Assessing the Feasibility of Artificial Recharge and Storage and the Effectiveness and Sustainability of Insitu Arsenic Removal in the North Buttes Area, Antelope Valley, California

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Groundwater pumpage for agricultural and municipal supply has resulted in water-level declines of more than 200 ft in some parts of the Antelope Valley groundwater basin and land subsidence of more than 6 ft in some areas. Future urban growth, increased agricultural demand, and limits on the supply of imported water will continue to increase the demand for groundwater.

Detailed map of the study area

Detailed Map of Map of North Buttes Area, Antelope Valley, California

(Public domain.

The Antelope Valley East Kern (AVEK) Water Agency is considering artificial recharge to supplement local groundwater and meet future demand. In addition to artificial recharge of imported water AVEK is considered using recharge through the unsaturated zone to remove arsenic from local groundwater. Previous work by the USGS has shown that naturally occurring alumina, iron, and manganese oxides on the surfaces of mineral grains sorb arsenic as water infiltrates through the unsaturated zone. If successful arsenic removal through sorption in the unsaturated zone would augment local supply and represent a savings of between 45 and 65 million dollars in arsenic treatment costs over the life of the project compared to sorption on conventional media.

AVEK has identified a potential site for an artificial-recharge and storage project in the North Buttes area on the west side of the basin. Prior to implementing the full-scale artificial recharge and storage program the following questions need to be answered. Is the site suitable for this artificial recharge? That is, what is the anticipated recharge rate, are there near-surface geologic layers that will prevent water from reaching the water table, is there sufficient storage volume, can the water be extracted economically, what is the insitu water quality, and how will recharging the groundwater basin with high-arsenic groundwater affect the water quality of the aquifer and the extracted water? What is the effectiveness, sustainability, and long-term impact on the unsaturated zone of insitu arsenic removal?

The objectives of this study are to: 1) determine if the North Buttes site in the western Antelope Valley groundwater basin is suitable for artificial recharge and storage; 2) determine the effects of artificial recharge on water levels and water quality; and 3) determine the effectiveness and sustainability of insitu arsenic removal in the unsaturated zone.

The study objectives will be met by a two-phase study approach. The first phase will evaluate the feasibility of the site for artificial recharge and storage using existing or readily collected data. If the Phase 1 results indicate that artificial recharge may be feasible, a pilot-scale artificial-recharge project will be implemented to evaluate the feasibility of artificial recharge via surface spreading. High-arsenic groundwater from nearby wells will be used for the pilot-scale project to determine the effectiveness and sustainability of insitu arsenic removal by alumina, iron, and manganese oxides on unsaturated materials.