Reservoir runoff will exceed county limit
By Greg Pearson STAFF WRITER

Phosphorus levels in the Swift Creek Reservoir are climbing as development continues to increase throughout the watershed.

When build-out of the approved residential and commercial development in the Upper Swift Creek Watershed occurs, annual phosphorous levels in the Swift Creek Reservoir will be 409 pounds over the county's limit of 25,000 pounds.

If additional properties are rezoned, those rezonings could increase the amount of phosphorous. Currently, hundreds of acres, which drain to the reservoir, are in the development pipeline for rezoning.

The county is also headed toward extending the Powhite Parkway nine miles through the watershed, which will spur growth. Impervious surfaces such as roads, rooftops, driveways and parking lots create the runoff since rainfall can't permeate the soil naturally where it falls.

"Before we assumed there was room for runoff in the reservoir," said Planning Commission Chairman Dan Gecker. "Now we know there isn't."

"Will future rezonings have to proffer no net increase in runoff?" asked Bermuda Planning Commissioner Jack Wilson.

"No," responded the county's environmental engineering department and an outside consultant, CH2MHill. There are actions that can be taken to counteract additional phosphorous including retrofitting BMPs (ponds that collect runoff), "pushing" developers to add BMPs even though their rezonings were approved without them, and other options.

But, some commissioners seemed puzzled by the suggestion of adding more BMPs since the commission was given data last month that showed the approximately 85 BMPs already in the watershed only took out 900 pounds of phosphorous a year.

"I've heard the numbers, but I don't know that I believe them or that we moved forward very much," observed Clover Hill Planning Commissioner Russ Gulley.

In an e-mail to this newspaper last Friday, Scott Flanigan, the county's water quality analyst, wrote, "Some developers paid into a fund for a master BMP plan instead of treating runoff onsite, but that plan has subsequently been discouraged by the Army Corps of Engineers. The county's environmental engineering department believes some developers, who may be considered vested, will contribute to controlling nutrient runoff in lieu of a fee. The worst case scenario estimated a potential phosphorus load of 32,000 pounds. This load represents the current development and the potential future load from land currently zoned and not developed. The second estimate [of 409 pounds over the 25,000 pound limit presented last week] applied levels of storm water treatment to development which would be required of those parcels not considered vested under the regional BMP plan."

Several county officials have predicted later this year the state may reduce the in-lake phosphorous runoff allowed to .04 milligrams per liter instead of the county's current .05 milligrams. Flanigan estimated that would require reducing the amount of phosphorous 3,000-4,000 pounds annually. Department Director Dick McElfish agreed to provide skeptical commissioners with a side-by-side comparison next month.

CH2MHill is currently compiling a report, detailing how future phosphorous runoff will impact the reservoir. The report will help commissioners decide what to recommend to county supervisors on future rezonings in the watershed.

According to Director of Utilities Roy Covington, more phosphorous does not threaten the reservoir as a source of drinking water. Swift Creek currently provides about 30 percent of Chesterfield's drinking water.

"Nutrients like phosphorous accelerate natural, biological growth in a lake," he explained. "Over time, biological growth…creates additional organic matter, and we remove those organics by adding chemicals. More phosphorous would affect our treatment…and increase the cost…but we treat it, and it's absolutely drinkable."

"If the phosphorous increases above the standard, we'll have more algae blooms, and the reservoir could become a poor fishing lake," said Tom Pakurar, of Hands Across the Lake.