Well Field Delineation
Delineation of Source Water Protection Areas WPAs is the first step in developing a Source Water Protection Program (SWPP). The purpose of the source water delineation is to define the surface and subsurface areas which will contribute to a well or wellfield over a one, five, or ten year time period. SWPA’s are also referred to as time-of-travel zones (TOTs).
The Consortium delineated a one, five, and ten year TOT using a numerical groundwater flow model known as MODFLOW. The program, developed by the U.S. Geological Survey for specialized groundwater investigations, considers a variety of aquifer characteristics when determining the boundaries of the TOTs. This includes the influence of recharge from surface water and precipitation, the ability of groundwater to move through the aquifer media “hydraulic conductivity”, and the influence of groundwater production wells.
The Consortium’s delineation resulted in the identification of four major SWPAs. These are:
Hamilton North Wellfield SWPA – 0.75 square miles sq. mi.. This SWPA extends into four jurisdictions: the City of Hamilton, Village of New Miami, St. Claire Township, and Fairfield Township.
Joint SWPA – 12.5 sq. mi. This is the main SWPA. The joint SWPA includes overlapping SWPAs for the City of Fairfield, City of Hamilton South Wellfield, Greater Cincinnati Water Works, and Southwest Regional Water District. Most of the area is in Butler County, but a small portion on the southwest end does extend into Hamilton County Colerain Twp.
Southwestern Ohio Water Company SWPA – approximately 3 sq. mi.. This SWPA, located at the southernmost portion of the project area, extends from Ross Township in Butler County into Colerain and Crosby Townships in Hamilton County.
The extensive nature of the SWPAs and the number of jurisdictions impacts by the SWPAs has required an unprecedented level of cooperation between all the affected communities.