Water Quality in Kerr and Lake Gaston

A Letter from VA Beach Public Utilities: To all, Although I have not communicated in a while, I wanted to let you know that Virginia Beach has not stopped monitoring water quality in Kerr and Lake Gaston. It is just that from the beginning of this event, given its location and size, we have been confident that the significant dilution provided by the Dan, Banister, and Roanoke Rivers combined with the sediment trapping properties of Kerr Reservoir would prevent any detectable amounts of contaminants to reach Lake Gaston, much less Pea Hill Creek. To date, that is what we have observed. All of these results are “Total” measurements. That means the sample is raw water and contains whatever silt and sediment is suspended in the water column at the point and time of sampling. It also means that the samples have been acid digested to make sure that any metals – even those that are naturally occurring and securely bonded to clay particles – are included in the results. With respect to the attached data, Clarkesville is at the headwaters of Kerr, and RRSA is at the headwaters of Gaston. Both act like lakes during low flows, but take on river characteristics during higher flows. Pea Hill Creek is a lake and has an entirely different watershed from Kerr and RRSA. Most of these contaminants are in the sediments, some naturally and some from man-made sources. So in the case of Clarkesville and the RRSA, changes in water quality might result from changes in flow, which in that system occur frequently. That is also why the results for aluminum are so much lower in Pea Hill Creek than at Clarkesville and the RRSA. Aluminum is a major component of clay. There is more clay sediment suspended in the water flowing past Clarkesville and the RRSA than in the quiet waters of Pea Hill Creek. Clay also contains trace amounts of many of the heavy metals that we are monitoring for, so their presence at low levels is natural. The data does indicate that we might have caught the spill moving by Clarksville on Feb 9, one week after the incident. This is in line with what we would have expected - several days to a week to reach the headwaters of Kerr. Please note that arsenic was only slightly above 1 ug/l. However, you have to be careful drawing to much of a conclusion from results at these very low levels. For example, while the copper “spike” to 60 ug/l on February 20 at the RRSA seems out of the norm, the Safe Drinking Water Act contaminant level for copper is 1,300 ug/l. Although we do not expect to be able to detect it, we would have thought that 3 to 6 weeks was a reasonable time period for any dissolved or suspended ash to reach the RRSA, and 2-3 months to reach the Pea Hill Creek intake. Again – we do not anticipate being able to detect anything significant, but we will keep looking. In the meantime, we are still not pumping. This is not because of any concern for water quality. It has been very wet and we do not need to pump. Let me know if you have any questions. Thomas Leahy Director of Public Utilities 2405 Court House Drive Virginia Beach, VA 23456 (757)385-8654