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JSAI TM ASR Evaluation 2nd Draft November 3 JOHN SHOMAKER & ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS 2611 BROADBENT PARKWAY NE DRAFT ALBUQUERQUE,NM 87107 505-345-3407; 505-345-9920 FAX www.shomakerxom i - TECHNICAL MEMORANDUM To: Adrienne Widmer, P.E., Las Cruces Utilities awidmer@las-cruces.org From: Andrew P. Feltman, C.P.G., P.G., Senior Hydrogeologist Annie McCoy, C.P.G., Senior Hydrogeologist Date: November 3, 2020 Subject: Evaluation of ASR Potential for Reclaimed Wastewater, City of Las Cruces,New Mexico—Draft 2 This Technical Memo details John Shomaker & Associates, Inc. (JSAI)'s desktop investigation of potential for Aquifer Storage and Recovery (ASR), also referred to as Underground Storage and Recovery (USR), in the City of Las Cruces (City). In this case, the source of water will be reclaimed wastewater from the East Mesa Water Reclamation Facility (EMWRF) or from the West Mesa Wastewater Treatment Plant. For this study, JSAI evaluated the potential for ASR application of the reclaimed wastewater with respect to aquifer hydraulic properties and availability of existing recovery wells, with the goal of identifying one or more sites with good potential for ASR. This Memorandum relates to Task 4 of the implementation of the 10-Year Water Development Action Plan. Aquifer Storage and Recovery ASR is a process in which excess water is stored in aquifers and later recovered via groundwater supply wells. Preferred injection locations maximize storage and limit losses, such as to surface-water systems, the regional aquifer, or pumping by other water rights holders. Water may be injected directly into the aquifer using existing or purpose-built wells. Water can be injected and recovered through the same well, or the injection well can work in tandem with a recovery well or wells. Alternatively,water may be allowed to infiltrate from above the water table through settling basins or through "dry wells" - uncased large-diameter boreholes backfilled with gravel. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 2 - DRAFT November 3, 2020 Overview of Regulatory Process The City is interested in pursuing ASR as an approach to alternate water supply with the support of State agencies. The New Mexico Environment Department Ground Water Quality Bureau (LAMED GWQB) and the New Mexico Office of the State Engineer (NMOSE) are the regulatory agencies involved with reuse and ASR projects.Permitting with NMED and NMOSE would be subject to public notice and protest. Per New Mexico Statues Annotated (NMSA) Section 72-5A-4, no governmental entity may perform ASR without a permit from the NMOSE. The regulations for performing ASR are described in New Mexico Administrative Code(NMAC) 19.25.8.The NMED GWQB regulates discharges to the ground surface and groundwater per the NMAC 20.6.2. A Notice of Intent to Discharge must be filed before any discharge is made. A Discharge Permit must be obtained for all discharges into the groundwater system, and many discharges to the surface. Water discharged into the groundwater system must meet defined standards. The Code also indicates that wells used for aquifer storage would be categorized as Class V Underground Injection Control wells. A Class V well completion is similar to that required by the NMOSE for an artesian well. However, neither of the purpose-built ASR wells completed by the City of Rio Rancho, and the Albuquerque Bernalillo County Water Authority, were completed in this fashion. Therefore, it is likely that ASR wells completed by the City would not have to be built as Class V injection wells, and could be constructed like traditional water wells. The NMOSE regulations for performing ASR include a pre-application meeting and project proposal that requires the submission of an essentially complete application. Pre- application documents include, but are not limited to,water rights, description of source water, site location, description of pilot project, water-quality parameters, potential hazards, and hydrogeologic information. Subsequent to that meeting, assuming the proposal is viewed favorably by the State Engineer, the next step in the application process is a pilot project. The objective of the pilot project is to implement a demonstration project to collect hydrologic and hydrogeologic data in order to evaluate the project at full-scale implementation. The pilot project would require monitoring wells and water-quality sampling. The results of the pilot project are presented in a capability report. This report includes the following components: • Executive Summary • Project Objectives • Evidence of Technical Capability • Evidence of Financial Capability • Evidence of Hydrologic Feasibility • Area of Hydrologic Effect of Proposed Artificial Recharge, Storage, and Recovery Proj ect • Hydrogeologic Characterization of the Area of Hydrologic Effect JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 3 - DRAFT November 3, 2020 • Evaluation of Impairment to Water Rights and Harm to Owners of Land Within the Area of Hydrologic Effect • Validity of the Source Water Right • Site Description • Facility Description • Facility Design • Facility Operation and Maintenance • Hydrogeographic Characterization of the Area of Hydrologic Effect • Effects Created by a Underground Storage and Recovery Project • Water Level Monitoring Plan • Description of Water Quality Monitoring and Treatment Plans Required by a State or Federal Agency or Department • Contingency Plan Based on the information provided in the capability report, the NMOSE will establish a storage account. A permittee may recover only the amount of water,as recognized and approved by the NMOSE,that has reached the aquifer,remained within the area of hydrologic effect, and may be recovered without impairment to water rights or harm to land owners within the area of hydrologic effect. A description of the full-scale project is then required to be submitted. Submissions would include, but are not limited to, pilot study results, groundwater modeling to assess full- scale implementation, description of project facilities, operation and maintenance, and other permits. Water stored in an ASR program is subject to an annual fee in the amount of fifty cents ($0.50)per acre-foot of water placed in storage during the period of time covered by the annual report. The New Mexico State Water Plan indicates the State's support for the development and permitting of ASR projects as a water supply and demand strategy (NMISC, 2018). However, the State's current regulatory framework poses major challenges that may discourage ASR as an approach for several reasons: • The State requires discharge permits issued for ASR projects to meet groundwater discharge water quality standards set forth in NMAC 20.6.2.3103. • Water injected directly into the aquifer must meet State primary drinking water standards, per the Underground Injection Control section in the Water Quality Control Commission Regulations (NMAC 20.6.2.5000). This level of water treatment for recharge water can be cost-prohibitive. • If the existing concentration of any water contaminant in groundwater is in conformance with the discharge standard(NMAC 20.6.2.3103), degradation of the groundwater up to the limit of the standard is allowed; however, if the existing concentration of any water contaminant in groundwater exceeds the standard, no further degradation of the groundwater beyond the existing concentration is allowed. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 4 - DRAFT November 3, 2020 • Extremely comprehensive demonstrations and pilot testing, as may be required, can also be cost-prohibitive. • NMAC 19.25.8.22.F indicates that ASR application must have a valid water right for recharge water which meets the Burden of Proof. The applicant has the burden of proving: A. the applicant has the technical and financial capability to construct and operate the project; B. the project is hydrologically feasible; C. the project will not impair existing water rights or the state's interstate obligations; D. the project will not be contrary to the conservation of water within the state; E. the project will not be detrimental to the public welfare of the state; F. the applicant has a valid water right for the recharge water quantified by one of the following legal processes: (1) a water rights adjudication; (2) a consent decree; (3) an act of congress,including a negotiated settlement ratified by congress; (4) a contract pursuant to the Colorado River Storage Project Act, 43 U.S.C. Section 620 (1986 and Supp. 1999); or (5) an agreement with an owner who has a valid water right subject to an application for a change in purpose,place of use or point of diversion G. the applicant will obtain all other permits for the project required by state and federal law. A project shall not be operated under the Act until an applicant has obtained all other state and federal permits required for the project; and H. the project will not impair water rights or cause harm to owners or land within the area of hydrologic effect. A licensed water right signed by the State Engineer is not included as one of the legal processes listed in NMAC. The City of Santa Fe is currently in talks with the NMOSE in an attempt to reinterpret the Burden of Proof requirement to include licensed water rights. The water coming into the EMWRF is a mix of East Mesa Well Field (some under LRG-430, some under East Mesa permit), Moongate water, former Jornada Water Company (LRG-47 et al. is a licensed right), and NASA water. The amount from each source is not currently measured. The City could benefit from exploring other approaches to ASR, possibly with other levels of water treatment, with cooperation and support from State regulatory agencies. The requirements listed above are in contrast to the more supportive regulatory framework for ASR in Texas, just 20 miles away from Las Cruces, and it would appear that New Mexico could benefit from examining the regulatory framework in other states such as Texas where water supply has already benefited from a greater number of successful ASR projects. New Mexico's ASR regulations could be reviewed and modified accordingly for a more streamlined process, and for variances based on local hydrogeologic conditions. JSAI is engaging in discussions with NMED and NMOSE that precede the pre- application process. We are discussing potential limiting factors, such as water treatment JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 5 - DRAFT November 3, 2020 requirements and water rights. These discussions are intended to give the State agencies an opportunity to support the City with an approach to ASR that would be viable,given the current regulatory framework. Hydrogeologic Setting The City of Las Cruces is situated in the Mesilla Basin along the Rio Grande. It extends into the West Mesa within the Mesilla Basin, and into the East Mesa area in the southern part of the Jornada del Muerto Basin. The Mesilla Basin and Jornada del Muerto Basin represent two sub-basins within the Lower Rio Grande Basin.These basins formed through faulting caused by the extension of the Rio Grande Rift, and were filled with sediment from surrounding highlands. The City relies on groundwater from its Valley Well Field (including the Interstate-25 Corridor area and Valley area) and West Mesa Well Field in the Mesilla Basin, and East Mesa Well Field in the Jornada del Muerto Basin,for its potable water supply(see Figure 1). Wells in these areas produce water from the alluvial deposits of the Upper and Middle Santa Fe Group, as well as the post-Santa Fe Group channel and floodplain deposits of the Rio Grande (Hawley and Lozinsky, 1992). The Mesilla and Jornada del Muerto Basins are hydraulically connected by a thin, discontinuous layer of saturated sediments that overlies the bedrock high that separates the two basins in some places. Some groundwater from the Jornada del Muerto Basin "spills" over this buried horst into the Mesilla Basin (JSAI, 2002). The horst acts as a partial barrier to groundwater flow, resulting in higher groundwater elevations in the Jornada del Muerto Basin to the east than in the Mesilla Basin to the west. The groundwater table is above the top of the horst in some areas south of U.S. Highway 70, but north of the highway, the groundwater table is below the top of the horst, largely restricting inter-basin groundwater flow in that region (Woodward and Myers, 1997). Geothermal water wells up along faults that bound the Jornada Horst, and can have significant local effects on groundwater temperature and quality (Finch, 1999). Figure 2 is a geologic map of the northern part of the Mesilla Basin and southern part of the Jornada del Muerto Basin, and Figure 3 is a southwest-to-northeast hydrogeologic cross- section of the City of Las Cruces area. Depth to water in the Mesilla Basin ranges from approximately 50 ft bgl in the Rio Grande floodplain to 300 ft bgl in the western and east-central part of the basin (see Figure 3). Analysis of water-level elevation contours (see Figure 4) shows that localized regions of water- level decline are developing beneath the communities of Dona Ana and Las Cruces. A cone of depression develops where groundwater water is being pumped out faster than water from other parts of the aquifer can flow in to replace it. Groundwater flow in the Mesilla Basin is generally to the southeast, with groundwater flowing from higher elevations to lower elevations, parallel to the course of the Rio Grande. There is also a steep water-table slope from the surrounding hills down into the basin-fill deposits (Wilson et al., 1981; Frenzel and Kaehler, 1990). The average water-table gradient in the Valley is about 25 feet per mile (0.005 ft/ft). Recharge to the Mesilla Basin is primarily from infiltration of surface water from the Rio Grande and associated irrigation works. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 6 - DRAFT November 3, 2020 Depth to water in the Jornada del Muerto Basin ranges from about 100 to 600 ft bgl,with the greatest depth in the area of highest basin-fill permeability (see Figure 3). The direction of groundwater flow in the Jornada del Muerto Basin is generally to the west and south,toward the Mesilla Basin (see Figure 3). The groundwater flow direction in the northern part of the basin is to the northwest, where groundwater discharges toward the Rincon Valley. The gradient is steepest in the mountains, and becomes flatter, about 5 to 8 feet per mile, in the western part of the basin. In the very southern end of the basin,the flow direction is to the southwest(Shomaker and Finch, 1996). Recharge to the Jornada del Muerto Basin is from infiltration of precipitation and runoff from the San Andres and Organ Mountains east of the basin. Groundwater elevation contours in the Rio Grande Valley of the Mesilla Basin are shown in Figure 4. Groundwater elevation contours have not been drawn in the West Mesa Well Field or East Mesa Well Field area of the Jornada del Muerto Basin due to scarcity of data. Hydraulic Properties The Mesilla and Jornada del Muerto Basins contain thick, unconsolidated Santa Fe Group basin-fill sediments and Rio Grande flood plain alluvium. The hydraulic conductivity of the basin-fill deposits is highly variable, but in general the younger sediments have higher hydraulic conductivity and relatively good water quality (total dissolved solids concentration below 1,000 mg/L), and typically the older sediments at depth have a lower hydraulic conductivity, and poorer water quality (Hawley and Lozinsky, 1992). The hydraulic properties of the aquifer are important in assessing the feasibility of an aquifer for storage and recovery of surplus water. The efficiency of an aquifer to receive water for storage and to recover stored water depends in part on hydraulic conductivity and transmissivity (hydraulic conductivity times aquifer thickness). If the aquifer targeted for ASR has a transmissivity that is too low,it is difficult to store large volumes of water without creating discharge at the surface, or in the case of relatively deep aquifers, creating the need to inject the water under high pressure. However, aquifers with very high transmissivity can carry injected water too far away from the well, reducing the efficiency of water recovery. Proving the ability to reclaim stored water may be critical for ASR permitting with the NMOSE. In general,Hawley and Lozinsky(1992) estimate the range in hydraulic conductivity of the Middle Santa Fe Group as 0.3 to 30 ft/day, and the Upper Santa Fe Group and Rio Grande floodplain sediments as 30 to 300 ft/day. Table 1 provides a summary of hydraulic properties for various portions of the Mesilla Basin aquifer. Typically, an aquifer with horizontal hydraulic conductivity exceeding 5 ft/d can yield several hundred gpm to wells,provided the aquifer has adequate saturated thickness. As shown in Table 1, the Rio Grande alluvium has a very high hydraulic conductivity but water is present at shallow depth, which can lead to inefficient recovery of injected water and loss of the water to other users and the surface water system (JSAI, 2002). The remaining portions of the Mesilla Basin, and the Jornada del Muerto Basin, appear to have adequate hydraulic properties for ASR proj ects. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 7 - DRAFT November 3, 2020 Table 1. Summary of hydraulic properties of the Mesilla Basin aquifer in selected areas (modified after JSAI,2002) specific hydraulic depth to capacity conductivity transmissivity water, well yield, of wells, of aquifer, of aquifer, area ft bgl gpm gpm/ft ft/day ft2/day 5 9d Rio Grande alluvium 10-25a 2,500+a 10-217a 1094d 12,600-15,200- Valley Well Field 25 to 320 500 to 3 to 30' 2 to 150h 2,7 10 to 19,3 00 h 2,000' upper 200 ft of aquifer 20 to 150 h 4,000 to 30,000'' aquifer from 200 to 600 ft 2 to 26.5 h 800 to 10,500'' aquifer from 600 to 1,200 ft 1.7 to 13 h 1,000 to 7,800 h a Wilson et al., 1981 ft bgl feet below ground level b Hamilton and Maddock,1993 gpm/ft gallons per minute per foot Conover,1954 W/day feet squared per day a Frenzel and Kaehler, 1990 9 Nickerson,1989 b Weeden and Maddock, 1999 'JSAI,2017 Description of Reclaimed Wastewater City of Las Cruces wastewater is treated at three facilities: (1) Jacob A. Hands Wastewater Treatment Facility, (2) East Mesa Water Reclamation Facility (EMWRF), and (3) West Mesa Wastewater Treatment Plant. Reclaimed water produced from the West Mesa Wastewater Treatment Plant and EMWRF represent water sources that are not fully utilized, and which are potential sources for alternate supply through ASR application. The Jacob A. Hands Wastewater Treatment Facility produces approximately 3,030,800,000 gallons(9,300 acre-feet)of effluent annually.All treated effluent from the facility is discharged as return flow to the Rio Grande. The West Mesa Wastewater Treatment Plant produces approximately 28,233,060 gallons (87 acre-feet) of effluent annually. Most of this is currently used for sprinkler-irrigation of native vegetation in the West Mesa Industrial Park,with the remainder being land-applied. The EMWRF effluent is currently used, in part, for landscape irrigation, dust suppression, and fire hydrants. The EMWRF has a capacity of 1,000,000 gallons per day (about 1,121 acre-feet/year). Peak summer demand from the facility is about 700,000 gallons per day; JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 8 - DRAFT November 3, 2020 however, the facility must ramp down in winter when there is very little demand for the water. Average water reuse diversions for the winter months of November through March represent about 60 percent of average water reuse diversions for the summer months of April through October, and reflect the lack of demand for reclaimed water during the winter months. Under- utilization of the facility during the winter months equates to about 350 ac-ft/yr. The EMWRF reclaims water to relatively high quality, though not necessarily to NMED/Drinking Water Bureau (NMED/DWB) drinking water standards. Table 2 includes recent EMWRF effluent water quality data provided by the City, compared with NMED groundwater discharge standards and drinking water standards. Table 2. Summary of ENMRF effluent water quality groundwater NMED/DWB time no. of drinking parameter period samples units min max discharge water standard standard TDS 2019- 20 mg/L 640 1,750 1,000 500a 2020 chloride 2019- 20 mg/L 205 374 250 250 a 2020 sulfate 2017 4 mg/L 151 211 600 250 a 2020 nitrate as N 2019- 20 mg/L 0.8 15.4 10 10 2020 ammonia 20 20 2020 19- 20 mg/L 0.21 7.6 ns ns TKN 2019- 20 mg/L 0.94 11.7 ns ns 2020 fluoride 2017 4 mg/L 0.26 0.47 1.6 4 2020 aluminum 2017 3 mg/L 0.0072 0.014 5 0.05 to 0.20' 2019 antimony 2017 2019 2 mg/L na <0.005 0.006 0.006 arsenic 2017 3 mg/L 0.0019 0.0028 0.01 0.010 2019 barium 2017 3 mg/L 0.059 0.068 2 2 2019 beryllium 2017 2 mg/L na <0.001 0.004 0.004 2019 cadmium 2017 6 mg/L na <0.002 0.01 0.005 2019 chromium 2017 3 mg/L na <0.005 0.05 0.1 2019 cobalt 2017 3 mg/L na <0.001 0.05 ns 2019 JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 9 - DRAFT November 3, 2020 copper 2017 3 mg/L 0.0018 0.0036 1 1.3 2019 iron 2017 3 mg/L <0.05 0.05 1 0.3 a 2019 lead 2017 3 mg/L na <0.0005 0.015 0.015 2019 manganese 2017 3 mg/L 0.028 0.038 0.2 0.05 a 2019 mercury 2017 3 mg/L na <0.0002 0.002 0.002 2019 molybdenum 2017 3 mg/L 0.005 0.006 1 ns 2019 nickel 2017 2019 3 mg/L 0.0014 0.006 0.2 ns Silver 2017 3 mg/L na <0.0005 0.05 0.1 a 2019 thallium 2017 2 mg/L na <0.002 0.002 0.002 2019 uranium 2017- 2 mg/L 0.00331 0.00439 0.03 0.03 total 2018 zinc 2017 3 mg/L 0.021 0.044 10 5.0 a 2019 boron 2017 3 mg/L <0.50 0.271 0.75 ns 2019 selenium 2017 3 mg/L na <0.005 0.05 0.05 2019 cyanide 2017 3 mg/L na <0.02 0.2 0.2 2019 volatile organics 2017- not low-level 2019 6 mg/L na detected various various EPA 624 Low total 2017- not naphthalene 2019 2 mg/L na detected 0.03 various EPA 625 semi-volatile not organics 2018 2 mg/L na detected various various EPA 625.1 chlorinated not pesticides 2018 2 mg/L na detected various various EPA 608.3 total 2017- 3 mg/L na <0.05 ns ns phenolics 2019 PCBs 2017-2019 3 mg/L na not detected 0.0005 0.0005 gross alpha 2018 1 Ci/L na 6.74 ns 15 gross beta 2018 1 Ci/L na 27.2 ns 50 b radium-226 20018 2 pCi/L 0.169 0.527 5 5 JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities _ 10 - DRAFT November 3, 2020 radium-228 2017 2 pCi/L 0.131 1.61 2018 pH 2016- 3 pH units 7.08 7.64 6 to 9 6.5 to 8.5 a 2018 several 2018- times a BOD 2019 week mg/L 1.03 6.84 ns ns during 3Q once a TSS 2018- week mg/L 0.70 3.20 ns ns 2019 during 3Q several fecal 2018- times aMPN/100 <500/100 mL coliform 2019 during mL 1.00 130 e 5 percent 3Q 2018- daily turbidity 2019 during NTU 0.24 1.32 ns d 3Q NMED/DWB-NM Environment Dept/Drinking Water Bureau a secondary drinking water standard(aesthetic-related,non-enforceable guideline) b NMED/DWB-defined level below which the equivalent radiation is below EPA mandated radiation threshold of 4 mrem/yr standard is for total coliforms,including fecal coliform and E. Coli:No more than 5 percent samples total coliform-positive in a month. d-For systems that use conventional or direct filtration,at no time can turbidity> 1 NTU,and samples for turbidity must be<0.3 NTU in at least 95 percent of the samples in any month. Systems that use filtration other than the conventional or direct filtration must include turbidity at no time>5 NTU. e general requirement for effluent discharge to a watercourse under 20.6.2.210LA NMAC mg/L-milligrams per liter pCi/L-picoCuries per liter NTU-nephelometric turbidity units MPN/100 mL—most probable number per 100 milliliters ns—no standard na—not applicable bold indicate exceedance of standard The EMWRF effluent appears to currently qualify as Class 1B under the rules of the NMED/DWB. This class of reclaimed wastewater is approved for impoundments (recreational or ornamental), irrigation of parks, school yards, or golf courses (with setback limitations), irrigation of urban landscaping (with setback limitations), snow making, street cleaning, toilet flushing, and backfill around non-potable piping. Total dissolved solids (TDS)and chloride concentrations in the EMWRF have generally exceeded NMED/DWB secondary drinking water standards,but these are aesthetic-related,non- enforceable guidelines. It is unclear whether NMED may require that reclaimed water meet groundwater discharge standards for TDS, sulfate, and other secondary standards for ASR application. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 11 - DRAFT November 3, 2020 Nitrate concentrations have occasionally exceeded the NMED/DWB primary (health- related) standard of 10 milligrams per liter(mg/L). However, of the 20 nitrate results reviewed, only 4 exceeded the standard(and 2 of those results were 10.1 mg/L, slightly elevated above the standard). Thus, for an ASR application, it may be possible to optimize the current water treatment system to maintain nitrate results below the standard, or NMED may allow the City to demonstrate that the average nitrate concentration of injected water would be below the standard. The primary issue for qualification as Class IA reclaimed wastewater(all uses) may be the presence of fecal coliform in the effluent. The primary drinking water standard is for total coliforms,including fecal coliform and E. Coli:No more than 5 percent of samples may be total coliform-positive (TC-positive) in a month. Every sample that has total coliform must also be analyzed for either fecal coliform or E. coli. A violation occurs if two consecutive TC-positive samples occur, and one is also positive fecal coliform or E. coli. For an ASR application, it is unknown whether NMED may allow for the presence of fecal coliform in water to be injected, if the City can demonstrate that it would be absent in water that is recovered. EMWRF—Aquifer Injection The City water system chiefly draws groundwater from the Mesilla Basin through wells in the Valley Well Field and the West Mesa Well Field, and from the Jornada del Muerto Basin through wells in the East Mesa Well Field. The EMWRF is located just east of the horst that represents the boundary between these two basins. Inactive wells in the Valley Well Field were considered for suitability for use as ASR wells to inject reclaimed water directly into the Mesilla Basin aquifer. Inactive wells under consideration are generally in the Interstate-25 Corridor area within relatively close proximity to the EMWRF, as well as Well 10 on the eastern edge of the Valley area. All well locations are shown in Figures 1 and 4. Selection criteria relative to each well location's appropriateness for ASR application are discussed below and summarized in Table 3 (listed numerically). Preliminary groundwater modeling by JSAI in the Interstate-25 Corridor area has informed the selection of sites with good potential for ASR application. Sites could be further prioritized based on proximity to the City's recycled water(purple pipe) distribution system. The condition of any production well which is considered for use as an ASR well should be evaluated. We recommend a video survey as well as a casing integrity test. Depending upon the condition of the well screen,rehabilitation may be required. In some cases,the existing well may be at the end of its serviceable life, and a replacement well may be required for ASR application. • Well 10 (LRG-430) is relatively isolated from active supply wells in the Valley Well Field. The site could be considered for injection and recovery, as no nearby recovery wells exist. The nearest downgradient wells are located approximately 4,500 feet east- southeast. These are the Paz Park Well and Well 18, which are used as sampling and plume capture wells related to the Griggs and Walnut site. Furthermore, Well 10 was JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 12 - DRAFT November 3, 2020 drilled in 1951, and may not be reliable for use as an injection well. We do not recommend existing Well 10 for use in an ASR program, but a replacement well could be considered for injection and recovery. • Well 19 (LRG-430-S-6) is used for groundwater monitoring and sampling related to the Griggs and Walnut site, and is not available for ASR application. • Well 20 (LRG-430-S-7) has been taken out of service due to effects on the Griggs and Walnut site, and is not available for ASR application. However, additional groundwater modeling could be used to determine if injecting water into Well 20 could be beneficial to the Griggs and Walnut remediation effort. • Well 21 (LRG-430-S-8)is located upgradient of the Griggs and Walnut site.No recovery wells exist between Well 21 and the Griggs and Walnut PCE plume. If Well 21 is used alone for injection and recovery, there is the possibility that injected water may be lost to the cone of depression around the Griggs and Walnut site. Therefore, we do not recommend Well 21 as an ASR injection well. If Well 54 is used as an injection well (see below), Well 21 could function as a downgradient recovery well. Additional groundwater modeling could determine if inclusion of Well 21 in an ASR program would have deleterious effects on the Griggs and Walnut remediation effort. Well 21 appears to have been completed in 1962 or 1964. The casing condition is unknown, and would need to be evaluated. • Well 23 (LRG-430-S-10) is located at the north end of the Valley Well Field. It is approximately 2,000 feet north-northwest, and upgradient, of active Well 62. We judge this to be a favorable site for ASR.A well in this location could be used for injection and recovery, or as an injection well alone, with Well 62 serving as a recovery well. However, Well 23 was completed in 1966. Based on a video survey conducted in 2016, JSAI concluded that the screen is no longer open, and substantial portions of the casing are missing. JSAI recommended that the well be plugged and abandoned, and a replacement well be installed. Use of the Well 23 site in an ASR program would require a replacement well to be drilled. • Well 24 (LRG-430-S-11) is located south, and upgradient, of City Well 61. LCU ceased municipal pumping of Well 61 in March, 2019 in order to minimize the potential for vertical and southward movement of the Griggs and Walnut PCE plume. There are no other active wells nearby which could serve as recovery wells.Nearby upgradient Wells 38 and 44 may be considered as injection wells.Additional groundwater modeling could determine if using Well 24 as a recovery well would have harmful effects on the Griggs and Walnut remediation project. However, we do not recommend using Well 24 as an injection well in the ASR program. • Well 26 (LRG-430-S-13) is used for groundwater chemistry sampling related to the Griggs and Walnut site, and is not available for ASR application. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 13 - DRAFT November 3, 2020 • Well 38 (LRG-430-S-4) is located 2,200 feet east, and slightly upgradient, of Well 24. Well 38 may be a good candidate for use as an injection and recovery well. Downgradient Well 24 could additionally function as a recovery well, provided groundwater modeling determines that pumping from Well 24 would not have harmful effects on the Griggs and Walnut remediation project. • Well 44 (LRG-430-S) is relatively isolated from active supply wells in the Valley Well Field. Regional groundwater flow is to the southeast. Well 44 could be considered for both injection and recovery. Active Wells 35 and 70 are located approximately 5,000 feet west-southwest, and downgradient. Additional groundwater modeling could determine if these wells are near enough to serve as recovery wells. • Well 54 (LRG-430-S-25) is located 3,000 feet north and upgradient of inactive Well 21, and 2,500 feet southeast of active Well 28. Well 54 could be considered as an injection well and recovery well, or as an injection well with Well 21 functioning as a recovery well. This would be dependent upon groundwater modeling determining that inclusion of Well 21 in an ASR program would not have deleterious effects on the Griggs and Walnut remediation effort. Well 21 was completed in approximately 1962, and the casing condition is unknown. Injected water that is not recovered from Well 21 would flow southeast, and may be lost to the cone of depression formed around the Griggs and Walnut Superfund site. • Well 57 (LRG-430-S-31) is located 4,500 feet east of the Griggs and Walnut site, and could be considered as an injection and recovery well. Regional groundwater flow is to the southeast, though this may be affected by the cone of depression around the Griggs and Walnut site. Additional groundwater modeling could determine if Well 57 would be a feasible injection and recovery well. There is also potential that discharge of water into upgradient Well 57 could benefit the Griggs and Walnut remediation effort. Nearby Wells 19 and 20 have been taken out of service due to effects on the remediation site. • Well 60 (LRG-430-S-35) sits near the interpreted divide between groundwater flow to the southwest, toward active Well 32B, and to the northeast, toward the Griggs and Walnut plume capture wells.The Well 60 site may be a good candidate for ASR injection and recovery. Additional groundwater modeling could establish whether Well 32B, 2,000 feet southwest, could also function as a recovery well. • Well 61 (LRG-430-S-37) is not in use. LCU ceased municipal pumping of Well 61 in March, 2019 in order to minimize the potential for vertical and southward movement of the Griggs and Walnut PCE plume. This site is not suitable for ASR application. However,additional groundwater modeling could be used to determine if injecting water into upgradient Well 61 could be beneficial to the Griggs and Walnut remediation effort. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 14 - DRAFT November 3, 2020 Table 3. Summary of inactive wells and potential for ASR application of EMWRF effluent, City of Las Cruces,New Mexico. sub- total screen casing depth to well region year depth, interval(s), diameter, water,ft potential for ASR number drilled ft ft in. bmp application (Y/N) Well 10 Valley 1951 381 270 to 370 16/12 94.2 Y (replacement well) I-25 348 to 363; 373 to 383; Well 19 1962 612 393 to 460; 16/12/8 225.7 N 532 to 540; 564 to 604 1-25 380 to 395; Well 20 1963 677 415 to 525; 16/12/8 236.6 N 615 to 673 Well 21 I-25 1962 632 366 to 620 16 235.3 Y (recovery only) Well 23 I-25 1966 592 452 to 592 16/12/8 231.3 Y (replacement well) Well 24 I-25 1966 591 381 to 591 16/12/8 206.1 Y (recovery only) Well 26 1-25 1969 700 410 to 510; 16/12 176.5 N 600 to 700 Well 37 WM 1982 640 440 to 640 12 320 Y Well 38 1-25 1984 780 320 to 400; 16/10 266.0 Y 480 to 780 Well 44 I-25 1987 620 400 to 600 16 161.1 Y Well 54 I-25 1972 480 272 to 480 12 269.6 Y Well 57 I-25 1990 532 408 to 516 12 292.9 Y Well 60 I-25 1994 700 350 to 690 16/12 104.8 Y Well 61 1-25 1995 1,070 610050 0 to 16/12 205.2 N JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 15 - DRAFT November 3, 2020 LRG- EM 1964 550 nd 8 350 Y(recovery only) 5039 LRG- EM 1969 550 nd 8 nd Y (recovery only) 5039-S LRG- EM 1990 600 350 to 600 12 333 Y 5039-S-2 I-25—Interstate-25 Corridor area in the Mesilla Basin WM—West Mesa area in the Mesilla Basin EM—East Mesa area in the Jornada del Muerto Basin nd—no data Reclaimed wastewater from the EMWRF could also be injected in the Jornada del Muerto Basin aquifer. The East Mesa Well Field produces groundwater from the Jornada del Muerto Basin, which is only shallowly connected to the Mesilla Basin. Depth to water in the area of the East Mesa Well Field is approximately 400 to 600 ft bgl. Wells in the East Mesa Well Field have shown non-pumping water-level decline of 3 to 6 feet per year. Addition of reclaimed wastewater would help to offset this decline. Inactive wells in the East Mesa Well Field were considered for suitability for use as ASR wells to inject reclaimed water directly into the Jornada del Muerto aquifer. Three inactive wells are located in the southwest area of the East Mesa Well Field. Well LRG-5039-S-2 was built in 1990 and may represent good potential for aquifer injection and recovery. There are two downgradient wells: Well LRG-5039-S (built in 1969) and Well LRG-5039 (built in 1964). If these wells are determined to be in sufficiently good condition, one or both could function as a recovery well. However, these wells are located at the west, and downgradient side, of the East Mesa Well Field. Water injection at this location would not likely offset the water-level decline observed in the rest of the well field. Depending on water system requirements, a well in the northeast side of the well field may be more beneficially converted to an ASR injection and recovery well. EMWRF—Vadose Zone Infiltration The use of vadose zone infiltration basins is a low-cost,low-maintenance mechanism to return reclaimed wastewater to the aquifer. Basins could be constructed to utilize existing topography for impoundment; such as adjacent to the earth dam in the Interstate-25 corridor, where the depth to water ranges from approximately 100 to 300 ft bgl. Infiltration basins can also be constructed as water features in parks.Large parcels of undeveloped property are present around Well 54 and Well 57 which could be used for infiltration basins.These could additionally be constructed as water features in park land. If a vadose zone infiltration basin method is selected,we recommend an infiltration study be conducted at the proposed site in order to determine the land surface area required for the desired volume and rate. Proposed sites could be evaluated with a series of auger boreholes JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 16 - DRAFT November 3, 2020 drilled to approximately 50 or 100 ft bgl. These boreholes would be used to collect samples to determine the characteristics and thickness of near-surface lithologic units as well as to perform constant-head infiltration tests to assess potential infiltration rates. In the lower Valley area, it may be possible to assess both saturated and unsaturated infiltration rates. At any site selected for infiltration basin(s), it must be demonstrated that the water applied to the basins will reach the water table soon enough to provide a demonstrable offset to drawdown due to pumping from recovery/supply wells. At sites where the depth to water is too shallow, the ability of the saturated sediments to accept water infiltration will limit the amount which may be stored, with an increased possibility that water may be lost to the river or other surface systems,or may become contaminated from other shallow sources (e.g. dry cleaners and underground fuel storage tanks). During periods of above-average precipitation, stored water could mound upward and cause discharge at the surface. Infiltration basins situated higher above the water table may be feasible, but may present regulatory difficulty in demonstrating that the water will reenter the aquifer, providing recharge, and be accessible for later recovery. The depth to water west of the EMWRF (west of the horst, in the Mesilla Basin) is on the order of 375 to 400 ft bgl. There are no production wells in this area to recover stored water. In order to employ an infiltration basin west of the EMWRF, a recovery well would have to be built. The depth to water in the East Mesa Well Field is between approximately 400 and 600 ft bgl. An infiltration basin nearby the pumping wells could help offset the large water-level decline (3 to 6 feet per year). It would be critical to establish that the water is reentering the aquifer and being recovered, in order to successfully permit an ASR program. Farther to the west, in the Valley area, the depth to water averages approximately 50 ft bgl. An infiltration area could be selected up-gradient and adjacent to the City's pumping wells in the Valley Well Field. In some areas, the shallow depth to water could limit the potential infiltration rate, and care would have to be taken to avoid loss of water to the Rio Grande. This would also require a longer pipeline, as the Valley Well Field is approximately 5 miles from the EMWRF. We recommend unsaturated and saturated hydraulic conductivity testing, conducted in a series of auger holes,be combined with groundwater flow modeling to establish the viability of an injection site in the Valley area. Environmental site assessments should be conducted at any proposed sites to avoid risk from any preexisting shallow environmental contamination, such as gas stations/storage tanks, dry cleaners, etc. Potential Influence on Griggs and Walnut PCE Plume Additional groundwater modeling would be beneficial to ensure that any ASR application of treated effluent in the Interstate-25 Corridor area does not have a deleterious effect on the Griggs and Walnut PCE plume remediation project. Alternatively, treated effluent from the EMWRF might be applied to assist remediation by helping to control and move the PCE plume toward the capture wells (Well 18 and Well 27). JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 17 - DRAFT November 3, 2020 Prior to the Wells 54 and 57 being taken out of service, the Griggs and Walnut PCE plume had migrated northeastward under the influence of pumping the two wells. Since these wells have been inactive, groundwater flow direction in the area has reverted to the southwest, toward the cone of depression formed around capture Wells 18 and 27. Upgradient addition of EMWRF effluent water, either by direct injection or infiltration, may assist in the remediation process. Water added at the Well 54 and Well 57 sites could move the plume in the direction of the capture wells. The large parcels of undeveloped property around each of these well sites could be used for infiltration of effluent water from the surface. The depth to water measured in 2020 in Well 54 is 268 ft bgl, and in Well 57 it is 290 ft bgl. Wells 20 and 61,which were taken out of service due to effects on the PCE plume, may also be suitable sites to inject reclaimed wastewater up-gradient of the plume. Another option would be to attempt to influence the PCE plume by injecting water at a low rate into a series of purpose-built small-diameter wells surrounding the plume. Direct injection into the wells would require effluent water to be treated to drinking water standards. Infiltration from the surface would require less water treatment. However, with infiltration from the surface, there is the potential for other contamination present in the sediments above the water table to migrate into the aquifer. This risk could be assessed by conducting an environmental site assessment possibly coupled with a soil boring program at any proposed infiltration site.Additional groundwater modeling could be used to determine the most effective option. West Mesa Wastewater Treatment Plant—Aquifer Injection There are fewer wells to be considered for ASR application in the West Mesa Well Field than in the Valley Well Field. With the groundwater flow direction being generally southeast, an injection site would best be located in the northwestern part of the West Mesa Well Field to allow for recovery of stored water from pumping wells located downgradient, and avoid loss to the Rio Grande. Well 37 is located on the West Mesa, approximately 1,800 feet south of the intersection of Interstate 10 and US Highway 70. The well is located west-to northwest of producing Wells 36, 46, and 63, making it upgradient or across-gradient. Well 37 may be a good candidate for ASR injection and recovery,with Wells 36,46, and 63 functioning as additional recovery wells. West Mesa Wastewater Treatment Plant—Vadose Zone Infiltration Depth to water in the area of the West Mesa Well Field averages approximately 300 ft bgl. General groundwater flow direction is to the southeast. An infiltration basin could be constructed near to, and upgradient of, the cluster of 3 active City wells: Wells 36, 46, and 63. The City has permits for a number of West Mesa wells which have not yet been drilled. These planned wells could also be used for recovery of stored water. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 18 - DRAFT November 3, 2020 Other ASR Projects In New Mexico Albuquerque—Bear Canyon Recharge Project • Water source: reclaimed wastewater blended with disinfected river water • Treatment standard: discharge standards • Water discharge method: infiltration basins • Water recovery method: existing municipal wells • Depth to water: 250 to 400 ft bgl • Volume stored: 4,500 AFY Albuquerque—Large Scale Recharge Project • Water source: reclaimed wastewater • Treatment standard: drinking water standards plus dechlorination • Water discharge method: dry well(vadose zone)& direct injection via purpose-built well • Water recovery method: existing municipal wells &pumping from injection well • Depth to water: 150 ft bgl • Volume stored: 5,000 AFY Rio Rancho • Water source: reclaimed wastewater • Treatment standard: drinking water standards • Water discharge method: direct injection via purpose-built well • Water recovery method: existing municipal wells • Depth to water: 800 ft bgl • Volume stored: 1,000 AFY Ruidoso (pilot study in progress) • Water source: reclaimed wastewater and treated surface water • Treatment standard: drinking water standards • Water discharge method: existing municipal well • Water recovery method: pump from injection well • Depth to water: 100 ft bgl • Volume stored: (to be determined in pilot study) Discussion As identified in the City's 40-Year Water Development Plan (2017), ASR is a potential way for the City to make use of reclaimed wastewater for alternate supply. Additionally, JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities _ 19 - DRAFT November 3, 2020 reclaimed wastewater may be used to offset regional water-level declines in the Mesilla and Jornada del Muerto Basins. Numerous locations exist within the City that have the potential for good ASR performance via injection through wells, or infiltration through vadose zone infiltration basins. Direct aquifer injection through existing or purpose-built wells can be used to efficiently mitigate water-level drawdown. Additionally, it may be easier to demonstrate successful recovery of stored water to the NMOSE when using direct aquifer injection together with nearby recovery wells. However, regulations require any water injected into the aquifer to be treated to drinking water standards. Some of the existing inactive wells should not be considered, due to well age or condition, and potential impact on the Griggs and Walnut Superfund site. Infiltration using vadose zone infiltration basins represents a lower-cost and lower- maintenance option than direct injection. Furthermore, the NMOSE requires water discharged at the surface, such as into a settling basin, to be treated to the less-stringent groundwater discharge standards. Table 4 contains a comparison of New Mexico groundwater discharge and drinking water standards. However, it may be more difficult to prove successful entry of this water into the aquifer and subsequent recovery of stored water to the NMOSE. Site-specific studies will be crucial for the proposed reclaimed wastewater ASR project, in order to (1) determine whether the water can be successfully returned to the water table and recovered for later use, considering both physical return of the water and NMOSE accounting, and (2) determine whether the proposed water treatment and aquifer-return approach is protective of environmental and human health standards. These studies may include: • Borehole infiltration testing should be conducted to assess potential infiltration rates at potential sites for vadose zone infiltration basins. • Groundwater flow modeling could be used to assess the ability of the Mesilla Basin aquifer to store injected water, and to evaluate potential loss to the Rio Grande. It can be determined whether wastewater applied in infiltration basins, rather than through injection wells,would reach the water table soon enough to provide a meaningful offset to drawdown due to pumping from supply wells. Then a conventional return-flow plan associated with the existing permits may be acceptable to the NMOSE and NMED. • A constant-rate pumping test should be performed in each selected injection well in order to assess the hydraulic properties of the aquifer, and a step-drawdown test should be carried out for evaluation of well efficiency. Then, water from the proposed source should be injected into the well during a 14-day period, followed by 14 days of recovery pumping. A long-term pumping test should be performed subsequent to the injection test to compare the pre- and post-injection hydraulic properties of the aquifer. The physical condition of any selected well would need to be evaluated prior to testing. • Water-quality data for the effluent from the West Mesa Water Treatment Plant and EMWRF should be reviewed and included in discussions with the NMOSE and NMED. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 20 - DRAFT November 3, 2020 • A geochemical mixing model should be constructed to assess compatibility and determine if introducing reclaimed water to the shallow groundwater would negatively impact the aquifer with respect to the development of mineral precipitation that would result in irreversible hardness, or plugging of the well or aquifer. Table 4. Comparison of New Mexico groundwater discharge and drinking water standards groundwater parameter units discharge drinking water standard standard TDS m /L 1,000 5001 chloride m /L 250 2501 sulfate m /L 600 2501 nitrate as N m /L 10 10 ammonia m /L ns ns TKN m /L ns ns fluoride m /L 1.6 4 aluminum m /L 5 0.05 to 0.201 antimony m /L 0.006 0.006 arsenic m /L 0.01 0.010 barium m /L 2 2 beryllium m /L 0.004 0.004 cadmium m /L 0.01 0.005 chromium m /L 0.05 0.1 cobalt m /L 0.05 ns copper m /L 1 1.3 iron m /L 1 0.31 lead m /L 0.015 0.015 manganese m /L 0.2 0.051 mercury m /L 0.002 0.002 molybdenum m /L 1 ns nickel m /L 0.2 ns silver m /L 0.05 0.11 thallium m /L 0.002 0.002 uranium (total) m /L 0.03 0.03 zinc m /L 10 5.01 boron m /L 0.75 ns selenium m /L 0.05 0.05 cyanide m /L 0.2 0.2 volatile organics low-level EPA 624 mg/L various various Low total naphthalene EPA 625 m /L 0.03 various semi-volatile organics EPA 625.1 m /L various various chlorinated pesticides EPA 608.3 m /L various various PCBs I m /L 1 0.0005 1 0.0005 JOHN SHOMAKER & ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 21 - DRAFT November 3, 2020 gross alpha Ci/L ns 15 gross beta Ci/L ns 50 b radium-226 Ci/L 5 5 radium-228 Ci/L H pH units 6 to 9 6.5 to 8.5 a fecal coliform MPN/100 mL <500/100 mLe 5 percent turbidity NTU ns d a secondary drinking water standard(aesthetic-related,non-enforceable guideline) b NMED/DWB-defined level below which the equivalent radiation is below EPA mandated radiation threshold of 4 mrem/yr standard is for total coliforms,including fecal coliform and E. Coli:No more than 5 percent samples total coliform-positive in a month. d-For systems that use conventional or direct filtration,at no time can turbidity> 1 NTU,and samples for turbidity must be<0.3 NTU in at least 95 percent of the samples in any month. Systems that use filtration other than the conventional or direct filtration must include turbidity at no time>5 NTU. e general requirement for effluent discharge to a watercourse under 20.6.2.210LA NMAC mg/L-milligrams per liter pCi/L-picoCuries per liter NTU-nephelometric turbidity units MPN/100 mL—most probable number per 100 milliliters ns—no standard JSAI is meeting with the NMED and NMOSE to discuss potential approaches and locations for ASR application of the City's reclaimed wastewater. These early discussions include conversations on such topics as: • Discharge of water via infiltration basins vs. wells (direct aquifer injection) • The role of depth to water, especially with regard to infiltration basins • Discharge water quality standards • Discharge/storage in the Mesilla vs. Jornada del Muerto Basins • Discharge water potentially interacting with the Griggs and Walnut Superfund Site(PCE plume) • Interpretation of the water rights Burden of Proof rules • Required geochemical/mixing modeling The results of these discussions should provide the City with guidance as to which potential approaches and locations may be most easily permitted, and any approaches that the NMOSE and NMED may reject out of hand. Following these preliminary meetings with NMOSE and NMED, the City may be in the position to perform additional, more detailed studies, such as evaluating more advanced water treatment and area-specific groundwater modeling. Establishing and permitting an ASR program in the current regulatory environment is a relatively long and expensive process. For example, the Albuquerque Bear Canyon Recharge Project was finally established after 5 to 7 years of study. It may be preferrable for the City to apply for return flow credit. This process requires a return flow plan, but does not require JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 22 - DRAFT November 3, 2020 demonstrated recoverability, as in an ASR plan. If the reclaimed wastewater is discharged to infiltration basins,this would not require treatment to drinking water standards. This reclaimed water could be discharged east of the EMWRF into the Jornada del Muerto basin in order to offset regional water-level decline. The conditions and process to apply for a return flow credit are set out in NMAC 19.26.2.11. Some water systems in New Mexico and elsewhere in the U.S. have explored direct potable reuse (DPR) of treated wastewater. At present, this represents a large — potentially insuperable — permitting obstacle. The Village of Cloudcroft, New Mexico permitted a DPR project in response to very limited water sources for the seasonal tourist population. However, the Village has not yet completed a discharge plan and permit for disposal of the small portion of un-treatable residual water, so the DPR system is not yet active. Disposal of the residual waste that results from a DPR project represents a unique permitting challenge. Public acceptance of DPR represents an additional obstacle. ASR has also faced public opposition in the past, but is now becoming more accepted. There is the potential that the reclaimed wastewater stream which may be returned to the aquifer via ASR or return flow plan in the near future may one day be exploited for DPR. At the present, however, direct reuse appears to be less feasible than ASR due to difficulty of permitting,water treatment, disposal of residual waste,negative public opinion, and high associated costs. APF:of Enclosures Figure I Aerial photograph showing locations of City of Las Cruces supply wells and landfill monitoring wells, and City of Las Cruces observation wells, used for water-level monitoring program Figure 2 Geologic map of the northern part of the Mesilla Basin and southern part of the Jornada del Muerto Basin showing the City of Las Cruces area and selected existing City of Las Cruces wells, Las Cruces Utilities, Dona Ana County,New Mexico. Figure 3 Southwest-to-northeast hydrogeologic cross-section A-A' of the City of Las Cruces Area Figure 4. Aerial photograph showing December 2019 water-level elevation contours, City of Las Cruces,New Mexico. JOHN SHOMAKER& ASSOCIATES, INC. WATER-RESOURCE AND ENVIRONMENTAL CONSULTANTS Las Cruces Utilities - 23 - DRAFT November 3, 2020 References Finch, S. T., Jr., 1999, Results from installation of ground-water monitoring system, and proposed ground water monitoring plan, Las Cruces Landfill, Las Cruces, New Mexico: Consultant's report prepared by John Shomaker& Associates, Inc. for the City of Las Cruces, 25 p. Frenzel, P. F., and Kaehler, C. A., 1990, Geohydrology and simulation of ground-water flow in the Mesilla Basin,Dona Ana County,New Mexico, and El Paso County,Texas: U.S. Geological Survey Open File Report 88-305, 179 p. Hawley, J. W., and Lozinsky, R. P., 1992, Hydrogeologic framework of the Mesilla Basin in New Mexico and western Texas: New Mexico Bureau of Mines and Mineral Resources, Open- File Report 323. [JSAI] John Shomaker & Associates, Inc., 2002, Aquifer Storage and Recovery Assessment, Mesilla and Jornada Basins,Dona Ana County,New Mexico:report prepared by John Shomaker & Associates, Inc.,for City of Las Cruces and Lower Rio Grande Water Users Organization, 36 p. plus figures and appendices. [JSAI] John Shomaker& Associates, Inc., 2017, Well report for replacement Well 3 1 B (LRG- 430-POD58), City of Las Cruces, New Mexico: well report prepared by John Shomaker & Associates, Inc., for Las Cruces Utilities, 18 p. plus figures and appendices. [LAMED] January, 2007. Ground Water Quality Bureau Guidance: Above Ground Use of Reclaimed Domestic Wastewater. January 2007 [NMISC] New Mexico Interstate Stream Commission, 2018, New Mexico State Water Plan, Part L Policies, prepared by NMISC, and adopted by NMISC on December 6, 2018, 53 p. plus appendix. Shomaker, J.W., and Finch, S.T., Jr., 1996, Multilayer ground-water flow model of southern Jornada del Muerto Basin, Dona Ana County, New Mexico, and predicted effects of pumping wells LRG-430-S-29 and —S-30: Albuquerque, New Mexico, John Shomaker & Associates, Inc., 26 p., 5 tables, 20 figures. Woodward, D.G. and Myers, R.G., 1997, Seismic investigation of the buried horst between the Jornada del Muerto and Mesilla ground-water basins near Las Cruces, Dona Ana County,New Mexico: U.S. Geological Survey Water Resources Investigations Report 97-4147, 45 p. JOHN SHOMAKER& ASSOCIATES, INC. 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