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SR 02-27-2018 3D City Council Report City Council Meeting: February 27, 2018 Agenda Item: 3.D 1 of 4 To: Mayor and City Council From: Susan Cline, Director, Public Works, Water Resources Subject: Differential Interferometry Synthetic Aperture Radar (DInSAR) Contract Modification Recommended Action Staff recommends that the City Council authorize the City Manager to negotiate and execute a second modification to agreement #3200 in the amount of $100,000 with Earth Consultants International, Inc. (ECI), a California-based company, for a supplemental Differential Interferometry Synthetic Aperture Radar (DInSAR) study of the Santa Monica Groundwater Basin (SMGB) to assist in identifying sustainable amounts of water available for future potable use and extend the term of the agreement. This will result in a five-year amended agreement with a new total amount not to exceed $172,740 with future year funding contingent on Council budget approval. Executive Summary A preliminary analysis of the Santa Monica Basin indicates there may be additional groundwater pathways that were previously unknown. Utilization of water from the Santa Monica Basin is a fundamental strategy in the City’s efforts to meet its goal of water self-sufficiency, and to maintain safe, sustainable local sources of water for Santa Monica. Additional study would determine whether those pathways exist or not. Therefore, staff recommends that Council approve a second modification to ECI contract #3200 in the amount of $100,000 and extend the term by 3 years to November 2021. ECI would conduct the required supplemental study as well as annual updates of the supplemental study to incorporate any new data that may become available. Background On November 15, 2016, the City retained ECI to conduct a preliminary Differential Interferometry Synthetic Aperture Radar (DInSAR) study to assess, among other things, whether historic pumping activities at the City’s well fields may have caused compaction of the aquifer sediments, which could contribute to less water being produced. The 2 of 4 preliminary study did not find evidence of significant sediment compaction but did identify previously unknown pathways for natural recharge of the City’s aquifers. If confirmed by this supplemental study, these previously unknown hydrogeologic pathways could be used to help site additional water supply wells in order to achieve and sustain long-term water self-sufficiency for the City. DInSAR is a satellite-based radar technology that is capable of measuring very small changes in surface elevation. The level of detail and broad area coverage that DInSAR data can provide makes it a valuable and cost-effective tool for the management of local groundwater resources and sustainability. The method has been used for more than 20 years by government agencies and research institutions to assess the conditions of groundwater basins and monitor land subsidence in areas with significant groundwater extraction rates. Discussion Staff now seeks to build on the preliminary work done with ECI to better understand how these newly identified pathways could benefit the City’s groundwater resources. If confirmed by this study, the seasonal recharge could increase the current estimate of how much groundwater the City can sustainably pump from the Santa Monica Basin and provide a powerful planning tool for adaptive management of the City’s groundwater resources. The additional data would also be useful for the City’s required Sustainable Groundwater Management Act (SGMA) efforts including creation of a state- mandated Groundwater Sustainability Plan for the Santa Monica Basin by 2022. The supplemental study would involve conducting a sequential analysis of paired interferograms (radar images), with an emphasis on more recent data obtained during the annual wet and dry seasons (October-April and May-September, respectively). The objective of the study is to determine whether short-term cyclical positive deformation (rising land levels) is due to inflow of seasonal natural recharge into the groundwater basin. These data, if confirmed, would be useful in refining calculations of basin 3 of 4 recharge volumes and for planning sustainable pumping schedules for the City’s long- term water self-sufficiency objectives to be discussed with Council this summer. Vendor/Consultant Selection In October 2016, the City issued a Request for Proposals (RFP) for a DInSAR study of potential land elevation changes related to groundwater extractions and recharge for the Santa Monica Basin. The RFP was sent to five consulting firms drawn from a prequalified list. Of the five firms, two responded. Responses to the RFP were reviewed by a selection panel of staff from the Public Works Department.  Tetra Tech  Earth Consultants International, Inc. (ECI) Evaluation was based on the following selection criteria: (previous experience, references, ability to deliver the scope of work, and specialized qualifications). Based on this criteria and criteria in SMMC 2.24.073, staff recommends ECI as the best qualified firm to perform DInSAR study. Completion of additional DInSAR analysis is critical to updating the preliminary sustainable yield analysis and updating the City’s Sustainable Water Master Plan, which are currently scheduled for presentation to City Council in summer 2018. Due to time constraints and the fact that ECI successfully completed the initial study, a second modification to the existing contract with ECI is recommended as the most cost effective and efficient way for the City to proceed. Financial Impacts and Budget Actions The agreement modification to be awarded to Earth Consultants International, Inc. is $100,000, for an amended agreement total not to exceed $172,740. Funds are available in the FY 2017-18 Capital Improvement Program budget in account C259223.589000. Future year funding is contingent on Council budget approval. 4 of 4 Prepared By: Thomas Watson, Water Resources Protection Programs Coordinator Approved Forwarded to Council Attachments: A. Santa Monica Basin DInSAR Report - September 2017 B. Oaks Initiative Disclosure Form - Earth Consultants International, Inc. 1642 E. Fourth Street  Santa Ana  California  92701  USA Telephones: 714-412-2654 & 544-5321  Facsimile: 714-494-4930  www.earthconsultants.com ECI Project No. 3615 September 15, 2017 To: City of Santa Monica Water Resources Protections Programs 1212 5th Street, 3rd Floor Santa Monica, California 90401 Attention: Mr. Thomas L. Watson, PG Water Resources Protection Programs Coordinator Subject: Report – Baseline Study to Evaluate the Value of Using Differential Interferometry Synthetic Aperture Radar (DInSAR) to Monitor Land Elevation Changes Related to Groundwater Extractions and Recharge for the Santa Monica Basin Earth Consultants International (ECI) are pleased to present this report describing the scope of work, methodology, findings and conclusions of a baseline study we conducted at your request and per your authorization for the Santa Monica Groundwater Basin (SMGB) region using Differential Satellite Interferometry (DInSAR). The purpose of this baseline study was to assess whether the rise and drop of the water levels in the aquifers in the SMGB area manifest at the surface as uplift and subsidence, respectively. We used DInSAR as the detection tool, given that this cost-effective method has a proven record of showing ground surface deformation associated with groundwater extractions and recharge under favorable circumstances in several other groundwater basins throughout the Western United States. As part of this study we downloaded, processed and analyzed dozens of SAR images dating from 1992 (when these satellite-based images were first collected) through 2016. In total, we generated 47 interferograms spanning the time period of interest, with this number dictated by the availability and quality of the radar images. Three of these interferograms covered the period between 1992 and 1996, a period when the City was pumping extensively from the aquifers, before the discovery of volatile organic carbons (VOCs) in the groundwater prompted the temporary cessation of pumping and/or minimized extractions within selected wellfields in the SMGB. This time period also spanned the 1994 Northridge earthquake, and we used the ground deformations associated with that tectonic event as a measure of the effectiveness of DInSAR to detect vertical movements in the region. Thirty-three of the interferograms we prepared covered the period between 1996 and 2010, when groundwater extraction from the basin was minimal, in an effort to observe potential land surface rebound while natural recharge continued. Finally, eleven interferograms covered the time period between 2010 and 2016, after pumping began again. The interferograms analyzed for this study show very little surface deformation occurring in the study area in the period between 1992 and 2016, and any correlations between the surface ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Cover Letter - Page 2 deformations observed and changes in the water level of the underlying water-producing aquifer are not statistically significant. The interferogram produced from SAR images from 1992 and 1996, which span the 1994 Northridge earthquake, shows ground deformation in the epicentral area at a scale in close agreement with survey-derived measurements of uplift. This in turn indicates that the interferograms generated for this study were properly processed and thus, that the lack of appreciable surface deformation indicated by the data is truly representative of the study area during the period covered by the analysis. We conclude from these analyses that the fine-grained, compressible layers in the aquifer are not responding to changes in the water level resulting from extractions and recharge. We postulate that the reason for this is that these strata were irreversibly compacted due to excessive pumping in the 1930s and 1940s, when the water levels in the aquifer were several tens of feet lower than the levels measured between 1992 and 2016. If future groundwater extractions in the SMGB cause the water levels to drop to or below the 1930-1940 levels, it is possible that the SMGB area could experience subsidence at levels detectable by the InSAR method. For this reason, we recommend continued monitoring of the SMGB region using DInSAR, augmented with several permanent, automated GPS monitoring stations. We hope that the information presented in the following report provides you with the data you need at this time. We appreciate the opportunity to provide these services to the City of Santa Monica. Should you have any questions regarding the above, please do not hesitate to contact us at your earliest convenience. Respectfully submitted, EARTH CONSULTANTS INTERNATIONAL, INC. Registered Geologists, Certified Engineering Geologists and Certified Hydrogeologists Anders Hogrelius Eric Hendrix, CHg 431, CEG 1531 Project Consultant Senior Project Consultant Tania Gonzalez, CEG 1859 Vice-President ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Table of Contents – Page i TABLE of CONTENTS Section Page No. 1.0 INTRODUCTION .............................................................................................................. 1 1.1 Purpose of the Study .......................................................................................................... 1 1.2 Regulatory and Practical Framework Guiding the Study ..................................................... 1 2.0 TECHNICAL BACKGROUND ............................................................................................ 2 2.1 Differential Interferometry Synthetic Aperture Radar (DInSAR) ........................................... 2 2.2 Ground Deformation Resulting From Groundwater Extractions .......................................... 3 2.3 Hydrogeologic Framework of the Santa Monica Groundwater Basin .................................. 4 2.3.1 Subbasins of the Santa Monica Groundwater Basin ................................................................ 6 3.0 WORK COMPLETED AND METHODOLOGY FOLLOWED ............................................... 7 4.0 FINDINGS AND DISCUSSION ......................................................................................... 9 4.1 Basin Key Wells and Extraction Centers ............................................................................. 9 4.2 DInSAR Results ................................................................................................................ 11 4.3 Correlation Between Interferograms and Key Well Data ................................................... 11 4.4 Other Sources of Ground Deformation in the Target Area ................................................ 13 5.0 CONCLUSIONS AND RECOMMENDATIONS ................................................................ 13 5.1 Conclusions ..................................................................................................................... 13 5.2 Recommendations ........................................................................................................... 13 6.0 REFERENCES AND SOURCES .......................................................................................... 15 TABLES (in the back) Table 1: Santa Monica Groundwater Basin Production History FIGURES and PLATE (in the back) Figure 1: Site Location Map Figure 2: Santa Monica Groundwater Basin, Subbasins and Well Locations Figure 3: Well Schematics and Stratigraphic Profile, Historical Water Depth, Rainfall, Groundwater Production and Surface Deformation for Charnock Well No. 16 Figure 4: Well Schematics and Stratigraphic Profile, Historical Water Depth, Rainfall, Groundwater Production and Surface Deformation for Santa Monica Well No. 3 Figure 5: Well Schematics and Stratigraphic Profile, Historical Water Depth, Rainfall, Groundwater Production and Surface Deformation for Arcadia Well No. 4 Figure 6: Well Schematics and Stratigraphic Profile, Historical Water Depth, Rainfall, Groundwater Production and Surface Deformation for Santa Monica Well No. 1 Figure 7: Composite Hydrograph for the Charnock Subbasin Comparing Pre-SAR-Era and SAR-Era Water Levels ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Table of Contents - Page ii Figure 8: Composite Hydrograph for the Arcadia Subbasin Comparing Pre-SAR-Era and SAR-Era Water Levels Figure 9: Hydrograph for the Olympic Subbasin (Santa Monica Well No. 3) Comparing Pre-SAR- Era and SAR-Era Water Levels Plate 1: Surface Deformation and Hydrologic Data at Pumping Centers, Santa Monica Groundwater Basin APPENDICES Appendix A: Additional Technical Information Regarding the DInSAR Method and Statistical Analyses Completed as Part of This Study Appendix B: Interferograms Analyzed Appendix C: Logs of Key Wells, Santa Monica Groundwater Basin ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 1 BASELINE STUDY TO EVALUATE THE EFFECTIVENESS OF DIFFERENTIAL INTERFEROMETRY SYNTHETIC APERTURE RADAR (DInSAR) TO IDENTIFY LONG-TERM LAND ELEVATION CHANGES RELATED TO GROUNDWATER EXTRACTIONS FOR THE SANTA MONICA BASIN 1.0 INTRODUCTION 1.1 PURPOSE OF THE STUDY At the request of the City of Santa Monica (City), Earth Consultants International (ECI) conducted a initial baseline study for the Santa Monica Groundwater Basin (SMGB) area using satellite-based Differential Interferometry Synthetic Aperture Radar (DInSAR). The purpose of the study was to evaluate whether land surface elevation changes in the form of negative deformation (subsidence) were discernible between 1992 and 2016 in the area overlying the SMGB or its subbasins (Figures 1 and 2). Subsidence of the ground surface in groundwater basins is typically the result of unsustainable groundwater withdrawals, and can, over time, affect aquifer characteristics by the irreversible compaction of sediments in the subsurface. A second-phase investigation will assess for the potential to discern inflow of natural recharge into the SMGB. 1.2 REGULATORY AND PRACTICAL FRAMEWORK GUIDING THE STUDY The SMGB is currently not adjudicated. In 2014, the State passed the California Sustainable Groundwater Management Act (SGMA), a piece of legislation comprised of three separate bills, including Assembly Bill 1739, Senate Bill 1319, and Senate Bill 1168 (California Department of Water Resources - CDWR, 2015). The SGMA, which went into effect on January 1, 2015, requires the formation of local Groundwater Sustainability Agencies (GSAs) whose role is to monitor and ensure that groundwater resources in the State are used and managed sustainably. As a result of the drought that California experienced during 2010 through 2016, and the increasingly larger number of water supply users, including agricultural, industrial, commercial and residential interests, many of the groundwater basins in central and southern California have been and are being mined (pumped) in excess of their natural rate of replenishment, with a resultant drop in the groundwater table. In some areas this in turn has led to compaction of the geologic sediments and significant land subsidence, with a concomitant damage to utilities, public infrastructure, and other natural resources such as groundwater-fed streams and springs. Senate Bill 1168 requires, among other things, the GSAs regularly measure and monitor the depth to groundwater in their basin, and calculate the maximum amount of water that can be pumped out of the basin in a year without causing an “undesirable result.” This amount of groundwater is referred to as “the sustainable yield.” An “undesirable result” can include any of the following: 1) chronic or persistent lowering of the groundwater level, 2) significant and unreasonable reduction in groundwater storage, 3) significant and unreasonable seawater intrusion, 4) significant and unreasonable degradation of water quality, 5) significant and unreasonable land subsidence, and 6) depletions of surface water that result in significant and unreasonable adverse impacts on beneficial uses (Water Education Foundation, 2015). Because groundwater is a resource not directly observable, the monitoring for any of these conditions is not particularly straightforward. Monitoring of available groundwater in storage is strongly contingent upon measurements of the static water levels in a network of piezometers and wells installed into the aquifers. This is readily done in existing wells, but in densely urbanized areas, such as Santa Monica, it is difficult to ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 2 add new monitoring stations in strategic places. However, because the lowering of the groundwater level and the reduction in groundwater storage is often accompanied by a lowering of the ground surface (subsidence), a method that has proven useful in some areas is to correlate the deformation of the ground surface to the rise or fall of the water level in the underlying aquifer(s). Some of the regions where this method has been used successfully include California's Central Valley, the Main Aquifer in the Orange County Groundwater Basin, and areas around Las Vegas, Nevada (Borchers et al., 2014). Furthermore, monitoring of ground deformation can help inform how planned groundwater extractions might impact a region, particularly in areas such as the City of Santa Monica, where future water use projections may possibly exceed the available groundwater supply and sustainable yield of the SMGB (Kennedy/Jenks Consultants - KJC, 2015; Richard Slade & Associates - RSA, 2017). Traditionally, the monitoring of ground surface deformation has been conducted using spirit- leveling (surveying) techniques. This method is very precise but time-consuming, and spatially and temporally sparse, as measurements are made at relatively few locations, and at temporal intervals typically measured in months or years (e.g., Poland et al., 1984). Other techniques that are used include a network of Global Positioning System (GPS) surveys, permanent continuous GPS measurements, and DInSAR. DInSAR has been used for more than 20 years by government agencies and research institutions to assess the conditions of topographic elevation changes, to monitor groundwater basins in order to quantify potential sediment consolidation, and to monitor surface deformation resulting from the extraction and/or recharge of groundwater (for a few examples of these studies, refer to the links provided in the References section of this report). Compared with the other direct-measurement methods briefly described above, DInSAR is considered more effective, as this method maps both the magnitude of the vertical deformation and the spatial distribution of the affected areas (i.e., it is sensitive to changes in land elevation and can cover large regional areas). Provided a relatively suitable number of satellite passes are available, DInSAR can also yield measurements over relatively short periods of time. Finally, relatively recent developments in the processing of interferograms to provide time-series analyses of the deformation have further increased the potential value of DInSAR as a tool for the monitoring of aquifers. The level of detail and broad areal coverage that DInSAR can provide makes it a potentially valuable tool for local GSAs looking to adopt sustainable management plans in response to the requirements of the California Sustainable Groundwater Management Act (SGMA) of 2014. 2.0 TECHNICAL BACKGROUND 2.1 DIFFERENTIAL INTERFEROMETRY SYNTHETIC APERTURE RADAR (DInSAR) The DInSAR method relies on the processing and comparison of two Synthetic Aperture Radar (SAR) images of the same portion of the Earth’s surface taken by the same satellite system on two different passes. The product resulting from the digital comparison of the two SAR images is called an interferogram; the resulting image illustrates and quantifies the changes in the ground surface that occurred between the two satellite passes used in the analysis. The method can detect vertical changes of the ground surface of as little as 5 millimeters (0.2 inch) for standalone interferograms, and changes below 5 millimeters (limit depending on the wavelength of the radar) when multiple interferograms are used together with a stacking algorithm. The commercially available SAR ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 3 images from the satellite platforms that we used for this study (discussed further below) have a pixel resolution of 25 meters (~82 feet) with no space between pixels. As of April 2017, when the analysis for this study was conducted, archived satellite data from four different satellite systems were available for the past 24 years (1992 to 2016), as follows: 1. European ERS-1 and ERS-2 satellites for the years between 1992 and 2000 (the first SAR images were taken in 1992, thus this is the earliest possible application of this technology), 2. Japanese ALOS and European ENVISAT satellites for 2000 to 2012, and 3. European Sentinel satellites for the period after 2012. Data from all satellite systems are available through the European Space Agency (ESA) and the Japanese Space Agency (JAXA). A radar image generated by one of these satellites cannot be directly compared to an image generated by another satellite system, so the interferograms that are generated have to be based on images from the same system. The interferograms generated, however, can be compared across satellite platforms. Interferometric patterns that may result from the comparison of two or more paired radar images from different time periods may be used to interpret subsurface structures defining the margins of aquifers, as well as internal structures and stratigraphy, especially when combined with data from other sources like groundwater extraction records, water level data and well logs. Once a baseline is established and calibrated, yearly, biannual or quarterly interferograms can be used as a cost- effective management tool for monitoring the conditions of the basins. Additional information on DInSAR, including the methodology used to process the data, is provided in Section 3.1 and Appendix A. 2.2 GROUND DEFORMATION RESULTING FROM GROUNDWATER EXTRACTIONS In California, land subsidence primarily occurs as a result of groundwater extraction, but can also result from tectonic (mountain forming and seismic) activity, natural consolidation of sediment, oxidation and compaction of organic deposits, hydrocompaction of moisture-deficient soil and sediments, and extraction of hydrocarbons (Poland et al., 1984; Galloway and Burbey, 2011; Borchers et al., 2014). Aquifer systems experience some degree of deformation in response to changes in hydraulic stress, which include additions such as natural (rainfall) recharge and/or artificial recharge, or withdrawals such as groundwater pumping or reinjection (Galloway and Burbey, 2011; Bawden, 2003). The seasonal cycle of discharge and recharge from unconsolidated heterogeneous aquifer systems, such as those underlying many locations in the Central, San Joaquin, Santa Clara and Antelope valleys, typically causes measurable elastic (recoverable) land subsidence and proportionate uplift (measured in millimeters to centimeters) of the land surface. Removing water from storage in fine-grained sediments (silts and clays) interbedded in the aquifer system can cause these highly compressible sediments to compact inelastically and permanently as pore pressure is reduced. Land subsidence from inelastic (non-recoverable) compaction is a common consequence of significant groundwater level changes that can result from development of groundwater as a resource (Borchers et al., 2014; Sneed, 2016). ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 4 There are some limitations to the use of ground surface deformation when monitoring aquifers. Specifically, for surface deformation to occur, there must be one or more compressible layers of sufficient thickness under static conditions below the top of the saturated zone, and this layer (or layers) needs to have been dewatered during extended periods of continuous pumping. Reversible (elastic) surface deformation may occur as the pore pressure within the compressible layers cyclically rises and falls during either seasonal or other forms of alternating short-period extractions and recharge. Alternatively, if the compressible layers are dewatered due to pumping without significant recharge for an extended period of time (i.e., several years), irreversible (inelastic) surface deformation will typically occur (Bawden, 2003; Borchers et al., 2014; Orange County Water District, 2015). Monitoring of surface deformation is thus primarily a useful tool if 1) the aquifers in question contain suitable compressible layers, and 2) those layers have not been previously dewatered for an extended period of time below a depth termed the “pre-consolidation stress” (e.g., prior historical low water level). 2.3 HYDROGEOLOGIC FRAMEWORK OF THE SANTA MONICA GROUNDWATER BASIN The Santa Monica Groundwater Basin (SMGB; see Figures 1 and 2) encompasses an area of roughly 50 square miles. The City of Santa Monica is the only purveyor in the Santa Monica Basin actively producing groundwater (KJC, 2015). Physiographically and hydrologically, the SMGB is adjacent to the Santa Monica Mountains watershed to the north, the Pacific Ocean to the west, the Hollywood Basin to the northeast, the Central Groundwater Basin to the southeast, and the West Coast Basin to the south. In addition to the City of Santa Monica, cities overlying the SMGB include Culver City and Beverly Hills, and the City of Los Angeles communities of Pacific Palisades, Brentwood, Venice, Marina del Rey, West Los Angeles, Century City, and Mar Vista. Groundwater recharge within the SMGB is believed to occur primarily by percolating rainfall across the basin and by surface runoff from the adjacent Santa Monica Mountains. According to available records, the City conducted limited subsurface injection of imported Metropolitan Water District (MWD) water via its wells at the Charnock wellfield for a period of approximately 13 years (between 1975 and 1988). Because of the degree of urbanization within the City and the surrounding SMGB areas, there appears to be insufficient land area to conduct future artificial recharge through the construction of spreading basins at the ground surface. Indeed, the City historically has never conducted any artificial recharge operations using spreading basins. However, the City is considering artificial recharge through recharge wells as part of its planned Sustainable Water Infrastructure Project (SWIP) in order to increase its drought resiliency and water sustainability. Present-day groundwater flow patterns are primarily southerly through all five subbasins of the SMGB, with eventual discharge towards the Ballona Gap (Figure 2), and then west towards the Pacific Ocean. Local flow-direction deviations occur towards the City’s three main pumping water supply wellfields within the Charnock, Olympic and Arcadia subbasins. The geology of the SMGB consists of unconsolidated and semi-consolidated fluvial and marine deposits (Poland et al., 1959; CDWR, 1961; Yerkes et al., 1965; Reichard et al., 2003). Primary fresh-water-producing units include the heterogeneous but primarily coarse-grained sediments of the Holocene alluvium, heterogeneous alluvial and shallow marine sediments of the Upper Pleistocene Lakewood Formation, and the ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 5 heterogeneous but chiefly coarse-grained deltaic deposits of the Lower Pleistocene San Pedro Formation. Holocene alluvium in the SGMB reaches a maximum thickness of approximately 90 feet and includes silts and clays of the Bellflower Aquiclude and the underlying Ballona Aquifer (also referred to as the “50-Foot Gravel”). The Ballona Aquifer was formed during the last sea-level low stand by a system of stream channels that eroded through elevated, older sediments to reach the new base level, resulting in the present Ballona Gap geomorphology at the southern edge of the SMGB. As sea level began to rise at the end of the Pleistocene and early Holocene, the carved channels were backfilled with alluvial sediments, forming the deposit known as the “50-Foot Gravel” or Ballona Aquifer. Within the southern portion of the SMGB, the "50-Foot Gravel" is generally separated from the underlying San Pedro Formation by a fine-grained confining layer (aquiclude); locally, however, the two stratigraphic units are in direct contact. The Lakewood Formation appears to be present primarily in the northern portion of the SMGB. Some of the City’s wells in the Arcadia and Olympic subbasins are interpreted to be screened across aquifers within both the Lakewood and San Pedro formations (KJC, 2011; RSA, 2013). Where the Lakewood Formation is present, its lower fine-grained member typically forms a leaky aquiclude above the deeper Silverado Aquifer (Reichard et al., 2003; GeoTrans, 2005; ICF, 2015). The most important water-bearing strata throughout the SMGB are typically the sands and gravels within the Silverado Aquifer in the upper San Pedro Formation (Poland et al., 1959; CDWR, 1961; RSA, 2013). The San Pedro Formation averages about 200 feet in thickness in the SMGB. The estimated transmissivity of the Silverado Aquifer within the study area ranges between 50,000 and 150,000 gallons per day per foot (gpd/ft) (CDWR, 1961; RSA, 2015, 2017a). Specific yield of this aquifer is estimated at up to 26 percent (CDWR, 1961). Constant-rate pumping tests performed within wells screening the Silverado Aquifer indicate an average storativity value of 0.02. These measurements confirm the semi-confined nature of the Silverado Aquifer, and the leaky nature of the overlying Lakewood aquiclude (GeoTrans, 2005; ICF, 2015). Beneath the Silverado Aquifer are generally low-permeability sediments of the lower San Pedro and upper Pico formations. The Newport-Inglewood Fault Zone, a known barrier to deep groundwater flow, forms the eastern boundary of the SMGB, whereas the Ballona Gap or Escarpment (an erosional feature) comprises its southern boundary (CDWR, 1961; KJC, 2011; RSA, 2013). Internally, several other faults are believed to impact groundwater storage and flow sufficiently to merit the partitioning of the SMGB into five separate subbasins (KJC, 2011; RSA, 2013) (Figure 2). These faults include the north- to northwest-trending Charnock and Overland Avenue faults, and the complex east- to east- northeast-trending Santa Monica Fault Zone (SMFZ). The SMFZ includes multiple en echelon and branching segments such as the Potrero Canyon fault near the coast (labeled the Brentwood fault on Figure 2 herein, after RSA, 2013), as well as other segments farther inland. The SMFZ was recently zoned under the criteria of the Alquist-Priolo Earthquake Fault Zoning Act (California Geological Survey, 2017; Olson, 2017), and is considered a Holocene-active fault (i.e., sections of the fault are interpreted to have moved at least once in the past 11,700 years). The Charnock and Overland Avenue faults are currently considered not active, as they do not appear to offset Holocene-age sediments, but additional studies are required to confirm this. Whether classified as active or not active, each of these faults has at least several tens of feet of vertical displacement, and thus has the ability to impact ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 6 groundwater flow. The fault-bounded subbasins that comprise the SMGB include the Charnock, Coastal, Crestal, Arcadia, and Olympic. These subbasins are discussed further in the subsection below. 2.3.1 Subbasins of the Santa Monica Groundwater Basin The Charnock subbasin is separated from the Coastal subbasin by the Charnock fault, and from the Crestal subbasin by the Overland Avenue fault (Figure 2). The Charnock subbasin has moved down relative to the Coastal subbasin to the west and the Crestal subbasin to the east across these faults. Therefore, the aquifers in the Charnock subbasin occur at a lower elevation and are notably thicker and more transmissive than those in either of the adjoining subbasins. This is the primary reason why the Charnock subbasin has the greatest historical productivity of all areas of the SMGB (see Table 1). Prior to 1980, groundwater elevations within wells in the Charnock subbasin (see Figure 3; Charnock Well No. 16 hydrograph) were between 30 and 40 feet below sea level. Between 1980 and 1995, groundwater levels rose, but were still below sea level. In 1996, City groundwater production ceased in this subbasin due to third party VOC contamination, and groundwater levels resultantly rose to roughly 10 feet above mean sea level in all subbasin wells over the approximately 13 years the field was shut down. Because of its historically low groundwater levels, regional SMGB groundwater flow has been directed towards the Charnock subbasin from adjoining areas. The fault boundaries of the Charnock subbasin behave as partial hydrologic barriers (general flux boundaries) with respect to groundwater flow through the San Pedro Formation, but do not appear to significantly affect flow within the overlying younger strata (Reichard et al., 2003; GeoTrans, 2005). The Olympic subbasin, as historically defined, lies between segments of Santa Monica Fault Zone (Figure 2). Displacement on these various segments appears to be generally down toward the south with commensurate southward groundwater flow within the Silverado Aquifer. However, local reversals of this trend have been observed or interpreted in some areas, such as within monitoring wells at the City Maintenance Yard (ICF, 2015), along the boundary between the southern Olympic subbasin and the Coastal subbasin. In general, the aquifers in the Arcadia subbasin to the north sit at higher elevations than those in the Olympic subbasin. As a result, groundwater levels in wells of the Olympic subbasin are generally lower than those in the Arcadia subbasin (compare the hydrograph for Santa Monica Well No. 3 in the Olympic subbasin [Figure 4] with that for Santa Monica Well No. 1 in the Arcadia subbasin [Figure 6]). The hydrograph for Well No. 3 suggests some hydraulic connectivity with the Charnock subbasin (GeoTrans, 2005; RSA, 2013), despite the presence of the Charnock fault as a partial flow barrier. The recent revisions to the locations of segments of the Santa Monica fault (Olson, 2017) might have some impact on the Olympic subbasin boundaries, groundwater in storage, groundwater flow and/or sustainable yield estimates. The Arcadia subbasin is bordered by the Santa Monica Mountains to the north and the northern segments of the Santa Monica Fault Zone (names vary) to the south, at the boundary with the Olympic subbasin. Because of this configuration, the Arcadia subbasin receives significant ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 7 groundwater recharge and surface runoff from the Santa Monica Mountains, which contribute to groundwater levels in the Arcadia subbasin wells being the highest in the entire SMGB (see Figures 5 and 6). In particular, the Santa Monica Well No. 1 hydrograph (Figure 6) shows that historic groundwater levels were more than 200 feet above sea level during the 1960s and 1970s (RSA, 2013). Historically, groundwater flow from the Arcadia subbasin into the Charnock and Olympic subbasins has been considered an important component of groundwater recharge into these subbasins. 3.0 WORK COMPLETED AND METHODOLOGY FOLLOWED Pursuant to our proposal dated September 1, 2016, ECI completed the tasks outlined below as part of this study. Where appropriate, specifics regarding the methodology followed are also summarized. A more detailed description of the DInSAR method is provided in Section 2.1 and in Appendix A. 1. Located suitable SAR image data from ESA’s and JAXA’s archives (ERS-1 and ERS-2, ENVISAT, and Sentinel-1 satellite databases), with the suitability of the data determined by date and/or season, and similarity in the path of the satellite passes (we looked for radar images acquired from orbits in the same direction and a Baseline Perpendicular Offset [BPerp] of less than 100 meters between the orbits of the satellites). To that end, we obtained several paired sets of images from each of the time periods of interest to generate the interferograms used in this study, with the final number of interferograms analyzed determined by the availability and quality of the radar images. We also acquired a reference (10-meter) Digital Elevation Model (DEM) for the target area available from the U.S. Geological Survey (USGS). This DEM was used to process the interferograms. 2. Processed the SAR image data and generated differential interferograms (DInSARs) either using pairs of SAR images, or with one master and two or more slave images, to generate a detailed map of the surface deformation (uplift and/or subsidence) that may have occurred during the time period considered. The processing was conducted using the software package GMTSAR. The interferograms generated are as follows:  For the period between 1992 and 1996, three (3) interferograms were used to evaluate changes in the surface elevations during “normal” groundwater pumping conditions (i.e., before 1996, when Volatile Organic Carbons [VOCs] prevented the use of water from the Arcadia and Charnock wellfields in the City). As discussed above, these satellite data first became available in 1992, hence the start-up date for the time period covered in this analysis.  For the period between 1996 and 2010, thirty-three (33) interferograms were generated to obtain information on potential land surface rebound when pumping was minimal.  For the period between 2010 and 2016, eleven (11) interferograms were generated to obtain data on potential surface deformation caused by increased water extraction by the City of Santa Monica, which began in 2010. 3. Once the interferograms were generated, we converted their units from phase shift to absolute elevation change (in millimeters, see Figures 3 through 6), to evaluate whether or not areas in the study region have experienced subsidence or uplift. ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 8 4. Performed a review of historical groundwater extraction data provided to us by the City, Richard Slade & Associates (RSA), and ICF International (ICF) to establish groundwater level trends for all periods analyzed using DInSAR. Various parties and consultants to the City of Santa Monica have collected water level measurements regularly in all pumping wellfields since 1975. We also obtained local precipitation data from the National Oceanic and Atmospheric Administration (NOAA) and other sources. All of these data for each of the areas analyzed are presented in graphical form on Figures 3 through 6, and on Plate 1. 5. Compared the completed interferograms to the groundwater data to determine whether or not the land elevation changes imaged by the interferograms appear to be temporally and/or spatially associated with changes in water pumping or recharge over time. Three tests were done with the individual interferograms to: 1) identify aquifer boundaries, 2) identify active tectonic movements that potentially can harm utilities and infrastructure, and 3) detect areas where uplift or subsidence that may be related to variations in the water levels in the aquifers has occurred during the time period considered for this study. The first test was to visually inspect the interferograms for any sharp changes in deformation within the target area. The second test was to use GIS tools to generate a number of profiles to detect changes and gradients in the deformation rate that are too weak to be detected with the naked eye. The third test was to extract point deformation data for key well locations and look for statistic correlations between any detected deformation and the well hydrographs. Specifically, point deformation data were extracted for the various pumping well locations, and compared with selected “key well” water-level hydrographs, well logs, rainfall records and groundwater production data provided to us by the City. Horizontal profiles were also extracted from both individual and stacked interferograms to search for surface deformation related to known pumping depressions in City well fields, as well as the faults that act as boundaries, impacting groundwater movement across the basin. Statistical analyses were run on the data to evaluate whether or not there is a correlation between the DInSAR and groundwater data. Details of these analyses and the results are included in Appendix A, and examples of the interferograms developed are included in Appendix B. All of the interferograms processed for this study are also included in the attached compact disk. 6. To evaluate further whether any areas undergoing deformation (subsidence) are in fact responding to dewatering of the underlying aquifers, we analyzed available water-well logs to identify saturated fine-grained stratigraphic horizons that could experience a reasonable magnitude of compaction during pumping-dewatering cycles. Copies of the water well logs used for this analysis are included in Appendix C. 7. Prepared this report and accompanying illustrations describing the work completed, and presenting our findings, conclusions and recommendations. We also prepared monthly progress reports and met with you to discuss our findings. ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 9 4.0 FINDINGS AND DISCUSSION 4.1 BASIN KEY WELLS AND EXTRACTION CENTERS Owing to the close spatial distribution of most City pumping wells which have historically produced localized and discrete pumping depressions, ECI opted to rely on the concept of “Key Wells” for comparison to potential surface deformation in these discrete zones. For consistency with previous and on-going groundwater studies in the SMGB, these key wells are similar to those identified by other consultants to the City of Santa Monica (RSA, 2013; 2017a), and are considered representative of the hydrogeologic conditions and production histories in those discrete areas of extraction and, by extension, any potential related ground surface deformations. Four Key Wells were utilized for this study; their selection was based in large part on the groundwater extraction histories of four critical subbasin areas of the SMGB (Figure 2). These Key Wells include Charnock subbasin well No. 16, Olympic Subbasin Santa Monica well No. 3, Arcadia subbasin well No. 4, and Arcadia subbasin Santa Monica well No. 1. Table 1 summarizes SMGB production history for each of these three subbasins from 1975 onwards, based on data provided to us by the City that includes the time period of available SAR images for this analysis. Pre-1975 extractions from the SMGB are also available, but production totals are not distinguished for individual pumping centers or subbasins (RSA, 2013). As discussed above, the City’s active SMGB pumping centers are located only within three distinct areas, namely the Charnock, Arcadia, and Olympic subbasins. The quantity and quality of the groundwater within those portions of the Coastal subbasin that lie within the boundaries of the City are unknown as the City does not pump from this subbasin. The Crestal subbasin has reportedly had minimal production between 1975 and 2016, chiefly from small private irrigation wells at local country clubs (KJC, 2011, 2015). The City of Santa Monica has extracted groundwater from the SMGB since 1924; cumulative groundwater extractions increased steadily to 6,969 acre-feet (AF) in 1940. In 1941, the City began receiving imported water deliveries from the Metropolitan Water District (MWD). During the late 1940s groundwater use was gradually discontinued, but by 1954 the City once again began to gradually utilize more groundwater as development and population increased and available annual MWD entitlements diminished. This trend continued through 1996, when third-party VOC contamination was discovered in both the Charnock and Arcadia subbasins, and selected wells were shut down as a result. The Charnock Wellfield has historically been the most productive in the SMGB, and has five active groundwater wells (Figure 2), including Charnock No. 13, Charnock No. 15, Key Well Charnock No. 16 (Figure 3), Charnock No. 18, and Charnock No. 19. These wells have a reported combined capacity of approximately 9,000 acre-feet per year (AFY) (KJC, 2011, 2015). However, this production rate is not considered to be viable as it exceeds the estimated sustainable yield (RSA, 2017a) from the Charnock subbasin (estimated at approximately 5,900 AFY). The Arcadia Wellfield has two active production wells: Key Well Arcadia No. 4 and Arcadia No. 5 (Figure 2). These wells have a combined rated capacity of 250 gpm, but the wells cannot be run simultaneously due to their close proximity to each other and pumping depression (radius of influence) interference. In 2008, the Arcadia wells produced approximately 381 AF, and in 2009 ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 10 production was approximately 366 AF (see Table 1 and Figure 5). The most recent RSA (2017a) estimate of sustainable yield for this subbasin is between 750 and 880 AFY. Santa Monica well No. 1, historically counted as part of the Olympic Wellfield, is actually located two miles west of the Arcadia Wellfield and draws from the Arcadia subbasin (Figure 2). This well forms its own discrete pumping center. Other wells (i.e., Santa Monica well No. 5) that historically extracted from this pumping center are not currently active. The Olympic Wellfield has two currently active groundwater wells (Key Well Santa Monica No. 3, and Santa Monica well No. 4). In 2008, the Olympic Wellfield produced approximately 1,997 AF; in 2009 it produced approximately 2,064 AF (Table 1). The extraction curves as a function of time for the four Key Wells are shown in green on the appropriate figures, and on Plate 1. Depth to water as a function of time for these same four Key Wells is shown in blue. The most recent estimate of sustainable yield for the Olympic subbasin is between 1,600 and 1,700 AFY (RSA, 2017a). Construction details for each of the four selected Key Wells, obtained from logs for these wells filed with the California Department of Water Resources (CDWR) are included in Appendix C, and on Figures 3 through 6. All City of Santa Monica production wells are considered to be screened in the Silverado Aquifer within the San Pedro Formation. However, Key Wells Santa Monica No. 1 and Arcadia No. 4 appear to be screened across aquifers within both the Lakewood Formation and the San Pedro Formation. As discussed above in Section 2.3, the semi-confined nature of the Silverado Aquifer results in hydraulic connection with the shallower aquifers, and dewatering of those shallow aquifers when pumping occurs in the Silverado Aquifer. Columnar sections (stratigraphic profiles) for each Key Well, derived from the logs included in Appendix C, are also illustrated on Figures 3 through 6. These generalized stratigraphic profiles distinguish the primarily coarse-grained strata from those fine-grained units most susceptible to compression when dewatered under low-water-level conditions. The columnar sections group the sediments reported in the logs into two primary divisions: coarse-grained and fine-grained. Because rainfall is considered to be the primary source of groundwater recharge, and thus, to pose an impact on the water levels in the SMGB, the Key Well graphs on Figures 3 through 6 and Plate 1 also depict precipitation curves in black. These data were provided by RSA (2017b), and are available from the NOAA Western Regional Climate Data Center (WRCDC) at the Desert Research Institute, University of Nevada – Reno. The rainfall data were measured in a continuous rain gage (WRCDC No. 042214) located in Culver City that is considered representative for the SMGB area. The curves of “Accumulated Departure of Rainfall” depicted on Key Well Graphs (Figures 3 through 6 and Table 1) show annual patterns in rainfall for the available period of record. The accumulated rainfall departure values on the figures are plotted relative to the long-term average annual rainfall of 11.95 inches for the period for which there are data available, which extends from 1934 to 2016. The accumulated departure curve illustrates the temporal trends in the rainfall (recharge) data, and provides a useful format of comparison to well-production trends. Likewise, this curve also provides a framework for comparison to potential ground surface subsidence or uplift during the period for which SAR data are available. The “zero line” on the accumulated departure curves represents the long-term average annual rainfall (11.95 inches). Points plotted above the zero line represent years of higher- ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 11 than-average precipitation, whereas points plotted below that line represent years of less-than- average precipitation. Annual rainfall values are plotted on the Key Well Graphs as percentages relative to the running annual average, in order to illustrate how accumulated rainfall trends can represent a meaningful measure of water budget, and thus useful comparison to groundwater extractions (Table 1) and resultant water levels. Even though there may have been protracted “dry” periods in the SMGB (1944 through 1950, 1978 through 1991, 2005 through 2009), precipitation in subsequent years was sufficient to keep the rainfall totals above the long-term average annual value, and the net water budget out of overdraft conditions. 4.2 DInSAR RESULTS The DInSAR analyses utilizing stacked interferograms show that changes in the water level within the system of aquifers underlying the SMGB writ large do not readily correlate with any appreciable basin-wide land surface subsidence. The vertical elevation changes, if any, related to the water level in the aquifers appear to be too small to be reliably detected with stacked interferometry as they are close to the lower detection limit for this method. The interferometry results also suggest that in the SMGB this method is unable to capture tectonic- related elevation changes that may be occurring along the boundaries of the aquifers (i.e., faults or other groundwater barriers), either as a result of water level changes or in response to tectonic movements. The DInSAR method was also unable to identify any appreciable vertical (seismic related) movement occurring across any of the known faults in the SMGB. However, we cannot entirely preclude the possibility of horizontal movements, either as discrete small events or creep on the boundary faults. There may be a geologic cause for this lack of definition, such as coverage of the faults by generally unconsolidated and more transmissive recent alluvium. The current lack of reliable data could be mitigated by the installation of fixed GPS monitoring stations and cube-corner radar reflectors to enhance satellite data returns. Interestingly, preliminary analysis of individual interferogram pairs from the more recent satellite data (2015 onward) indicate the method could be utilized to detect positive deformation (surface inflation) due to recharge. 4.3 CORRELATION BETWEEN INTERFEROGRAMS AND KEY WELL DATA Noise in the satellite data caused by atmospheric disturbances, as well as surface deformation caused by tectonic activity, required the application of statistical methods in order to assess for a potential correlation (if any) between the DInSAR data and the well hydrographs. For each well where hydrographs were available for the same time period as the stacked interferograms, point deformation data were extracted from the "synthetic" interferograms representing the modeled deformation. These data were then tested against the hydrographs for a best-fit using a statistics software application. As the synthetic interferograms capture the change in elevation over the time period between acquisitions of the satellite images, the hydrographs were converted to reflect this as well, using the change in water level, rather than the absolute water level, in the statistical tests (discussed below). Furthermore, as the sampling intervals in both datasets are irregular and unevenly spaced, both datasets were resampled and trimmed (see appendix A). The first statistical test applied evaluated whether the sample populations of both the surface elevation and water level changes ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 12 follow normal (Gaussian) distributions. This test needed to be conducted prior to any correlation tests because standard normal distributions of parametric data improve the significance of subsequent test results. If both sets of data follow a Gaussian distribution, the attempted correlation would then be between the change in surface elevation (Δhsurface) and the change in water level ( Δhwater), with the assumption of a linear best-fit model using some specified confidence interval, ideally 95 percent or greater. The result of the statistical test would yield an equation for the best- fit line or curve, and an R2 value (Pearson correlation) describing how well the model correlates the ground surface response to the measured water level changes. The R2 value is always between 0 and 100 percent, with a higher value representing a better correlation between the model and the data (i.e., positive linear correlation between random sample populations of the two variables). When all point deformation (non-stacked) data were plotted in a single graph, it became apparent that there was noise present, as the graphs were all nearly identical in shape. Given that the wells are located in different subbasins, if the main source of ground surface deformation is groundwater extraction alone, the surface deformation should not be similar from one subbasin to the next, as groundwater extraction varies between subbasins. Similarly, deformation associated with local tectonic events should vary across the subbasins. Thus, we concluded that the source of the noise is likely either humidity in the atmosphere, or remaining phase-ramps that the SAR processor is unable to remove. As all points lie within a relatively small geographic area, we made the assumption that the disturbances are of the same magnitude and sign for all points in the region in each respective interferogram. To remove the noise we calculated the median for all data points belonging to a given interferogram, and subtracted this median value from the deformation values for each of the well locations. Finally, the deformation data for the key well locations were plotted together with the hydrological data on Figures 3 through 6 to visually make an initial non-quantitative correlation test (the surface deformations are shown in red on these figures and on Plate 1). The visual observations indicate that there appears to be a weak correlation between the localized surface deformation (subsidence) and groundwater water levels in the SMGB pumping centers for the time period between 1992 and 2016. Quantitative statistical correlation tests have not been able to show a correlation between the surface deformation and the hydrographs at a reasonable significance level because the bivariate Pearson coefficients (R2) for these correlations in all key wells resulted in values well below 50 percent. This can, at least in part, be explained by the gaps where data are missing in the hydrographs time-series, as well as the gaps in the interferometric data (e.g., dates for which images were not available, or are of too low coherence to be processed). Another explanation is that historical excess pumping that occurred beginning as early as the 1930s and 1940s, coupled with period intervals of drought, may have dewatered the compressible (fine- grained) strata for periods long enough to result in some degree of irrecoverable (inelastic) compaction (see Figures 7 and 8). ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 13 5.0 CONCLUSIONS AND RECOMMENDATIONS 5.1 CONCLUSIONS Based on the data and methodology presented above, we conclude the following:  Only a weak, low-magnitude water-level-related surface deformation (subsidence) can be interpreted for the SMGB area from the stacked interferograms for the period between 1992 and 2016.  No long-term or regionally extensive compaction of sediments due to low groundwater levels has been observed outside the limited area of subsidence associated with the existing pumping centers.  The localized low magnitude of water-level-related surface deformation adjacent to the City’s wellfields is most likely the result of irreversible compaction due to dewatering of compressible strata that began as early as the 1930s and 1940s, when water levels in the aquifers were reportedly very low.  Because of the observed weak correlation between ground deformation and water levels as discussed above, some degree of future residual sediment dewatering and compaction cannot be ruled out near the Key Well pumping centers during periods of high rates of pumping.  A sequential analysis of paired interferograms through time is recommended, with an emphasis on more recent data obtained during the annual wet and dry seasons (October- April and May-September, respectively) that may provide useful information pertaining to short-term cyclical positive deformation (topographic inflation) due to inflow of natural recharge into the basin from distal sources and the subsequent short term topographic deflation due to dissipation of recharge in the subsurface via natural groundwater outflow. These data, if confirmed, would be useful in refining calculations of basin recharge volumes for sustainable yields and for planning adaptive pumping schedules. 5.2 RECOMMENDATIONS As a result of this study, ECI recommends the installation of between four and eight automated GPS monitoring stations within the City. The GPS stations would measure and record any future vertical displacements related to sediment compaction or tectonic activity and, possibly, more importantly, temporary topographic inflation caused by seasonal aquifer recharge. We recommend that these stations be installed in locations both proximal and distal to the Key Wells. The GPS station locations should be selected so that the system captures both the rapid response to pumping activities, and the slower response that occurs farther away as the groundwater levels rise and fall in cyclical response to natural recharge or the City’s planned reinjection for indirect potable reuse. To assist with adaptive management of the City’s groundwater, the automated GPS data should be correlated with future precipitation totals and static groundwater-level monitoring data collected by the City of Santa Monica pursuant to prevailing SGMA and California Statewide Groundwater Elevation Monitoring (CASGEM) requirements. The benefit of an automated GPS system to augment ground elevation data is that it will enable a more rigorous statistical correlation to water level time-series due to future reinjection ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 14 or pumping of the City’s closely clustered wells. The GPS system could help in identifying new potential well locations. Lastly, the GPS base stations would constitute a valuable planning resource for future City of Santa Monica Public Works Department Differential GPS (DGPS) and Real Time Kinematic (RTK) surveys. It is also recommended that the City of Santa Monica continue with annual InSAR surveys to be used in combination with the collected GPS data to help refine water resource planning and modeling efforts. To provide a more robust signal for the interferometry, we also suggest the installation of three to four permanent cube-corner radar reflectors in the area, as these will further increase the sensitivity of the interferometric surveys. ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 15 6.0 REFERENCES AND SOURCES Amelung, F., Galloway, D.L., Bell, J.W., Zebker, H.A., and Laczniak, R.J, 1999, Sensing the ups and downs of Las Vegas: InSAR reveals structural control of land subsidence and aquifer- system deformation: Geology, Vol. 27, pp. 483–486. Argus, D.F., Heflin, M.B., Donnellan, A., Webb, F.H., Dong, D., Hurst, K.J., Jefferson, D.C., Lyzenga, G.A., Watkins, M.M., and Zumberge, J.F., 1999, Shortening and thickening of metropolitan Los Angeles measured and inferred by using geodesy: Geology, Vol. 27, pp. 703-706. Bawden, G.W., 2003, Separating groundwater and hydrocarbon-induced surface deformation from geodetic tectonic contraction measurements across metropolitan Los Angeles, California; In Prince, K.R. and Galloway, D.L., (editors), Proceedings of the Subsidence Interest Group Conference Technical Meeting held in Galveston, Texas, November 27-29, 2001: U.S. Geological Survey Open-File Report 03-308; available from http://pubs.usgs.gov/of/2003/ofr03-308/. Borchers, J.W., Carpenter, M., Kretsinger-Grabert, V., Dalgish, B., and Cannon, D., 2014, Land Subsidence from Groundwater Use in California: Water Education Foundation and Luhdorff & Scalmanini Consulting Engineers, 161p. California Department of Water Resources (CDWR), 1961, Planned Utilization of the Ground Water Basins of the Coastal Plain of Los Angeles County: Bulletin No. 104. California Department of Water Resources (CDWR), 2015, Sustainable Groundwater Management Program Draft Strategic Plan, 31p. California Geological Survey, 2017, Preliminary Review Map, Earthquake Fault Zones of Required Investigation, Beverly Hills 7.5 Minute Quadrangle, released July 13, 2017, to be superseded on or about January 11, 2018. Castle, R.O. and Yerkes, R.F., 1976, Recent Surface Movements in the Baldwin Hills, Los Angeles County, California: U.S. Geological Survey Professional Paper 882. Galloway, D.L. and Burbey, T.J., 2011, Review: Regional land subsidence accompanying groundwater extraction: Hydrogeology Journal, Vol. 19, No. 8, pp. 1459-1486. GeoTrans, Inc., 2005, Charnock Basin Groundwater Modeling – Groundwater Modeling Subtask 21.2: Technical Memorandum submitted to the Charnock Engineering Committee (CEC), July 22, 2005. Hu, J., Ding, X.L., Lia, Z.W., Zhang, L., Zhu, J.J., Sun, Q., and Gao, G.J., 2016, Vertical and horizontal displacements of Los Angeles from InSAR and GPS time series analysis: Resolving tectonic and anthropogenic motions: Journal of Geodynamics, Vol. 99, Sept 2016, pp. 27-38. ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 16 ICF International Inc., 2015, Olympic Wellfield Site Conceptual Model, City of Santa Monica; consulting report, 34p. plus plates. ICF International Inc., 2017, Personal communication via email with G. Clarendin regarding Olympic Wellfield Water Level Elevations, Q3_2011 to present (Excel© spreadsheet) and Water Level Elevations Chart, Olympic Wellfield. Johnson, A.M., Fleming, R.W, Cruikshank, K.M. and Packard, R.F., 1996, Coactive faulting of the Northridge earthquake: U.S. Geological Survey Open-File Report 96-523. Kennedy/Jenks Consultants (KJC), 2011, Feasibility Report for Development of Groundwater Resources in the Santa Monica and Hollywood Basins; consulting report prepared for Los Angeles City Department and Power, December 2011, 158p. Kennedy/Jenks Consultants (KJC), 2015, City of Santa Monica Sustainable Water Supply Master Plan; consulting report prepared for the City of Santa Monica, 225p. Lanari R., Lundgren P., Mariarosaria M., and Casu, F., 2004, Satellite radar interferometry time- series analysis of surface deformation for Los Angeles, California: Geophysical Research Letters, Vol. 31, No. 23, 16 Dec., 2004, 5p. Olson, B.P.E., 2017, The Hollywood, Santa Monica and Newport-Inglewood Faults in the Beverly Hills and Topanga 7.5’ Quadrangles: California Geological Survey Fault Evaluation Report No. FER-259, dated June 28, 2017, released July 13, 2017, 72p. Orange County Water District, 2015, Groundwater Management Plan 2015 Update, 10p. Poland, J.F., (editor) and others, 1984, Guidebook to Studies of Land Subsidence due to Ground- Water Withdrawal: Studies and Reports in Hydrology, prepared for the International Hydrological Programme, Working Group 8.4: United Nations Educational, Scientific and Cultural Organization, Paris, France, 305p. plus appendices; available from http://unesdoc.unesco.org/images/0006/000651/065167eo.pdf Poland, J.F., Garrett, A.A., and Sinnott, A., 1959, Geology, Hydrology, and Chemical Character of Ground Waters in the Torrance-Santa Monica Area, California: U.S. Geological Survey Water-Supply Paper 1461. Reichard, E.G., Land, M., Crawford, S.M., Johnson, T., Everett, R.R., Kulshan, T.V., Ponti, D.J., Halford, K.J., Johnson, T.A., Paybins, K.S., and Nishikawa, T., 2003, Geohydrology, geochemistry, and ground-water simulation – Optimization of the Central and West Coast Basins, Los Angeles County, California: U.S. Geological Survey Water Resource Investigation Report 03-4065. Richard C. Slade & Associates (RSA), 2013, Conceptual Groundwater Basin Model and Assessment of Available Groundwater Supplies, Santa Monica Groundwater Basin: consulting report prepared for the City of Santa Monica, 119p. plus appendices. ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Report - Page 17 Richard C. Slade & Associates (RSA), 2017, Draft Preliminary Study of the Sustainable Yield of the Santa Monica Groundwater Basin; consulting report prepared for the City of Santa Monica Water Resources Division. Richard C. Slade & Associates (RSA), 2017, Personal communication via e-mail with E. LaPensee who provided to us hydrographs of Santa Monica Wells in an Excel spreadsheet, on 25 Jan. 2017. Sneed, M., 2016, Land Subsidence: The Lowdown on the Drawdown: U.S. Geological Survey and California Groundwater Resources Association Webinar, March 23, 2016. Water Education Foundation, 2015, The 2014 Sustainable Groundwater Management Act: A Handbook to Understanding and Implementing the Law; available from http://www.watereducation.org/publication/2014-sustainable-groundwater-management- act Yerkes, R.F., McCulloh, T.H., Schoellhamer, J.E., and Vedder, J.G., 1965, Geology of the Los Angeles basin, California—An Introduction: U.S. Geological Survey Professional Paper 420-A, 57p. ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Figures and Plate FIGURES and PLATE Water depth below top-of-well casing (in Feet) Rainfall (percent cumulative departure from annual average for the period between 1975 and 2016) Annual subbasin groundwater production (in Acre-Feet) Explanation Chiefly fine-grained compressible sediments (CL,CH,ML,MH,SC,GC) Chiefly coarse-grained sediments with low compressibility (SW,SP,SM,SG,GP,GW) Surface deformation (in Millimeters) Well Construction Schematic (Depth=ft bgs) B l a n k C a s i n g P u m p C o l u m n P e r f o r a t e d I n t e r v a l 2 2 0 -3 9 0 f t b g s P u m p a t ??? T.D.=410 ft bgs G e n e r a l S t r a t i g r a p h i c P r o f i l e (F e e t B e l o w G r o u n d S u r f a c e ) S t a t i c W a t e r D e p t h B e l o w G r o u n d S u r f a c e (F e e t ) Date R a i n f a l l G r o u n d w a t e r P r o d u c t i o n (A c r e -F e e t ) S u r f a c e D e f o r m a t i o n (M i l l i m e t e r s ) -400 -300 -200 -100 0 100 200 300 400 500 6000 20 40 60 80 100 120 140 160 180 200 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 0 5 10 15 20 25 30 Key Well:Charnock Subbasin Charnock Well No.16 0 ft Project Number:3615 Date:September 2017 Figure 3WellSchematicsandStratigraphicProfile,Historical Water Depth,Rainfall,Groundwater Production and Surface Deformation for Charnock Well No.16 -300 -200 0 100 200 300 400 500 6000 20 40 60 80 100 120 140 160 180 200 1990 1995 2000 2005 2010 2015 2020 0 500 1000 1500 2000 2500 3000 3500 -400 -100 Key Well:Olympic Subbasin Santa Monica Well No.3 S t a t i c W a t e r D e p t h B e l o w G r o u n d S u r f a c e (F e e t ) -7 -6 -5 -4 -3 -2 -1 0 -8 Figure 4 Water depth below top-of-well casing (in Feet) Rainfall (percent cumulative departure from annual average for the period between 1975 and 2016) Annual subbasin groundwater production (in Acre-Feet) Explanation Chiefly fine-grained compressible sediments (CL,CH,ML,MH,SC,GC) Chiefly coarse-grained sediments with low compressibility (SW,SP,SM,SG,GP,GW) Surface deformation (in Millimeters) Well Construction Schematic (Depth=ft bgs) G e n e r a l S t r a t i g r a p h i c P r o f i l e (F e e t B e l o w G r o u n d S u r f a c e ) Perforated Intervals 210-270 300-380 410-430 490-530 ftbgs P u m p C o l u m n B l a n k C a s i n g 0 ft R a i n f a l l G r o u n d w a t e r P r o d u c t i o n (A c r e -F e e t ) S u r f a c e D e f o r m a t i o n (M i l l i m e t e r s ) Project Number:3615 Date:September 2017 Well Schematics and Stratigraphic Profile,Historical Water Depth,Rainfall,Groundwater Production,and Surface Deformation for Santa Monica Well No.3 Date 1975 1980 1985 T.D.=550 ft bgs Project Number:3615 Date:September 2017 Well Schematics and Stratigraphic Profile,Historical Water Depth,Rainfall,Groundwater Production,and Surface Deformation for Arcadia Well No.4 Date G e n e r a l S t r a t i g r a p h i c P r o f i l e (F e e t B e l o w G r o u n d S u r f a c e ) R a i n f a l l Date G r o u n d w a t e r P r o d u c t i o n (A c r e -F e e t ) S u r f a c e D e f o r m a t i o n (M i l l i m e t e r s ) Well Construction Schematic (Depth-ft bgs) B l a n k C a s i n g P u m p C o l u m n P e r f o r a t e d i n t e r v a l s : 8 5 -2 1 8 f t b g s P u m p a t ??? T.D.=235 ft bgs Figure 5 Key Well:Arcadia Subbasin Arcadia Well No.4 -400 -300 -200 -100 0 100 200 300 400 500 6000 20 40 60 80 100 120 140 160 180 200 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 0 100 200 300 400 500 600 700 800 900 10000ft S t a t i c W a t e r D e p t h B e l o w G r o u n d S u r f a c e (F e e t ) -40 -35 -30 -25 -20 -15 -10 -5 0 Water depth below top-of-well casing (in Feet) Rainfall (percent cumulative departure from annual average for the period between 1975 and 2016) Annual subbasin groundwater production (in Acre-Feet) Explanation Chiefly fine-grained compressible sediments (CL,CH,ML,MH,SC,GC) Chiefly coarse-grained sediments with low compressibility (SW,SP,SM,SG,GP,GW) Surface deformation (in Millimeters) Water depth below top-of-well casing (in Feet) Rainfall (percent cumulative departure from annual average for the period between 1975 and 2016) Annual subbasin groundwater production (in Acre-Feet) Explanation Chiefly fine-grained compressible sediments (CL,CH,ML,MH,SC,GC) Chiefly coarse-grained sediments with low compressibility (SW,SP,SM,SG,GP,GW) Surface deformation (in Millimeters) Project Number:3615 Date:September 2017 Figure 6 -400 -300 -200 -100 0 100 200 300 400 5000 20 40 60 80 100 120 160 180 200 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 S t a t i c W a t e r D e p t h B e l o w G r o u n d S u r f a c e 140 B o t t o m o f s c r e e n 2 5 0 ' T.D.=275bgs 0 ft P e r f o r a t e d I n t e r v a l 1 5 1 '-2 5 0 ' P u m p C o l u m n Pump at ??? 1 4 " B l a n k C a s i n g 50 100 150 200 250 300 350 400 0 Key Well:North Arcadia Subbasin Santa Monica Well No.1 G r o u n d w a t e r P r o d u c t i o n (A c r e -F e e t ) R a i n f a l l -25 -20 -15 15 -10 -5 0 S u r f a c e D e f o r m a t i o n (M i l l i m e t e r s ) Well Schematics and Stratigraphic Profile,Historical Water Depth,Rainfall,Groundwater Production,and Surface Deformation for Santa Monica Well No.1 Well Construction Schematic (Depth=ft bgs) G e n e r a l S t r a t i g r a p h i c P r o f i l e (F e e t B e l o w G r o u n d S u r f a c e ) Date ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Table TABLE ECI Project No. 3615 September 15, 2017 YEAR Arcadia Charnock Olympic ("Santa Monica")TOTAL 1975 872 5,475 1,382 7,729 1976 812 5,039 1,580 7,431 1977 646 5,356 1,260 7,262 1978 476 3,237 503 4,216 1979 545 3,555 1,446 5,546 1980 516 4,355 1,019 5,890 1981 411 5,340 233 5,984 1982 74 4,901 2,177 7,152 1983 - 5,506 3,173 8,679 1984 75 6,168 3,119 9,362 1985 376 5,644 2,884 8,904 1986 377 6,598 2,574 9,549 1987 371 7,513 834 8,718 1988 372 8,111 387 8,870 1989 357 6,363 457 7,177 1990 389 4,132 469 4,990 1991 417 4,728 387 5,532 1992 396 6,486 981 7,863 1993 390 6,153 2,867 9,410 1994 419 5,906 3,126 9,451 1995 542 6,322 3,176 10,040 1996 370 2,284 3,044 5,698 1997 - - 2,820 2,820 1998 - - 2,642 2,642 1999 - - 2,937 2,937 2000 - - 2,912 2,912 2001 387 - 2,809 3,196 2002 467 - 1,824 2,291 2003 455 - 593 1,048 2004 137 - 385 522 2005 395 - 1,495 1,890 2006 387 - 1,365 1,752 2007 374 - 1,619 1,993 2008 360 - 1,663 2,023 2009 340 - 1,722 2,062 2010 290 593 2,436 3,319 2011 269 4,222 1,967 6,458 2012 258 5,458 2,734 8,450 2013 273 6,141 2,454 8,868 2014 355 8,284 1,541 10,180 2015 378 8,015 2,287 10,680 2016 339 8,372 2,246 10,957 Sources: City of Santa Monica Water Resources Protection Program; Richard C. Slade & Associates February, 2013 report and personal communication, 2017 . Table 1: Santa Monica Groundwater Basin Production History, 1975-2016 Annual Production (in Acre-Feet) By Wellfield / Subbasin DInSAR Study of the Santa Monica Groundwater Basin Area Table 1 ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Appendix A APPENDIX A: ADDITIONAL TECHNICAL INFORMATION REGARDING THE DInSAR METHOD AND STATISTICAL ANALYSES COMPLETED AS PART OF THIS STUDY ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Page A-1 APPENDIX A: ADDITIONAL TECHNICAL INFORMATION REGARDING THE DInSAR METHOD AND THE STATISTICAL ANALYSES COMPLETED AS PART OF THIS STUDY More In-Depth Description of the DInSAR Method as Used in This Study DInSAR as utilized in this study is a satellite, airborne, radar-based system that generates high- resolution remote sensing imagery. The onboard signal processing system uses the magnitude and phase of the received signals over successive pulses from elements of a 'synthetic aperture' to create an image consisting of pixels containing both the phase and amplitude information. The distance the SAR device travels over a target in the time taken for the radar pulses to return to the antenna creates the large "synthetic" antenna aperture (the "size" of the antenna). Typically, the larger the aperture, the higher the image resolution will be, regardless of whether the aperture is physical (a large antenna) or 'synthetic' (a moving antenna). This allows SAR to create high- resolution images with the comparatively small antennas that fit onboard a satellite or aircraft. The phase information of each image pixel represents the complex vector sum of the radar echoes from all scattering elements within a corresponding resolution cell on the ground, covering an area of approximately 20 x 5 meters for the ERS-1, -2 and Envisat satellites. Other satellites may have different resolution cell sizes, but the final pixel size is usually resampled to a square shape of 20 to 50 meters regardless of the size of the original cells. The return phase of the signal from each scattering center has its phase determined by the two-way range to the satellite and this will typically vary by several hundred wavelengths (ERS-1, -2, Envisat 56.66 mm) across a typical resolution cell. The phase of an image pixel by itself is thus a random and not very meaningful parameter. There is, however, a correlation between the phase information in corresponding pixels in scenes covering the same area, and any movements that have occurred between the acquisitions of the scenes will be represented by a phase shift. For this assumption to be valid the satellite needs to be located very precisely over the target area and any difference in the repeat orbits will introduce phase shifts that need to be removed mathematically. Depending on the intended use of the interferograms, detecting ground movements or generating Digital Elevation Models (DEMs), the maximum allowable offsets in the orbits differ. For DEM generation, a maximum value of the perpendicular offset (offset between orbits) is around 1100 m, whereas values of less than 250 m are needed to measure surface deformation. A high degree of control over the orbits of the satellites is also imperative if the SAR images are to be used for interferometric purposes. In addition to problems with phase shift introduced by offsets in the orbits, other problems will also occur. Examples are loss of coherence caused by differences in the viewing geometry, and ambiguities caused by the relief giving false signals in the interferogram. There are also other factors that may reduce or even totally compromise the quality of the DInSAR results. The most important one is related to temporal decorrelation phenomena caused by the variation of the electromagnetic properties of the radar targets. If the phase reflectivity value of a certain image pixel changes with time, the generation of an interferogram, i.e. the computation of the difference between the phase values of two SAR images; cannot highlight the displacement values. The impact of temporal decorrelation phenomena increases as the temporal baseline of the interferogram (i.e. the time lag between the two SAR acquisitions) increases. Apart from phase decorrelation, propagation effects in both the troposphere and the ionosphere can differ significantly during the first and the second ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Page A-2 acquisition, thus creating phase disturbances that at best will hinder the interpretation of SAR interferograms, or at worst, completely prevent the processing of the satellite data. Given all these potential issues, only a small number of the available archived scenes are suitable for the generation of interferograms. In general, it can also be said that the availability varies between the ages of the different satellite systems, with more modern systems having greater reliability. This is mostly the result of better control of the orbits of the satellites, but also because of developments that have given the onboard signal processing systems and computers better capabilities. The interference pattern is a function of the geometries of the orbits as well as the topography of the target area. By analyzing the interference patterns, and knowing the precise orbits, the topography can be calculated and, if the topography also is known, any changes in the topography can be calculated from the interferogram by removing the topographic effects utilizing an existing DEM. The difference in phase between the SAR images is usually represented by color bands in such a way that a movement corresponding to half the wavelength of the radar is shown as a complete color cycle in a color band. Apart from phase information, the quality of the correlation, (the ‘coherence') between two SAR images can also be determined. Such coherence values are related to the nature of the ground surface. Any chaotic movements of the scatterers in the target area between the acquisitions will cause the coherence to be low. Open water and active agricultural areas are usually totally decorrelated, whereas urban areas and areas free of vegetation are more likely to have a high coherence over extended periods of time. Low coherence makes it impossible to calculate the phase shift, and thus a high degree of coherence is imperative in the areas of interest. Processing the raw SAR data to create interferograms is a multi-step operation involving Fourier transforms to extract the radar echoes, and other complex mathematics. The technical details of these procedures are beyond the scope of this report, but are described in detail in Lanari et al. (2004), and Hu et al., (2016). Although several InSAR processing packages are available, we chose GMTSAR, which was developed by the Scripps Institution of Oceanography and the University of Hawaii. There are two reasons for choosing GMTSAR over other available software packages. First, the software is in the public domain and free to use by anyone without restrictions, as it is currently released as open source under the GNU General Public License. Second, when the European Space Agency opened their archives of ERS satellite data for general use in early April 2017, we found that they had changed the data format and virtually no other commercially available software was capable to read the new format. The open nature of GMTSAR allowed us to write a new pre-processor for the new file format, allowing us to process the data successfully. The software can be divided into three parts: a. A pre-processor responsible for importing and converting satellite data (ERS-1/2, ENVISAT, ALOS-1, TerraSAR-X, COSMOS-SkyMed, Radarsat-2, Sentinel-1A/B, and ALOS-2) to the internal native format used by GMTSAR. b. The InSAR processor, which focuses and aligns stacks of images, maps topography into phase, and forms the complex interferograms. c. The post-processor, which filters the interferograms and constructs interferometric products of phase, coherence, phase gradient, and line-of sight displacement in both radar and geographic coordinates. ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Page A-3 As described above, the interferograms produced by subtracting phase data from separate radar images result in an image where every pixel describes the displacement that has occurred between the acquisitions of the images. However, the detected displacement will also contain an error of unknown magnitude due to atmospheric interference, which means that any deformation along line-of-sight only can be taken as an approximation for a single interferogram. The SBAS algorithm uses a number of interferograms (>3) and applies a least squares curve fitting on every corresponding pixel in the included interferograms to create an image where the pixels represent the velocity in millimeters per year that best fits any displacement that occurs over time. In addition, the software also outputs "synthetic" interferograms with the cumulative displacement that has occurred between the acquisitions of the radar images. It is also creating maps showing the residuals between the expected and measured displacements. A small residual means that there is a good fit between the model for the displacement and the interferometrically detected displacement of the same pixel. ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Page A-4 Specific Statistical Analyses Used to Compare the Changes in Ground Elevation (Delta h) with Depth to Water (DTW) Minitab Regression Analysis: Delta_h versus DTW, Santa Monica Well No. 1 Analysis of Variance: Source DF Adj SS Adj MS F-Value P-Value Regression 1 62287 62287.4 2491.02 0.000 DTW 1 62287 62287.4 2491.02 0.000 Error 7533 188361 25.0 Lack-of-Fit 7206 187396 26.0 8.82 0.000 Pure Error 327 965 2.9 Total 7534 250648 Model Summary: S R-sq R-sq(adj) R-sq(pred) 5.00048 24.85% 24.84% 24.82% Coefficients: Term Coef SE Coef T-Value P-Value VIF Constant 1.993 0.312 6.39 0.000 DTW -0.10580 0.00212 -49.91 0.000 1.00 Regression Equation: Delta_h(mm) = 1.993 - 0.10580 DTW(ft) ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Page A-5 Minitab Regression Analysis: Delta_h versus DTW, Santa Monica Well No. 3 Analysis of Variance: Source DF Adj SS Adj MS F-Value P-Value Regression 1 2648.6 2648.61 844.28 0.000 DTW 1 2648.6 2648.61 844.28 0.000 Error 8355 26210.8 3.14 Lack-of-Fit 7685 25959.1 3.38 8.99 0.000 Pure Error 670 251.7 0.38 Total 8356 28859.4 Model Summary: S R-sq R-sq(adj) R-sq(pred) 1.77120 9.18% 9.17% 9.14% Coefficients: Term Coef SE Coef T-Value P-Value VIF Constant 0.535 0.122 4.37 0.000 DTW -0.027913 0.000961 -29.06 0.000 1.00 Regression Equation: Delta_h(mm) = 0.535 - 0.027913 DTW(ft) ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Page A-6 Minitab Regression Analysis: Delta_h versus DTW, Charnock Well No. 15 Analysis of Variance: Source DF Adj SS Adj MS F-Value P-Value Regression 1 423524 423524 17718.47 0.000 DTW 1 423524 423524 17718.47 0.000 Error 7000 167321 24 Lack-of-Fit 6659 166009 25 6.48 0.000 Pure Error 341 1311 4 Total 7001 590845 Model Summary: S R-sq R-sq(adj) R-sq(pred) 4.88907 71.68% 71.68% 71.67% Coefficients: Term Coef SE Coef T-Value P-Value VIF Constant 45.271 0.203 223.54 0.000 DTW -0.25082 0.00188 -133.11 0.000 1.00 Regression Equation: Delta_h(mm) = 45.271 - 0.25082 DTW(ft) ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Page A-7 Minitab Regression Analysis: Delta_h versus DTW, Charnock Well No. 16 Analysis of Variance: Source DF Adj SS Adj MS F-Value P-Value Regression 1 201243 201243 5928.61 0.000 DTW 1 201243 201243 5928.61 0.000 Error 8660 293958 34 Lack-of-Fit 8045 293150 36 27.74 0.000 Pure Error 615 808 1 Total 8661 495201 Model Summary: S R-sq R-sq(adj) R-sq(pred) 5.82618 40.64% 40.63% 40.61% Coefficients: Term Coef SE Coef T-Value P-Value VIF Constant 35.776 0.244 146.43 0.000 DTW -0.16149 0.00210 -77.00 0.000 1.00 Regression Equation: Delta_h(mm) = 35.776 - 0.16149 DTW(ft) ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Page A-8 Minitab Regression Analysis: Delta_h versus DTW, Arcadia Well No. 4 Analysis of Variance: Source DF Adj SS Adj MS F-Value P-Value Regression 1 28888 28888.1 237.15 0.000 DTW 1 28888 28888.1 237.15 0.000 Error 8752 1066092 121.8 Lack-of-Fit 7054 1037442 147.1 8.72 0.000 Pure Error 1698 28649 16.9 Total 8753 1094980 Model Summary: S R-sq R-sq(adj) R-sq(pred) 11.0368 2.64% 2.63% 2.58% Coefficients: Term Coef SE Coef T-Value P-Value VIF Constant -25.177 0.296 -85.16 0.000 DTW 0.14624 0.00950 15.40 0.000 1.00 Regression Equation: Delta_h(mm) = -25.177 + 0.14624 DTW(ft) ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Page A-9 References Hu, J., Ding, X.L., Lia, Z.W., Zhang, L., Zhu, J.J., Sun, Q., and Gao, G.J., 2016, Vertical and horizontal displacements of Los Angeles from InSAR and GPS time series analysis: Resolving tectonic and anthropogenic motions: Journal of Geodynamics, Vol. 99, Sept 2016, pp. 27-38. Lanari R., Lundgren P., Mariarosaria M., and Casu, F., 2004, Satellite radar interferometry time- series analysis of surface deformation for Los Angeles, California: Geophysical Research Letters, Vol. 31, No. 23, 16 Dec., 2004, 5p. ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Appendix B APPENDIX B: INTERFEROGRAMS ANALYZED ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Appendix B- Page B-1 List of satellite scenes used in the study: ERS, Stack 1 Date Time Track Orbit Satellite 19920914 18:34:29 442 06098 ERS-1 19960214 18:34:28 442 23977 ERS-1 19991111 18:34:17 442 23843 ERS-2 19991216 18:34:17 442 24344 ERS-2 20000921 18:34:32 442 28352 ERS-2 ERS, Stack 2 Date Time Track Orbit Satellite 19950823 18:34:28 442 21472 ERS-1 19960912 18:34:26 442 07310 ERS-2 19970619 18:34:25 442 11318 ERS-2 19981126 18:34:14 442 18833 ERS-2 19990311 18:34:17 442 20336 ERS-2 20001026 18:34:27 442 28853 ERS-2 20001130 18:34:20 442 29354 ERS-2 ENVISAT Stack 1 Date Time Track Orbit Satellite 20021028 05:43:01 392 03452 ENVISAT 20030106 05:42:56 392 04454 ENVISAT 20040614 05:43:07 392 11969 ENVISAT 20041101 05:43:08 392 13973 ENVISAT 20050321 05:43:01 392 15977 ENVISAT 20060515 05:43:00 392 21989 ENVISAT 20060619 05:43:03 392 22490 ENVISAT 20070219 05:42:58 392 25997 ENVISAT Also downloaded and processed but not used in any stacks due to low coherency. Date Time Track Orbit Satellite 20021202 05:42:59 392 03953 ENVISAT 20041206 05:43:04 392 14474 ENVISAT 20051121 05:43:05 392 19484 ENVISAT 20061211 05:43:04 392 24995 ENVISAT 20070709 05:43:02 392 28001 ENVISAT Standalone ALOS interferogram Date Time Path Orbit Granule ID 2008-01-20 06:22:21 217 10593 PASL10C0801200622261208200010 2010-07-28 06:23:39 217 24013 PASL10C1007280623441208200011 ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Appendix B- Page B-2 Sentinel-1, Stack 1 Date Time Absolute orbit Swath 2015-01-26 13:51:57 4343 3 2015-07-25 13:52:00 6968 3 2015-08-18 13:52:01 7318 3 2015-10-29 13:51:59 8368 3 2015-11-22 13:51:57 8718 3 2015-12-16 13:51:56 9068 3 2016-03-21 13:51:55 10468 3 2016-05-08 13:51:57 11168 3 2016-06-01 13:52:01 11518 3 2016-08-24 13:52:15 12743 3 2016-11-16 13:52:01 13968 3 2016-11-28 13:52:15 14143 3 ECI Project No. 3615 September 15, 2017 DInSAR Study of the Santa Monica Groundwater Basin Area Appendix C APPENDIX C: LOGS OF KEY WELLS, SANTA MONICA GROUNDWATER BASIN REFERENCE: Agreement No. 10631 (CCS)