ARCHIVED REPORTS XR0006098 - Laserfiche WebLink

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aquifer while not significantly affecting the lower It also indicated that the presence of the cross- zonal well would make the de-watering of the upper zone impractical ASSUMPTIONS FROM LITHOLOGY AND GROUNDWATER MEASUREMENTS. Both the A-Zone and the B-Zone are under confined conditions The groundwater head has come to an equilibrium state on-site because of the presence of the cross-zone wells Further away from the site in MW6A and MW613 there is a difference of 0 02 feet between the pressure head in the two zones Examination of the lithology of the two zones indicates that there should be a significant difference in the hydraulic conductivity (K) of the two zones The A-Zone with its silty to clayey sands should have a much lower K than the B-Zone with its clean sands This difference could be up to two orders of magnitude The top of the A-Zone is at an elevation that a high pump rate combined with the lower expected K could cause the aquifer to pass from the confined to the unconfined conditions with the lowering of the groundwater head by approximately 3 feet PLAN FOR PUMP TEST Without the previously proposed destruction of MWI, MW2 and MW3, some modification must be made in the previous pump test plan In order to collect significant data about the individual properties of the two zones it is advisable to install four piezometer wells between RIA and MWI, two in each zone These wells will allow for the observation of the drawdowns resulting from the test prior to the advent of cross zonal flow Because of the confined/semi-confined nature of the water bearing zones at this site, it is necessary to collect baseline groundwater head data prior to performing the pump test Both the A and the B zones are in a confined condition This allows the potentiometric head of both zones to respond to changes in the barometric pressure, tidal influences and surface loading on the adjacent ground surface In order to help determine the possibility of these effects on the system, pressure transducers will be placed in RW I A, RW i B and MWI one week prior to the pump test Because of the complex interaction of the two groundwater zones and the interconnecting well, a ,number of test will be preformed In order to test the possibility of de-watering the A-Zone in the old tank pit area a step drawdown test will be performed in RW 1 A A step drawdown test will be performed in RWO 1 B, to test the possibility of de-watering the area next to old pit into the top of the B-Zone In order to gain some knowledge of the actual aquifer parameters of A and B Zones, constant rate drawdown tests will be performed in RIA and in RIB 2 Rev Pump Test Plan- 10/11/02