Water samples were taken during the rainstorms on August 23, 2007
(Figure 1) and October 24, 2007 (Figure 2). A total of 26 samples
were taken between the two rain storms which represent 4 hours of
rain water activity. Concentrations of TPH were compared to flow
rate with the following results:
The rainstorm on August 23, 2007 (Figure 1) showed increasing TPH
concentrations with increasing flow rates.
These results are supported by previous literature involving NPS water
pollution. The sudden increase in TPH concentrations associated with
flow rate is referred to as a first flush and is considered to have the
largest impact on TPH concentrations. During the first flush
approximately 710 grams or 1 liter of gasoline entered the area
surrounding drain 4 on the USCA campus.
Rain activity after a “first flush”
is assumed to contribute relatively small amounts of TPH
to the environment. The
rainstorm on October 24, 2007 (Figure 2) supported this assumption
by
contributing concentrations of TPH below the detection limit of our
Immunoassay kits.