Dames & Moore, 1999 - USDA Forest Service

in wells TP1- 1A. TPl-2A, TPI-3A, TPI-5A and during the spring round only in monitoring well TP I -
6A. Zinc was above the MTCA Method B cleanup level (4800 pgk) in samples collected in the spring
and fall from monitoring well TPl-3A and in the spring from wells TPI-SA and TPI-6A. All other
metals were below MTCA cleanup levels where established. Iron concentrations in the wells screened
below tailings pile 1 ranged from not detected (< 20 pg/L) at TPI-4A in fall 1997 to 1,690,000 pg/L at
TPl-2A in fall 1997. With the exception of TPl-4A, concentrations of iron were greater than 79,500
pg/L, Field pH ranged from 4.1 to 5.5 SU. Concentrations plots for pH, aluminum, cadmium, copper,
iron, manganese, and zinc are shown on Figures 5.4-3 through 5:4-16.
Groundwater samples were collected from lysirneters (TPl-2L, TPI-3L, TPI-4L, and TPl-6L) completed
within the tailings in tailings pile 1. Sample results for dissolved metals were collected in the spring and
fall of 1997. Generally, dissolved metal concentrations for lysimeter and groundwater monitoring wells
were similar at the same locations. Exceptions were aluminum, copper, cadmium, iron, manganese, and
zinc, which showed increases and decreases dependent upon location and may be indicative of the
varying material deposited in the tailings pile, as well as the level of saturation.
Seep samples were collected from SP-1 and SP-2 at the base of tailings pile 1. SP-I was sampled in May
and July 1997.. SP-2 was sampled in May, July, and September 1997. Additionally, samples were
collected at SP-2 weekly from May 18 to June 16 to assess event-related variability and after a rain event
in October 1997. Concentrations of aluminum, cadmium, copper, iron, manganese, and zinc ranged from
27,100 to 121,000 pg/L, 6 to 22.8 pg/L, 101 to 914 pg/L, 487,000 to 1,260,000 pg/L, 3,380 to 6.3 10
pg/L, and 2,050 to 6,120 pg/L, respectively. pH ranged from 2.9 to 3.9 SU. Concentrations of cadmium
and iron were similar at SP-1 and SP-2. Aluminum, copper, manganese, and zinc generally were higher
at SP-2 than SP-I, but within an order of magnitude.
The concentration of aluminum, cadmium, copper, manganese and zinc generally decreased at SP-2
during the weekly sampling from May 18 to June 16, 1997. Iron increased during the same timeframe.
pH ranged from 2.9 to 3.2. Concentrations for aluminum, copper, iron, and manganese increased in July
and then decreased in September. pH was 2.9 to 3.1 SU. The sample collected after the rain event in
October 1997 contained concentrations of metals similar to those detected in September.
SP-I and SP-2 were sampled in May 1998. Concentrations of aluminum, manganese, and zinc are similar
to 1997 results. Cadmium and copper appeared to decrease in 1998 and iron increased, but results were
well within an order of magnitude compared to 1997.
Samples were collected from SP-I and SP-2 in May and July for analysis for PCBs and TPH. PCBs and
TPH were not detected. A sample was collected from SP-2 in September for TPH analysis. TPH was not
detected.
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