Water Quality: The Pacifica development site encompasses about 8.3 acres of which 6.0 acres have been cleared for the development. A large wooded buffer (left of figure 1) along the downslope edge of the development was left undisturbed (figure) to provide opportunities for infiltration and treatment of stormwater prior to leaving the site. Stormwater from the site that passes through the buffer enters Dry Gulch which is a tributary of Bolin Creek. Downstream sections of Bolin Creek were identified as having an impaired biological community in the 1996 basinwide management plan published by the NC Division of Water Quality. Instream habitat degradation associated with urban nonpoint source pollution is a possible cause of the impairment. In addition, Bolin Creek eventually drains into B. Everett Jordan Lake, which is classified as a nutrient sensitive water of the state. Excess loading of nitrogen and phosphorus impair the use of the lake for drinking water and recreation. Hence, minimizing any additional loading of pollutants to this system is a high priority.
Location: The proposed project will be conducted on a single site of 8.3 acres located in downtown Carrboro, NC. The site and building plans incorporate low impact development (LID) design principles, green building, and Smart Growth strategies. For example, the Pacifica site plan allocates 40% of its 8+ acres to critical riparian open space while also fulfilling urban infill criteria-using a densely developed housing model while locating it residents within 0.75 miles of shops and services of Carrboro thereby utilizing existing utility resources and social infrastructure. Further, the housing units are designed to use passive solar energy, minimize unit footprints (vertical design), limit construction waste, and maximize the use of on-site plant/building materials. In addition, the design includes features that will facilitate the use of alternative transportation methods (greenway access, bike racks, and bus stop).
Stormwater Treatment: Pacifica's site design facilitates the "treatment train" approach for stormwater management, which uses a combination measures to minimize stormwater and associated pollutant export from the site. The volume of stormwater runoff produced will be minimized by reducing the footprints of dwellings, installing a roof runoff collection system, using pervious pavement where practical, establishing community gardens, installing grassed swales and bioretention areas, and minimizing impervious road area. Stormwater volume, velocity, and peak flows will be reduced by bioretention areas and swales, a stormwater retention/irrigation pond, grass strips and level spreaders, and a riparian buffer. Each device works in combination with another to provide a train of treatment for stormwater (figure 2).
In summary, this site offers a comprehensive approach to controlling nonpoint source pollution from urban and suburban environments using multi-pronged strategies low impact building and site design practices followed by on-site stormwater retention, water conservation and reuse, and on-site pesticide and nutrient reduction.
