MAINTAINING GROUND WATER RECHARGE IN MASTER PLANNED COMMUNITIES: CASE HISTORIES FROM EASTERN KING COUNTY, WASHINGTON

Long term ground water level monitoring programs from two Master Planned Communities in east King County, Washington demonstrate the effectiveness of integrated site planning and stormwater management in maintaining aquifer recharge. Redmond Ridge, Trilogy at Redmond Ridge and Redmond Ridge East have collectively been approved as a Fully Contained Community (FCC) and encompass more than 2,580-acres in the Novelty Hill area of King County, Washington. Baseline water level monitoring was conducted three years prior to initial site development at Redmond Ridge, continued throughout multiple phases of development, and has continued into a post-development phase. Water level data has been obtained from a network of over 35 wells geographically distributed throughout the FCC properties. Ground water response from the monitoring wells demonstrates a direct relationship to precipitation trends and show no reductions in water levels associated with development.

Snoqualmie Ridge and Snoqualmie Ridge II include approximately 2,075 acres located on the Lake Alice Plateau in Snoqualmie, Washington. Long term ground water level and instream flow monitoring demonstrates aquifer water levels have been successfully maintained throughout project buildout and post-construction monitoring phases. Snoqualmie Ridge II stormwater management design included the construction of combination infiltration/Underground Injection Control well facilities, up to 160 feet deep, designed to convey stormwater below perched ground water to maintain in-stream flows and avoid adverse impacts to nearby steep slopes. Maintaining aquifer recharge provides direct environmental benefit to ground water and surface water resources such as baseflow to springs, streams, wetlands and water supply wells.