The East Hopewell Township Supervisors have determined incorrectly that calculations are acceptable to determine the availability of water resources in the township.
Calculations are fine for sand and gravel but generally useless in other aquifers. In a sand and gravel aquifer uniformity is assumed therefore a theoretical formula is acceptable.
“Availability
The availability of ground water in the area depends on the capacity of the rocks to store and transmit water. An estimate of the transmissive and storage characteristics of the rocks is generally made by test pumping a well and measuring the discharge from the pumped well and the effect of pumping on the water level in one or more nearby observation wells. Frequently the observed data are the substituted in to one of the equations of well hydraulics (Ferris and others, 1962; Bentall, 1963; Walton, 1962), which is then solved for the appropriate aquifer properties. This approach was not followed in the present study, as the simplifying assumptions made in deriving the equations of well hydraulics are generally not satisfied in the aquifers of the study area. Transmission of water in these aquifers occurs through secondary openings such as fractures and solution cavities and is usually dissimilar to flow through a uniform porous medium.”
P31, Water Resource report 42, 1977, Commonwealth of Pennsylvania, Department of Environmental Resources, Bureau of Topographic and Geologic Survey, Arthur A. Socolow, State Geologist.
The area referred to is the Wissahickon Aquifer. The area extends from the Maryland line on the south, the Susquehanna on the east, to Red Lion in the north and streaches west to the west end of Manheim Township.
“ECS, Ltd. used professional judgment and past experience in similar settings when considering the selection of available data to be used in this study.”
ECS, Ltd. Wrote the hydrology report for Marsteller. ECS used hydrologic budget equation and/or water balance equation. These are the equations referred to in the study.
ECS made an incorrect assumption that the Muddy Creek Drainage Basin (not the size a factor in the equation ) is uniform, and it isn’t. Flow, porosity, and permeability cannot be assumed to be uniform. However, ECS admits that no on site study was attempted nor requested by Marsteller. A proper study would prove to be very expensive.
On the practical side, I doubt the supervisors or their solicitor would recognize the above theory or the logic.