Hydrogeologic Evaluation of a Radial Collector Well as a Water Supply for the City of Manchester, New Hampshire
Hydrogeologic evaluation included a step drawdown and two over 30-day constant rate withdrawal tests to evaluate groundwater capture, sustainable yield, and potential adverse impacts. Groundwater-surface water interactions and relative contributions to the withdrawal were evaluated. Constant rate tests were conducted during summer and winter conditions to evaluate effects of seasonal variations in viscosity on yield, capture, and groundwater-surface water interactions. Relative contributions of surface water and groundwater were also evaluated based on water quality including anion and cation data.
Hydraulic head data were collected from over 25 monitoring wells and selected residential water supply wells including wells screened in shallow and deep overburden and bedrock. Hydraulic head and water temperature data were also collected from the caisson and three multilevel monitoring locations constructed within the riverbed. Riverbed monitoring data were also used to identify the presence of restrictive layers within the riverbed.
The results of the withdrawal testing indicate a sustainable withdrawal rate of over 5,000 gallons per minute, with over eighty percent of the withdrawal from induced infiltration. The relative percentage of contributions to the well varies by up to 10 percent dependent upon temperature.