Water Works 9 - 3/17/03

Recharge Data Inaccurate for Lockatong Aquifer

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

At the heart of the issue is the requested 9.319 mgm allocation for QVF in the already over-allocated Lockatong Creek basin (7:20A-2.5(a)7(ii)). (i)

The NJGS GSG Aquifer Test Report (ii) touched on the issue of the basin allocation. Strangely, the NJGS included all 54.4 square miles of the basin in their estimates of basin yield and their impact analysis, which includes all the area downstream from Franklin Township. The allocations listed in the NJGS report are all located in the headwaters of Lockatong Creek in Franklin. The reported area of the Lockatong basin headwaters in Franklin Township is 5.3 square miles (Leggette, Brashears, and Graham (LGB), 1996).

Even using the 5.3 square miles of drainage area is generous, as the diversions are located in the upstream portion of the basin in Franklin. Kingwood and Delaware Townships are downstream from Franklin Township and cannot contribute water into the upstream basin. Letters were supplied to the NJDEP in 1999 addressing this issue, which have not been evaluated by the NJDEP as required in NJAC 7:20A-2.5(f).

The NJGS report of 1999 applied a recharge rate of 6.4 inches per year (305,000 gpd/mi2) to evaluate the impacts on stream flow for the QVF allocation. This rate of recharge is very different than the 2.54 inches (121,000 gpd/mi2) developed for Franklin Township by LGB in 1996. The recharge number selected by the NJGS is higher than any recharge rate referenced in Table 3 of the LGB township report. Why was such a high recharge rate selected for this analysis?

Groundwater recharge is based on stream flow hydrograph separation data. The following are stream baseflows (Posten method) for the Triassic bedrock units, unglaciated area (drift thin or absent) of New Jersey (see Canace et al., 1992): Walnut Creek, 6.41 inches/year; Royce Brook, 4.23 inches/year; Neshanic River, 5.51 inches/year; Green Brook, 5.00 inches/year; Stony Brook, 5.12 inches/year; Raritan Manville (net), 5.85 inches/year.

These streams are predominately underlaid by the Passaic formation, a much higher yielding geologic unit than the Lockatong formation, where QVF is located. The Lockatong formation underlies Walnut Creek. The higher yield of the Passaic formation is reflected in the Franklin Township Report of LBG (see Attachment 3). Other studies in the area, specifically Lewis-Brown and Jacobsen (1995) also substantiate the higher yield for the Passaic formation than the Lockatong formation.

Walnut Creek has the highest base flow of any stream. However, Walnut Creek is non-representative of the region, as the stream basin is located within the Flemington Fault system. Unusually high well yields were reported for this area and correspond to the unusually high baseflow for Walnut Creek. The drainage area of Walnut Creek is also relatively small, 2.2 mi2. The Walnut Creek basin, located on a major regional fault zone, is not representative of the geology of Franklin Township.

Hordon (1987) conducted a study for Delaware Township and developed recharge rates for the Lockatong formation based on data from Wickecheoke Creek and Lockatong Creek. This study actually includes stream flow data from areas of Franklin Township. The recharge rate found in the Hordon study, 80,000 gpd/mi2, is much more in line (lower, in fact) than the bulk of the data presented in Table 3 of the LGB study of Franklin Township. The low recharge values are not surprising, as the Lockatong formation has long been recognized as one of the poorest aquifers in New Jersey. (See Kasabach, 1966).