SIDNEY — Sidney City Council heard information Monday night on a recent water wellfield pump condition assessment study and the steps necessary to re-establish safe yield volumes to city well No. 9.
In February, City Council passed a resolution to advertise for bids for Sidney’s Hodge-Barret Wellfield pump condition assessment study. Finance Officer Renee DuLaney told council members in February the purpose of the assessment was three-fold:
1) To determine the cause of continued reduction of safe water volume yields from well No. 9 and No. 10;
2) Conduct methods to remedy the cause and take necessary steps to re-establish safe yield volumes to well No. 9 and No. 10;
3) Establish proper well construction design criteria to incorporate for proposed well No. 8.
Monday, Utilities Director William Blakely introduced hydrogeologists Allen Comeskey and Stuart Smith, owners of Ground Water Science, who provided their findings about well No. 9 and recommendations to establish long term production wells from the wellfield. Comeskey and Smith both hold a Master of Science degree hydrogeology.
“The wellfield,” Blakely summarized, “in itself has ample supply of water to meet the future 10 MGD withdrawal level. Well development, proper screen size and placement, and routine well cleaning are all important factors in long term well operations and production.”
Comeskey and Smith took turns navigating through their power point presentation. Hydrogeologists, they said, are ground water specialists. They also have additional expertise in mechanisms and processes that clog and degrade wells such as groundwater chemistry and natural microbial processes. They have a long history of assessing causes of problems, designing solutions and working with utilities and well contractors to implement short- and long-term solutions and were brought on to plan a model cleaning program for wells, and documenting results.
They found the following multiple issues with the well:
• Significant decline in production as manifested in declining specific capacity;
• Pumping fine sand, which is getting into the pumps;
• Challenging water quality. Quite high iron and some manganese that can cause clogging;
• Well rehabilitations with limited or short term success;
• Well tower design limited well rehabilitation options;
• Well construction may not meet Ohio Environmental Protection Agency (OEPA) public water supply well standards.
The result of sand pumping may be the voids visible in the sediments outside the screen, the report showed; they also provided pictures to help better explain the issues.
They next provided a techincal, detailed history of the declining specific capacity and limited rehab success of the well, explained about how the pumping of sand works, as well as information on water quality analysis and observed encrustation.
Smith and Comeskey also detailed the following past and present well rehabilitation events:
• Challenged by the nature of the installations that makes working over the well complicated and difficult, limiting options;
• Professionally workmanlike and accomplished;
• The problem is systemic, the wells themselves;
• Current cleaning by National Water Service resulted in a very clean well, but one that still had voids behind the screen;
• Voids cause turbulence and poor performance: low specific capacity.
The way forward, Comeskey and Smith said, is to replace wells No.9 and No.10 with new wells (outside of the towers), which will:
• Provide water sources that can meet production expectations from 2008- 2009 planning for the long term – They think the aquifer can supply the water to a well-constructed water supply well.
• Construct wells that meet current OEPA construction regulations.
• Allow design and construction of proper gravel pack screen — bring the water, leave the fine sand in the formation.
• Allow proper well development technique and time. This refines the constructed well to optimize performance.
• Allow a well head completion that facilitates well rehabilitation. This will be a part of life going forward
They said they don’t see repeated rehabilitation of these wells having positive cost-benefit. Rectifying well design and construction with long-term asset management can cause the promise of this major investment to be realized, the experts said.
At the conclusion of their presentation, they were asked what happens next, if City Council approves a contract for the needed work. Council was told the civil engineer and EPA has to agree they know what they are doing and sign off on the project. After a brief discussion, Blakely was directed to bring back legislation for council to consider entering into a contract for the work.