Springfield Water Diversion Impact Assessment

The project evaluated the feasibility of reactivating the Springfield Well Field, consisting of approximately 60 wells in varying states of operability, which the Water Company discontinued operating in 1989 due to water quality problems which included high VOCs and total dissolved solids. Since the well field had existed since the late Nineteenth Century, it had been generally forgotten that the region had once been characterized as having shallow water table conditions. Thus, a largely residential area had developed on what was once wetland. When the well field ceased operation, more than 3 million gallons per day (MGD), which had been diverted was suddenly available to replenish storage. The resulting flooding problem was part of the reason that HMM was called upon to evaluate the hydraulics of the aquifer and its relationship to the surface water in the area, including much of the upper Rahway River Basin.

The hydrogeologic study evaluated optimizing the yield of the field using as few wells as possible to produce a desired diversion of 2.4 MGD, which would provide an additional reserve of water to Central New Jersey, which occasionally needs to restrict water usage, and also provide some relief to homeowners in the region suffering from flooded basements.

A total of seven pumping tests, ranging in duration from 24 to 72 hours, were performed in a region that covered parts of three townships and two counties, in order to adequately characterize the aquifer for the purpose of creating and calibrating a numerical hydrologic model of the Rahway River basin and its interaction with the underlying stratified drift and fractured bedrock aquifers. A two-aquifer hydraulic model of the hydrologic basin between the Watchung Mountains and Arthur Kill was created using literature values for aquifer properties and was calibrated against surface water heads throughout the area. In the region of the well field, the model was also calibrated against the static levels in local wells and against the results of the seven pumping tests, which in turn were simulated and the aquifer parameters adjusted until the drawdowns and leakage effects observed in the actual tests were satisfactorily duplicated.

The calibrated model was used to determine the most efficient use of individual wells for obtaining the desired yield, considering mutual interference between wells, induced recharge from surface water, the known specific capacities of several wells, and an economically practical lower discharge limit for an individual well. It was also determined that the desired pumping rate would convert all the water courses in the area of the well field from their current hydrological status as "gaining streams" into "losing streams." The amount of water diverted from the river basin was calculated by the model. Impacts to static water levels and to the available yields of wells in outlying municipalities were also part of the model output. The modeling demonstrated that the desired diversion would be sufficient to alleviate the basement flooding problem.

Project Highlights:

• Testing indicated that the hydraulic connection between the aquifer and surface water was not as significant as expected, which was subsequently confirmed by modeling.  Consequently, induced recharge could not be relied upon to boost yields.
• The modeling predicted that reactivating the system would entirely alleviate the basement flooding problem, which was in fact demonstrated within a few weeks after actual reactivation of the well field.