Hydrogeologic Evaluation of a Radial Collector Well as a Water Supply for the City of Manchester, New Hampshire

Tuesday, December 5, 2017: 10:40 a.m.
101 AB (Music City Center)
James Wieck, PG , GZA, Bedford, NH
Steven R. Lamb, PG, CGWP , GZA GeoEnvironmental, Inc., Bedford, NH
Greg Smith , Wright-Pierce, Manchester, NH

A case study is presented describing hydrogeologic evaluation of a radial collector well installed adjacent and beneath the Merrimack River in Hooksett, New Hampshire. The well includes an approximately an 70-foot-deep, 16-foot-diameter vertical caisson, and six horizontal laterals constructed in a fan-like pattern beneath the riverbed. Laterals are an average of 200 feet in length. Phases of subsurface exploration and preliminary withdrawal testing were performed to collect stratigraphic and hydraulic information for design of the radial collector well, and provide monitoring locations for water quality and level response monitoring. Data collected supported application for a New Hampshire Large Groundwater Withdrawal permit and water supply permitting 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.


Slides in PDF
James Wieck, PG, GZA, Bedford, NH
James Wieck is a Senior Hydrogeologic at GZA in Bedford, New Hampshire. Jim focuses on water supply development and contamination investigation and remediation projects.

Steven R. Lamb, PG, CGWP, GZA GeoEnvironmental, Inc., Bedford, NH
Steven Lamb, PG, CGWP, is a principal at GZA GeoEnvironmental with more than 25 years of experience conducting projects in the New Hampshire Corrective Action Program with regard to state lead petroleum release and hazardous waste sites, brownfield sites, and CERCLA sites. He has an extensive background in hydrogeologic investigations, groundwater engineering, contaminant transport evaluations, and remedial design and implementation of remedial strategies at industrial facilities, brownfield sites, landfills, gasoline and waste oil sites, and other sites impacted by disposal, chemicals, and waste materials.

Greg Smith, Wright-Pierce, Manchester, NH
Greg Smith is the Lead Hydrogeologist at Wright-Pierce working out of their Manchester, New Hampshire office. Greg focuses on water supply development projects throughout the east coast of the United States. Greg's work includes water supply exploration projects and developing solutions to water quantity and quality challenges.

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