ARCHIVED REPORTS XR0006109 - Laserfiche WebLink

Home Browse Search

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 MW6B there is a difference of 0 02 feet between the pressure head in the two zones Exairunation 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 With the destruction of MWI the closest well that is completed in both aquifers is MW3 In order to collect significant data about the individual properties of the two zones four-piezometer wells were installed between RIA and MW3, two in each zone These wells allowed 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 was 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 were placed in RW i A, RW 1 B and MW3, and a barometric meter was placed in RW IA 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 were preformed In order to test the possibility of de-watering the A-Zone in the old tank pit area a step drawdown test was performed in RWIA A step drawdown test was also performed in RWO1B, 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 were performed in RIA and in RIB i 2 Pump Test ]{20-27/03