Many regions of the United States are experiencing rapid population growth and face the challenge of meeting the demands placed on their water supply for potable, irrigation, industrial, and ecosystem preservation uses. To meet these challenges, many water purveyors are turning to aquifer storage recovery (ASR) as an alternative water supply source. In most areas, ASR is used to store treated drinking water; however, in recent years, increasing attention has focused on potential storage of reclaimed water.
ASR systems can be used to meet a variety of storage needs at a significant savings when compared to the cost of building storage reservoirs. In addition, ASR systems are considered to be more environmentally friendly than surface reservoirs and offer more protection from tampering. Potable ASR can provide:

Seasonal Storage – In areas such as Nevada, ASR wells are used to meet enormous seasonal variations in drinking water demand. ASR wells inject drinking water into the aquifer during low demand months to make up the difference between supply and demand. This underground reserve is pumped to meet demand in dry months.

Long-Term or “Water Banking” – ASR systems can store drinking water during periods when supply, treatment, and distribution facilities have spare capacity, allowing recovery during doubt years.

Emergency Storage – Water stored in ASR systems provides an emergency supply or strategic reserve to meet demands when the primary source of water is unavailable due to accidental loss/contamination, an intentional hostile disruption, or a natural disaster.

Maintenance of Distribution Flow – Aquifer storage at those locations within a utility distribution system that experience seasonal low flows can help to maintain adequate disinfectant residuals and other indicators of water quality. This can be an alternative to flushing pipelines to waste.

Deferred Expansion of Water Facilities – ASR can be sized to meet maximum day demands, reducing the treatment needs of an associated water treatment facilities can be deferred and downsized with substantial cost savings.

Reclaimed Aquifer Storage and Recovery ASR wells are proving to be valuable tool in water management. ASR well technology now allows utilities to recharge treated wastewater into the ground for a variety of beneficial purposes, including:

Reclaimed Water Storage for Reuse – High-quality reclaimed water may be stored seasonally in brackish aquifers for recovery to meet irrigation demands. This eliminates the need for expensive above-ground storage often required during periods when the seasonal demands for irrigation water is reduced.
Salinity Barrier – In Florida and other coastal areas, ASR wells are being used to inject fresh-water along shorelines to prevent salt-water intrusion. In these areas, seawater gradually encroaches into land where freshwater wells provide drinking water for residents. Without the barrier provided by the ASR wells, salt water would creep into the drinking water supplies, rendering the once freshwater wells useless.

Groundwater Level Restoration – Trends toward the continuing decline of groundwater levels can be reversed by incorporating an ASR system into a regional water management plan. A small percentage of the stored water can be left in the aquifer each year, or accumulated through increased storage during wet years, to eventually increase levels to historic elevations.

Improved Water Quality – ASR systems can provide water quality improvements, including pH stabilization or adjustments, trihalomethane (THM) and haloacetic acid (HAA) reduction, iron and manganese reduction, hydrogen sulfide reduction, blending with native groundwater, and softening. Nutrient and coliform reduction may also occur where these constituents are present in recharge water.
Carollo has specialized experience in the permitting, design, and construction management of ASR systems. We also have a thorough understanding of the cutting-edge issues regarding the fate of emerging contaminants, such as pharmaceuticals and personal care products, in the subsurface environment. Recent projects include:

City of Chandler, Arizona-Tumbleweed Park Recharge Facility Phase 3 ASR Well No. 1 – The City of Chandler was recently ranked as the second fastest growing city in the nation around cities with populations over 100,000. Chandler faced the challenge of providing adequate water supplies to meet growing demands, coupled with the need to dispose of the large quantities of effluent produced by its wastewater treatment facilities. Adding to the city’s water management woes was a gradual decrease in the performance of the first three vadose recharge wells on the Tumbleweed Recharge Facility site.

Carollo provided permitting, design, bid assistance, and construction management for Chandler’s Water Management Through Aquifer Storage project. Carollo designed ASR well No. 1 in the Tumbleweed Recharge Facility to recharge the upper alluvial unite during low-demand periods and recover the water during pack demand periods to supplement the reclaimed water system. The design also allows the well to be periodically back flushed, or purged, to maintain recharge capacity. The Tumbleweed Recharge Facility is integrated into an 80-acre regional ark site with minimal impact to park users. To meet a very aggressive completion schedule, the Carollo completed design, review, and permitting of the ASR well project in just three months.
Reclaimed water ASR, irrigation, and aquifer recharge elicit public and scientific concerns regarding the potential introduction of pharmaceuticals, hormonally-active chemicals, and other wastewater microcontaminanats into the aquifer. Carollo is leading a team of recognized experts investigating the fate of the constituents of greatest concern as reclaimed water is stored and recovered in ASR wells. AS part of this effort, Carollo developed a defensive process to identify the microcontaminants of greatest concern. The project includes monitoring as four ASR sites located in Florida, Arizona, and Australia during injection, storage, and recovery. To ascertain the degree of risk to public health and the environments as a result of reclaimed ASR operation, Carollo will compare observed constituent concentration with established standards, guidance concentrations, and toxicity levels.