Prospects for Managed Underground Storage of Recoverable Water (2008) / Chapter Skim
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6 Project Development, Monitoring and Management
6 Project Development, Monitoring and Management
Pages 223-268
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From page 223... ...
and managers of MUS systems that have not been discussed earlier. It should be noted up front that the entire project development, monitoring, and management process is likely to be more successful if a broad approach to water resources planning is taken.
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From page 224... ...
deals in depth with public perception issues. As noted above, there are many different ways to organize an MUS project from beginning to end.
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From page 225... ...
, pH, redox potential, trace elements, microbial quality, trace organic contaminants; • Treatment needs and existing capacity -- desilting to prevent clogging by suspended or settleable solids, pH adjustments or other methods to reduce adverse changes in metal concentrations, reverse osmosis for removal of salts and trace organics, and advanced oxidation for destruc tion of trace organics; unused capacity of existing treatment facilities; • Capture and conveyance facilities needs -- stormwater capture im poundments, temporary storage prior to recharge, pipelines or channels for conveyance, pumping needs; and • Public perception -- outreach program needs, existing perceptions of groundwater quality, different outreach needs depending on source wa ter, especially reclaimed water, different outreach depending on percep tions of water resource needs and impacts of the MUS project, (e.g., drought protection vs. growth inducement)
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From page 226... ...
. Therefore, the effect of depth should be evaluated for each situation, and land availability might make surface recharge basins more economical even with shallow groundwater depths.
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If less than 100-200 m, direct injection may be cost competitive with surface If greater than 100-200 m, surface recharge recharge should be considered Is cost-effective land available at an appropriate location? If No, If Yes, Vadose zone injection wells Surface recharge basins may may be appropriate be appropriate FIGURE 6-1 Sample decision tree for selection of groundwater recharge method.
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Phase II: Components The following text summarizes components typically addressed in an MUS pilot program. Note that these components vary slightly between surface spreading and well recharge systems.
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In most cases, the time and spatial scales used in the field investigations and pilot testing will be smaller than those of the full-scale project. Because of this, it is important to consider how field investigation results can be extrapolated for the full-scale MUS project.
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From page 230... ...
For recharge basins, the removal of inorganic suspended solids is the major concern for maintaining infiltration rates. When vadose zone or recharge wells are used, infiltration rates may be reduced by suspended solids (especially critical for the former since there is no mechanism to backwash solids from the wells)
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some other form of suspended solids removal should be done If yes, then removal of organic carbon or addition of a disinfectant residual will be necessary FIGURE 6-2 Decision tree for treatment requirements before recharge with respect to hydraulics. Pre-design Results from the field investigations and pilot testing should be evaluated thoroughly and utilized to prepare the project description.
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discuss the use of a groundwater model for managed underground storage using the La Luz well field in Alamogordo, New Mexico. The pre-design phase typically concludes with preparation of a pre-design report that includes the project description and a description of the primary features of the project, including the facilities to be constructed and the estimated project cost.
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From page 233... ...
Phase IV: Construction and Start-up The following text summarizes components typically addressed in the construction and start-up phase of an MUS system. • Construction -- MUS facilities are sometimes constructed in environ mentally sensitive areas; it is important that construction be imple mented in accordance with relevant environmental laws and regula tions.
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From page 234... ...
Surface Spreading Operational Challenges Surface spreading using recharge basins is the most common method for recharging untreated surface water or reclaimed water into MUS systems. Removal of clogging material that retards percolation is the main maintenance activity with recharge basins.
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From page 235... ...
Where silts and clays are a more significant factor in clogging, ripping and disking can have the adverse effect of driving fine sediments deeper where they may contribute to a long-term decline in percolation capacity that is more difficult to restore. For recharge basins where heavily silt laden stormwater is recharged, percolation capacity can be reduced very rapidly (Figure 6-4)
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From page 236... ...
Wind agitation and varying water levels can provide a natural cleaning process for the sidewalls of some deeper recharge basins that are not amenable to more conventional cleaning processes. Abandoned gravel pits have been used in some areas for groundwater recharge, and very steep slopes preclude the use of surface scraping to remove clogging material.
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This type of system allows clogging material to be removed while avoiding the water loss and expense associated with the downtime for draining and cleaning basins. Photo courtesy of Greg Woodside, Orange County Water District.
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Certain types of beach cleaning equipment may offer the potential to remove only curled chips of clays and silts and leave the clean sands behind. The greatest operating expense for recharge basins is the cost of removing the clogging material that retards percolation.
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From page 239... ...
Even the regulation of MUS systems needs to evolve as more information is developed about the effects of introduced water on underground systems. Both regulators and MUS project managers need to reevaluate on a regular basis the effectiveness of existing procedures and regulations designed to protect water resources in light of the performance of MUS systems.
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From page 240... ...
In this case, the panel was a requirement in the draft California Department of Health Services groundwater recharge regulations because of the high percentage of reclaimed water proposed to be recharged and it became a requirement of the GWR System permit issued by the California Regional Water Quality Control Board, Santa Ana Region. A complementary exercise to the above would be a comprehensive status report approximately three to five years after the commencement of operations of an MUS project.
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From page 241... ...
In a recharge basin for example, one of the most common clogging potential estimates involves use of infiltrometers, which are installed in the field to measure local infiltration rates. Results of laboratory column studies are particularly useful as well.
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A particularly robust method, Easy Leacher® 4.6 (Stuyfzand, 2002) , predicts the accumulation rate and chemical composition of clogging sludge layers in recharge basins.
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MONITORING ISSUES Monitoring is an integral part of MUS site selection, design, and operation. Successful MUS involves careful and thorough project-specific assessment that includes chemical and microbiological monitoring to document system perform
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• Determine the need for pre- or posttreatment of the water, such as re moval of particles and biodegradable organic matter from the source water or removal of excessive dissolved constituents in the extracted water. • Comply with regulatory requirements.
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Unless geophysical methods or other detailed studies are conducted, there may be considerable uncertainty regarding the direction and rate of movement of stored water in karst systems. The point of compliance for many regulatory programs is the location at which the source water is first introduced into the subsurface.
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Most systems recharging drinking water through ASR wells or river water through channel beds or recharge basins into underground storage are essentially unregulated. Water quality monitoring requirements are therefore very limited.
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Some of these compounds will eventually be regulated with MCLs, but many will have only guidance levels for many years. Where waters used for MUS are derived from more impaired sources subject to a wider range of contaminants than more protected surface waters, monitoring for compounds with such guidance levels may be appropriate since these compounds are targets of concern in drinking water supplies.
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From page 248... ...
NDMA is a contaminant in some industrial wastewaters and is a disinfection by-product, particularly with chloramine disinfection. Because of these factors, NDMA is a particular concern for recharge of reclaimed water and should be included in monitoring programs to verify suitable water quality for MUS systems intended for drinking water supply.
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Surrogates and Indicators for Trace Organics Traditional measures of organic matter, such as biochemical oxygen demand (BOD) , chemical oxygen demand (COD)
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• Treatment prior to recharge, if any • Type of recharge (i.e., direct recharge or surface spreading) • Regulatory requirements (e.g., drinking water standards, antidegrada tion requirements)
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Microbial Indicators The quality and safety of drinking water and groundwater have always been measured via fecal indicator organisms and in some cases the presence of viruses and other surface water associated pathogens such as Cryptosporidium and Giardia Environmental Protection Agency (EPA) proposed groundwater rule)
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Thus, unless this water is pretreated to drinking water standards or infiltration systems are used to effectively remove some percentage of the microorganisms, the source or stored water will contain these microbes. The native groundwater could also contain some bacteria (Legionella)
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An example of this assessment process is the Hazard Analysis and Critical Control Point (HACCP) plan implemented for a stormwater to drinking water project in
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As clear trends in performance emerge along with consistent sampling results, the monitoring frequency can be decreased with confidence. A frequent sampling schedule in the early stages of operation will help to build trust of consumers and improve public perception of the project.
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PROJECT DEVELOPMENT, MONITORING AND MANAGEMENT FIGURE 6-6 ASTR project site and scope of the HACCP plan. Available online http://www.clw.csiro.au/publications/technical2005/tr20-05.pdf.
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From page 256... ...
Nevertheless, although underground storage of water has not been a high-profile issue in many communities in the United States, public education and involvement constitute an important step in any type of water management undertaking. The general public has legitimate interests in, and concerns about, the quality and reliability of its water supplies.
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summarized what it termed "best practices" to ensure that "well planned indirect potable reuse projects receive fair consideration in water supply decisions." It listed 25 such best practices, many of which overlap with others discussed here. Some of those considered to be the most critical are summarized below.
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Orange County, California The Orange County Water District in Orange County, California, has implemented a successful public involvement program as part of its Groundwater Replenishment System, a managed underground storage project. In addition to community research and program evaluation activities, the public outreach effort included community presentations, appearances on local and public access cable television programs, distribution of materials to and through libraries and other public gathering places, a media relations program, and site and project tours (Wildermuth, 2001)
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required to be treated to drinking water standards. However, legislation before Florida state lawmakers was being proposed to relax water quality standards (e.g., fecal coliforms)
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Operational and maintenance costs include cost of the water to be stored, cost of any additional treatment required, cost of acquiring the necessary easements and permits, and monitoring costs. For some systems using reclaimed water, monitoring costs may be a significant factor affecting the final cost of the stored water and the feasibility of the MUS project.
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. Thus, ASR enables facility owners and operators to shift the demand on treatment facilities to non-peak periods by treating the stored water to drinking water standards prior to recharge.
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In an effort to restore seriously overdrafted regional aquifers the state allows only 85 percent of the water stored underground to be extracted and recovered in designated critical zones of the state. The remaining 15 percent of stored water reverts to the state.
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For an unconfined aquifer, source water can be recharged into the aquifer through recharge basins, vadose zone recharge wells, and deep recharge wells. Stored water can be recovered by production wells or ASR wells, or it can enhance baseflow to neighboring streams.
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Recommendation: Water quality monitoring programs should be designed on a case-by-case basis to assess water quality changes for elements, compounds, and microbes of concern, optimizing the potential for documenting any improvement in the quality of the source water and to collect samples representing any adverse water quality changes. A proactive monitoring plan is needed to respond to emerging contaminants and increase knowledge about potential risks.
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2000. Effect of drinking water sources on reclaimed water quality in water reuse systems.
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2003. Comprehensive Characterization of Dissolved and Colloidal Organic Matter in Waters Associated with Groundwater Recharge at the Orange County Water District.
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1998. Issues in Potable Reuse: The Viability of Augmenting Drinking Water Supplies With Reclaimed Water.
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- Salisbury Stormwater to Drinking Water Aquifer Storage Transfer and Recovery (ASTR) Project: CSIRO Land and water Techical Report No.
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