Preliminary Design of the Seawater Extraction Barrier

Transcription

1 Technical Memorandum To: San Juan Basin Authority (SJBA) Technical Advisory Committee (TAC) Cathrene Glick, Program Manager From: Wildermuth Environmental Inc. (WEI) Black & Veatch (B&V) Date: Draft: September 8, 2015 Revised: December 7, 2015 Subject: Preliminary Alternative Descriptions for the San Juan Basin Groundwater and Desalination Optimization Program Elements (Tasks 2.2, 2.3, 2.4 and 2.5 of the FAF Grant Scope of Work) Introduction Per the Foundational Action Funding (FAF) grant scope of work for the San Juan Basin Groundwater and Desalination Optimization Program (the Program), the objective of Tasks 2.2 through 2.5 is to describe the alternative configurations of facilities and associated operating plans that achieve the goal of the San Juan Basin Groundwater Facilities and Management Plan (SJBGFMP) 1 to increase yield through enhanced recharge and production. During Task 3, the hydrologic feasibility of a range of project alternatives identified herein will be evaluated using surface and groundwater modeling tools. The project operations and facilities will be refined for economic analysis in Task 3 based on the results of the hydrologic analysis. The SJBGFMP recommended the implementation of either Alternative 6 or Alternative 10. Alternative 6 will increase the sustainable yield of the basin through the development and implementation of the following Program Elements: a seawater extraction barrier that will desalt seawater, generate a new supply of water, and protect the basin from seawater intrusion; instream recharge facilities to increase storm water recharge and to recharge recycled water; and expanded groundwater production and treatment facilities to recover the new recharge. Alternative 10 is identical to Alternative 6, except that there is no seawater extraction barrier project. Alternative 10 assumed that the South Orange County Ocean Desalination (SOCOD) project would be implemented and that the operation of the off-shore SOCOD slant wells would prevent seawater intrusion, thus eliminating the need for a seawater extraction barrier project. Although the SOCOD project assumed in Alternative 10 is not being implemented, the South Coast Water District (SCWD) is currently evaluating the feasibility of implementing a similar ocean 1 Wildermuth Environmental, Inc. (2013) San Juan Basin Groundwater and Facilities Management Plan. Prepared for the San Juan Basin Authority, November 2013.

2 Technical Memorandum Page 2 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 desalination program using slant wells (the Doheny Desalination program). The projects to be evaluated as part of the Program under the SJBA s FAF scope of work are those defined in Alternative 6 of the SJBGFMP. For the purpose of defining and evaluating the project operations and facilities designs in Tasks 2 and 3, it is assumed that no ocean desalination program is implemented and thus the extraction barrier is needed to protect against seawater intrusion. The development of the FAF Task 4 implementation plan should consider the likelihood and timeline of implementation of the SCWD s proposed ocean desalination project given that its project may eliminate the need for the seawater extraction barrier evaluated herein. Table 7-2 of the SJBGFMP report contains the production and potential yield 2 for the Alternative 6 projects. The yield of the seawater extraction barrier was projected to be 3,000 acre-feet per year (afy). The yield of the in-stream storm and recycled water recharge enhancements were projected to be 800 afy and 8,000 afy, respectively. In addition to the in-stream recharge enhancements, Alternative 6 projected that 400 afy of yield could be obtained from an in-lieu recharge 3 element, which is achieved by providing private groundwater pumpers, such as the San Juan Hills Golf Course, with an alternative water supply 4. The total projected increase in sustainable yield resulting from these programs is 12,200 afy. New recharge capacity of at least 11,000 afy and new production and treatment capacity of about 16,000 afy is required to achieve this yield, assuming the enhanced storm water recharge and in-lieu recharge can be recovered with existing capacity. This technical memorandum (TM) describes the operating schemes and facilities required for each project at a conceptual level 5, discusses some of the potential operational challenges associated with each project, and describes the recommended project alternatives for hydrologic evaluation in Task 3. Preliminary Design of the Seawater Extraction Barrier Initial Well Field Configuration and Capacity The reconnaissance-level engineering work for the SJBGFMP suggested that the plausible range of coastal groundwater production required to create a groundwater barrier to seawater intrusion was 3,000 to 6,000 afy. That same effort suggested that with conventional seawater desalination technology, the treated product water produced would be about 50 percent of the 2 The yield is the volume of potable water that is generated by the project; the volume of raw water pumped by a project would be greater than the yield because of losses in the treatment process. 3 In-lieu recharge is the process of decreasing the amount of groundwater pumped from an aquifer, in combination with increasing supplemental water deliveries to replace the groundwater supply. In-lieu recharge of an aquifer does not include artificial recharge through spreading or injection wells. 4 The SJBA is currently investigating the extent of private water production throughout the San Juan Watershed. The precise pumpers who should or could receive replacement water will be identified in Task 4 of the Program. 5 In this TM, only the general facility needs are described. The scale and scope of the projects may be changed based on the results of the hydrologic analysis in Task 3. The full facility details will be described at that time.

3 Technical Memorandum Page 3 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 extraction barrier production 6. The number of extraction wells needed to achieve a raw water supply was calculated based on the following assumptions: Each well will have a utilization rate of 90 percent. Each well will have an effective production capacity of 800 gallons per minute 7 (gpm). Two backup wells will be included in addition to the minimum number of wells to extract 6,000 afy. Based on these assumptions, the extraction barrier well-field requires at least eight production wells to produce 6,000 afy: six running wells and two backup wells. Figures 1a and 1b show the conceptual well siting areas for eight wells for two similar well-field configurations. A detailed well siting investigation is beyond the scope of work proposed in the investigation -- hence the use of the term well site areas. The hydrologic analysis to be conducted in Task 3 will subsequently refine the well site area locations, the project size, and production rates. Figures 1a and 1b illustrate the application of the spatially-related well siting criteria described in the Task 2.1 TM and used to select the well site areas, including: contours of equal depth of the alluvial aquifer (in feet-below ground surface or ft-bgs), and offsets for storm drains and sewer lines, and septic tanks. The following criteria were used for the initial siting of the extraction barrier well site areas 8 : The depth to the effective base of the freshwater aquifer is approximately equal to or greater than 120 ft-bgs. The well field layout was configured to ensure high production capacity when the barrier is fully developed and to completely cutoff seawater intrusion. Wells must be at least 50 ft away from any sewer line or storm drain (see Table 4 of Task 2.1 TM). Because the diameter of both the sewer lines and the conceptual wells borehole is unknown, the setback between the sewer lines and wells was set at to be 60 feet Wells must be at least 100 ft away from any septic tank (see Table 4 of Task 2.1 TM). The well field in Figure 1a has some wells located on private property (EBW-1, -2, -3, and -4). Figure 1b is an almost identical well field configuration with these well locations shifted slightly (in a hydrologic sense) to lands in public ownership. At the present level of hydrologic evaluation, these locations are essentially identical. These two preliminary well field location maps are 6 The assumed recovery rate (50 percent) of the extraction well barrier desalter was assumed to be the same rate as that assumed by MWDOC, as contained in the presentation entitled "SOCOD Project Decision Making: Spring 2013" prepared in December 2012, and the handout from the SOCOD March 21, 2013 TAC meeting. 7 A production rate of 800 gpm was selected in Task 2 as an initial estimate based on a production capacity of other municipal wells in the basin. This production rate may be revised in Task 3. 8 As noted in the Task 2.1 memo, Orange County requires that well sites be located at least 100 ft away from the FEMA 100-year flood boundary. After further analysis of the existing production wells in the San Juan Basin, it was determined that the majority of wells are inside the 100-year flood boundary as mapped by FEMA and so it is assumed that there is some flexibility in this requirement. As such, this criterion was not considered for preliminary siting of the extraction barrier well field. If the extraction well barrier project is pursued, this assumption will need to be verified by the SJBA.

4 Technical Memorandum Page 4 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 demonstrative of what the extraction barrier well field could look like. The recommended well site areas and associated production rates will be refined in Task 3 when the extraction barrier operations are integrated with the other Program Elements and all the Program Elements are operated together. Potential Challenges for Implementing a Seawater Extraction Barrier The main challenges associated with developing the extraction well barrier include: conflicting land uses at conceptual well sites, siting raw water conveyance and treatment facilities, potential for mobilization of groundwater contamination by leaking underground storage tanks (LUSTs), sensitive species and habitat in the lagoon, and ocean brine disposal. Table 1 summarizes the conflicts, wells affected by the conflict, and potential solutions to the conflicts. The recommended well site areas will be identified in Task 3 and the environmental challenges and their resolution will be described as part of Task 4 of the Program. Preliminary Well Fields for Evaluation of the Seawater Extraction Barrier WEI developed two basic well fields to ascertain the range of sustainable groundwater production in the extraction barrier well field and to test the effectiveness of the extraction barrier. Well Field 1A. Pump 6,000 afy from the six wells located closest to the coast, specifically EBWs 1 through 6. This package of wells represents the wells expected to be used during normal operations. Well Field 1B. Pump 6,000 afy from the wells EBWs 1, 3, 4, 5, 7 and 8. This package of wells represents the wells expected to be used if and when EBWs 2 and 6 are concurrently down for maintenance. The intent in this alternative is to test the robustness when the center of the well field is out of service a worst case operating scenario. If production is sustainable for Well Field 1A then Well Field 2A should be tested. If production for Well Field 1A is not sustainable, then Alternative 2B should be tested. Well Field 2A. Pump 8,000 afy from the eight wells shown in Figures 1a or 1b. If production is sustainable at this rate and the SJBA desires to increase the capacity of the extraction barrier supply then two additional backup wells sites will need to be sited and subsequently tested. Well Field 2B. Pump 4,000 afy from the six wells located closest to the coast, specifically EBWs 1 through 6. The well fields will initially be evaluated as a stand-alone project by Geoscience using the regional fine-grain San Juan Basin Model that was recently updated by the SCWD for the Doheny Desalter Feasibility Investigation. The Geoscience evaluation of the well fields and subsequent revision to the project operations based on the results will be discussed in the Task 3 TM.

5 Technical Memorandum Page 5 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 Conveyance and Treatment Facilities for the Extraction Barrier The preliminary facilities layouts for the extraction barrier program element are shown in Figures 2a and 2b for Well Field 1A and 1B configurations, respectively. These facilities are described below. Groundwater Desalter A groundwater desalter/treatment plant would be required to treat the groundwater supplied by the extraction barrier wells to drinking water standards. Potential locations for this treatment facility have yet to be considered at this stage of the study as specific location options will be evaluated in Task 3. However, for conceptual-level planning purposes, there appear to be a couple of initial options: Vacant property north of Stonehill Dr. and on the east side of San Juan Creek SCWD s 30-acre property located on the east side of the San Juan Creek between Pacific Coast Highway and just south of Stonehill Dr. and includes the District s existing Groundwater Desalter Facility. A new SCWD operations facility/community center is being planned for implementation in the next 10 years and there may not be space available for additional facilities 9. During dry periods, it is expected that most or all of the water pumped by the extraction barrier wells would be of seawater quality, which has a TDS concentration around 35,000 mg/l. During wet periods, groundwater from the upstream side of the well field could also be captured by the extraction barrier wells and would reduce the TDS levels in the water. In either case, a full advanced treatment level (reverse osmosis (RO) typically) would be required to reduce the high TDS levels to drinking water quality and to meet California potable use standards. The treatment plant concept will be refined in Task 3. Raw Water Conveyance Based on preliminary conceptual-level planning, each of the eight extraction wells would be located on 100-ft by 100-ft plots just north of Highway 1 and Doheny Beach. Pipelines would also be needed to convey groundwater pumped by the eight extraction barrier wells to a groundwater treatment plant. Approximately 6,500 feet of pipeline ranging from approximately 12 to 24 inches would be needed to convey the groundwater to the treatment plant. The pipes were sized preliminarily assuming 10,000 afy of groundwater and assuming approximately 2,000 gpm per well at a maximum velocity of 6 ft/s, which is a typical design criteria for pipelines. Based on the groundwater desalter being located near SCWD s existing Groundwater Desalter, the conceptuallevel alignment of the Groundwater Conveyance Pipeline would follow the industrial access road 9 A portion of this property is currently being considered for use by the Doheny Desalination Facility. However, as previously noted on Page 2, for the purpose of defining the project operations and facilities designs, it is assumed that no ocean desalination program is implemented (SOCOD, Doheny Desalination, or other). The development of the Task 4 implementation plan should consider the likelihood and timeline of implementation of the SCWD s proposed ocean desalination project given that the project may eliminate the need for the seawater extraction barrier evaluated herein.

6 Technical Memorandum Page 6 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 just east of the San Juan Creek embankment. The conveyance pipelines will be refined in Task 3 and should take into consideration existing or planned utilities in the area as well as potential community impacts. Brine-Concentrate Disposal Line A typical desalter/treatment plant utilizing seawater will recover about 50 percent of the water and would require disposal of the brine-concentrate flows back to the ocean. This would be most easily accomplished by discharging the brine-concentrate flows to the South Orange County Wastewater Authority s (SOCWA) 57-inch San Juan Creek Ocean Outfall. Additionally, the Chiquita Land Outfall is located on the east side of the San Juan Creek near the potential groundwater treatment plant locations. This line has available capacity and could be used to convey brine-concentrate from the groundwater treatment plant to the San Juan Creek Ocean Outfall. The brine-concentrate disposal options will be refined in Task 3. Product Water Conveyance Treated water from the new groundwater desalter would require product water conveyance facilities to convey product water to end users. For planning purposes, it is assumed that the product water would be conveyed from the new groundwater desalter to the existing Water Importation Pipeline (WIP). The WIP is part of the Joint Regional Water Supply System (JRWSS), which is an entity that owns and operates several pipelines that deliver imported drinking water from the Metropolitan Water District of Southern California (MWD). The JRWSS connects to where MWD regional pipelines terminate in Irvine and brings treated water to the City of San Juan Capistrano s distribution system. SCWD is the Designated Operator of the JRWSS. For this alternative, approximately 250 feet of 12-inch diameter pipeline would be required to convey the product water from the potential groundwater treatment plant location to the WIP. As shown on Figures 2a and 2b, the WIP is shown to be immediately west of the concept treatment location. These facilities requirements will be refined in Task 3. This option would be the least costly as it would require the least amount of piping but would require the participating agencies to make institutional arrangements in sharing this water as a local supply source. The other option (not shown in the figures) would be to construct pipelines to each of the participating agencies water distribution systems. The product water conveyance options will be refined in Task 3. Preliminary Design of the Storm Water and Recycled Water Recharge and Recovery Alternatives Recharge and Recovery Options The SJBGFMP recognized that in-stream recharge is the only viable large-scale recharge method for the San Juan Basin due to the lack of suitable off-stream sites for stormwater storage and recharge, and the inability of the basin to accept large amounts of recharge at a specific site 10. However, during the review of the draft SJBGFMP report many stakeholders commented that there were no recommendations for diversion of stormwater to off-stream recharge facilities 10 A full discussion on the issue can be found in Section 6 of the SJBGFMP on Page 6-7.

7 Technical Memorandum Page 7 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 included in the SJBGFMP. Thus, the SJBGFMP recommended that the conclusion to exclude offstream recharge options should be revisited prior to or during the next SJBGFMP update. Both in-stream and off-stream options were included in the Program scope of work and will be discussed herein. Storm Water Recharge In-Stream Options The term in-stream recharge, as used herein, refers to the use of the existing Arroyo Trabuco and San Juan Creek channels for recharge. These channels contain natural bottoms that are highly permeable and will readily recharge water that is flowing in them. In the SJBGFMP, WEI developed two in-stream recharge concepts for storm water recharge that included: The construction of temporary in-stream T and L levees in San Juan Creek between Stonehill Drive and I-5. The conceptual location for these facilities is shown in Figure 3. Figure 4 shows a typical set of T levees operated for recharge on the Santa Ana River. The construction of rubber dams in San Juan Creek between Stonehill Drive and the I-5, and in the Arroyo Trabuco between its confluence with San Juan Creek and the end of the concrete channel revetment. The conceptual location where recharge is accomplished with rubber dams is shown in Figures 5a, 5b and 5c for rubber dam sizes ranging from 7- ft and 5-ft 11, 9-ft and 7-ft, and 11-ft and 9-ft, respectively. Figure 6 shows a rubber dam in operation on the Santa Ana River. The estimated increase in storm water recharge expected to occur from these recharge approaches requires complex hydrologic modeling that will be performed in Task 3 and thus estimates of new storm water recharge will be developed and presented in the Task 3 TM. Storm Water Recharge Off-Stream Options Pursuant to discussions with the TAC on September 21, 2015, options for off-stream recharge options were requested from and provided by the TAC members. The following table summarizes the known off-stream stormwater basins, provided by the SJBA TAC members, which could be considered for stormwater capture and diversion to recharge. The table lists the basin name, a general description of its location, the existing storage capacity and whether or not the basin overlies the alluvial groundwater basin. Several agencies provided information on the Galivan Basin, and the City of San Juan Capistrano provided information on the Calle Arroyo, Acu Canyon, and La Novia basins. The approximate locations of these basins is shown in Figure A-1 of Appendix A of this TM. 11 The first value corresponds to the rubber dam height for dams on San Juan Creek and the second value corresponds to rubber dam height for dams on the Arroyo Trabuco.

8 Technical Memorandum Page 8 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 Basin Name Existing Overlies Location Description Storage Alluvial (see Appendix A) Capacity Basin? (af) Galivan Basin West of Oso Creek between 1-5 and Cabot Road 215 Yes Calle Arroyo North-west bank of San Juan Creek along Calle Arroyo, between Sundance Dr. and Paseo Esteban 15* Yes Acu Canyon North of Camino Las Ramblas and South of 70* No Connemara Drive (east of I-5) La Novia South-east of La Novia Avenue, near crossing with Via Cerrro Rebal Unknown No *Based on information provided by Eric Bauman of the City of San Juan Capistrano As shown in the table, the storage capacity of the off-stream basins is very small, ranging from 15 af to 215 af. The largest off-stream basin, the Galivan Basin, has been studied by the SJBA in the past and found to be an unfeasible option for recharge due to shallow groundwater, lowpermeability of underlying sediments, small storage, and the landslide and liquefaction potential that could be exacerbated by constant inundation 12,13. Additional detail on the challenges with Galivan Basin are included in Appendix A of this TM. The remaining three basins are very small, and the two basins located off the stream channel (Acu Canyon and La Novia) would need conveyance facilities to discharge the water to the San Juan Creek channel given that they do not overly the alluvial basin. Given these limitations, and that the basins do not meet the design criteria in the WEI Task 2.1 TM, these off-stream basins are not recommended for hydrologic evaluation in Task 3 and the facilities needs will not be described in this TM. The facilities needs and economics of these off-stream areas can be revisited in Task 3. Recycled Water Recharge Pursuant to the FAF Program scope of work, the hydrologic feasibility of recycled water recharge facilities will be conceptualized for in-stream recharge and groundwater injection wells. The instream concepts include: Incidental recharge from the discharge of recycled water in the Arroyo Trabuco downstream of the I-5 and in San Juan Creek between Stonehill Drive and Ortega Highway. The term incidental recharge, as used herein, refers to recharge that occurs in the stream channels by virtue of diverting water into the stream and managing the diversion rate to ensure that all the water recharges in the stream. Other than the discharge point itself there are no new facilities in the channel and no active management 12 Psomas, Galivan Retarding Basin Conjunctive Use Feasibility Study. Prepared for the San Juan Basin Authority, August Psomas, San Juan Basin Conjunctive Use Project Feasibility Study. Prepared for the San Juan Basin Authority January 2006.

9 Technical Memorandum Page 9 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 of the channels. The reaches conceptualized for incidental recharge are shown in Figure 7. A combination of incidental recharge and in-stream temporary T and L levees. The reaches conceptualized for T and L levees and incidental recharge are shown in Figure 3. In-stream impoundments formed by rubber dams. The reaches conceptualized for rubber dams are shown in Figures 5a, 5b, and 5c. A combination of incidental recharge and rubber dams. The reaches conceptualized for rubber dams and incidental recharge are shown in Figures 5a, 5b, and 5c. The same in-stream improvements used for storm water recharge can be used to recharge recycled water during the dry-weather period of May through September. The facility layouts and operating schemes for these concepts will be developed to recharge up to 10,000 afy and are described herein. Balance of Recharge and Discharge and Adaptive Production Management The SJBGFMP included a program element called adaptive production management whose purpose was to set annual groundwater production limits to ensure sustainable production. As contemplated in the SJBGFMP Alternative 1, the annual sustainable production would be established each year based on the volume of groundwater in storage in the spring. The SJBGFMP Alternative 1 included only adaptive production management with existing facilities. The SJBGFMP Alternative 6 includes new recharge in the amount of about 11,500 afy (from the combination of estimated storm water recharge [average of 1,000 afy], recycled water recharge [average of 10,000 afy], and in-lieu recharge through replacement of private pumping with alternative water sources [average of 500 afy]). Therefore, groundwater production will need to increase by 11,500 afy to balance the increase in recharge and produce a project yield of 9,200 afy 14,15. And, because of the hydrogeologic properties of the basin, the location and capacity of new well fields need to be strategically designed to ensure that this new recharge can be safely stored and recovered. Each storm and recycled water recharge alternative considered herein will require a customdesigned well field to recover the water recharged. These well fields were approximately identified and are described herein. Habitat and Liquefaction Constraints on Recharge Figure 8a shows the location of habitat constraints based on Environmentally Sensitive Index Maps produced by NOAA 16. The reaches of San Juan Creek from the Pacific Ocean to near I-5 and the Arroyo Trabuco from its confluence with San Juan Creek and I-5 are habitat for the endangered Steelhead Trout. A portion of the Arroyo Trabuco just downstream from the I-5 14 See Table 7-2 of the SJBGFMP. 15 The 9,200 afy value is based on a the production of 11,500 afy (equal to the new recharge), desalinating that water to meet Title 22 drinking water requirements and a treatment process recovery rate of 80 percent. 16 NOAA Office of and Restoration (

10 Technical Memorandum Page 10 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 crossing is habitat for the endangered Coastal California Gnatcatcher. The reach of San Juan Creek from just upstream of I-5 through the upstream limit of the active management area is habitat for the endangered Arroyo Toad. The recharge alternatives described herein have been developed consistent with these habitat constraints in that they either do not impact them or they include mitigation as described herein. In the absence of the SJBGFMP, the entire groundwater basin in the active management area has been listed as susceptible to liquefaction. Figure 8b shows the areal extent of liquefaction hazard in the basin 17. Liquefaction occurs when vibrations or water pressure within a mass of soil cause the soil particles to lose contact with one another. As a result, the soil behaves like a liquid, has an inability to support weight and can flow down very gentle slopes. This condition is usually temporary and is most often caused by an earthquake vibrating water-saturated fill or unconsolidated soil. The recharge of storm and recycled waters and its subsequent storage and recovery must be managed so as to not exacerbate liquefaction potential. In this investigation liquefaction potential will be evaluated in Task 3 by determining, through numerical groundwater-flow modeling, whether the recharge, storage and recovery of storm and recycled waters would contribute to more frequent and higher groundwater elevations than would have occurred without the SJBGFMP. Recharge Options, Capacities, and How they Work Incidental Recharge Incidental recycled water recharge would occur during the dry-weather period of May through September (a period of 153 days). The location and magnitude of the discharge(s) would be managed to maximize the recharge in the stream system and not discharge to the Pacific Ocean. Two discharge points will be contemplated, one located on San Juan Creek near the Ortega Highway crossing and one on the Arroyo Trabuco near I-5. The stream reaches where incidental recharge can occur are shown in Figure 7. Assuming a nominal flow width of 20 feet and a sustained infiltration rate of 1 foot per day, the incidental recharge capacity of the San Juan Creek and the Arroyo Trabuco for selected reaches are: Reach Description Corresponding Reach on Figure 7 Capacity (afy) San Juan Creek from I-5 to near the Ortega Hwy crossing A 1,080 Arroyo Trabuco from the end of concrete revetment to I-5 B 680 Arroyo Trabuco from its confluence with San Juan Creek to I-5 B + C 980 San Juan Creek from Stonehill Drive to Ortega Highway crossing; and Arroyo Trabuco from its confluence with San Juan Creek to I-5 A + B + C + D 2, California Department of Conservation (

11 Technical Memorandum Page 11 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 T and L Levees and Incidental Recharge Temporary T and L levees would be constructed in the San Juan Creek reach 18 in the area highlighted in yellow on Figure 3, allowing discharge in the channel to flow bank to bank for smaller storm water events, thereby maximizing the wetted area and recharge. Figure 4 is a photograph illustrating T and L levees in operation on the Santa Ana River. The T and L levees would be constructed by October 1 st each year. During the wet period of October 1 st through April 30 th (a period of 212 days), the T and L levees will likely need to be either repaired or completely reconstructed after some storms. The number of maintenance events per year will depend on the number and magnitude of storms each year. The increase in storm water recharged from the construction and operation of the T and L levees will be estimated in Task 3. The SJBA would recharge recycled water using the T and L levees during the dry-weather period of May through September (a period of 153 days). Inundation depths for the recycled water recharge would be managed to ensure that the ponds can be dewatered by infiltration in advance of storms. With about 40 acres of inundation and an assumed sustained infiltration rate of 2 feet per day the T and L levees would provide up to 12,200 afy of recycled water recharge capacity. Combined with incidental recycled water recharge upstream of the T and L levees in San Juan Creek and in the Arroyo Trabuco (the green highlighted areas on Figure 3), the total recycled water recharge capacity of this in-stream recharge combination is about 14,260 afy. Rubber Dams and Incidental Recharge Figures 5a, 5b and 5c show instream rubber dam schemes that can be used to recharge storm and recycled waters (see yellow highlighted areas and the colored bars that represent dam locations: red bars are dams on San Juan Creek; green bars are dams on Arroyo Trabuco). Each scheme consists of rubber dams of different sizes that will create a series of ponds in the stream channels and making discharge in the channel flow bank to bank thereby maximizing the wetted area and recharge. Using rubber dams of different heights results in different amounts of storage, wetted area and number of dams required: entertaining multiple schemes will allow for determining the most cost-efficient scheme in Task 3. Figure 6 is a photograph illustrating a rubber dam with an integrated energy dissipater and grade stabilizer in operation on the Santa Ana River. During the wet period of October 1 st through April 30 th (a period of 212 days), the rubber dams would remain inflated as long as the flow in the channel results in a stage less than one-foot greater than the rubber dam crest. When this stage limit is exceeded, the rubber dam would deflate restoring the full flood capacity of the channel. The rubber dam would re-inflate as soon as the flow in the channel is reduced can again be safely passed with the dams inflated. Thus, after a storm has passed, water will be stored behind the rubber dam for subsequent recharge. Table 2 lists some of the hydraulic characteristics of the three rubber dams configurations discussed herein. For rubber dams of 7 and 5 feet high on San Juan Creek and the Arroyo Trabuco, 18 The Arroyo Trabuco is too narrow to construct T and L levees.

12 Technical Memorandum Page 12 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 respectively, the amount of in-stream storage is about 200 af and the deflation discharge is about 530 cfs and 280 cfs, respectively. Each rubber dam will require the construction of an integrated grade stabilizer and energy dissipater to anchor the dam to the bottom of the channel and protect the channel from erosion near the dam; and each rubber dam will require a fish ladder to enable Steelhead trout migration during storms. The increase in storm water recharged from the construction and operation of the rubber dams will be estimated in Task 3. During the dry-weather period of May through September (a period of 153 days), the SJBA would recharge recycled water. Inundation depths for the recycled water recharge would be shallow to ensure that the ponds can be dewatered by infiltration in advance of storms. Table 2 contains the estimated wetted area and recharge capacity for several different rubber dam sizes. With about 45 acres of inundation area and an assumed sustained infiltration rate of 2 feet per day the rubber dams would provide up to about 16,340 afy of recycled water recharge capacity during the dry-weather period. The potential capacity of the rubber dams conceptualized for each stream system is summarized below: Stream System San Juan Creek Arroyo Trabuco Rubber Dam Height (ft) Capacity During Wet-weather Period (afy) Capacity During Dry-weather Period (afy) Total Capacity (afy) 5 16,960 12,240 29, ,910 13,650 32, ,050 12,310 29, ,630 12,000 28, ,460 2,490 5, ,900 2,090 4, ,730 2,690 6,420 Combined with incidental recycled water recharge upstream of the rubber dams, the total recycled water recharge capacity could be as much as 18,400 afy. Injection Well Recharge The potential areas where injection well fields capable of recharging up to 10,000 afy of recycled water are shown in Figure 9 as the blue shaded areas on San Juan Creek and Arroyo Trabuco. The design assumptions to site these well-fields include: injection capacity of 750 gpm (1,090 afy with 90 percent utilization) well location and capacity sized to meet injection goal, maximize underground retention time and provide for greatest dilution with non-recycled waters matched to down-gradient recovery well capacity minimize rising water

13 Technical Memorandum Page 13 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 The injection wells will likely be located in a linear fashion along San Juan Creek and the Arroyo Trabuco. Injection is assumed to occur-year round. Conceptually, twelve injection wells would be constructed with ten injection wells used to recharge 10,000 afy of recycled water with backup wells. More precise injection well location areas and injection rates will be identified in Task 3 through modeling work, with well locations and injection rates set such that storm and recycled water recharge can be recovered and groundwater elevations are managed to safe levels. Facilities Required for Recharge and Recovery The recycled water facilities required for recharge water options are described below. Recycled Water Source One of the potential the sources of recycled water for the SJBGFMP Alternative 6 recharge is the Jay B. Latham Plant. The plant s current average daily flow is about 6.6 mgd (7,390 afy) and its effluent is discharged to the ocean. The plant will have to be upgraded to enable it to produce Title 22 recycled water for recharge. Additional recycled water may also be available at water recycling plants located upstream of the recharge area. The upstream plants include the Chiquita WRP, Oso Creek, and the 3A Plant. The availability, including seasonal limits, of wastewater or recycled water flows at these upstream plants is being evaluated in coordination with the SJBA member agencies. The amount of recycled water available from each plant will be described in the Task 3 TM. Recycled Water Conveyance Facilities for Incidental Recharge Figure 3 shows the reaches where incidental recharge is proposed and the recycled water facilities to convey recycled water from the Jay B. Latham Plant to the points of discharge. In this option, two recycled water delivery pipelines would be constructed, one leg ending on the Arroyo Trabuco just downstream of I-5 and one leg ending on San Juan Creek just downstream of the Ortega Highway. The recycled water conveyance pipelines would require approximately nine miles of 24-inch diameter pipeline as shown on Figure 7. There are several alignment alternatives for the necessary pipelines needed to convey recycled water from the plant to the recharge locations. Figure 7 shows the initial conceptual alignments based on a preliminary review of potential street options, rights-of-way, and existing land uses. The potential alignment alternatives will be refined in Task 3. The conceptual alignment leaving the Jay B. Latham Plant follows Del Obispo Street to the north and crosses the San Juan Creek either on the Del Obispo bridge or via jack and bore under the channel. On the east side of the channel, the pipe would bifurcate and one branch would head north and the other would head east. The north branch would follow portions of Paseo Adelanto, the Trabuco Creek Trail, Avenida de la Vista, and Camino Capistrano to avoid the congested downtown area and Mission San Juan Capistrano. The east branch would follow Del Obispo to Camino Capistrano and turn south to San Juan Creek Road and cross under I-5. From there, the alignment follows San Juan Creek Road south of the equestrian property all the way to Ortega Highway. This route would avoid the more heavily residential area to the north of San Juan Creek. In addition to turnouts at the end of each line, two to four additional recycled water turnouts will

14 Technical Memorandum Page 14 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 be designed along the alignments to maximize the wetted area and provide operational flexibility. The conveyance options will be refined in Task 3. This recharge option also includes construction of a five-foot temporary earthen berm across San Juan Creek upstream of Stonehill Drive to ensure that no recycled water and other dry-weather flows will discharge to the ocean during dry weather conditions. This berm will be designed to wash out when storms occur and have to be rebuilt prior to discharging recycled water to the Arroyo Trabuco and San Juan Creek. T and L Levees and Incidental Recycled Water Recharge Figure 3 shows show the location of the reaches where T and L levees would be constructed, where incidental recharge would occur and the recycled water facilities to convey recycled water from the Jay B. Latham Plant to the points of discharge. The levees would be constructed from in-situ channel bottom sediments in a balanced cut and fill arrangement. The levees would be about five feet high when constructed and would be designed to wash out during storm events. A recycled water conveyance pipeline would be routed from the Jay B. Latham Plant to the levee recharge areas along San Juan Creek below I-5 as well as the incidental recharge areas along San Juan Creek north of I-5 and along the Arroyo Trabuco. Five to six turnouts from the recycled water conveyance pipeline would be needed to convey water to each of the levee sections to maximize wetted area and recharge and provide operational flexibility. Therefore, to minimize long turnout lateral pipelines, the initial concept is to locate the recycled water conveyance pipeline extending from the Jay B. Latham Plant along the east bank of San Juan Creek. This would require installing the pipeline across the creek from the Jay B. Latham Plant and then under a channel access road on the east side of San Juan Creek. The east bank was initially considered as the west bank contains several 20-inch and larger sewer lines. The Chiquita Land Outfall is located in the east bank and would have to be protected in place if another line was installed near it. Additional options, including utilization of abandoned pipelines in the area, will need to be considered in Task 3 as construction in the channel bank may prove to be infeasible upon further investigation. This main recycled water conveyance pipeline to the levee sections would then split and continue into the recycled water conveyance pipelines that would carry water to the incidental recharge areas described above and as shown in Figure 3. This alternative would also include the same five-foot temporary earthen berm across San Juan Creek upstream from Stonehill Drive to ensure that no recycled water and other dry-weather flows would discharge to the ocean. Rubber Dams and Incidental Recycled Water Recharge Figures 5a, 5b and 5c show the location of the reaches where rubber dams would be constructed, where incidental recharge would occur and the recycled water facilities to convey recycled water from the Jay B. Latham Plant to the points of discharge. Rubber dams would be constructed in San Juan Creek in the reach between I-5 and Stonehill Drive and in the Arroyo Trabuco in the reach from about 2,000 feet upstream of the Del Obispo St. bridge to the confluence with San

15 Technical Memorandum Page 15 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 Juan Creek. The number of rubber dams required is a function of the dam height. The table below summarizes the number of dams required based on logical ranges of inflated rubber dam heights: Inflated Dam Height (ft) San Juan Creek Arroyo Trabuco of Dams Required of Recycled Water Turnouts Required Similar to the other in-stream recharge options, recycled water turn outs would be located downstream of I-5 on San Juan Creek and along the Arroyo Trabuco to maximize wetted area and recharge, and to provide operational flexibility. The number of turnouts required is equal to the number of dams and is listed in the table above. This recharge option would include the same main recycled water conveyance pipeline as the T and L Levee option. However, as shown in Figures 5a, 5b and 5c, the spilt in the line going to the Arroyo Trabuco leg would need to be made at the confluence with San Juan Creek in order to provide turnouts to the rubber dams along Arroyo Trabuco between the confluence and the end of the concrete-lined section of the channel. This split would require tunneling under San Juan Creek. These lines would then continue and connect with the recycled water conveyance pipelines that would carry water to the incidental recharge areas described above. As discussed above, additional options will need to be considered in Task 3 as construction in the channel bank as well as tunneling under the Creek may prove to be infeasible upon further investigation. Injection Wells In this alternative, the method of recycled water recharge would be through injection. The injection well field would be designed to recharge 5,000 to 10,000 afy: Seven injection wells would be required to recharge 5,000 afy with five in continuous use and two serving as back up wells. The locations of these wells could be either along the Arroyo Trabuco upstream of its confluence with San Juan Creek, San Juan Creek upstream of its confluence with the Arroyo Trabuco, or the wells could be split up and located along both creeks. Twelve injection wells would be required to recharge 10,000 afy with ten in continuous use and two serving as back up wells. The locations of these wells will be along the Arroyo Trabuco upstream of its confluence with San Juan Creek and San Juan Creek upstream of its confluence with the Arroyo Trabuco.

16 Technical Memorandum Page 16 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 Figure 9 shows the location of the conceptual injection well fields and the recycled water facilities to convey recycled water from the Jay B. Latham Plant to the points of injection. The exact well locations will be narrowed down following hydrologic analysis in Task 3. This option includes recycled water conveyance pipelines that would follow the same alignments as the incidental recharge option. The location of turnouts to each injection well and their design features will be more fully described when the injection well site areas are more precisely located in Task 3. Recovery Well-Fields The new groundwater recovery wells will be constructed to work with existing wells to recover the new storm and recycled water recharge and ensure there is no rising discharge to the ocean and no groundwater discharge to the ocean. Groundwater production associated with recovering the new recharge is assumed to occur year-round. Twelve wells would be constructed, with ten running continuously to recover 10,000 afy with two backup wells. Seven wells would be constructed with five running continuously to recover 5,000 afy with two backup wells. More precise recovery well site areas and production rates will be identified in Task 3 through modeling work, with well locations and production rates set such that the storm and recycled water recharge can be recovered and high groundwater elevations are managed to safe levels. In the case that groundwater injection causes rising groundwater or other undesirable high groundwater elevations within the injection well field itself and cannot be practically mitigated through injection well siting and capacity adjustments, some of the extraction wells may have to be sited within the injection well field to act as relief wells. This issue will be identified and resolved through groundwater modeling in Task 3. Figure 9 shows the location of the extraction well fields used to recover the injected recycled water. Figure 10 shows the location of the extraction well fields used to recover the recharge of storm and recycled waters. Both recovery options could be configured to recover 5,000 to 10,000 afy of groundwater. The typical well site size would be 100-ft by 100-ft and the locations of the wells would be dependent on the specific recharge alternative, site conditions, and hydrogeological needs. Groundwater Desalter A new or upgraded groundwater desalter/treatment plant will be required to treat the groundwater supplied by the recovery wells to drinking water standards. Given the proximity of the recovery wells to the recharge areas, the recycled water contribution (RWC) of water extracted will likely be greater than 20 percent 19 and so full advanced (RO typically) treatment would be required. Based on the assessment of recycled water contribution in Task 3, the treatment requirements for the groundwater desalter will be refined. Based on a conceptual level of review, there are two initially identified locations being considered for the plant. One plant location option would be to construct a new plant on the 19 The recycled water contribution is the percent of recycled water found in a given production well. The typical recycled water contribution allowed in a recharge project utilizing tertiary recycled water is 20 percent.

17 Technical Memorandum Page 17 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 vacant parcel north of Stonehill Drive. The second plant location option would be to replace the City of San Juan Capistrano s existing groundwater recovery facility or modify its treatment trains to treat the groundwater to the required quality. Both location alternatives are shown in Figures 9 and 10. Raw Water Conveyance Conveyance facilities would be required to convey groundwater pumped by the extraction wells to an existing or new groundwater treatment plant. The preliminary pipeline lengths for the treatment plant options are summarized in the table below. The pipeline type, lengths and sizes will be determined in Task 3 once the well site areas and production capacities are identified. Well Field Option Injection Well Recharge Recovery Well Field (Figure 9) In-Stream Recharge Recovery Well Field (Figure 10) Approximate Length of Raw Water Pipeline (ft) New Plant Site City of San Juan Near Stonehill Capistrano GRF Drive 19,200 11,000 9,800 10,000 Brine-Concentrate Disposal Line Similar to the extraction barrier option, these alternatives would also require a brine-concentrate disposal pipeline to convey the RO reject waste from the plant to the existing Chiquita Land Outfall, which connects to the San Juan Creek Ocean Outfall across San Juan Creek from the Jay B. Latham Plant. The existing land and ocean outfalls are shown in Figures 9 and 10. Product Water Conveyance Product water from both treatment plant options would be conveyed with a new product water conveyance pipeline from the treatment plant to end users. For planning purposes, it is assumed herein that the product water would be conveyed from the plant to the existing WIP with a new tie-in at Stonehill Drive. The product water conveyance facilities alignments and capacities will be determined in Task 3. Recommended Alternatives for Hydrologic Evaluation in Task 3 Baseline First, a baseline alternative is required to establish a baseline yield in the absence of the Program. The City of San Juan Capistrano and the SCWD provided a maximum production goal, which represents the maximum amount of water they would extract from the basin. Production goals for private pumpers were estimated based on recent research performed for the SJBA 20 and from 20 Hunt Thornton Resource Strategies, LLC (2015). Technical Memorandum, Existing Wells, Owners, Locations and Use in the San Juan Basin, California. Prepared for the San Juan Basin Authority, August 20, 2015.

18 Technical Memorandum Page 18 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 the baseline production plan used in model Run 2h of the South Orange Coastal Ocean Desalination Project Phase 3 Extended Pumping and Pilot Plan Testing Volume 3 San Juan Basin Regional Watershed and Groundwater Models (Geoscience, 2013). Actual annual production will vary from year to year and will be determined in Task 3 through modeling, which limits production at wells when groundwater levels drop below sustainability thresholds. The baseline groundwater production goals of the pumpers are summarized as follows: Producer Maximum Production Goal (afy) City of San Juan Capistrano (from 8 GWRP wells) 7,705 City of San Juan Capistrano (from non-gwrp wells) 1,023 South Coast Water District 1,300 Private Pumpers 866 Total 10,894 Program Alternatives Table 3 summarizes the Program Elements and a series of conceptual facilities layouts that could be used to implement each project within a Program Element. For recycled water recharge, two project scales are contemplated: 5,000 afy (half the goal of the SJBGFMP Alternative 6) and 10,000 afy (the full goal of the SJBGFMP Alternative 6). For example in Table 3, a 5,000 afy injection well field along San Juan Creek could be conceptualized in three ways: R8: Adjacent to San Juan Creek upstream of I-5 and north of the Creek R9: Adjacent to San Juan Creek upstream of I-5 and south of the Creek R10: Adjacent to San Juan Creek upstream of I-5 and on both sides of the Creek Projects from each Program Element will be combined together to comprise a Program Alternative. Each Program Alternative includes an extraction well barrier and a recharge and recovery plan. The extraction barrier needs to be evaluated together with the storm and recycled water recharge and recovery projects to realistically establish the capacity of the extraction barrier and evaluate its effects on the existing SCWD and CSJC groundwater recovery facilities. For the seawater extraction barrier, the well package and project size will be determined in Task 3 based on the initial modeling work performed by Geoscience. Table 4 lists the logical combinations of project layouts and recovery schemes from Table 3 for four Program Alternatives: Alternative 6-1: 5,000 afy In-stream Recycled Water Recharge, Enhanced Storm Water Recharge, In-Lieu Recharge, Extraction Well Barrier 6-2: 10,000 afy In-stream Recycled Water Recharge, Enhanced Storm Water Recharge, In-Lieu Recharge, Extraction Well Barrier

19 Technical Memorandum Page 19 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, : 5,000 afy Injection, In-Lieu Recharge, Extraction Well Barrier 6-4: 10,000 afy Injection, In-Lieu Recharge, Extraction Well Barrier Each Program Alternative will require a unique adaptive production management plan, which will be refined and articulated in Task 3. The generalized recovery plans shown in Tables 3 and 4 include the baseline production of the City and SCWD, whose production goals for existing wells will remain the same as articulated above for the baseline alternative. The private pumper production is reduced by 500 afy to achieve the in-lieu recharge goal. It is only practical to model some of the project combinations listed in Table 4. There are a minimum of five alternatives that need to be hydrologically evaluated in Task 3 the baseline and one representation of each of the four Program Alternatives. The four recommended project combinations for hydrologic evaluation are highlighted in yellow in Table 4 and summarized as follows: Program Alternative Extraction Barrier Raw-water Production (afy) Program Element and Description Recharge Options and Capacities Recovery Requirements New Yield (afy) Baseline na na na na In-stream recharge via incidental recharge and rubber Dams on San SJBGFMP Seven new TBD* Juan Creek: 1,000 afy of storm water; 6-1 wells 5,000 afy of recycled water; 8, afy in-lieu SJBGFMP 6-2 SJBGFMP 6-3 SJBGFMP 6-4 TBD* TBD* TBD* In-stream recharge via incidental recharge and rubber Dams on Arroyo Trabuco and San Juan Creek: 1,000 afy of storm water; 10,000 afy of recycled water; 500 afy in-lieu 5,000 afy of recycled water injection along San Juan Creek; 500 afy in-lieu recharge 10,000 afy of recycled water injection along San Juan Creek and Arroyo Trabuco; 500 afy in-lieu recharge Twelve new wells Seven new wells Twelve new wells 12,200 7,400 11,400 * For the seawater extraction barrier, the well package and project size will be determined in Task 3 based on the initial modeling work performed by Geoscience.

20 Technical Memorandum Page 20 of 20 Subject: Task 2 Technical Memorandum September 8, 2015; revised December 7, 2015 The basis for selecting the specific project combinations and sizes for the Four Program alternatives is described below: Initially the groundwater extraction capacity for the Seawater Extraction Barrier will be based on the initial Geoscience evaluation in Task 3. Geoscience will evaluate the barrier at an initial capacity of 6,000 afy. The recharge capacity using only incidental recharge in San Juan Creek and the Arroyo Trabuco is too low to achieve 5,000 afy and thus it will not be further evaluated on its own. The recycled water recharge capacity for both the T and L levees and rubber dam options for in-stream recharge both exceed the minimum recharge capacity required to meet the yield goals and thus only two alternatives for in-stream recharge will be hydrologically evaluated, one each for 5,000 and 10,000 afy. For this physical evaluation, both the 5,000 and 10,000 afy alternatives for in-stream recharge will be modeled based on the use of rubber dams because it will maximize the storm water recharge potential (as described earlier, the rubber dams have a larger combined recharge capacity than the T and L levees). Although there is sufficient capacity for meeting the recharge goals using only the rubber dams, incidental recharge upstream of the rubber dams will support riparian vegetation. For the 5,000 afy injection alternative, all water will be injected along San Juan Creek because there appear to be more potential well siting areas in this arm of the basin. The 10,000 afy injection alternative will be evaluated with half of the capacity (5,000 afy) being injected along each of the upstream reaches of San Juan Creek and the Arroyo Trabuco as shown in Figure 9. The general areas for locating the extraction wells to manage groundwater levels and recover the injected water is also shown in Figure 9. Attachments Tables 1 to 4 Figures 1 to 10 Appendix A Off-Stream Recharge Areas. Appendix B - COMMENTS AND RESPONSES TO JULY 23, 2015 DRAFT TASK MEMORANDUM DEVELOP PRELIMINARY ALTERNATIVES FOR A SEAWATER EXTRACTION BARRIER) Appendix C - COMMENTS AND RESPONSES TO JULY 23, 2015 DRAFT TASK MEMORANDUM 2.2/2.3 - DEVELOP PRELIMINARY ALTERNATIVES FOR STORM WATER RECHARGE, AND RECYCLED WATER RECHARGE FACILITIES AND DEVELOP PRELIMINARY ADAPTIVE PRODUCTION MANAGEMENT ALTERNATIVES Appendix D - COMMENTS AND RESPONSES TO SEPTEMBER 8, 2015 DRAFT PRELIMINARY ALTERNATIVE DESCRIPTIONS FOR THE SAN JUAN BASIN GROUNDWATER AND DESALINATION OPTIMIZATION PROGRAM ELEMENTS (TASKS 2.2, 2.3, 2.4 AND 2.5 OF THE FAF GRANT SCOPE OF WORK)

21 Table 1 Potential Conflicts and Solutions for Implementing a Seawater Extraction Barrier Conflict Land-Use Water Conveyance Water Quality Lagoon Habitat Ocean Brine Disposal Possibly Affected Wells EBW-1 EBW-2 EBW-4 EBW-3 EBW-5 EBW-8 EBW-6 EBW-7 EBW-1B EBW-2B EBW-3B All Wells All Wells All Wells All Wells Conflict Description Land is privately owned; competing land use with planned future development on site. Owner is not listed. Assume owner is private and there is a competing land use. Land is publicly owned by Orange County Flood Control. Land is publicly owned by SOCWA. Space is limited on the property based on siting criteria. Land is publicly owned by City of Dana Point; potentially competing land use. Land is publicly owned by the California Department of State Parks. Permitting is difficult. Water lines needed on public or private properties. Crossing under San Juan Creek required. There are four known LUST sites in proximity to the proposed well field. Pumping by the wells could cause migration of groundwater contaminants into the well field. Lower groundwater levels in the vicinity of the lagoon could impact water availability to the lagoon. Other potential conflicts are unknown. An ocean outfall exists, but permitting is difficult. Additional brine-concentrate flow in conjunction with withdrawal of wastewater flows will result in changes in outfall water quality. Increase in toxicity may be of particular concern with current permit requirements. Conflict Solution An agreement between SJBA and the owners will be required to proceed. Easements or land purchase will be required on most of pipelines segments. Permit from Orange County Flood Control District will be required for Creek crossing. Treatment technology may need to be incorporated at the affected wells or the desalination facility to handle the constituents of concern. If the lagoon is impacted significantly, some of the water extracted from the extraction barrier wells will be diverted into the lagoon. Existing San Juan Creek outfall can be used for brine disposal. The SJBA will need to work in conjunction with SOCWA in assessing potential impacts to outfall water quality and current permit requirements. SJBA/SOCWA will need to work with the San Diego Regional Water Quality Control Board to address and update the current water quality limitations for this outfall. Changes to the outfall facilities may be required to mitigation water quality impacts _Table_EWB v3.xlsx--table-1_conflict 9/8/2015

22 Table 2 Recharge Capacity of Selected Rubber Dam Configurations for In-Stream recharge Stream System San Juan Creek Arroyo Trabuco Combined Facilities Recharge Rates Combined Nominal Recharge Rates Rubber Dam Height (ft) Infiltration (ft/day) Infiltration (ft/day) , , , , , , , and 5 15, and 7 13, and 9 14, and 5 9 and 7 11 and 9 of Rubber Dams Length of Permeable Inundation Area (ft) Permeable Inundation Area (acres) Bottom Width Rubber Dam (ft) Top Width Rubber Dam (ft) Recharge Rate (afd) Recharge Rate (cfs) Storage Capacity (af) Average Deflation Discharge (cfs) Extension of Inundation Area above Improved Channel (ft) _Table 1 Rech_Alts_test.xlsx -- Table_2_RubberDams Created 07/09/2015 Printed 9/4/2015

23 Program Description Elements Figure(s) Showing Facilities Seawater Extraction Barrier Extraction Barrier Wells E1 Extraction well package (up to 6,000 afy, final volume TBD) 2a or 2b (TBD) In stream Recharge In Channel Recharge Improvements for Storm and Recycled Water Recharge Rubber Dams R1 San Juan Creek from Stonehill Drive to the I 5 Figures 5a, 5b, 5c (red bars) R2 Arroyo Trabuco from confluence with San Juan Creek to end of concrete revetment Figures 5a, 5b, 5c (green bars) Incidental Recharge R3 San Juan Creek from I 5 to near the Ortega Hwy Crossing Reach A on Fig. 7 R4 Arroyo Trabuco from the end of concrete revetment to I 5 Reach B on Fig. 7 R5 Arroyo Trabuco from its confluence with San Juan Creek to I 5 Reach B + C on Fig. 7 R6 San Juan Creek from Stonehill Drive to the Ortega Highway Crossing and the Arroyo Trabuco from its confluence with San Juan Creek to I 5 Reach A + B +C + D on Fig. 7 "T" and "L" Levees Year Round R7 San Juan Creek from Stonehill Drive to the I 5 Figure 3 Injection Wells 5,000 afy Injection Well field (Recycled Water Source) R8 Adjacent to the north side of San Juan Creek upstream of I 5 Eastern Area on Fig. 9 R9 Adjacent to the south side of San Juan Creek upstream of I 5 Eastern Area on Fig. 9 R10 Adjacent to both sides of the San Juan Creek upstream of I 5 Eastern Area on Fig. 9 R11 Table 3 List of Program Elements and Descriptions Adjacent to the west side of Arroyo Trabuco upstream of confluence with San Juan Creek Western Area on Fig. 9 R12 Adjacent to the east side of Arroyo Trabuco upstream of confluence with San Juan Creek Western Area on Fig. 9 R13 Adjacent to both sides of Arroyo Trabuco upstream of confluence with San Juan Creek Western Area on Fig. 9 10,000 afy Injection Well field (Recycled Water Source) R14 Adjacent to the north side of San Juan Creek upstream of I 5 Eastern Area on Fig. 9 R15 Adjacent to the south side of San Juan Creek upstream of I 5 Eastern Area on Fig. 9 R16 Adjacent to both sides of the San Juan Creek upstream of I 5 Eastern Area on Fig. 9 R17 Adjacent to the west side of Arroyo Trabuco upstream of confluence with San Juan Creek Western Area on Fig. 9 R18 Adjacent to the east side of Arroyo Trabuco upstream of confluence with San Juan Creek Western Area on Fig. 9 R19 Adjacent to both sides of Arroyo Trabuco upstream of confluence with San Juan Creek Western Area on Fig. 9 Groundwater Production Baseline Production P0 Production from existing wells, which are assumed to have excess capacity to capture enhanced Blue and green circles on Figures 9 stormwater and in lieu recharge and 10 5,000 afy Production Well field P1 Well package to recover in channel recycled water recharge Figure 10 P2 San Juan Creek well package to recover injection well recharge East recovery field on Fig. 9 P3 Arroyo Trabuco well package to recover injection well recharge West recovery field on Fig. 9 10,000 afy Production Well field P4 Well package to recover in channel recycled water recharge Figure 10 P5 San Juan Creek well package to recover injection well recharge East recovery field on Fig. 9 P6 Arroyo Trabuco well package to recover injection well recharge West recovery field on Fig. 9 Tables 3 and 4 New Table 3 Universe of PE Created 07/23/2015 Printed 12/6/2015

24 Table 4 Logical Combinations of the Program Element Projects from Table 3 to Create Four Program Alternatives Program Alternatives Recharge Options Production Plan New Yield 1 5,000 afy In stream Recycled Water Recharge, Enhanced Stormwater Recharge, In Lieu Recharge, Extraction Well Barrier a R1 P0+P1+E1 8,200 b R1+R3+R4 P0+P1+E1 8,200 c R7 P0+P1+E1 8,200 d R3+R5+R7 P0+P1+E1 8, ,000 afy In stream Recycled Water Recharge, Enhanced Stormwater Recharge, In Lieu Recharge, Extraction Well Barrier a R1+R2 P0+P4+E1 12,200 b R1+R2+R3+R4 P0+P4+E1 12,200 c R3+R5+R7 P0+P4+E1 12, ,000 afy Injection, In Lieu Recharge, Extraction Well Barrier a R8 or R9 or R10 P0+P2+E1 7,400 b R11 or R12 or R13 P0+P3+E1 7,400 c R10+R13 P0+P2+P3+E1 7, ,000 afy Injection, In Lieu Recharge, Extraction Well Barrier a R14 or R15 or R16 P0+P5+E1 11,400 b R17 or R18 or R19 P0+P6+E1 11,400 c R16+R19 P0+P5+P6+E1 11,400 Recommended alternative for hydrologic evaluation in Task 3. Refer to Table 3 for the definition of each short hand scheme used to describe the recharge and production options (e.g. R1 is the rubber dam alternative on San Juan Creek from Stonehill Drive to the I 5). "+" indicates that these project alternatives are performed at the same time. "or" indicates that one of the listed project alternatives can be selected to achieve the program scale. Assumes 1,000 afy of stormwater recharge. Actual stormwater recharge will be determined in Task Tables 2 and 3 List of Alternatives Table 4 Logical Combination Created 07/23/2015 Printed 9/4/2015

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30 Figure 4 T Levees in the Santa Ana River

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34 Figure 6 Rubber Dam in the Santa Ana River Source: OCWD

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40 Appendix A Page 1 of 2 Appendix A Storm Water Recharge Off Stream Options The following table summarizes the known off stream stormwater basins, provided by the SJBA TAC members, which could be improved for stormwater capture and diversion to recharge: Basin Name Location Description (see Appendix A) Existing Storage Capacity (acre feet) Overlies Alluvial Basin? Galivan Basin West of Oso Creek between 1 5 and Cabot Road 215 Yes Calle Arroyo Acu Canyon North west bank of San Juan Creek along Calle Arroyo, between Sundance Dr. and Paseo Esteban North of Camino Las Ramblas and South of Connemara Drive (east of I 5) 15 Yes 70 No La Novia South east of La Novia Avenue, near crossing with Via Cerrro Rebal unknown No The approximate locations of these basins is shown in Figure A 1. Galivan Basin The Galivan Basin is owned and managed by Orange County to reduce flood damage on Oso Creek. The Galivan Basin is a flow by basin that reduces the peak discharge for extreme events by scalping the peak part of the Oso Creek discharge through a side channel spillway into the facility. The water diverted into the facility subsequently infiltrates into the ground or is lost to evaporation. For high frequency storm events (e.g. low flow storm events), the basin receives no storm water inflow from Oso Creek. Galivan Basin has previously been evaluated as a potential facility for stormwater capture and recharge (PSOMAS, ; ). Both evaluations concluded that storm water recharge at Galivan Basin is unfeasible. According to these studies, the main limitations to using Galivan Basin for stormwater recharge are: Groundwater in the area is too shallow likely less than 5 feet below ground surface. The sediments underlying the basin are not conducive to recharge. Storage in the alluvial basin in the area is limited due to the shallowness of the Capistrano Formation bedrock. 1 Psomas, Galivan Retarding Basin Conjunctive Use Feasibility Study. Prepared for the San Juan Basin Authority, August Psomas, San Juan Basin Conjunctive Use Project Feasibility Study. Prepared for the San Juan Basin Authority January 2006.

41 Appendix A Page 2 of 2 The basin is adjacent to areas of geologic hazards such as landslides and liquefaction, which can be exacerbated by continuous inundation of the basin. Groundwater samples collected in the area indicated that TDS concentrations are high (as much as 8,960 mg/l). An increase in storm water recharge in Galivan Basin would thus force this degraded water further downstream into production wells and contribute to increases in TDS at those wells. Due to these recharge limitations at Galivan Basin, its use as a recharge alternative will not be analyzed further.

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