Water Works 12 - 3/20/03

Geologic Survey Under-Estimates Impacts on Aquifer, Creek and Wells

( Excerpts from Fellow Correspondent’s letter, continued. )

Nowhere in the background hydrogeology section of the NJGS report (i) does it characterize the Lockatong formation as one of the poorest aquifers in New Jersey. Why was this characterization not presented?

Why is the aquifer portrayed as simply as shown in Figure A-5, without presenting water levels from neighboring wells? Well QVF-2 had a pretest static elevation of 580.35 feet as compared to my well at 573.08 feet. This well is substantially deeper than the neighbor’s well. The elevations of the water in these two wells indicate a vertically upward groundwater flow gradient in this area. Well QVF-2 had 20.3 feet of drawdown during the test, which put the end of test level 13 feet below the elevation of the neighbor’s well and reversed the gradient. Vertical leakage of water was also indicated at QVF-2 during the test (see NJGS Table 2). The neighboring well, although not heavily affected during a 4-day test, has been affected over the past few years. The well has lost water elevation since the 1999 use of QVF-3 began. This is an excellent indication of over-extraction of groundwater resources at QVF even under the existing 3.1 mgm allocation.

The NJGS report states that neighboring wells should not be affected. However, the water level data suggests that impacts have already occurred. The NJGS report also projects drawdown in other wells, but limits the long-term drawdown because of the vertical leakage effects (ii) observed during the 4-day test. However, the NJGS report also states that the potential source of vertical leakage is only the thin soil zone. Once that soil zone is dewatered and/or Lockatong Creek is dewatered, the source for vertical leakage is stopped and the wells will then continue to decline beyond what is calculated by the NJGS. Therefore, it is probable that the NJGS has under-estimated the amount of drawdown that will occur around the GSG/QVF wells. This problem with estimated drawdown should be re-evaluated with recent water level data before the application proceeds.

The test data indicate substantial vertical leakage during the test. An obvious source of vertical leakage is Lockatong Creek. Was the water level or flow monitored in Lockatong Creek during the test? If Lockatong Creek is a source of vertical leakage, what will happen to the 7Q10 low flow of this stream? (iii)

The NJGS uses a mass-balance approach on page 11 of their 1999 report to develop a limit of impact. However, a very high recharge rate of 6.4 inches/year for Walnut Creek was used. This analysis should be redone with the 2.5 inches/year recharge rate that was developed for Franklin Township. I also have serious reservations about applying the NJGS groundwater recharge methodology referenced on page 11. This method is based on a basin factor initially developed for two basins very distant from this area of New Jersey and this geology. In fact, the basin factor was changed in NJGS Technical Memorandum 99-01.

The entire groundwater recharge analysis of this report should present an evaluation at 2.5 inches per year, and does not. The NJGS report also describes large east-west impacts. However, the drawdown plot is elongated north-south more along the strike of the bedding planes and towards Quakertown. This elongation along strike is expected in this area of New Jersey.

There are many more questions concerning the 1999 NJGS report, including questions on the hydrographs presented in the report. Several of the wells do not appear to fully recover from the pump test. However, the scale of the data plots makes interpretation difficult. This includes the hydrograph for QVF-2, the Cruz well, GSG-5, the Neave well, and my well, which appeared to drop late into the test. Further explanation for the apparent lack of recovery of these wells and the significance of the lack of recovery must be included in this report.