13.01.2013 Views

Dames & Moore, 1999 - USDA Forest Service

Dames & Moore, 1999 - USDA Forest Service

Dames & Moore, 1999 - USDA Forest Service

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

5.3.1.2 Area Background Compared to WQC<br />

0 The area.background concentrations (as determined by the total data set) for arsenic, beryllium, cadmium,<br />

chromium, copper, iron, lead, mercury, nickel, selenium, silver, and zinc were compared to WQC. For<br />

those metals requiring hardness correction, background values were compared to the WQC using a<br />

minimum hardness of 6.7 ppm. This value was selected as it is representative of the lower hardness<br />

values obtained in the RI data and provides the most conservative WQC levels. Hardness concentration<br />

in Railroad Creek varied from 6.7 to 31 mgL dependent upon the station location and sampling event.<br />

The lowest hardness values generally occurred in stations upstream of the Holden Mine. The background<br />

values were also compared to WQC based on 25 pprn hardness as this is the minimum hardness allowed<br />

for WQC under the federal guidance when actual hardness values are below 25 ppm. The WQC and<br />

background values are summarized below.<br />

Metal<br />

Arsenic<br />

Beryllium<br />

Cadmium<br />

Chromium<br />

Copper<br />

lron<br />

Lead<br />

Mercury*<br />

Nickel<br />

Selenium<br />

Silver<br />

Zinc<br />

Background<br />

Concentration<br />

(cl%L)<br />

0.9<br />

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!