Designing aquifer pumping tests for the installation of groundwater recovery and treatment systems

A combination of short-term and long-term pumping tests were conducted at two sites, one located in New York and the second located in Maryland, to provide the data necessary for the design of a groundwater recovery and treatment system at each site. Data collected during the pumping tests made it possible to estimate aquifer transmissivity, specific yield, hydrogeologic boundary conditions, degree of anisotropy, and yield and water quality of each recovery well. Data collected from typical aquifer tests conducted as part of site characterization are often insufficient to design a recovery and treatment system where multiple wells are used to recover groundwater. This paper presents a methodology for conducting a combination of short and long-term pumping tests to collect the data required for the design of a network of recovery wells and a groundwater treatment system in an efficient, economical manner. Two systems were designed using data collected from a combination of long-term (30 to 60 hours) and short-term (2 to 8 hours) step-drawdown tests. The long-term tests were conducted to estimate transmissivity, storativity, and well yield and assess the influence of hydrogeologic boundary conditions at each site. The short-term step-drawdown tests were conducted to estimate well yield and well losses at each recovery well. An average of three groundwater samples were collected during selected pumping tests to evaluate contaminant concentrations under pumping conditions. The results of the short- and long-term pumping tests were used to design the recovery wellfield (number, spacing and discharge rate). After all recovery wells had been installed, water quality and well yield were estimated for each well. A mass balance equation was developed and the total flow and the flow averaged water quality of the groundwater entering the treatment system were estimated. This information was used to design the groundwater treatment system at each site