A low impact development/green infrastructure retrofit master plan was developed for the 31-acre Gwinnett County Water Resources Department main facility. Funding was available for the construction of Phase 1 of the master plan and a green infrastructure project was designed and constructed in summer of 2011. Subsequent to construction the project was added to the WERF sponsored green infrastructure monitoring program. In light of current and proposed stormwater rules which will require some level of on-site volume reduction, Gwinnett County developed a master plan to ascertain the ability and cost to retain the 95% storm (about 1.7 inch) entirely onsite. A bioretention area was designed and built with USEPA Section 319(h) grant funds to demonstrate treatment of stormwater runoff using green infrastructure techniques. During construction, a power utility was encountered which required redesign of the project to a smaller size. The project illustrates the benefits and challenges of implementing green infrastructure in an urban environment.

No abstract

Gwinnett County, GA, located in metro Atlanta, with a population of approximately 750,000 owns and operates a relatively young storm sewer system consisting of about 1,300 miles of storm sewer pipe. Growth has slowed and the county is maturing from its development phase and is moving swiftly towards a redevelopment and maintenance footing.Following some preliminary analyses, conducted several years ago, the county understood that it was facing a significant short to mid term financial threat in the management of much of this donated storm sewer system. Fully 80% of the County owned storm sewer in Gwinnett was constructed with various types of corrugated metal pipe (CMP) which is estimated locally to have a median useful life of approximately 30 years. With replacement costs averaging $480/lf, and several hundred miles of galvanized and bituminous coated CMP already older than 20 years, the county considered and adopted a Stormwater Utility in 2006 with the primary purpose of funding the rehabilitation or replacement of the aging storm sewer system. In 2009 Gwinnett's Stormwater Utility fee will provide dedicated stormwater management funding in the order of $31M.