System Cyanide Emissions Quantification, CC&V, VictorColorado, April 24, 1999). Twenty-three samples were collected at the Cresson Valley LeachFacility, one replicate sample was collected at an older and inactive pad where the gravel isapproved for use in the mining operations ("Pad 4"), and two replicate samples were collected fromanother inactive pad from which the cyanide compounds had been removed using bacteria ("VictorPad"). The data for the valley leach facility represent areas undergoing leaching and those that arenot (not all of the area is leached at any one time).

The data from the samples were grouped into 5 classes based on leach activity and location. Eachgroup was treated as area sources. ATSDR simplified the area sources into squares with the centerof each square the approximate center of the Cresson Valley Leach Facility.

The areas and average emission rates for each class were obtained from Card (1999). The averageemission rates and square dimensions are shown below. The arithmetic averages were usedbecause the data from the active leach areas were better represented by a normal distribution asindicated by skewness and kurtosis.

1) Phase 1 Active Leach Area,
4.13e-7 µg/s/m2
366 meters by 366 meters

2) Phase 2 Active Leach Area,
4.13e-7 µg/s/m2
394 meters by 394

3) Cresson Valley Inactive Leach Areas,
8.18e-9 µg/s/m2
305 meters by 305

4) Pad 4, and
8.18e-9 µg/s/m2
236 meters by 236 meters

5) Process Tanks
5.28e-6 µg/s/m2
27 meters by 27 meters

Although the areas are represented in the model by square, the source are actually comprised of apatchwork quilt of dry (inactive) and wet (active) areas that are mixed differently as time changes). If adequate data were available to assign individual emission rates to areas undergoing leaching fordifferent periods, as well as areas in which leaching had not taken place for various periods of time,the source term would be better represented.

For this analysis, ATSDR assumed that Pad 4 was located at the Cresson Valley Leach Facilityalthough it is located north of Victor. This assumption would produce slighter higher simulatedambient concentrations and is considered conservative for this screening analysis (i.e. produces afalse positive).

For the ISC3ST model, we included complex terrain and a decay factor for HCN. The complexterrain algorithms require United States Geological Survey (USGS) digital elevation models(DEM). The DEM was obtained from the USGS website(http://edcwww.cr.usgs.gov/glis/hyper/guide/usgs_dem#7m7) Exiting ATSDR Website.

The decay factor, as measured by the half life, was obtained from ATSDR (Cyanide ToxicologicalProfile [Cyanide (Update) (PB/98/101207/AS) ]. The reported atmospheric half-life based onhydroxyl radical reactions for HCN range from 1.4 to 2.9 years. ATSDR used 1.4 years. Becauseof the relative size of the study area compared to the half life and area modeled, the decay of theHCN did not reduce the air concentrations. Although ATSDR used 1.4 years for modelingpurposes, HCN breakdown may be greater due to processes other than hydroxyl radical reactionincluding (Smith et al 1991):

Removal by precipitation events

  1. Removal by humidity, coupled with the acidity of water droplets, which cause thehydrolysis of HCN and conversion of HCN to formate (ammonium formate orformic acid)
  2. Removal by ozone in air demonstrated to cause conversion to cyanate (HCNO).
  3. Removal through ultraviolet light conversion of HCN to cyanate (HCNO).

Since these process have not been quantified, ATSDR was not able to include greaterdegradation rates.

The model was run with the rural setting option.

References for Appendix C Hydrogen Cyanide Modeling

Rogers, Felix, J., George G. Killough, Shirley J. Thompson, Cheryl L. Addy, Robert E.McKeown, and David J. Cowen. Estimating environmental exposures to sulfurdioxide from multiple industrial sources for a case-control study, Journal ofExposure Analysis and Environmental Epidemiology, November-December 1999(Volume 9, Number 6), 535-545.

Card 1999. Memorandum from Tom Card, Environmental Management Consulting toMason Estes, Cripple Creek & Victor Gold Mining Company regarding CyanideEmissions Assessment, April 25, 1999.

Card, Thomas R., and Charles E. Schmidt, 1999. Leach System Cyanide EmissionsQuantification, Cripple Creek and Victor Gold Mining Company, Victor Colorado,April 24, 1999.

Machovec 1998. Memorandum from Chuck Machovec to Chip Hancock, ColoradoDepartment of Public Health and Environment, Air Pollution Control Divisionregarding the Cripple Creek and Victor Cresson Mine - National Ambient AirQuality Standards Compliance Issues, November 16, 1998.

Smith, Adrian and Terry Mudder, 1991, The Chemistry and Treatment of Cyanidization Wastes, Mining Journal Books Limited.


APPENDIX D: EXPOSURE PATHWAYS

Table 1.

Completed Exposure Pathway
Pathway Name Source Medium Route of Exposure Point of Exposure Receptor Population Time Exposure Activities Chemicals of Concern
Ambient AirUnknownAirInhalationOff-siteResidentsPast,Current,FutureNormal DailyActivitiesPM10


Table 2. Potential Exposure Pathway

Table 2.

Potential Exposure Pathway
Pathway Name Source Medium Route of Exposure Point of Exposure Receptor Population Time Exposure Activities Chemicals of Concern
Ambient AirUnknownAirInhalationOn and off-siteWorkers andResidentsFutureWorking andNormal DailyActivitiesHydrogenCyanide


APPENDIX E: PUBLIC COMMENTS

Response to Public Comments

ATSDR issued a draft for the public comment petitioned public health assessment on June 14, 2000for the Cripple Creek and Victor Gold Mining site. Between June 14, 2000, and August 15, 2000,the public had the opportunity to provide comments on the draft public health assessment. Duringthat time, ATSDR received written comments and questions from the Colorado Department ofPublic Health and Environment (CDPHE), Cripple Creek and Victor Gold Mining, and communitymembers. These comments/questions are presented below. Each italicized comment is followed by aresponse from ATSDR.

Colorado Department of Public Health and Environment

Comment: The Air Pollution Control Division (APCD) generally agrees with the ATSDR'sassessment of CC&V is an indeterminate public health hazard. Gaps in air monitoring data andmodeling uncertainties require that additional study (ambient air monitoring) be conducted toprovide a definitive answer to the human health hazard questions.

Response: ATSDR has responded to the specific comments presented below and has made changesto the public health assessment as appropriate in response to APCD.

Comment: A more thorough and careful discussion regarding hydrogen cyanide referencebased concentrations and risk is needed for a final report. The June 14, 2000 public healthassessment does not mention risk-based concentrations or any health guidelines for hydrogencyanide exposures.

Response: ATSDR typically uses modeling results as predictors of environmental conditions, notpredictors of public health impact. On page 7, public health guidelines are mentioned, but notdetailed. To compare modeled data to health-based concentrations and exposure guidelines ismisleading because of the potential inaccuracy of the modeling results. The ambient hydrogencyanide (HCN) concentrations predicted by the ISC3ST model are below all state HCN regulationsand guidelines (all states who have defined these). However, ATSDR cannot use these modelingdata to evaluate potential human health problems. Once ambient air concentrations of HCN arecollected and confirmed, ATSDR can evaluate if these levels are of health concern by consideringsite-specific exposure scenarios, health-based comparison values, epidemiological data, and healthstudies referenced in scientific literature.

Comment: ATSDR should ascertain that there are no decimal errors in the text, with respect toconcentrations of HCN discussed on page 7 of the report, e.g., 0.015 mg/m3, 0.15 mg/m3, 1.5mg/m3, and 15 mg/m3.

Response: There is a potential uncertainty level of two orders of magnitude when using the ISC3STto predict ambient air concentrations of chemicals (as described on page 7). The two orders ofmagnitude refers to the entire range of values, not just the upper and lower end. All models used topredict environmental conditions have uncertainty factors. Accounting for this uncertainty factor, thepredicted 24-hour maximum HCN concentrations could range 0.15 to 15 µg/m3. The predictedannual average HCN concentrations could range from 0.015 to 1.5 µg/m3. Several states useguidelines and regulations for 24-hour averages ranging from 40 to 250 µg/m3 [1]. Two states haveguidelines for annual averages of 5 and 20 µg/m3 [1].

Comment: The data validation draft of the public health assessment reviewed on May 25, 2000indicates that EPA's risk-based concentration (RBC) for HCN is 3.1 mg/m3. Several of theprojected levels cited are of concern. We note that a sizable portion of the uncertainty range forpredicted HCN concentrations exceeds the EPA's RBC. It should also be noted that 1.5 mg/m3 -the projected 24-hour maximum at the western edge of Victor- is one half of the RBC. This issignificant in view of the fact that CC&V operators have requested they be allowed to double thesize of their operations. It is anticipated that the operators will double the size of the heap leachpit, using roughly twice the amount of HCN as is used today. This could cause ambient HCNconcentrations to double- potentially hitting the 3.1 mg/m3 RBC level.

Response: EPA's RBC of 3.1 mg/m3 was not included in the public health assessment (publiccomment draft) because this concentration is considered acceptable based on a lifetime exposure(i.e., 70 years) to HCN. The models used for estimating HCN levels near CC&V generated a 24-hour maximum and an annual average. Comparing a long term (chronic) exposure level to estimatedshort term (acute) exposure levels is inappropriate. Also, relating modeling results to "risk levels" isinappropriate because of the uncertainty in the modeling results. RBC values are also derived byincorporating uncertainty factors (anywhere from a factor of 10 to 1000) into them based on dataextrapolations from relevant human and animal toxicity studies. In the case of hydrogen cyanide,EPA applied a 1,000-fold uncertainty factor to worker-related cyanide exposure studies and deriveda reference concentration (similar to the RBC) of 3 µg/m3 for chronic exposure to cyanide in air.

Upon receiving ambient air HCN results, ATSDR will evaluate appropriate health guidelines andtoxicological and epidemiological studies to determine the possibility of adverse health effectsoccurring from HCN exposure.

Comment: In light of the operators' recent request to double the size of operations at CC&VGold Mine, the APCD recommends continuous monitoring for hydrogen cyanide to begin assoon as feasible. Monitoring for HCN should continue through CC&V's expansion period, andbeyond throughout its operating years.

Response: This is a direct recommendation from APCD to CC&V; ATSDR cannot comment onthis recommendation until ambient HCN concentrations are quantified.

Comment: Within the town of Victor, CC&V has monitored with small-volume samples that arenot EPA reference method samplers. Because this is where human exposures are likely to occur,the APCD recommends that in addition to conducting HCN ambient air sampling (ATSDRRecommendation No. 2, page 10), the agency monitor for PM-10 using EPA reference methodsamplers, sited per EPA guidance in the town.

Response: It should be noted that high volume samplers have been used since 1993 to measurePM10 levels on- and off-site. The mini-volume samplers are voluntarily used by CC&V assupplemental PM10 measurements.

ATSDR often uses mini- and medium-volume pumps to measure dust in residential areas todetermine if a health threat exists. These samplers are quieter, portable, easier to move, and use lesselectricity (or can run on a battery pack) than the high-volume samplers. In some cases, they may bepreferred over high-volume samplers to evaluate the public health impact because they can beoperated easier in residential areas or inside homes. The method is recommended by the NationalInstitute for Occupational Safety and Health (NIOSH) (#0600) for occupational monitoring but canbe adjusted to measure a longer time period. To use this method for making a health determination,it is essential that sufficient volumes of air are collected so the detection levels are appropriate.CC&V added two mini volume samplers to measure PM10 in Victor and on-site (Bateman Creek).In the past, five on-site high-volume samplers were actively measuring PM10 levels. Currently oneon-site high-volume sampler near Victor is active (Rigi). The results received from these pumpscombined are adequate to evaluate if a potential health impact from dust exists.

Comment: The APCD believes that with filter pad analyses we could establish whether in-townPM is largely reintrained road dust (as we suspect, and as is the case in Cripple Creek), orwhether it may consist of mined materials, e.g., if it had a larger metals component.

Response: Such correlations would only be possible if someone sieved the dust and soil samples tothe same sized particles. If the metals and the dust are not a problem, no one is needed to sieve. It isexpensive and the results would not produce any public health action.

Comment: The statement is made that, "PM10 has been monitored weekly from 1993 to 1999."This is technically incorrect. The CDPHE commenced sampling 1994 on an every-sixth-dayfrequency. In 1995 this was changed to every-day frequency.

Response: On April 7, 1999, CDPHE provided ATSDR with 1993 PM10 monitoring results(every-sixth-day) for the south monitoring site for the CC&V project. However, page 5 has beenmodified to reflect the correct monitoring regime.

Comment: In the same paragraph mention should be made of the annual PM10 NAAQS, whichis an annual average standard of 50 mg/m3. The ATSDR should provide annual averageconcentration data to compare with this standard.

Response: ATSDR states the annual average NAAQS on page 5. Of the data that ATSDR have,the only monitoring station that slightly exceeded the NAAQS annual average was the 1995 CrippleCreek sampling location (Bennet Avenue and 2nd Street) at 51.5 µg/m3. This is because the PM10concentration peaks detected in December of that year are believed to be from the road sanding. Allother annual averages were below the NAAQS.

Comment: Regarding Page 6, the first paragraph uses forms of the word exceedance threetimes. To conform to EPA usage, the word should be spelled "exceedance."

Response: The document has been modified to conform with EPA usage.

Comment: On page 6, the statement "The cause(s) of particulate matter exceedances in thetown of Cripple Creek in December 1995 through February 1996 are from excess roadsanding... (and)... do not appear to be related to mining activities because of the distancebetween the mine and Cripple Creek (approximately 15 miles) (sic) and the monitoring locationslocated at the mine did not pick up high levels of PM10." The mining area is extensive. Theclosest edge of the mine is only about 1 mile from Cripple Creek. The nearest active miningareas are about 500 ft above town and hidden by steep, complex terrain. As part of the Statepermitting process, dispersion modeling has been done to estimate the mine's impact on thetown of Cripple Creek. Modeling for a permit in 1998 suggests impacts from the mine rangefrom about 5 to 13 mg/m3 in town on the worst day. Proposed modifications for a revised permitin May 2000 suggest impacts in town might increase from 5-13 mg/m3 to about 13-27 mg/m3 onthe worst day. The maximum impacts from the mine will not necessarily occur on the same dayas maximum local PM10 concentrations in Cripple Creek. The modeled impacts in CrippleCreek were estimated with a steady-ste Gaussian model (ISCST3). Thus, because of complexmeteorology and terrain, the model estimates contain significant uncertainty at receptors in thetown of Cripple Creek. The model probably tends to overestimate actual impacts in CrippleCreek.

Response: ATSDR inquired of the active surface mining area during the PM10 peaks December1995 through February 1996 and verified it was approximately one mile from the Cripple Creekcity limit. ATSDR appreciates APCD's correction and changed page 5 to note the correct distance.However, there is sufficient evidence that the peak PM10 levels are primarily attributed to sourcesother than surface mining. The prevailing wind direction is northwest from Cripple Creek toward themine. No other PM10 peaks were detected other than during the road sanding events even thoughsurface mining continued.

Comment: Regarding the statements, "The PM10 exceedance detected from the on-sitemonitoring station (Range View) in September 1999 was from a motor vehicle hill climb race....This maximum onsite PM10 concentration was twice the NAAQS PM10 standard..."

The onsite exceedance level (183 mg/m3) is not twice the level of the PM10 standard. (InDecember 1995 there was an exceedance in the City of Cripple Creek that was twice thestandard.) We note again that at its closest point, the City is only one mile from the mine.Depending on wind direction, the mine could affect the municipalities, just as reintrained roaddust from Victor or Cripple Creek could affect PM10 levels at the mine site.

Response: This correction was applied to page 5.

Comment: ATSDR could clarify its discussion regarding metals by inserting a table that showsthe background levels, levels on site, and human health guidelines.

Response: Since there are only three metals discussed in this section, describing the levels detectedand the typical background levels in the text instead of a table provides sufficient technicalinformation.

Comment: Regarding page 7. The statement, "The state has also compared ISCST3 results withair monitoring for particulates at the mine and found in one case (emphasis added), the modeloverpredicted the particulate concentrations by a factor of 3.7."

The statement that the model overpredicted by a factor of 3.7 implies too much certainty aboutthe model evaluation method. The model evaluation method was casual and not statisticallyrobust. It would be more accurate to say that "The state has also compared ISCST3 results withair monitoring for PM10 at the mine and found in one case that the ISCT3/AP-42 modelingsystem appears to have overpredicted PM10 concentrations by as much as a factor of three."

Response: ATSDR has changed the text as suggested.

Comment: Regarding page 9. The birth defects statistics seem high intuitively (18%). Additionaldiscussion regarding birth defect types seen, rates elsewhere-both in similar and dissimilarareas, and any known contributing factors is needed here.

Response: Health outcome data were analyzed and provided to ATSDR by CDPHE under acooperative agreement. There were 18% of the children born in this time frame were reported ashaving one or more eligible conditions (such as low birth weight, prematurity, young maternal age).There were actually about 10% of children diagnosed with major congenital anomalies (e.g.,significant cardiac, cognitive or developmental effects). These data do not show a statisticallysignificant difference between the major anomaly rate for this region and the Colorado state anomalyrate at an alpha level of 0.05. It is important to note that the statistical power of this test wassomewhat limited due to the small sample size (number of live births). These details have beenadded to the public health assessment. The health outcome data were reported on February 23, 2000in a health consultation titled "Cancer Incidence and Birth Defects Prevalence, Victor, TellerCounty Colorado."

Cripple Creek & Victor Gold Mining Company

Comment: A Note of Explanation: This page appears to be boilerplate language to explain thehealth assessment process. One concern identified was usage of the phrase "potentiallyresponsible parties," which is a term-of-art under the Comprehensive Environmental Response,Compensation, and Liability Act ("CERCLA"). 42 U.S.C. §§ 9601 et. seq. The primary focus forthe Agency for Toxic Substances and Disease Registry ("ATSDR") is to perform healthassessments for sites designated under CERCLA to the National Priorities List ("NPL"). See 42U.S.C. § 9604(i)(6)(A). Beyond this primary focus, the ATSDR may perform health assessmentsas requested by individual persons or licensed physicians under certain circumstances. See 42U.S.C. § 9604(i)(6)(B). The health assessment performed of the CC&V operations was not of asite on or nominated for inclusion on the NPL; rather, the assessment was performed at therequest of an individual person or persons. As such, an uninformed reader could get theincorrect perception about CC&V's mining operation in light of the reference to "potentiallyresponsible parties" and its relation to CERCLA. We request that ATSDR either delete referenceto "potentially responsible parties" or provide clarification so that the public is not misinformedabout the health assessment and realizes that CC&V's operation is neither on, being consideredfor inclusion, or nominated to the NPL.

Response: The standard language used in the section entitled, " The ATSDR Pubic HealthAssessment: A Note of Explanation", is applicable to all public health assessments prepared byATSDR, both NPL and non-NPL sites. The CERCLA legislation authorizing public healthassessments does not restrict ATSDR public health assessments to NPL sites. Instead, the legislationclearly mandates ATSDR to respond to licensed physicians and individual persons concerned withhuman exposure to hazardous wastes from many types of sites which can include active miningoperations not on the NPL. ATSDR does not believe a change is needed in the section.

Comment: Forward: This page appears to be boilerplate language to provide background onATSDR. One concern identified was reference to "hazardous waste sites" in the first and secondparagraphs. As noted above, ATSDR conducts health assessments in two instances: site on orbeing nominated to the NPL or site request by an individual person or licensed physician. A siteon the NPL would be a "hazardous waste site." However, a site requested for consideration byan individual person or licensed physician is not automatically a "hazardous waste site" merelybecause ATSDR conducts a health assessment. Moreover, and most importantly in this instance,CC&V's operation is not a "hazardous waste site." We request that ATSDR either deletereference to "hazardous waste site" or provide clarification so that the public does not get theincorrect perception about CC&V's operation.

The second paragraph of the Forward again refers to the NPL. As indicated under thecomments in the previous section, the health assessment performed of the CC&V operations wasnot of a site on or nominated for inclusion on the NPL; rather, the assessment was performed atthe request of an individual person or persons. As such, an uninformed reader could get theincorrect perception about CC&V's mining operation in light of the reference to the EPA NPL. We request that ATSDR either delete reference to the NPL or provide clarification so that thepublic is not misinformed about the health assessment and realizes that CC&V's operation isneither on, being considered for inclusion, or nominated to the NPL.

Response: ATSDR has modified the Foreword.

Comment: Summary: It is noted on page 1 that "[t]he local drinking water supply does notappear to be impacted by mining activities" (underline added by us). We believe that the morecorrect statement is that the "local drinking water supply is not impacted by CC&V's miningactivities." As correctly noted on page 8 of the document, the Victor municipal water supplyoriginate from three watershed sources: East Fork of West Beaver Creek, Bison Creek, andBoehmer Creek. More specifically, the water supply is derived from two reservoirs that are up-gradient and quite some distance away from CC&V's mining operation. Water is conveyed fromthe reservoirs to Victor via a 12-inch diameter pipeline with no potential influence from themining operations. As such, we request that ATSDR modify this sentence as suggested above sothat the public is not inappropriately and incorrectly informed about this critical matter.

Response: ATSDR has changed the text as suggested. Text in the Drinking Water section of thisdocument has also been changed to the same affect.

Comment: Purpose and Health Issues: The forth sentence of the introductory paragraph startswith "Community members are concerned..." This statement is factually incorrect. Weunderstand that the health assessment was requested by an individual person or, at most acouple of persons. The health assessment was not requested by the entire populous of the City ofVictor or by its duly elected civil leaders. As such, we request ATSDR to revise this sentence bychanging "community members" to "the petitioner" or "some community members" (as isfactually correct) to avoid this factual inaccuracy. A similar request applies to the last sentenceof the introductory paragraph. Please replace "community health concerns" with healthconcerns raised by the petitioner" in the last sentence.

Response: ATSDR concurs with CC&V's first recommendation and has changed the textaccordingly. However, regarding the second recommendation, ATSDR believes that "communityhealth concerns" is accurate when describing the health concerns voiced by several communitymembers in a representative manner.

Comment: Site Background: The second sentence states: "This mining district contains over500 mining and ore processing sites scattered over a 30 square mile area." Those readersunfamiliar with the Cripple Creek Mining District may not realize that CC&V's operations arethe only active mining presently occurring in this District. As such, CC&V requests that thesecond sentence be revised as follows: "During the 110 year history of this district, over 500different mining enterprises have existed, with the CC&V activities being the only activeoperation at the present time."

Response: ATSDR revised the text to reflect CC&V as the present sole mining operation.

Comment: Mining Operations (pages 2-3): The first full sentence at the top of page 3 should berevised for accuracy as follows: "Approximately 50,000 tons of ore and 85,000 tons ofoverburden are mined each day[2]."

Response: ATSDR changed the text as suggested.

Comment: Mining Operations (pages 2-3): The third sentence of the first full paragraph onpage 3 should be revised for clarity as follows: "This leaching of gold takes place outside in a"valley leach facility" (Appendix A) that has been constructed in a valley that has been double-and triple-lined [2]." This change reflects addition of the word "double" and deletion of theword "bathtub".

Response: ATSDR changed most of the text as suggested. However, this sentence is furtherclarified by explaining that the valley leach facility is either double- "or" triple-lined (instead of"and") depending on its use.

Comment: Mining Operations (pages 2-3): The sixth sentence of the first full paragraph onpage 3 should be revised for clarity as follows: "The dilute sodium cyanide solution movesthrough the ore toward the bottom of the lined facility and dissolves gold and other metals toform their metal compounds in solution." This change reflects insertion of the word dilute toproperly qualify the solution being used by CC%V, replacement of the word "bathtub" with"lined facility", and substitution of "dissolves" for "exchanges sodium with".

Response: ATSDR modified the text to more accurately describe that water is added to a solid formof sodium cyanide to yield a solution. It is this sodium cyanide solution that is applied to the ore toleach (or dissolve) the metals out of the ore.

Comment: Mining Operations (pages 2-3): The tenth sentence of the first full paragraph onpage 3 should be abbreviated as follows "The solution is contained within the pore space of theore until it is pumped into the ADR facility [2]." This change reflects deletion of "There are noexternal ponds for the hydrogen cyanide leach solution," which is accurate with the deletion ofthe word "hydrogen," for the current operations but unnecessary in the context of this sentenceand the report.

Response: ATSDR has changed the text as suggested.

Comment: Mining Operations (pages 2-3): The third sentence of the second full paragraphshould be revised by replacing the word "solution" with "solid".

Response: ATSDR has changed the text as suggested.

Comment: Environmental Investigations (page 3): The fifth sentence of the last paragraph onpage 3 notes that "Teller County and the city of Victor regulate noise, wastewater disposal (i.e.,septic tanks), water supply, and blasting.: This sentence is factually incorrect as related to theCity of Victor and CC&V's mining operation. CC&V's operation is wholly within unincorporatedTeller County, and subject to applicable regulations related to land use activities as adopted byTeller County. CC&V has a contractual arrangement with the City of Victor to purchase waterfrom the City; however, this contractual arrangement does not provide the City with anyregulatory authority over CC&V's mining operation. Teller County regulates noise, wastewaterdisposal (i.e, septic tanks), and blasting, the latter only to the extent not already regulated by theState of Colorado. We request that ATSDR modify the specified sentence to delete reference tothe City of Victor to avoid this factual inaccuracy.

Response: ATSDR has modified the text accordingly.

Comment: Environmental Investigations (page 3): The eighth sentence of the last paragraph onpage 3 references "mine tailing pile" in relation to CC&V's mining operation. This is factuallyincorrect. "Tailing" is a term-of-art related to residual material from a mill. CC&V has neveroperated a mill from which tailing material would be produced. CC&V conducts surface miningactivities with overburden placed in engineered overburden storage piles and ore transported tothe lined Mining District at least 50 years ago, which significantly pre-dates CC&V's activities inthe District. We request that ATSDR modify this sentence to delete reference to "mine tailingpile" to avoid this factual inaccuracy (and correct a similar statement on page 4 under"COMMUNITY HEALTH CONCERNS").

Response: ATSDR has modified the text as suggested.

Comment: Environmental Investigations (page 3): The eighth sentence of the last paragraph onpage 3 references "mine tailing pile" in relation to CC&V's mining operation. This is factuallyincorrect. "Tailing" is a term-of-art related to residual material from a mill. CC&V has neveroperated a mill from which tailing material would be produced. CC&V conducts surface miningactivities with overburden placed in engineered overburden storage piles and ore transported tothe lined Mining District at least 50 years ago, which significantly pre-dates CC&V's activities inthe District. We request that ATSDR modify this sentence to delete reference to "mine tailingpile" to avoid this factual inaccuracy (and correct a similar statement on page 4 under"COMMUNITY HEALTH CONCERNS").

Response: ATSDR has modified the text as suggested.

Comment: Community Health Concerns: The last sentence of the first full paragraph on page 4references that the "community is concerned" about potential impacts of CC&V's miningoperation to drinking water. This statement is factually incorrect. As previously noted above, weunderstand that the health assessment was requested by an individual, or at most, a couple ofpersons; the health assessment was not requested by the entire populous of the City of Victor orby its duly elected civic leaders. We request that ATSDR revise this sentence by deleting"community is" and inserting "a community member is" or "some community members are"(whichever is factually correct) to avoid this factual inaccuracy (and correct a similar statementin the second sentence of the carry-over paragraph at the top of page 5).

Response: ATSDR has modified the text on page 4. Within the context of page 5, "communityconcern" does not imply the entire community.

Comment: Community Health Concerns: The last sentence of the second full paragraph onpage 4 notes that communities, such as the City of Victor, "can choose more stringent localnoise codes with public health and welfare as their basis for noise control." The sentence isfactually incorrect as applied to CC&V's mining operation. CC&V's operation is wholly withinunincorporated Teller County, and subject to applicable regulations related to land useactivities as adopted by Teller County. Teller County regulates noise related to CC&V's miningoperation; the City of Victor has no regulatory authority over CC&V's mining operation since itonly can regulate those activities within its jurisdiction. We request ATSDR delete the lastsentence of the second paragraph on page 4 to correct this factual inaccuracy.

Response: ATSDR modified this sentence in the Community Health Concerns section to refercitizens to Teller County for concerns regarding noise levels.

Comment: Air Discussion: The fourth sentence of the last full paragraph on page 5 states"[s]ome metals were also monitored on CC&V property from 1993 to 1996." The report noteson page 6 that such sampling occurred from 1994 through 1996. The metals samplingconducted by CC&V occurred from 1993 to 1996, and was discontinued upon approval by theColorado Department of Public Health and Environment (CDPHE), Air Pollution ControlDivision (APCD) after this governing regulatory agency determined that low metals concentrationsobserved in collected samples did not warrant continuation of this monitoring program. We requestthat ATSDR revise the document so that metal sampling is noted as occurring from 1993 to 1996.

Response: ATSDR changed the text as suggested.

Comment: Air Discussion: The sixth sentence of the last full paragraph on page 5 notes analleged exceedance of the PM10 standard in September 1999 and provides additionalinformation on this matter in the first full paragraph on page 6 noting that the "PM10exceedance detected from on-site monitoring station (Range View) in September 1999 was froma motor vehicle climb race that occurred on one of the roads at the mine near this monitoringstation" (underline added by us). This discussion is factually incorrect. CC&V's Range Viewmonitoring station recorded and apparent exceedance of the PM10 daily standard in September1999. The apparent exceedance was caused by a road race that occurred on a Teller County dirtroad adjacent to CC&V's mine site and near the monitoring station. The CDPHE investigatedthis matter and concurred that there was no exceedance of the PM10 daily standard due toCC&V's mining activities. The high reading was solely related to the vehicle race on theadjacent County road. We request that ATSDR correct this factual inaccuracy by replacing theclause underlined above with "...on Teller County Road 84"."

Response: ATSDR changed the text as suggested.

Comment: Air Discussion: In the forth sentence in the first paragraph on page 6 states: "Thismaximum on-site PM10 concentration was twice the NAAQS PM10 standard...". This statementis factually incorrect. The PM10 value recorded on the day of the vehicle race in September1999 was 183 mg/m3. This value is about 22 percent higher than the applicable 150 mg/m3 24-hour NAAQS. As such, CC&V requests that the word "twice" be replaced with "...about 22percent higher than..."

Response: ATSDR has modified this statement.

Comment: Air Discussion: The seventh sentence of the last full paragraph on page 5 notes thatseveral high PM10 readings were recorded in the town of Cripple Creek and provides additionalinformation on this matter in the first full paragraph on page 6 noting that the "cause(s) ofparticulate matter exceedances in the town of Cripple Creek in December 1995 throughFebruary 1996 are from excess road sanding during these months to control ice [10]. Theexceedances do not appear to be related to mining activities because of the distance between themine and Cripple Creek (approximately 15 miles) and the monitoring station located at the minedid not pick up high levels of PM10" (underline added by CC&V). This discussion is factuallyincorrect. CC&V's mining activities are not 15 miles from Cripple Creek. During the referencesperiod, CC&V's mining activities in the Main Cresson Mine and stored overburden material inthe Arequa Gulch overburden storage area and Ironclad/Globe Hill surface mine areas asbackfill. The distance between the Main Cresson Mine and Cripple Creek during this time periodwas approximately 1.7 miles, the distance between the overburden storage area in the ArequaGulch and Cripple Creek was approximately 2.2 miles, and the distance between theIronclad/Globe Hill backfill area and Cripple Creek was almost one mile. Moreover, thepredominant air flow is from Cripple Creek towards CC&V's mining operation. Enclosed arewind direction frequency distributions indicating that the predominant air flow is from the north-northwest to south-southeast, that is, from Cripple Creek towards CC&V's mining operation.Also, CDPHE investigated the cause of PM10 exceedances in Cripple Creek and identified streetsanding during winter months and unpaved roads during other months as causes for dust;CDPHE has not identified CC&V's mining operation as a contributing factor in light of therelevant facts. We request that ATSDR correct these factual inaccuracies and specify that theexceedances "are not related" to CC&V's mining activities.

Response: ATSDR has modified this statement.

Comment: Hydrogen Cyanide Discussion: The first sentence in the first paragraph on page 7should have "... to determine if..." inserted between the words "concentrations" and "nearby".

Response: This is the sentence the previous comment addresses: "ATSDR estimated HCN airconcentrations nearby residents could be exposed from the heap leach emissions at the CressonValley Leach Facility." ATSDR actually did estimate HCN concentrations in residential areas thatresidents could be exposed to as the current sentence implies.

Comment: Hydrogen Cyanide Discussion: The forth and fifth full paragraphs on page 7 discussmodeling using ISC3ST. The document notes that actual monitoring data collected by CC&Vreveals that the ISC3ST "overpredicted particulate concentrations by a factor of 3.7." However,the document next notes uncertainty of ISC3ST, with a reference to an article addressing sulfurdioxide, as two orders of magnitude, and then adjusts hydrogen cyanide concentrationsapplicable to CC&V's mining operation in the remainder of the document based on thisperceived two orders of magnitude uncertainty. We believe that actual, site-specific data fromour particulate matter monitoring should be used as the basis of evaluation, rather than using ageneric level of uncertainty. The site-specific monitoring of particulate matter strengthens thefactual accuracy of the document. Thus, we request that subsequent discussions highlighting therange of emissions based on this perceived two orders of magnitude be deleted and replaced byhighlighting the range of emissions based on the overprediction by a factor of 3.7.

Response: ATSDR rechecked the reference [18] that stated the uncertainty of the ISC3 model incomplex terrain is two orders of magnitude. The two orders of magnitude refers to the entire range ofvalues, not just the upper and lower end. So, the 24-hour maximum concentration of 1.5 µg/m3could range from 0.15 to 15 µg/m3.

ATSDR considered this comment taking into account site-specific factors and did not make anyadditional changes because:

The overprediction of the ISC3 model of 3.7 over that monitored is based on particulates whileATSDR's evaluation was studying gaseous HCN. The transport of particulates and gaseouspollutants are different because of particulate deposition. Hence a more generic uncertainty may beapplicable.

The ISC3 model used for particulates was based on site specific emission factors. The uncertainty ofthe emission factors as applied to Cripple Creek is not known but contributes to the overalluncertainty. The uncertainty of the emission factors could offset uncertainty in the ISC3 modelresults. For example, a lower than actual emission factor could compensate for an overpredictingmodel. Therefore, the site-specific uncertainty factor may not be applicable to an application whereemission factors are not applicable.

Comment: Drinking Water Quality: The third sentence of this section states that "Miningactivities do not appear to have affected the local drinking water" (underline added by CC&V).As correctly noted in the first sentence, the Victor municipal water supply originates from threewatershed resources: East Fork of West Beaver Creek, Bison Creek, and Boehmer Creek. Morespecifically, the water supply is derived from two reservoirs that are up-gradient and quite somedistance away from CC&V's mining operation. Water is conveyed from the reservoirs to Victorvia a 12-inch diameter pipeline with no potential influence from the mining operations. As such,we request ATSDR modify this sentence as by deleting the words "...do not appear to..." andadding the word "not" after the word "have" and before the word "affected".

Response: ATSDR has modified this statement.

Comment: ATSDR Child Health Initiative: The first sentence of the first paragraph refers tohazardous waste sites. As previously indicated, CC&V's operation is not a "hazardous wastesite." We request that ATSDR either delete reference to "hazardous waste site" or provideclarification so that the public does not get the incorrect perception about CC&V's operation.

Response: ATSDR has modified this general sentence to include "industrial facilities".

Comment:Health Outcome Data: The first sentence of the first paragraph on page 8 states that"Residents of Victor and surrounding communities expressed concern that potential exposuresto emissions from CC&V mining activities are responsible for increased cancer incidence andbirth defects prevalence in their communities". As written, this sentence implies that there is amore widespread concern than actually exists. We understand that the health assessment wasrequested by an individual person or, at most, a couple of persons. The health assessment wasnot requested by the entire populous of the City of Victor, or the surrounding communities, or byits duly elected civic leaders. As such, we request that ATSDR revise this sentence by adding theword "Some" before "residents" or replacing "Residents of Victor and surroundingcommunities …" to "The petitioner …".

Response: There are several residents with this common concern from Victor and other locations.ATSDR believes in this particular context, the sentence does not imply every resident in Victor andthe surrounding communities.

Comment:Cancer Data: The last sentence of the first partial paragraph on the top of page 9states: The CDPHE reported no significant increases for the rate of …" (underline added byCC&V). CC&V believes the word "differences" should be substituted for the word "increases"in this context, as occurs later on the same page.

Response: Health outcome data were prepared and analyzed by CDPHE. Observed versus expectedstatistical analysis of cancer incidence employed a two-tailed test. Therefore, it would be correct tosay that "The CDPHE reported no significant differences for the rates...." The point of concern forcommunities, however, is whether rates are greater than expected, hence, "...significant increase forthe rates..." Since a time-series analysis was not done, using the word "increase" does not in thiscontext mean a rise in the rate. Although the use of the word may be considered "epi-jargon", forconsistency and clarity, ATSDR used the word "increase" throughout the entire Health Outcome Data section.

Comment:Cancer Data: The last sentence of the first full paragraph on page 9 states: "Sincespecific environmental exposures and other health risk factors are not known, ATSDR …". CC&V believes the words "to exist" should be inserted after the word "known" and before"ATSDR".

Response: In the context of this sentence, all types of environmental exposures to chemical agentsand environmental conditions are considered to be occurring or have occurred in the past to a certaindegree (i.e., exposure to pesticides, cleaning agents, ultraviolet light, etc.). Individual health risks,such as poor diet, smoking, excessive alcohol consumption, and genetic probability to a certaindisease, are also not known.

Comment: Conclusions: CC&V has been advised that the ATSDR is reluctant to base a healthdetermination exclusively on air quality modeling information for hydrogen cyanide ("HCN"),hence the "Indeterminate Public Health Hazard" rating. However, when taken together, CC&Vbelieves that the following factors should result in at least the "No Apparent Public HealthHazard" if not the "No Public Health Hazard" category being specified:

· the prevailing wind direction,
· the low level HCN emissions at the source,
· the low modeled HCN concentrations in Victor,
· the long distance to the nearest potential receptors,
· the tendency of the air quality dispersion models to over predict, and
· the known instability of HCN in the atmosphere.

CC&V understands that ATSDR is planning to conduct ambient air HCN sampling in the vicinityof Victor. Although direct measurements of targeted parameters in ambient air are typicallypreferred, CC&V is not aware of any reference method with detection limits sufficiently low toconfirm the concentrations predicted in the dispersion modeling. As such, CC&V suggests thatATSDR use any sampling results in conjunction with the six factors itemized above in the finalhealth determination.

Response: ATSDR will factor in all scientific and relevant information when making a final healthconclusion regarding the CC&V site.

Comment:Public Health Action Plan:

Actions Completed - The term "gaseous" should be deleted under the second "bullet". Theword "hot weather" should be replaced with "dry conditions"

Action Ongoing - The second word "are" should be replaced with "continues to" and"monitoring" changed to "monitor".

Response: ATSDR modified the text as requested.

Reference for Public Comment and Response Section

  1. U.S. Department of Health and Human Services. February 20, 1996. Toxicological Profile for Cyanide. Table 7-1. Atlanta, GA.

APPENDIX F: EXPOSURE INVESTIGATION: HYDROGEN CYANIDE SAMPLING

Background

On June 14, 2000, ATSDR released a petitioned Public Health Assessment (PHA) for the CrippleCreek and Victor Gold Mining Company in Victor, Colorado. The company mines and processesore to extract gold and other precious metals. At the company's Cresson Valley Leach facility, asodium cyanide solution is applied by drip irrigation tubes to piles of crushed ore to extract gold. Ifhydrogen cyanide gas (HCN) were released during this operation, it could migrate off site, andresidents living in the area could be exposed to the chemical in ambient air. (The closest privateresidences are located about 3,500 feet from the edge of the leach field.) In the PHA, ATSDR notedthat no ambient air monitoring data were available to assess the risk associated with potentialexposures to hydrogen cyanide emissions from the facility. Therefore, the purpose of this ExposureInvestigation (EI) was to collect ambient air monitoring data that could be used to assess whetherresidents in the area are being exposed to hydrogen cyanide at levels of public health concern.

Materials and Methods

Air sampling was conducted from October 10 to October 12, 2000. ATSDR used a combination ofNIOSH methods 7904 and 6010 to monitor for ambient air hydrogen cyanide. Air samples werecollected for six consecutive 8-hour periods using a personal sampling pump operated at a flow rateof about 1 liter/minute. Hydrogen cyanide in the air samples was trapped in a bubbler apparatuscontaining 15 ml of 0.1 N potassium hydroxide (KOH) (NIOSH method 7904). Before and aftereach sampling event, the air flow rate through the collection apparatus was measured using aprimary standard (Gilian Gilbrator).

At the end of the 8-hour sampling period, the KOH solution in the bubbler was transferred to a glassvial. The bubbler was rinsed with 2 ml of 0.1 N KOH, and the rinsate was added to the sample vial. At the end of the 48-hour monitoring period, the samples were sent by overnight mail to DataChem(Salt Lake City) for analysis. The samples were analyzed spectrophoto-metrically for HCN asdescribed in NIOSH Method 6010.

ATSDR collected ambient air samples at five locations: (1) 450 feet northwest of the leach field[NW-01], (2) 600 feet southeast of the leach field [SE-01], (3) 1,400 feet southeast of the leach field[SE-02], and (4) at two residential properties on the west edge of Victor. These private residenceswere located about 3,500 feet southeast of the leach field. The locations of the sampling points aredepicted on the map in Figure 1. The exact locations of the sampling points were determined usinga Global Positioning System.

Samples were collected every 8-hours for a period of 48 hours, which yielded 6 samples persampling location. Because of air pump failures, sampling was limited to four 8-hour samples at thetwo private residences. One KOH field blank was collected at each sampling location.

ATSDR obtained local meteorological data for the sample periods from the Bateman meteorologicalstation, which is located 1,800 feet south of the leach field.

Informed Consent

Prior to testing, ATSDR obtained the written, informed consent of the owners of the propertieswhere the air monitoring devices were located.

Results

Hydrogen cyanide was not detected in any of the ambient air samples collected at two residentialproperties. The detection level for hydrogen cyanide in these samples ranged from 0.1 to 0.2 partsper billion (ppb), depending on the volume of the air sample. The two private residences wereselected because they were among the homes in Victor that were closest to the leach field. Thelocations of the monitoring stations are shown in Figure 1.

Two of the on-site sampling locations (SE-01 and SE-02) were chosen to be between the leach fieldand the town of Victor. Another on-site sampling station (NW-01) was located on the opposite side(northwest) of the leach field. Low concentrations of hydrogen cyanide were detected in 6 of the 18on-site air samples. Hydrogen cyanide was not detected in the other 12 air samples at a detectionlevel of 0.1 to 0.2 ppb. A summary of the on-site air sampling data is presented in Table 1. Asindicated, the quantifiable air concentrations of hydrogen cyanide ranged from 0.26 to 0.63 ppb.

At sampling station SE-01, the pump stopped sometime during one of the sampling periods. Theestimated hydrogen cyanide air concentration from this sample (1.86 ppb) is the minimum possibleconcentration assuming that the pump operated for 8-hours and pumped 500 liters of air. The actualair concentration cannot be determined because the sample volume is not known. However, theestimated concentration seems reasonable, since the ratio of the hydrogen cyanide concentrations atstations SE-01 and SE-02 for this sampling period (05) is similar to the ratio detected during anearlier sampling period (02).

Discussion

Low concentrations of hydrogen cyanide were detected in ambient air samples collected atmonitoring stations located 450 to 1,400 feet from the cyanide leach field. However, hydrogencyanide was not detected at the two stations at private residences. These findings are plausible, sincethe private residences were further away from the leach field, and cyanide concentrations in airwould be diluted with increasing distance from the source.

There is no National Ambient Air Quality Standard for hydrogen cyanide in air. However, the U. S. Environmental Protection Agency has derived a Reference Concentration (RfC) for hydrogen cyanide of 3 µg/m3 (2.8 ppb). A RfC is protective of the general population, including sensitive subgroups, for chronic exposures. Chronic exposures refer to exposures that last for as long as a lifetime. Hydrogen cyanide was not detected in air samples from residential properties. Furthermore, the hydrogen cyanide concentrations detected in on-site air samples collected near the leach field for 8-hour periods were below the RfC. Therefore, none of the hydrogen cyanide concentrations detected in this investigation posed a public health hazard.

This conclusion is based on ATSDR's sampling over a 2-day period. The cyanide leach fieldoperates continuously for 24 hours/day and 365 days/year. Therefore, ATSDR does not expect thatthere would be large day-to-day variations in cyanide release from the leach field. However, on-siteand off-site hydrogen cyanide air levels could be significantly affected by wind direction and speed,precipitation, temperature, and other meteorological conditions. During ATSDR's sampling, theweather was cool (40-58 F) and dry. Winds were variable (5-19 mph), but predominantly blewfrom the northwest and west, that is, across the leach field toward sampling stations SE-01, SE-02,and the residential stations. Therefore, if there were significant emissions from the leach field, theywould have been detected during the two days of sampling. Since only low concentrations ofhydrogen cyanide were intermittently detected, ATSDR concludes that hydrogen cyanide emissionsfrom the leach field do not pose a public health hazard under current operating conditions.

Conclusions

ATSDR did not detect hydrogen cyanide in ambient air samples collected from on-site and off-site residential locations at concentrations of health concern.

Recommendations

If there are significant changes in the operation of the leach field, or if the size of the leachfield is significantly increased, ATSDR recommends that additional air monitoring beconducted to ensure that hydrogen cyanide emissions do not pose a health hazard for on-site workers or off-site residents.

Prepared by:

Kenneth G. Orloff, Ph.D., DABT
Exposure Investigations Section
Exposure Investigations and Consultations Branch
Division of Health Assessments and Consultation

Peter J. Kowalski, CIH
Health Consultations Section
Exposure Investigations and Consultations Branch
Division of Health Assessments and Consultation


Reviewed by:

John E. Abraham, PhD
Branch Chief
Exposure Investigation and Consultations Branch
Division of Health Assessments and Consultation

Susan Metcalf, MD
Section Chief, Exposure Investigation Section
Exposure Investigations and Consultations Branch
Division of Health Assessments and Consultations


Locations of the air monitoring stations for the Exposure Investigation.  The location and dimensions of the leach pad are estimated.
Figure 1. Locations of the air monitoring stations for the Exposure Investigation. The location and dimensions of the leach pad are estimated.

Table 1.

Hydrogen cyanide (ppb) in ambient air samples from on-site monitoring stations
   

Station Number

 
  NW-01 SE-01 SE-02
Sampling Time Period      
01 ND 0.51 ND
02 0.26 0.63 0.26
03 ND ND ND
04 ND ND ND
05 ND >1.86* 0.60
06 ND ND ND

ND - none detected

(*) estimated value based on an assumption that the pump operated for 8-hours and pumped an air volume of 500 liters

Cresson Project Crushing Circuit
Cresson Project Crushing Circuit

Crossection of Cresson Leach Facility
Crossection of Cresson Leach Facility

Information Form


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