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

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

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!