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The Carpenter Snow Creek - Neihart Residential Soil Site is located in Cascade County, and the City of Neihart, Montana. The Site is located along Highway 89 and consists of several residential properties in the south and north ends of town. Also, there are two historic mill sites that impact residential properties, and a tailings impoundment next to Belt Creek.
Description of Threat:
Historic milling activities and spread through the Community by various means, including flooding along Belt Creek, annual runoff following heavy snow melting, plowing during winter, and excavation associated with construction of residences and roads has spread and exposed mine waste. It appears that at least 10% of the residential properties and several non-residential (i.e., community recreational areas) on the Site have lead at levels of concern to the Removal Program. The major threat posed by this Site is ingestion of lead-contaminated soils by young children. In addition, portions of the site are adjacent to Belt Creek, which does support cold water fisheries. Historically, flood events have caused mine waste to discharge to the creek.
Remvoal Site Inspection Results
The majority of an estimated 128 residential properties, including a community center, a parking lot, an abandoned “ball mill” area, and an unpaved roadway (that was formerly a rail line leading away from the ore processing mill and is now a common pathway through the community), were sampled by EPA’s Response Action Contractor (CDM) between 2003-2004. Of the samples, taken from approximately 100 separate properties and analyzed for 17 heavy metals plus arsenic, approximately 10% exceeded 2900 parts per million (ppm) lead. with the highest level at 44,000 ppm (See Exhibit 1 - attached). Arsenic is also present at elevated levels with the lead contamination.
RESPONSE INFORMATION:
Properties will generally be included in the Removal Action if the average surface or near surface soil concentration exceeds 2800 ppm of lead, or if it exceeds 390 ppm arsenic. In addition to designated residential sites, the following non-residential areas appear to qualify for cleanup: 1) an ore load-out/source area on a steep slope, at the north end of town, adjacent to the two of the residential properties (cleanup/stabilization to prevent future contamination of the remediated residential areas); 2) the community center area; 3) an abandoned “ball mill” area; and 4) a portion of the unpaved roadway ,formerly a rail line leading away from the ore processing mill, which are all public/recreational areas now a common pathway through the community. The average depth of soil removal will be18 inches; soil removal depths may range from 12 to 24 inches. Removal depths may be less in areas where rock and boulders preclude effective excavation. In those cases, cover material may be used to provide a cap over the contamination.
On August 23, 2004 EPA’s removal contractor mobilized to the Site. Specific actions to date include the following:
* Site preparation including placing silt fencing along drainage features and standing water, locating utilities, septic systems and establishing staging areas for soil fill and waste;
* The City of Neihart is providing a lay-down area as needed at the Community Center for equipment and soil and the City is providing water for dust suppression and decontamination.
* Sampled to delineated excavation areas in south and north residential zones;
* Storage site (Neihart Tailings Impoundment) preparations: Federal, State and local agency contacts made including MTDOT and FWP 124 permit applications provided for information only to state agencies regarding temporary bridge contstruction;
* Excavation to approximately 2 feet in southern residential area is 50 % complete and backfill started.
* Protective structures placed in north residential zone behind homes (concrete barriers, plywood);
* North Slope stabilization behind homes is underway with toe cut 75% complete.
* Temporary bridge constructed (60 x 16 feet) over Belt Creek without entering the creek channel.
* Contaminated soil stockpiles are ready for hauling to storage site.
* Backfill material from site 24 miles south of Neihart is being delivered at approximately 20 loads a day as of 8/30/04;
Enforcement: (TBD)
Excavation and backfill will continue in the residential properties for approximately 3 weeks.
The north slope area will be excavated and shaped as necessary to allow for stabilizing the waste rock from eroding down slope to the residential properties.
Storage site (Tailings Impoundment) will be prepared for placement of contaminated soils and receive approximately 5000 cubic yards of contaminated soil. It will receive a temporary cover of 12 inches of fill/soil mix.
No key issues at this time
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