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Dames & Moore, 1999 - USDA Forest Service

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' Water<br />

Portal Drainage<br />

quality measured at P-l (main portal) and P-5 (confluence with Railroad Creek) as overland flbw<br />

indicates that metals presented in the following table were above regulatory surface and groundwater<br />

quality regulatory levels.<br />

These dissolved metals concentrations are influenced by seasonal changes in groundwater flow<br />

discharging from the main portal. The loading analysis reflects these differences.<br />

. MayIJune - The portal drainage discharge flows were as high ai approximately 3.5 cubic<br />

feet per second (cfs) in May 1997 and approximately 1.8 cfs in May 1998, and accounts for<br />

more than 65 percent of the load of dissolved cadmium, copper, and zinc to the creek<br />

during the spring snowmelt period.<br />

OctoberISeptember - Discharge flow rates were measured as low as approximately 0.10 cfs.<br />

The drainage accounts for less than 1 percent of the copper load, and approximately one-<br />

third of the cadmium and zinc load to Railroad Creek.<br />

The portal drainage overland flow represents the primary source of dissolved copper, cadmium and zinc<br />

to Railroad Creek during spring conditions; however during the fall, the concentrations of these metals is<br />

greatly reduced.<br />

Groundwater<br />

The groundwater geochemistry in the east and west portions of the Site is different due to the different<br />

source rock types (mine ore deposit versus tailings) and differences in oxygen availability and water flow.<br />

Groundwater data from monitoring wells and expressed as seeps and springs were used to evaluate<br />

groundwater quality associated with the Site, particularly for the west side of. the Site. Groundwater<br />

underlying the Site is not currently being used as drinking water.<br />

West Portion of the Site<br />

The west portion of the site includes the following source areas: underground mine and Honeymoon<br />

Heights, portal drainage, west waste rock piles, and the mill building. Groundwater monitoring wells are<br />

not present in these areas; therefore, seep water .quality was used to evaluate groundwater quality<br />

exceedances, source areas and loading to Railroad Creek. Concentrations of cadmium, copper; and zinc<br />

were above the MTCA Method B levels in goundwater in the western portal of the site.<br />

G:\WPDATA\OOSWEPORTSWOLDEN-2WECVnVE SUMMARY.doc<br />

17693-005-019UuIy 28,<strong>1999</strong>;12:16 PM;DRAFT FINAL RI REPORT' ES-7

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