A new laboratory permeameter was developed for measuring the hydraulic conductivity of gravels ranging from 0.1 to 2 m/s. The release of pneumatic pressure applied to the test specimen induces an underdamped oscillatory response of the water level above the permeameter, similar to an underdamped in situ slug test response in monitoring wells. A closed form model was derived to calibrate the hydraulic minor losses in the permeameter and the hydraulic conductivity of the specimen by performing tests without and with a specimen. The majority of each test series performed on individual specimens produced hydraulic conductivity values within 10% of the average, which is very small for such a measurement. Tests were performed using the permeameter on a collection of subrounded and angular gravels prepared to measured grain size distributions and porosities. The surface area was determined by evaluating the shape and angularity using a method developed in this research and these parameters were used with the measured tortuosity and hydraulic conductivity, to back calculate the packing factor of the Kozeny-Carman equation. The results show that the packing factor for the gravels and materials tested is proportional to the tortuosity cubed. These results provide a valuable update to the Kozeny-Carman equation for predicting the hydraulic conductivity of gravels. Field slug interference tests were performed in pairs of monitoring wells installed at the same elevation in a floodplain deposit of silty sand in Dedham MA. Slug tests were performed in one of the wells while the response was monitored simultaneously in both wells. The measured responses were both analyzed by modifying the KGS model of Hyder et al. (1994) to consider the wellbore storage and filter packs effects. This modification was found to produce estimates of hydraulic conductivity based on the slugged well response that compared well with that estimated based on the observation well's response. Calibrated hydraulic conductivities for the pairs of wells tested ranged from 4x10-6 to 1.5x10-5 m/s and specific storage ranged from 2x10-5 to 7x10-4 m-1.

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / The southern bed of the ogallala aquifer is hydrologically isolated from all outside areas of recharge, requiring local precipitation for all natural recharge. Current withdrawals are so much greater than natural recharge that it appears that artificial recharge affords the only means of establishing at least a pseudo-balance. A number of observation wells were drilled at Texas Tech University, and subsequently capped until recharge water became available. The initial recharge was 2.5 af over 12 days, at a rate of 120 gpm for about the first day, after which 60 gpm was relatively constant. Approximately 1 month later, 1.2 af were recharged over 3 days at rates ranging over 140-90 gpm. It became evident that a cavity was present at the bottom of the hole being recharged. On a later recharge occasion, the cavity seemed to have enlarged. During a period of 2 years more than 28 af of surface runoff water have been recharged through the shallow hole with increases in recharge rates for each subsequent recharge period. The nature of this phenomenon and the cavities are not understood. This may represent the long sought after answer to recharge of the aquifer, but much more extensive research needs to be done.

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / Sewage effluent is commonly used for the irrigation of crops that are not consumed raw. Due to continued population growth in the Salt River Valley, Arizona, economic reuse of municipal waste waters is becoming essential. The salt river bed has about 3 ft of fine loamy sand underlain by sand and gravel layers to great depth and a groundwater table at about 10 ft depth. These conditions are very favorable for high-rate waste water reclamation by groundwater recharge. The activated sludge plant in phoenix will probably be discharging 250 mgd by the year 2000. At 4.5 ft average annual water use, this could irrigate about 70,000 acres, possibly more than agriculture will need at that time. A sewage effluent renovation pilot project was located about 1.5 miles from the plant. It contains 6 parallel recharge basins 20 to 700 ft each, spaced 20 ft apart. The basins were covered by grass, gravel or were left bare. Observation wells were installed at various locations in the area. Results indicated that infiltration rates were fastest in the grassy basins. Phosphate, nitrogen and median fecal coliform levels were all lower after this form of tertiary treatment. Practical details of the application of this water reclamation method in the Salt River Valley are outlined. Costs would be 5 dollars/af, less than 1/10 the equivalent costs of in-plant tertiary treatments.