Monday, April 16, 2012

The Rural Crescent an Essential Part of Our Green Infrastructure

At the regular March meeting of the Prince William County Board of Supervisors while considering requests for exceptions to the comprehensive plan, Supervisor Martin Nohe supported by the other county Supervisors seemed to feel that it was time to reconsider some of the planning and development decisions that had been made in the past and asked for staff to produce an analysis of the usefulness of the Rural Crescent in achieving those goals. The request was made by Supervisor Nohe to Prince William County staff and noted in the minutes.

The Rural Crescent was created in 1998 and has been chipped away at with exception requests every year. Higher density development means money to developers and landowners. There is much passion when money is on the table. The Rural Crescent in Prince William County was originally intended as an urban growth boundary for the county designed to preserve our agricultural heritage and force redevelopment along the Route 1 corridor rather than Greenfield development in the remaining rural areas. Maintaining the emphasis on redevelopment of areas with preexisting infrastructure would allow Prince William County to improve storm water management, achieve nutrient and sediment reductions for the EPA mandated TMDL, revitalize older areas of the county and preserve the Greenfields. The Rural Crescent may have started with different intentions; but today the Rural Crescent is about water, groundwater and ecosystem preservation.

Supervisor Nohe’s interest in transforming the 80,000-acre rural crescent where development has generally limited to one home per 10 acres with no access to public sewer is of great concern. Even though I believe that Supervisor Nohe is interested in moving towards sustainable community concepts, high density communities utilizing the strategies of Low Impact Development, LID, which include dedicated open space will not guarantee the preservation of our ecosystem and water. When development disturbs more than 10% of the natural land by covering surfaces with roads, driveways, walkways, patios, and homes the natural hydrology of the land is disturbed, irreparably disturbed. These developments while much better than traditional developments still disturb more than half the land area by significantly increasing allowed building density.

 While it has been demonstrated that LID strategies can reduce the impact of development, there is no demonstrated strategy of how communities can control and maintain natural storm water features and preserve and maintain the safety and ecology of preserved open space. There are no regional groundwater studies, regional ecosystem pans and no budgets for maintaining the open space.  Access control and prevention of improper use (underage drinking, drug use and sale,  other illicit activities, dirt bike racing) addressing deer population management and hunting adjacent to high density homes, litter and trash removal, maintenance of natural landscapes and supervision all cost money and time. No legal structures exist that guarantee open spaces will not be developed in the future to defray maintenance costs.  Why the Rural Crescent was formed is less important than understanding that the Rural Crescent provides a significant portion of our green infrastructure to our community.  

Green infrastructure connects the still intact habitat areas through a network of corridors that provide for wildlife movement and trails as well as pathways for pollinators. Maintaining intact, connected natural landscapes is essential for basic ecosystem and watershed preservation to ensure that there will always be clean air and water in Northern Virginia. Maintaining a tree canopy and controlling runoff to prevent stream bank erosion and water quality impairments and maintaining adequate water flows through groundwater and surface recharge are vital to ensuring safe water supplies, water recreation and the ecological integrity of the region. The Northern VirginiaRegional Commission (NVRC) has developed a Conservation Corridor PlanningProject which is a regional effort to identify essential green infrastructure and help area governments to avoid the mistakes of the past and maintain the few remaining green corridors along the rivers and reservoirs in Fairfax and integrate green infrastructure planning into the future development planning of Prince William and Loudoun counties.  

According to NVRC there are three priority regional conservation corridors in Prince William County.  Bull Run Mountain and Catoctin Mountain corridor is a north-south corridor connecting the foothills of the Blue Ridge Mountains in Northern Virginia.  The corridor provides significant intact habitat for Northern Virginia wildlife.  North of Leesburg, the corridor is the karst terrain of Loudoun underlain by limestone, and highly susceptible to pollution that provides a significant ground water recharge.

Karst aquifers are highly vulnerable to contamination. This vulnerability results from: sinkholes, widened flow paths, and rapid velocities of ground water and contaminants. Contaminants can be transmitted quickly from entry in a sinkhole to wells and springs in the vicinity. Sinkhole creation, sinkhole flooding, and groundwater contamination are the major hazards associated with karst terrain, and unlike other natural hazards they are chronic in nature. South of Route 50 the Bull Run Mountain ridge is the location of a significant area of recharge for the groundwater that ultimately maintains and feeds Bull Run and the Occoquan River. This area is part of a fractured rock system with limited overburden and no natural attenuation. A polluted plume could be carried for miles without dilution.

The second priority conservation area is begins at the Bull Run Mountains and heads east across Route 15 to Manassas covering the land between Route 50 and 29 to the confluence of the Occoquan River with Belmont Bay. This corridor is rich in water and environmental resources that ultimately deliver drinking water to over one million Northern Virginia residents. The Occoquan Reservoir, one of the country’s first water reclamation facilities where sewage treatment water is returned to provide water recreation. The western portion of the area is part of the Culpeper Basin Important Birding Area and the Culpeper Basin Groundwater Aquifer. Preventing water contamination and ensuring adequate groundwater recharge are vital to ensuring safe water supplies, recreation opportunities and the ecological integrity of the region.

The third priority conservation area is the Potomac Gorge and Quantico Corridor, the greenbelt that connects Prince William National Forest Park with Manassas Battlefield. This area includes large tracks of undeveloped private land. The western portion of the Rural Crescent was not identified by NVRC as a high priority conservation area because they failed to consider the importance of the groundwater aquifer. The Culpeper basin is part of a much larger PiedmontGeologic Province and has only begun to be studied thanks to the carefulgroundwater measurements taken by Loudoun County as excessive development ofthe western part of the county began to impact water supplies.  Groundwater quantity and quality in our region impacts not only groundwater wells, but stream flow and recharge to the surface water. In short all the drinking water in Prince William County. Groundwater recharges at various rates from precipitation and other sources of infiltration. The recharge is not spread evenly across the land. Pave over the land, change surface flow and infiltration and groundwater recharge are reduced.

Important regional waterways, such as Goose Creek, Bull Run, the Potomac River and Occoquan Reservoir thrive because they are shaded by trees and vegetation that filter stormwater, prevent erosion, and facilitate ground water recharge and moderate temperatures. Green infrastructure maintenance ensures the forested buffers are maintained and enhanced over time, protecting public health and water quality. Maintaining and enhancing forested buffers near Northern Virginia’s waterways requires focus on how to maintain and protect these ecological resources. The EPA has identified nitrogen, phosphorus and sediment as the three primary pollutants that must be reduced to restore the health of the Chesapeake Bay and its tributaries. They have mandated to Virginia and the other Chesapeake Bay Watershed states and Washington DC an approximate 25% reduction in these pollutants. A wide range of approaches can address these impairments, including reducing runoff and restoring stream banks and buffer areas. Adding more development in the Rural Crescent will not reduce the current level of sediment and nutrient pollution, and will not assure our water resources and ecology. 

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