Sent: Wednesday, October 15, 2008 1:24 PM
To: Distribution List
Subject: Wet Weather MPA Test Results Post TS Hanna
I am sending this to a wide distribution list so that I may immediately notify all of you.
I received the wet weather MPA test results today regarding the sampling event following Tropical Storm Hanna. We decided to sample several locations to see if the potential surface water influence was broad ranging or isolated. Locations included our drinking water supply wells (PW-1 and PW-2), two drinking water supply wells from Selma, and the Raspberry Falls Golf Course irrigation well 3 (RASP 3). We sampled our Raspberry supply wells twice because the bacteria levels from the event approximately 3 days after the storm were about 1 count/100 mL for total coliform and non-detect for E. coli. The second sampling event took place 11 days after the storm. PW-1 had a total coliform count of 200.5 before and after the test, with non-detectable E. coli. PW-1’s counts were 7.5/ND for total and E. coli before and after the test. This appeared to be just after the peak, because a day earlier, we detected 5.3 counts/100 mL of E. coli in PW-1. Results from all 7 samples returned MPA risk factors of “0.”
With these results, we will turn PW-1 back on tomorrow. (10/16/2008)
We will also be working internally to determine what the results mean with respect to path forward. For example, should exploratory well drilling be put on hold because MPA risk factors are tending to indicate that there is not a strong surface water influence? We will need to get a feeling from the community at the meeting on October 28 as to their confidence with the water system, as results are more strongly indicating that with the source water that we have, the current system is adequately protecting public health.
Regardless of the results, demand is such that additional storage is still required. This would provide additional chlorine contact time for the bacteria that is present after rain events.
I will speak more with you soon. Thanks.
Todd A. Danielson, P.E., BCEE
Manager of Community Systems
44961 Loudoun Water Way
PO Box 4000 | Ashburn, VA 20146
Tel 571.291.7835 | Fax 703-726-0684