By Christy Goodman
Washington Post Staff Writer
Thursday, July 24, 2008

Water quality in Mill Creek and other tributaries to the Solomons harbor is diminishing, probably because of dense development and old septic systems, according to an annual report by the Chesapeake Biological Laboratories.

The report shows increases in chlorophyll concentrations in drought years, such as last year, said Wayne Boynton, a scientist with the laboratories, a branch of the University of Maryland Center for Environmental Science.

"What I think we are seeing is, the near-surface groundwater that flows from all the housing and septic fields down a slope into the harbor is having an effect," Boynton said. "The effect is it is growing more algae. When you have more algae in the water, then you have more depressed oxygen conditions in the water as well."

Low oxygen levels contribute to poor growth in water grasses and destroy marine habitats.

Typically during rainy years, more pollutants and other runoff, such as nitrogen and phosphorus, flow in from different locations. In a dry year, however, nitrogen and phosphorus enter the harbor through the groundwater, creating "a simpler picture" for scientists, Boynton said.

The testing of Mill Creek, Back Creek, St. John's Creek, the Narrows and the harbor began in 1987 and has been done every year except 1989. Testing is conducted between May and September, when biological activity is at its peak, dissolved oxygen is more easily measured and less oxygen from the air combines with surface water, giving a more accurate picture of water conditions.

Calvert County began the study because its commissioners were interested in enlarging the Solomons Town Center but wanted to "keep a pulse" on the water's quality, said David Brownlee, the county's environmental planner. "Of course, they didn't want to lose the asset of the harbor," he said, adding that the harbor is not only attractive but an economic asset for the county.

Development in Calvert's southern end is among the densest in the county, Brownlee said. An estimated 12 percent of the land has impervious surfaces, such as rooftops, driveways and other surfaces that rainwater cannot penetrate.

"Scientific data said once you approach 10 percent, things are getting pretty bad in a watershed," Brownlee said.

Calvert commissioners asked county staff members last week to develop an action plan, and the commissioners approved two grant proposals to help pay for the work. One grant will fund more sampling in the Mill Creek watershed, including Lake Lariat and surrounding waters, as well as pay for educational programs for the watershed's residents.

The other grant will fund work identifying road systems where new storm water management technology could be implemented, said Greg Bowen, director of planning and zoning for the county.

Commissioner Barbara A. Stinnett (D-At Large) said the county is placing "most of the emphasis" on the creeks in Calvert's south end. "I think we need to do a base study for Fishing Creek" in Chesapeake Beach and creeks in the northern end, she said.

The county has begun a program that replaces an estimated 45 septic systems per year with nitrogen-removing systems in areas within 1,000 feet of tidal waters.

"An estimated 45 systems a year is not going to have much impact on the total nitrogen load, based on the total expected growth," Brownlee said. He said the county needs to focus on replacing existing systems because more homes are built than planned.

Commissioners are working to establish a monitoring program for the new nitrogen-removing systems.

County officials have held seminars explaining the importance of fertilizing in fall instead of spring to reduce harmful runoff. A limited number of free soil tests are available to help homeowners measure whether they need to fertilize, Brownlee said.