In working with groundwater resources one thing is clear, things do change including knowledgeable personnel. This fact can lead to confusion and loss of critical information your system needs to properly develop and manage your groundwater resources. Here are Case Studies of how OAI's research opened new possibilities for groundwater systems.
At OAI test wells are planned when necessary to provide water quality information along with aquifer head data. The hydraulic data they provide are used to serve only as a reference point for our understanding of what area aquifers can do not what the test well’s hydraulic performance did do. In a 2008 exploration effort, a test well was installed and, while water quality and water levels were favorable, the test well's specific capacity of 0.61 gallons per day per foot of drawdown was going to torpedo further development efforts of the aquifer at this location. However, relying on OAI's knowledge of the area's aquifers and, more importantly, their production capabilities OAI formally recommended the installation and development of a full production well at this site in the aquifer tapped by the test well.
Aquifer testing on the production well indicated the targeted aquifer’s transmissivity is 121,600 gpd/ft, its storativity is 1.1 x 10-4 and its specific capacity is 36 gallons per minute per foot of drawdown (59 times that seen in the test well!!). The new public supply well tested out at 1,950 gallons per minute and was completed with a design production rate of 1,300 gallons per minute. Not bad for what would have been an abandoned site and a costly test well.
Has your “Test Well” program left you asking the question: “Test wells, what are they good for?” Has your potential wellsite been condemned based on hydraulic data from the test well alone? If so, add OAI to your exploration effort. OAI works with you to maximize your exploration dollars and uses our understanding of what test wells provide to develop aquifers rather than condemn them. Contact OAI today.
O’Donnell & Associates, Inc. finished a hydrogeologic study for one of our long time clients. This project, the sixth OAI has completed for them, involved investigating and evaluating three locations in the water system’s service area for their potential success in developing a high volume public supply well. The locations under review were picked by the system's current engineer to boost their ability to provide water in these locations as opposed to producing it in far off areas and pumping it to the locations.
Hydrogeologic studies are one of many services OAI makes available to our 40+ public water supply system clients. This was the first hydro study requested of OAI by this client. The study included compiling public and private hydrogeologic information on the locations, developing an understanding of the aquifers underlying them, assessing their potential for supplying water acceptable for public supply purposes and presenting our findings clearly to the Board. Bad News
The hydro study was initiated with the goal of finding the best location for developing a new well at one or all of the three locations targeted by the engineer. The study found the following:
- Location 1 is underlain by three sand or sand and gravel aquifers to a depth of 2,450 feet. Correlation of these aquifers from this area to areas where they produce indicated the water in the aquifers at this location contain brackish to saltwater that would not be suitable for public supply without extensive post-production treatment.
- Location 2 is located adjacent to another water system’s wells. The three aquifers at this location are present from about 800 to 2,600 feet deep. Two of the three had documented chloride concentrations greater than 900 parts per million. The third aquifer, used by the neighboring system, has chlorides at the 250 ppm MCL limit. An additional well in this aquifer was ruled out so as not to jeopardize the other system’s water supply.
- Location 3 was actually explored by the system with a 1,620 foot test bore and a 1,260 foot test well 19 years ago. This long forgotten* exploration effort, identified through OAI’s research, confirmed our initial findings that there was no chance of developing a fresh water supply in this area. It was also used to condemn Location 1.
At first glance, it seems OAI’s report delivered nothing but bad news to the system for their plans at the three sites. However, by completing this study before Locations 1 and 2 were drilled or before Location 3 was re-drilled, the system saved the $159,600 to $209,000 completing a deep exploratory bore and test well would have cost. These savings can now be applied to other options that have a greater chance of success in developing more water for the system. Much like this project, OAI’s first project with this system also delivered bad news. However, that initial bad news opened the door for OAI to present an "out of the box" solution that, when implemented by the system, met their need for more water at a fraction of the cost of the budgeted new well that, as it turned out, they did not need. Good news indeed.
*This is not the first time OAI’s research identified past exploration efforts that were previously unknown to water systems’ current Boards and managers.
This municipal system was under the gun to locate a new source of supply due to increasing levels of TTHM in their current supply. To complicate matters, the system is located on an island four miles from the mainland. OAI was contacted to evaluate their options. We began with a thorough review of their system and the efforts it had taken over the years in developing their water supply. Our research identified an unsuccessful exploration completed in 1967 that the current personnel had no knowledge of. Although the 1967 program was unsuccessful, OAI recognized an aquifer that was not tested but showed promise. A new exploration program was planned by OAI with this promising aquifer as its target. Testing indicated the lower portion of the aquifer contained water of a sufficient quality to be used by the system and a 1,200 gpm well was completed in it.
This Oklahoma municipal water system utilizes surface water for its source of supply and has over the years been the victim of drought. OAI became aware of the situation and learned that groundwater was not an option due to a "previous unsuccessful effort" at developing a groundwater source back in the 1970s. The previous effort targeted deep aquifers and testing determined production rates from these aquifers were on the order of 50 gpm or less. OAI's research found that the earlier exploration program missed a prolific aquifer capable of supporting production rates in the range of 450 to 750+ gpm. Further research by OAI located wells in the same aquifer with production rates exceeding 1,200 gpm with excellent water quality. This aquifer is currently available for development but remains overlooked by this drought prone municipal system due to the failed exploration program of the past. Perhaps it will get the attention it deserves when the next drought comes calling.
While working with this small town municipal system, OAI located an old well in the shop yard that nobody on the current staff or Board knew existed. The well was originally completed in 1935 with a flow of 500 gpm. The well is cased to 121 feet and completed open hole to 256 feet in the same limestone aquifer their new 1978 well was completed in. As demand increases for this system, the old well could be modified to current well standards and placed into service or serve as a "test well" for a new production well at this location. In either case, the old well can provide valuable information as the system begins the planning for their next well and lead to significant savings for the system as they work to increase their supply to meet demand.
If your system has been around for 40 years or more it is a good bet that you would benefit from comprehensive review of your system's infrastructure and the aquifers underlying your service area. If you had an unsuccessful exploration program in years past the dimmed hope for new sources of supply, it is time for a review? Contact OAI today to begin the research needed to identify all your options for development of your groundwater resources.