We are pleased to announce that Mr. Brent Johnson has joined Todd Groundwater as Associate Hydrogeologist.
Mr. Johnson is a registered professional geologist in California. He has more than five years of experience as a consulting geologist for both public and private sector clients. He has experience planning and directing field investigations, collecting and managing data, and conducting water quality analyses. He has managed and conducted numerous remedial site investigations and environmental assessments and has worked on a broad array of projects including post closure landfill monitoring, hazardous site characterizations, monitoring well installations, and geotechnical investigations.
He is currently engaged in a variety of projects with Todd Groundwater: these include SGMA planning, technical support for numerical modeling, and design of production wells.
— March 2018
Todd Groundwater (originally David Keith Todd Consulting Engineers) was founded in May 1978 by Dr. David Keith Todd, author of the widely used textbook Groundwater Hydrology which is recognized as the first textbook to go beyond hydraulic equations to address groundwater basin management and critical issues of perennial yield, overdraft, and seawater intrusion.
The longevity and stability of our company attests to our ethic of providing excellent and responsive service to our clients and a stimulating and supportive work environment for our staff. We have participated in many changes in the groundwater industry over the years, from some of the first groundwater contamination investigations to the recent enactment of the California Sustainable Groundwater Management Act in 2014. As the groundwater industry has evolved and changed responding to threats to groundwater quality and supply, Todd Groundwater has been there to provide technical support. We look forward to continuing that support for many years to come.
Leadership of Todd Groundwater has evolved over the years. In 2003, Dr. Todd took on the role of Chairman, Dr. Iris Priestaf became President, and Ms. Phyllis Stanin was promoted to Vice President. Dr. Todd passed away in April 2006, but we carry on his vision of managing groundwater resources to benefit society and the environment.
— March 2018
Amber joined Todd Groundwater in 2013 following her completion of a Master of Science degree in Hydrogeology from Illinois State University, plus a certification in GIS applications. She has become an integral member of our staff, gaining substantial field experience with technical observation of monitoring, test, and production well installations; well monitoring, testing, and sampling; and feasibility investigations of managed aquifer recharge projects.
Her field experience encompasses a variety of hydrogeologic settings from the low Colorado Desert to the Monterey coast. She also has contributed her GIS, data management, and analytical skills to a breadth of groundwater projects.
— June 2017
Through his academic training and hands-on experience, he has developed particular expertise in managed aquifer recharge evaluations, and has published papers on well clogging mechanisms and pre-treatment options for Aquifer Storage and Recovery (ASR) in cooperation with the Australian Commonwealth Scientific and Industrial Research Organisation. He offers advanced skills in GIS and database development, groundwater flow and vadose zone modeling, geochemical analyses, and advanced environmental statistics.
Edwin is an accomplished project manager, capable of developing and implementing large and complex projects that are technically excellent and cost effective. He is recognized for his responsiveness to his clients.
— January 2017
AWWA, California-Nevada Section.
As a Water Use Efficiency Practitioner, Ms. Reilly has the education and experience to prepare water conservation plans, estimate water demands on a variety of scales, and assist agencies to assess water usage, identify water waste, and evaluate regional water issues and resources.
— July 2016
Sustainable Groundwater in California. This conference, presented by Law Seminars International on June 6 and 7 in Sacramento, recognizes that SGMA is in full swing: new regulations are being adopted — most notably the regulations for preparation of Groundwater Sustainability Plans, which were developed through an intensive public process involving State agencies, water providers, and stakeholders.
Dr. Priestaf will address technical issues of developing a Groundwater Sustainability Plan.
— May 2016
Todd Groundwater Presents at the Association of Groundwater Agencies/American Groundwater Trust Annual ConferenceSally McCraven, Principal Hydrogeologist with Todd Groundwater, speaks on Groundwater Modeling for Optimal Injection Well Design at the AGWA/AGWT Annual Conference in Ontario, California. The two day (February 17 and 18, 2016) conference is being held with support from the Groundwater Resources Association of California and the California Groundwater Coalition. This year’s conference is titled Everything Aquifers and Groundwater Management.
Ms. McCraven is an invited speaker for the February 17th session titled Water Reuse — A Growing Feature of California’s Supply Solutions. Sally will present findings from recent modeling conducted to help site and design advanced treated recycled water injection wells in the Montebello Forebay of the Central Basin in California
— January 2016
Dr. Priestaf will address the elements of a Groundwater Sustainability Plan, including evaluation of sustainable yield and assessment of practical methods for getting to sustainability.
For more information, visit Groundwater Regulation in California.
— September 2015
Sustainable Groundwater Management Comes to California: Time for Planners to Get Their Feet Wet and is intended to provide an introduction to the recent Sustainable Groundwater Management Act for planners, engineers, and legal experts. The panel will be moderated by Pete Parkinson, AICP, Independent Consultant. Other panelists are Mike Novo, Planning Director for County of Monterey, and Richard Shanahan, Partner with Bartkiewicz, Kronick & Shanahan.
For more information, visit http://www.apacalifornia-conference.org/.
— September 2015
Mr. Maley is a specialist at applying groundwater flow and transport models for groundwater management and water quality studies. He has developed basin-wide 3D numerical models to provide groundwater basin evaluations, sustainable yield estimates, water quality assessments, and analysis of groundwater-surface water interactions. His work has provided engineering design and CEQA/NEPA support for several large groundwater banking, recycled water and regional planning projects.
Mr. Maley has worked with several water districts to develop and implement groundwater management plans. He is recognized for his communication skills and his ability to frame complex hydrogeologic concepts and to anticipate issues for the intended audience. Through these efforts, he has developed strong working relationships as a trusted advisor.
— September 2015
Oil, Gas, and Groundwater: Wise Production and Protection of Our Valuable Natural Resources held in Long Beach, California on February 18 and 19, 2015. The symposium was sponsored by the Groundwater Resources Association of California (GRA) and the Los Angeles Basin Geological Society.
The program provided the latest information on petroleum industry practices — including hydraulic fracturing — relating to California groundwater, as described by recognized experts in the field. Ms. Stanin presented Todd Groundwater’s recent work on the California Statewide Programmatic Draft Environmental Impact Report titled Analysis of Oil and Gas Well Stimulation Treatments in California, published in January 2015. Ms. Stanin was part of an expert panel with Dr. Steven Bohlen, State Oil and Gas Supervisor for the Division of Oil, Gas, and Geothermal Resources (DOGGR) and Jonathan Bishop from the State Water Resources Control Board.
— March 2015
Todd Groundwater Completes Groundwater Impacts Analysis for Statewide EIR Regarding Well Stimulation Treatments Including Hydraulic FracturingTodd Groundwater completed the groundwater and hazardous materials impacts analysis for the California Statewide Programmatic Draft Environmental Impact Report (EIR), Analysis of Oil and Gas Well Stimulation Treatments in California, published January 14, 2015. Working as a subconsultant to Aspen Environmental Group, Todd Groundwater developed the statewide analysis of well stimulation — including hydraulic fracturing — as it relates to hazardous materials (led by Dr. William Motzer), and groundwater resources (led by Phyllis Stanin and Liz Elliott).
The EIR provides the public with detailed information on potential environmental impacts associated with well stimulation treatments. The EIR was prepared in compliance with recent legislation: Senate Bill 4 (SB 4), adopted in 2013. Also in compliance with SB 4, the California Division of Oil, Gas, and Geothermal Resources (DOGGR) adopted regulations regarding well stimulation practices, including hydraulic fracturing. Although the DOGGR SB 4 regulations contain numerous protective measures for groundwater, the analysis concluded that well stimulation could have significant impacts to both groundwater quantity and quality without further mitigation. Seven key mitigation measures were developed. Collectively, the mitigation measures, DOGGR SB 4 regulations, and the resource protection standards incorporated into the project, along with required groundwater monitoring under SB 4, provide comprehensive protection for groundwater resources.
The Draft EIR contains 2,771 pages plus appendices. It can be obtained from the DOGGR website. Public comments are due by March 16.
— March 2015
Groundwater Regulation and Management in California. This conference, scheduled for March 2 and 3, 2015 in Sacramento, will address statewide perspectives in groundwater management, legal implications of the new laws, practical approaches and requirements for forming Groundwater Sustainability Agencies and developing Groundwater Sustainability Plans, the role of state agencies, funding issues, and practical examples of how real life groundwater disputes are resolved today.
Dr. Priestaf will address elements of a Groundwater Sustainability Plan, including evaluation of sustainable yield and assessment of practical methods for getting to sustainability.
— January 2015
The Act, defined in three linked legislative bills (Senate Bill 1168, Senate Bill 1319, and Assembly Bill 1739), is detailed and comprehensive. It provides a priority list of groundwater basins, defines Groundwater Sustainability Agencies (GSAs), outlines the contents of Groundwater Sustainability Plans (GSPs), establishes the roles of State agencies, and sets a timeline with deadlines. Specifically, it mandates the preparation of management plans for more than 100 groundwater basins by 2022 with subsequent achievement of sustainability in another 20 years. While building on previous management legislation, it more than ever requires acknowledgment of multiple benefits and uses of groundwater, including maintenance of stream flows and environmental benefits, and supports collaboration between water agencies and planning agencies.
Todd Groundwater has been engaged for the past 35 years in assisting local water agencies, cities, and counties in groundwater management planning. For us, this is part of the legacy of Dr. David Keith Todd who placed groundwater management at the core of his textbook Groundwater Hydrology, defined the concept of perennial yield, and pioneered groundwater management techniques.
We stand ready to continue assisting local agencies, guided by this new policy of the State, that:
sustainable groundwater management is best achieved locally through the development, implementation, and updating of plans and programs based on the best available science.
— September 2014
Todd Groundwater Presents Talk and Poster at the 14th Biennial Symposium on Managed Aquifer Recharge
TALK — Groundwater Replenishment in the Seaside Basin: Increasing Basin Yield with Recycled WaterPhyllis Stanin, Vice President and Principal Geologist with Todd Groundwater, will present a talk at the Groundwater Resource Association (GRA) of California and Arizona Hydrological Society's 14th Symposium on Managed Aquifer Recharge at 3:55pm on July 31, 2014.
Monterey Regional Water Pollution Control Agency and Monterey Peninsula Water Management District are developing a groundwater replenishment (GWR) project to substantially increase the perennial yield from the Seaside Groundwater Basin. A new advanced water treatment plant will be constructed to produce recycled water from numerous source waters including stormwater, industrial wash-water, agricultural drain water, and municipal wastewater. Recycling of these water sources has the potential for significant environmental benefits while enhancing the critically-limited water supply for the Monterey Peninsula area.
The project will provide replenishment to the two primary drinking-water aquifers in the basin. The deeper, semi-confined Santa Margarita aquifer will be recharged with deep injection wells (900 feet deep). The shallower, unconfined Paso Robles aquifer will be recharged using vadose zone wells about 200 feet deep. Water levels in both aquifers are currently below sea level and are at risk of seawater intrusion.
The project is being developed to coordinate with an ongoing Aquifer Storage and Recovery (ASR) project, which is operated to recharge and recover available Carmel River water through four ASR wells.
A field program was conducted in late 2013 and early 2014 to address knowledge gaps for recharging the shallow aquifer through vadose zone wells. The program included:
The data were used to support geochemical modeling in order to evaluate the geochemical compatibility of GWR water, ambient groundwater, and Carmel River ASR water. The presentation describes the results of the field program and demonstrates the need for and use of key hydrogeologic data for the GWR project planning and implementation.
POSTER — Optimizing Recharge and Recovery in the Pauba Valley: Balancing Short-Term Recovery with Long-Term StorageRancho California Water District ("District") operates a series of groundwater recharge percolation ponds, referred to as the Valle de los Caballos Recharge and Recovery Facility (VDCR/RF), to provide a sustainable groundwater supply for the greater Temecula and Murrieta area. Artificial recharge during the winter allows for subsequent recovery during peak demands periods.
The District has embarked on a study to optimize the Upper VDCR/RF operations through local-scale numerical modeling of numerous recharge and recovery scenarios. Operational scenarios evaluated included increased recharge in certain ponds or sub- portions of ponds, use of recovery wells adjacent to the ponds to control groundwater mounding, and selective operation of key downgradient recovery wells to increase extraction of the recharged water. Todd Groundwater applied numerical groundwater modeling and particle tracking to determine the fate of the recharged water.
A local-scale five-layer MODFLOW groundwater model was developed and well calibrated to simulate aquifer response to historical recharge events, and subsequently used to analyze various recharge and recovery alternatives. The local model is essentially a telescopic mesh refinement of a regional groundwater flow model with additional layer refinement.
Simulations showed that operation of new recovery wells could increase the recharge capacity of the Upper VDC Site to 60 cubic feet per second.
The District has proceeded with expansion plans for the Upper VDC Site and recently constructed additional facilities to increase recharge and recovery operations. Dan Craig, Senior Hydrogeologist/Modeler with Todd Groundwater, is an author along with District Staff Warren Back and Rich Ottolini.
— July 2014
Water in the West at Stanford University, Before the Well Runs Dry: Improving the Linkage Between Groundwater and Land Use Planning, calls attention to the diminishing supply of groundwater in many basins in California — a problem heightened by the persistent drought that is affecting the state — and offers suggestions for improving the linkage between groundwater and land use.
Groundwater is a critical resource in California, providing from 30% of the state’s water supply in normal years to 40% or more in dry years. As unsustainable groundwater use driven by land use changes continues in many basins around the state, there is growing consensus that more effective integration of land use planning and groundwater management is needed. To address this growing concern, Water in the West convened thirty groundwater managers, land use planners, water lawyers, consultants, and academics at Stanford University in September 2013 in an Uncommon Dialogue, designed to bring leaders from different sectors to develop practical solutions to pressing environmental challenges centered on water. This report, shaped in part by the Dialogue, provides the background and regulatory context for land use planning and groundwater management in California, shares case studies that highlight the intersection of groundwater and land use, and makes specific recommendations to improve the linkage between land use decisions and groundwater management in the state.
Dr. Iris Priestaf, President of Todd Groundwater, assisted in organizing the Uncommon Dialogue, participated in the process, and provided review of the report. The report is available on the Water in the West website, at http://waterinthewest.stanford.edu/resources/publications-directory/groundwater_landuse.
— April 2014
San Benito County Water District and other stakeholders received approval of the Northern San Benito County Salt and Nutrient Management Plan (SNMP) from the Central Coast Regional Water Quality Control Board in April 2014. The plan, conducted in accordance with the State Water Resources Control Board’s Recycled Water Policy, is one of the first plans approved in the state.
SNMPs are intended to facilitate the implementation of recycled water projects by characterizing all salt and nutrient sources (including recycled water projects) and their impacts to groundwater quality. SNMPs also identify implementation measures to manage salts and nutrients in a sustainable manner to protect beneficial groundwater uses
— April 2014
Dr. David Keith Todd, a world-renowned expert in groundwater hydrology founded our company in 1978 to provide groundwater consulting services based on integrity, using sound science, and recognizing real-world practicalities. With this legacy, Todd Engineers developed into a cohesive group of groundwater specialists — engineers, hydrogeologists, and scientists — dedicated to the planning, development, management, and protection of groundwater resources.
The legacy of our founder and our specialization in groundwater is the basis for our new name, Todd Groundwater.
Our updated website provides more information about our consulting services, our legacy and our vision. vCards are provided for your convenience on our Staff biography pages.
— January 2014
Ms. Elliott is a registered professional geologist and certified hydrogeologist in California. She has over 15 years of consulting experience in hydrogeologic and multidisciplinary water resources, numerical modeling, remedial investigation and environmental assessment projects. She has particular expertise in the fate and transport of contaminants in groundwater, combining field work with advanced analytical techniques and hydrogeologic support to numerical modeling. Her master’s thesis (UC Davis, 2002) addressed Comparative Groundwater Flow and Transport Models to Investigate the Effect of Geologic Heterogeneity.
Ms. Elliott is recognized as a top-tier consultant. She is an experienced project manager, known not only for her technical expertise, but also for her communication skills, integrity, and responsiveness to clients.
— November 2013
Managed Aquifer Recharge (MAR) in the Urban Environment: Technical and Policy Challenges in Burlingame, California. Mr. Lin presented a paper, titled Regional Water Quality Changes from Recycled Water Recharge in the Central Basin and West Coast Basin (CBWCB), Los Angeles County. Mr. Lin described how MAR facilities recharging recycled water, including the Montebello Forebay Spreading Grounds and three seawater intrusion barriers, currently provide 60 percent of the total recharge in the CBWCB.
Planned expansion of key water reclamation plants will increase the availability of tertiary and advanced-treated recycled water for recharge and reduce local reliance on imported water. Mr. Lin described Todd Engineers’ development of a Salt and Nutrient Management Plan for the CBWCB to characterize ambient salt/nutrient groundwater quality and evaluate the impact of salt/nutrient loading from existing and future planned MAR projects against anti-degradation criteria set forth in the State Water Resources Control Board’s Recycled Water Policy.
Todd Engineers was a sponsor for the symposium.
— June 2013
WateReuse California Annual Conference in Monterey, California entitled Approaches to Salt and Nutrient Management Plans on Sunday March 17, 2013 2:00pm to 5:00pm.
The objective of the Salt and Nutrient Management Plan (SNMP) is to manage salts and nutrients (S/N) from all sources on a basin-wide or watershed-wide basis in a manner that ensures attainment of water quality objectives and protection of beneficial uses. This SNMP workshop focuses on the practical methodologies and technical analyses that are being applied for recently completed and ongoing SNMPs.
Sally McCraven, Principal Hydrogeologist with Todd Engineers, helped coordinate the workshop and Edwin Lin, Senior Hydrogeologist with Todd Engineers, presented technical approaches for S/N loading. The workshop agenda and presentation summaries are available at https://www.watereuse.org/conferences/california/13/workshops. In addition, Ms. McCraven’s session presentation entitled Calibration – An Important Tool in Making Loading Assumptions for Salt and Nutrient Management Plans describes Todd Engineers’ approach for several SNMPs being conducted across the state shown by the red stars on the map at right.
— March 2013
Mr. Yates is an accomplished Senior Hydrologist and water resources expert. His extensive experience -- initially with the USGS and also as a consulting hydrologist -- has been science-based and focused on projects that require critical thinking skills and the application of hydrologic principles and methods. Mr. Yates is technically skilled with the ability to use data creatively and practically in combination with field investigations, computer models, statistics, and traditional analysis methods. He is recognized for his breadth of knowledge in multiple disciplines -- including soils, geology, geomorphology, climatology, land use, water use, agronomy, vegetation ecology, fisheries biology, and riparian ecology -- and for his comprehension of the critical aspects of complex natural hydrologic and water supply systems.
Mr. Yates is an experienced project manager with exceptional communication skills, who has consulted successfully with public agencies, private-sector clients, and non-profit groups in groundwater and surface water hydrology, biohydrology, and water resources management. He is an acknowledged expert in basin yield analysis, groundwater modeling, quantification of groundwater budgets, and evaluation of groundwater flow and quality.
— March 2013
— February 2013
Association of California Water Agencies (ACWA), which represents about 440 water agencies with responsibility for 90% of the state’s distributed water. ACWA has recently developed a policy, Framework for Groundwater Management, which supports groundwater sustainability as a key goal and understands the local level as most appropriate for sustainable management. Key recommendations include encouragement of AB 3030/SB 1938 management plans and incorporation of land use elements in county general plans that support effective groundwater management plans.
Dr. Priestaf’s presentation to the CCPCA summarized the critical role of groundwater as an integral part of California’s water supply, especially in light of today’s water supply challenges. She focused on the California’s long history of managing groundwater from the ground up -- namely through locally controlled programs and agencies, with guidance and support from the State. Specifically, the 1993 Groundwater Management Planning Act (known as AB 3030 and later strengthened by the 2002 Senate Bill 1938) has become the most effective and widely used means of groundwater management. This was substantiated in the presentation by the latest results of a state-wide survey by the California Department of Water Resources. The map at right illustrates the extent of AB 3030 Plans, with blue indicating pre-Senate Bill 1938 plans and green indicating post-Senate Bill 1938 plans.
Dr. Priestaf noted the importance of coordination of state and local water agencies with city and county planning agencies. Such coordination has been encouraged by subsequent legislation that mandates certain groundwater management actions and promotes sharing of information. For example, the 2009 Water Package included a Senate Bill (SBx7-6) that requires groundwater level monitoring of all groundwater basins in California. The resultant California Statewide Groundwater Elevation Monitoring (CASGEM) program, based on local monitoring entities, now provides public online access to groundwater level data from across the state. Also, the 2011 Assembly Bill 359 amends the water code, requiring that AB 3030/SB 1938 groundwater management plans include a map that delineates areas of significant groundwater recharge. When the groundwater management plan is adopted, the local water agency is required to provide this map to local planning agencies.
— January 2013
Dr. Motzer has extensive experience in conducting surface and subsurface water quality chemistry and environmental forensic investigations. He is a recognized expert in forensic geochemistry, with particular expertise in stable and other isotopic "fingerprinting" and age dating techniques, water quality/contamination, and emerging contaminant geochemistry. He has been responsible for more than 400 environmental projects throughout California and other western states.
— July 2011
Environmental Forensics: What Methods to Use? An On-going Challenge for the Forensic Scientist at the Groundwater Resource Association (GRA) of California 6th Symposium in the Series on Tools and Technology: Environmental Forensics in a Era of Emerging Diagnostic Methods. The symposium will be held on April 11, 2011 and Dr. Motzer's talk will commence at 3:50pm.
Environmental forensics has been defined as the systematic examination of environmental information used in litigation. For the past decade, techniques such as fuel fingerprinting, stable and radiogenic isotope analyses have been used to determine and assess contaminant sources. However, forensic scientists have other investigative tools and techniques at their disposal, which can be tailored to the investigation; examples are described below. Dr. Motzer will present three case studies of how environmental forensics were used by Todd Engineers to solve environmental problems.
DNA Fingerprinting of Coliform BacteriaA northern California water district needed to determine whether coliform bacterial in surface water was from human or animal sources. DNA fingerprinting of different E. coli strains along with characterization of gaining and losing conditions in the stream were used to determine that 1) seasonal E-coli bacterial patterns were coincident with gaining stream stretches where groundwater discharges to surface water, and 2) the E-coli DNA was from human sources.
Using Surrogates to Determine Groundwater Contaminant SourcesFor a central California Mother Lode gold mine that included open pits, a pit lake, and waste rock and mill tailings piles, a key issue was the potential off-site migration of dissolved metals such as arsenic in groundwater. Because groundwater arsenic analyses were inconsistent, surrogates such as sulfate and TDS were used to determine pathways for arsenic movement in groundwater. The investigation showed that the arsenic source was from tailings impounded adjacent to the pit lake, which was acting as a hydrologic sink. In addition, determination of predicted pathways allowed selection of interceptor monitoring/pumping wells sites.
Using Multiple-Faceted Hydrogeological and Geochemical InvestigationsIn a California Coastal Area of Special Biological Significance, adjacent to two marine protected areas, groundwater seepage had significantly increased along portions of the coast. Such seepage can be a problem by fostering nonindigenous vegetation growth and by creating stagnant pools with poor quality water. Water samples were analyzed for selected inorganic constituents and stable oxygen-deuterium isotopes to identify seepage sources. Chloride and sulfate (mostly attributable to irrigation and soil amendments) were identified as useful inorganic forensic indicators for seepage, while oxygen-deuterium isotopes provided useful signatures for differentiating drinking water, background water, and precipitation.
— March 2011
Managed Aquifer Recharge Symposium, on January 25-26, 2011, in Irvine, California. This two-day symposium specifically focused on issues and needs regarding augmenting aquifers through recharge basins with surface waters, including river water, recycled water, and storm water.
On Tuesday, January 25 in Session 6b: Modeling of Recharge Basin Performance, Dan Craig, Senior Hydrogeologist with Todd Engineers presented: Optimizing Recharge and Recovery at Recharge Basins in the Pauba Valley and Phyllis Stanin, Vice President of Todd Engineers, presented: Recharge and Supply Allocation in the Ames Valley Basin - Making it Happen.
Optimizing Recharge and Recovery at Recharge Basins in the Pauba ValleyRancho California Water District (District) operates seven groundwater recharge ponds, referred to as the Valle de los Caballos (VDC) ponds, to provide a sustainable groundwater supply for the greater Temecula area. Recharge basins have been constructed along Temecula Creek in two areas of the Pauba Valley. The Upper VDC Ponds consist of five recharge basins. A limiting factor at the Upper Ponds is compliance with a Department of Public Health (DPH) permit that requires maintenance of a 40-foot vadose zone beneath the basins for pathogen removal. The Lower VDC Ponds consist of two adjacent spreading basins covering 15 acres. The sources of the recharge water are raw water supplied by Metropolitan Water District and releases from upstream Vail Lake.
In order to maximize their recharge and recovery operations, the District has embarked on two recharge optimization studies. For both studies, an improved understanding of the hydrogeology and local-scale numerical modeling were keys to optimizing recharge and recovery.
At the Lower Ponds, alluvial fan and fluvial processes have deposited permeable channel sands that typically result in high infiltration rates and groundwater storage capacity. However, heterogeneity in the alluvial aquifers has created some problems of infiltration in certain areas.
Two local-scale MODFLOW models, based on the District's regional model, have been constructed by Todd Engineers over each area to simulate various scenarios of recharge and recovery. Numerous operational scenarios were evaluated including increased recharge in certain ponds, use of wells adjacent to the basins to control groundwater mounding, and selective operation of key downgradient wells to increase recovery of the recharge water.
Recharge and Supply Allocation in the Ames Valley Basin - Making it HappenThe Bighorn-Desert View Water Agency (BDVWA) is located within the boundaries of the Mojave Water Agency (MWA) in the western Mojave Desert. Groundwater is the primary source of water supply in the region, but increasing water demand is expected to stress limited groundwater resources in the future.
Todd Engineers constructed a groundwater model of the Pipes and Reche subbasins in the western Mojave Desert to verify basin sustainable yield, characterize groundwater flow conditions, and evaluate the hydraulic impacts of the planned recharge facility. The model included complex hydrogeologic features, including faults that serve as partial barriers to groundwater flow.
Todd Engineers assisted BDVWA in development of a GWMP for the basin, which included a description of the state of the groundwater basin, water supply and demand, basin management objectives, basin management strategies, and implementation plan, and a monitoring program (for levels, quality, storage, and subsidence).
Total future pumping allocations may exceed average basin perennial yield during future dry years. Imported water recharge will be conducted to increase storage and supplement supply. Based on future storage changes, pumping reductions may be implemented.
— updated March 2011
Groundwater Resource Association's 19th Annual Conference and Meeting on September 15-16 2010. Entitled Thinking Outside the Pipe: Exploring and Protecting Local Water Supplies, the conference was held close to the San Francisco Airport in Burlingame.
The three presentations described below are illustrative of Todd Engineers' current projects.
"Old" and "New" Emerging ContaminantsRecognizing the rapidity with which emerging contaminants are identified and addressed, Dr. William Motzer, Senior Geochemist, presents an approach to emerging contaminants as "post" emergent and "new" emergent contaminants. He describes the parameters to define post-emergent contaminants, including MTBE, perchlorate, hexavalent chromium, and 1,4-dioxane, and proposes four "new" emergent contaminants including pharmaceuticals and personal care products (PPCPs), nanomaterials, platinum group metals, and prions.
Dr. Motzer gave his talk on Wednesday, September 15, 2010 from 2:30 to 3:00pm in Session 2B: Emerging Contaminants -- From the Source to Groundwater.
City of San Jose South Bay Water Recycling Groundwater Monitoring and Mitigation Program UpdateThe potential impacts of recycled water irrigation on groundwater quality have been an issue for decades. Daniel Craig, Senior Hydrogeologist/Modeler, will summarize findings of a detailed analysis for the City of San José's ongoing groundwater monitoring program. Different evaluation methods were applied, including chemical mass balance, overall geochemistry, and changes in concentration trends for the pre-irrigation "baseline" period and post-recycled water irrigation period. For the recycled water irrigation period, trend analysis of selected constituents revealed statistically significant increasing and decreasing trends. Todd Engineers concluded that the City's monitoring program is effective in monitoring groundwater quality changes, and that other influences besides recycled water irrigation have affected groundwater quality.
Mr. Craig presented his team's findings on Wednesday, September 15, 2010 from 3:30 to 4:00pm in Session 4B: Recycled Water Groundwater Recharge.
Todd Engineers evaluated natural (or intrinsic) water quality parameters (primarily sodium, calcium, chloride, and sulfate ions) using Brine Differentiation Plots, which proved to be a powerful tool to differentiate the relative amounts of blended injectate, seawater, and baseline groundwater. Brine Differentiation Plots were effective in verifying the amounts of recycled water in WCBBP monitoring wells, identifying the influence of seawater, and in documenting the travel time of injected water to monitoring wells.
Mr. Lin gave his presentation on Thursday, September 16, 2010 from 9:00 to 9:30am in Session 4B: Recyceld Water Groundwater Recharge
— updated March 2011
Sally McCraven has been promoted to Principal Hydrogeologist with Todd Engineers. Sally will celebrate her 22nd year with Todd Engineers in 2010 and her new title recognizes her substantial contributions to the firm. Her recent and long-term clients, such as the Los Angeles County Sanitation District, Santa Clara Valley Water District, and City of Los Angeles, know her to be a highly responsive project manager and a strong technical lead, who can be relied on to get the project completed successfully. Sally's experience covers a broad range of projects including basin-wide water supply feasibility studies, litigation support, monitoring program design, emerging compounds assessments, groundwater vulnerability studies, and recycled water recharge evaluations, with a particular focus on groundwater protection.
Chad Taylor has been promoted to Senior Hydrogeologist with Todd Engineers. Chad joined Todd Engineers in 2007 bringing ten years of hydrogeology experience in California and Colorado. Chad has quickly established himself at Todd Engineers as a key team member and effective project manager. Chad is a licensed Professional Geologist and Certified Hydrogeologist. He has a breadth of professional experience in the development, management, and protection of groundwater, with a focus on water supply.
Congratulations, Sally and Chad!!
— January 2010
The design intent of the well was to extract water previously recharged to the area at a design capacity of 2,500 gallons per minute (gpm). The 24-inch diameter well was constructed using a combination of mild steel louver screen and stainless steel wire wrapped screen to maximize open area and conserve material costs. A battery of aquifer tests indicated that the well is capable of producing in excess of 3,000 gpm with less than 30 feet of drawdown! Metropolitan is currently assessing how best to incorporate this new well into their system.
— December 2009
http://www.grac.org/amagenda). The conference is entitled Water Crisis and Uncertainty: Shaping Groundwater's Future. The presentation will take place on Tuesday, October 6th at 2pm as part of the Groundwater Quality Sustainability in Urban and Agricultural Settings session.
The presentation discusses the methodology and findings of a recently completed Groundwater Vulnerability Study conducted for the Santa Clara Valley Water District (District) (http://www.valleywater.org). The talk was coauthored by Vanessa De La Piedra and George Cook of the District and Michael Maley of Kennedy/Jenks Consultants (http://www.kennedyjenks.com).
With the growing uncertainty of traditional California water supply sources, protection of the water quality of existing groundwater resources is a critical groundwater management task. As such, the primary objective of the Groundwater Vulnerability Study is to assist local resource management and planning agencies in understanding the potential impacts of future land use changes on groundwater and prioritizing monitoring and groundwater protection activities.
Groundwater Vulnerability is a combination of Groundwater Sensitivity and Potentially Contaminating Activities (PCA) Risk. Groundwater Sensitivity is defined as the relative ease with which a contaminant on or near the land surface can migrate to the aquifer of interest as a function of the intrinsic characteristics of the aquifer and vadose zone materials. Groundwater Vulnerability is defined as the relative ease with which a contaminant on or near the land surface can migrate to the aquifer of interest under a given set of land use management practices and contaminant characteristics, and incorporating groundwater sensitivity conditions.
For the groundwater sensitivity analysis, hydrogeologic factors, including depth to water, degree of aquifer confinement, recharge rates, and hydraulic conductivity, were correlated with nitrate concentrations in groundwater using logistic regression analysis to identify the factors that most influence groundwater quality. Identified factors were used to develop a groundwater sensitivity regression equation. The statistical evaluation used in this study provides a more rigorous and reliable approach compared to simple index ranking methodologies commonly used for these types of assessments, such as USEPA's DRASTIC method.
PCAs were inventoried and ranked based on their association with regulated contamination cases and other criteria. PCA risk and sensitivity were combined to characterize the relative vulnerability of the study area to contamination. The sensitivity, PCA risk, and vulnerability were mapped and a web-based GIS tool was developed to allow easy viewing of information used in the analyses, uploading of new hydrogeologic data and land use information, and re-evaluation of groundwater vulnerability due to proposed land use changes.
— September 2009
Field Evidence of Biodegradation of N-Nitrosodimethylamine (NDMA) in Groundwater with Incidental and Active Recycled Water Recharge was authored by Quanlin Zhou of Lawrence Berkeley National Laboratory; Sally McCraven and William Motzer of Todd Engineers; Julio Garcia of Calpine, The Geysers; Monica Gasca of the County Sanitation Districts of Los Angeles County; and Theodore A. Johnson of the Water Replenishment District of Southern California.
The paper presents findings of a two-plus year field investigation of the fate and transport of NDMA in surface water and groundwater. Laboratory incubation work conducted by others indicates that NDMA can be biodegraded under both aerobic and anaerobic conditions. Until this study, however, direct field evidence of in situ biodegradation in groundwater has been very limited.
NDMA, an emerging contaminant in groundwater, is a byproduct of wastewater treatment processes. The County Sanitation District of Los Angeles County operates three water reclamation plants (WRP) that provide highly treated recycled water that is actively recharged at spreading grounds in the Montebello Forebay of the Central Groundwater Basin in Los Angeles County, California and incidentally recharged along upstream unlined river reaches.
For this study, NDMA was monitored in an extensive network including effluent locations, surface water stations, and groundwater monitoring and production wells to assess the fate and transport of NDMA. Monitoring results and surface water/groundwater modeling indicate that significant biodegradation of NDMA occurred in groundwater, accounting for an estimated 90 percent mass reduction over the seven-year monitoring period.
A copy of the paper can be purchased from http://www.elsevier.com/salesoffices.
— March 2009
For large development projects, the Water Code (section 10910, commonly referred to by its original legislation, Senate Bill 610 or SB 610) requires that water suppliers prepare a water supply assessment that determines whether water supplies are sufficient for the project and other planned growth over the long-term. If the water supply for the proposed project includes groundwater, the assessment must analyze the sufficiency of groundwater to meet the projected demand of the project.
In O.W.L. Foundation vs City of Rohnert Park, a key issue was the scope of the groundwater analysis. O.W.L. interpreted the water code to require analysis of all current and future pumping on the basis of a groundwater basin, with specific reference to groundwater basins as defined by the Department of Water Resources. The Court of Appeal rejected O.W.L.'s narrow interpretation, noting the large size of some groundwater basins and the impracticality of collection and analysis of basin-wide data in the 90-day statutory deadline for completion of a water supply assessment.
O.W.L. also argued that the study area used by Rohnert Park was inappropriate because it was based on watershed boundaries; these boundaries had been defined in large part by Todd Engineers in a 2004 study for Sonoma County, Groundwater Study for the Canon Manor West Subdivision Assessment District. However, the Court found the watershed study area to be legally adequate, indicating the Todd study not only provided an independent analysis, but also a rationale and evidentiary support including a discussion of the relationships between watershed boundaries and groundwater divides.
The Court's decision provides valuable guidance for preparation of water supply assessments and affirms that water suppliers and their experts must have discretion in selecting the study area and methodologies, as long as there is adequate empirical data and analysis.
— November 2008
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