When the average person thinks about drinking water wells, they probably envision a deep, dark hole in the ground protected by a stone wall and topped with a little roof — the kind of thing you might toss a penny into and make a wish. But a wishing well falls short of what water utilities need to provide the millions of gallons of water that communities demand. At Woodard & Curran, we have the bench of expertise to support our water utility clients across the country with the full scope of building a new drinking water supply well from site selection to design to construction oversight to operations.
How Do You Site a New Supply Well?
The anatomy of a well and where it is drilled is far more complex than just a deep hole drilled in a random location. At Woodard & Curran, our team of engineers and hydrogeologists recognizes the importance of optimizing water quality and aquifer production at depth, while also optimizing how and where groundwater supplies are pumped. Well siting can be an overwhelming challenge because there are a lot of factors to consider, such as availability of land, location of water demand, proximity to existing infrastructure, strategies on how and where supplies can be pumped into the distribution system, depth of the potable aquifer, and capital costs.
Determining where to locate a new supply well varies throughout the nation. For example, in Florida potable aquifers with high productivity are typically in layered fractured and consolidated limestone units, whereas in New England, potable aquifers are in shallow thin bedded unconsolidated sands and gravels units. In California, water could be hundreds of feet deep, and potable aquifers could span hundreds of feet in unconsolidated sands, gravels, and finer-grained units.
Our watersheds team is focused on coupling the best groundwater quality with the highest aquifer productivity for these new water supply wells. Some of the technologies we employ to achieve this goal include geophysical tools that directly measure where water is flowing or where water is not present at great precision and accuracy. Once we identify the most productive portions of the aquifers, we then test the water quality to confirm if it meets potable drinking water standards or requires well head treatment.
Once we have optimized the water quality and aquifer productivity, we pump test the new well to identify the best pump and motor system that will meet current and future supply demands into the distribution system. Ideally, the optimal site will also be at the top of the system’s pressure zone. When that is not the case, we work with our municipal clients to identify the most cost effective, energy efficient manner to pump the water to the treatment plant or direct supplies to the distribution system. Our comprehensive approach across multiple site options and manner of connection to the water system demonstrates to our clients the optimal location to meet demands.
Innovation in supply well design
For wells drilled in unconsolidated sediments, the borehole diameter is drilled larger than the well casing diameter so that annular materials (filter pack media) can be installed to enhance hydraulics and limit formational sands from entering the well damaging the pump bowls. However, over extended periods of time or due to lack of maintenance, well production rates can lag because sand and sediment clog the filter material. To address this common problem, we are replacing commonly used filter media with engineered glass beads.
We have found that the physical properties of these well-rounded glass beads create a consistent pore space that reduces the amount of sand and sediment that tends to clog in other forms of filter media. Under hydraulic stresses, the spherical shape and uniformity of the beads prove to hold up better reducing grain-on-grain abrasion during pump and recharge operations. Furthermore, with prolonged testing from existing wells, glass beads have resulted in sustained and stable well hydraulics and reduce operations and maintenance costs.
