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Making the most of our water resources

Purveyors are seeking technical solutions for maintaining water supplies.

By JOSEPH BECKER
Robinson & Noble

Developing new water resources is expensive. In the current highly politicized regulatory environment, new water developments can be delayed or prevented based on ecological, financial, or growth management factors.

Consequently, it is more important than ever for water purveyors to maintain and upgrade current water sources. Additionally, the demands of a growing population, often in limited areas, are forcing purveyors to find new solutions to provide water to people when it’s needed most. Highly technical projects such as artificial storage and recovery (ASR) are gaining viability as resource management tools.

aquifier
The specific conditions of the Mirror Lake Aquifier -- one of the major source aquifers for the Lakewood Water District -- allow for the possibility of large-volume artificial storage and recovery.

Maximizing water sources For groundwater purveyors, an increasing demand on limited resources (whether a physical or regulatory limitation) is increasing the time and effort required in system maintenance. Gone are the days where a failing water source was simply replaced with a new well or surface diversion. Purveyors must now proactively monitor aquifer water levels, well production, and pumping efficiencies. The rehabilitation of current well sources and maximizing the use of currently held water rights are key concerns to purveyors.

Take, for example, Lakewood Water District’s new View Road treatment plant. This $2.8 million water quality treatment facility was put in place to remove excess manganese from a pair of deep wells. The wells had been drilled in the 1960’s, but due to the undesirable water quality, were not used as primary water sources.

Lakewood, faced with growing needs and a limited chance of getting new water sources approved, turned to a technical solution to make the wells useable. The District asked Robinson & Noble to define the capabilities of the wells after 30 years of minimal use. Based on our recommendations, Lakewood engaged Kennedy/Jenks Consultants to design and oversee the plant construction. The facility was completed in 1998 and currently produces over one million gallons of high quality water per day.

After all this expenditure of time and money, the District is naturally anxious to protect these wells from any mechanical failure or efficiency problems. In order to do this, they installed pressure transducers in the wells to monitor the minute-to-minute changes in the water levels with electronic telemetry to relay the data back to the District offices. Such remote data collection offers many opportunities to water system managers, from daily system adjustments to long-term trend analyses of aquifer changes.

At Robinson & Noble’s recommendation, the District is collecting water level and production data that can be compared to initial testing of the wells completed prior to the building of the plant. By comparing the current conditions to these previous tests, the District is given a benchmark of performance for the wells. If this performance declines, it may suggest changes in well efficiencies that could lead to long-term problems if ignored.

The monitoring program is important because declines in well efficiency often occur at a slow rate and are not immediately obvious. Additionally, decline in well production are not necessarily due to changes in well efficiency, but many have other causes such as regional declines in aquifer water levels or interference from other wells. Proper monitoring can allow for the diagnosis of these differing causes of production loss. With a slowly declining efficiency, the cost of producing a given volume of water from a well can slowly increase as the pump has to work harder to produce water.

A loss of efficiency can have many causes, including corrosion, encrustation, biofouling (buildup of bacterial growths), formation settling or collapse, and poor well construction. Once diagnosed, a water purveyor with well efficiency problems must decide if the decline in well yield or increased production cost is acceptable. If not, the well will need to be rehabilitated or replaced. Replacement wells should be considered if the loss of efficiency is great, the cost of rehabilitation is high, or if the well is old or damaged.

Redevelopment

Rehabilitation, also called redevelopment, can be risky, sometimes causing irreparable damage or failing to correct (or even exacerbating) an existing efficiency problem. This is particularly true for old or pre-damaged wells. In many cases, however, well rehabilitation can successfully recover all or a portion of the lost efficiency at a cost lower than well replacement, especially if the rehabilitation effort is made prior to the problem becoming severe. Many well rehabilitation techniques exist, and the exact method of rehabilitation recommended depends on the cause of problem. Often redevelopment involves the removal of the pump and the cleaning of the well screen (or perforations) with downhole tools. Other methods involve the injection of acids or bases into the screen and surrounding aquifer.

plant
The Lakewood Water District’s new $2.8 million View Road water quality treatment plant was built to remove excess manganese from a pair of deep wells. The wells had been drilled in the 1960’s, but due to the undesirable water quality, were not used as primary water sources. Lakewood, faced with growing needs and a limited chance of getting new water sources approved, turned to a technical solution to make the wells useable. The facility was completed in 1998 and currently produces over one million gallons of high quality water per day.

Regardless of the method used, rehabilitation efforts should be guided by a hydrogeologic consultant who can determine if the effort is, in fact, helping or harming the well. A hydrogeologist will usually determine this by analyzing the results of several specific capacity tests conducted on the well prior to, during, and after the redevelopment effort. Hydrogeologic input is also recommended in analyzing monitoring data, diagnosing well problems, and designing rehabilitation programs.

Stocking up for summer

Sometimes, however, all of this work is not enough to supply the needed amounts of water to a thirsty community. By investigating new technologies, such as ASR, some purveyors are taking advantage of a truism of life in Washington: most of our water arrives in winter, when we need it least. Artificial storage projects capture water (often from surface sources) that would otherwise simply flow back to the sea without being used, and pump it into the ground where it is stored until needed most during the summer months.

Lakehaven Utility District has been studying the concept of ASR for a number of years. The specific conditions of one of the major source aquifers for the District, the Mirror Lake Aquifer (MLA), allow for the possibility of large-volume ASR.

Numerical groundwater modeling conducted by Robinson & Noble for the district suggests that the annual storage and recovery volume in the MLA is approximately 9.5 billion gallons. Under existing agreements with the City of Tacoma, and with the planned Pipeline 5 construction, Lakehaven will have access to water collected as "surplus" wintertime flow to place in storage within the MLA to be used in the following summer months. Robinson & Noble is currently assisting the District in the development of this ASR project, known as OASIS (Optimization of Aquifer Storage for Increased Supply), with the drilling of three new test wells to confirm and better quantify the project's feasibility.

Following the development of injection wells for ASR projects such as OASIS, the concepts of monitoring and maintenance become key to keeping the process working properly. Technically, pumping water into a well is no difference than pumping it out. Where this is done, though, special care must be taken to prevent stressing the well, either mechanically or biologically, especially because injection wells are more prone to declines in efficiency than production wells.


Joseph Becker is president of Robinson & Noble


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