Client project details
Merrimack Village District, NH (Well MVD-6 – Wellhead Protection)
The Merrimack Village District (MVD) was forced to discontinue use of its highest yielding Production Well (Well MVD-6) in 1988 after a VOC spill at a neighboring metals recycling facility contaminated the sand and gravel aquifer that hosts the well. A pump-and-treat remediation system subsequently was installed at the source of the contamination, limiting the ability of additional contamination to escape from the recycling facility property, and gradually reducing VOC concentrations in the aquifer. Because Well MVD-6 is capable of producing peak yields of nearly 1,500 gpm (>2 MGD), MVD wanted to determine the feasibility of returning this well back into service.
EGGI designed and carried out a 30-day pumping test of Well MVD-6. Purposes of the test included: 1) determining whether the well could be pumped at a targeted rate of 800 gpm without entraining additional VOC’s from the contaminant source area; 2) determining whether VOC concentrations at the Production Well would exceed federal drinking water standards in response to sustained pumping; 3) delineating accurately the combined wellhead protection area (WHPA) for MVD-6 and neighboring wells MVD-7 and MVD-8, and 4) obtaining approval for use of the well as a public drinking water supply.
During this extended pumping test, EGGI measured water levels at more than 30 monitoring points, including observation wells, shallow piezometers, and surface water measuring points. Water samples for VOC analysis were collected from the pumping well and from a network of monitoring wells at intervals throughout the monitoring period. Using the results of the pumping test, EGGI constructed a numerical flow model which was used both to delineate the WHPA and to make predictions about the effects of pumping on the residual VOC contaminant plume. EGGI then produced a report on the pumping test to support MVD’s application to the relevant state agencies for re-permitting Well MVD-6 as a public water supply.
The pumping test indicated that MVD-6 could be pumped at 800 gpm without entraining new contamination from the contaminant source, and suggested that VOC concentrations would not exceed drinking water standards at the Production Well. MVD is considering obtaining approval to resume use of the well as a public drinking water supply.
"During my six years plus, working with Jamie Emery and EGGI, I have seen only the finest quality of hydrogeological services. Their exceptional communication skills keep everyone on the same page as projects move forward. Reports are presented in a timely and understandable manner which allows for a clear picture of each phase of the project and possible future issues that may need to be addressed. EGGI's overall professionalism and work efforts are unquestionable. Their services should be seriously considered by anyone who has the need for hydrogeologic work.”
James A. McSweeney, Business Manager/Superintendent, Merrimack Village District
The pumping test indicated that MVD-6 could be pumped at 800 gpm without entraining new contamination from the contaminant source, and suggested that VOC concentrations would not exceed drinking water standards at the production well."