Study of Potential for Groundwater Contamination from Past Dry Cleaner Operations in Santa Clara County

Santa Clara Valley Water District | September 20th, 2007

The threat of groundwater contamination posed by dry cleaning operations is primarily a legacy issue. Dry cleaners today have greatly improved usage and handling of solve

The threat of groundwater contamination posed by dry cleaning operations is primarily a legacy issue. Dry cleaners today have greatly improved usage and handling of solvents. Perchloroethylene (PCE) remains the most prevalent solvent used for dry cleaning. Dry cleaning machinery has evolved substantially and is designed to be leak-proof, air-tight, and to minimize waste generation. Dry cleaning facilities are subject to multiple permits, and are regularly inspected. A few dry cleaners have switched to “environmentally safe” solvents in their operations. Failures and operator error can nonetheless occur, representing a minor continuing threat to groundwater. The greater threat to groundwater quality is from past dry cleaning operations from as long as 50 years ago, a threat which remains significant today. This study catalogued the locations and years of operations for current and former dry cleaning operations in Santa Clara County. Past dry cleaner operational practices, solvent usage, groundwater subbasin vulnerability, and municipal supply well vulnerability are explored to develop a system to rank the relative risk of groundwater contamination from dry cleaner solvent releases. The systematic ranking of the threat posed by dry cleaners provides a means of prioritizing dry cleaning sites for further investigation. The ranking system will be useful to regulatory agencies for determining which cases warrant more aggressive investigation and remediation.

Study role of climate change in extreme threats to water quality

Nature Portfolio (Springer Nature) | July 21st, 2016

With concerns about climate ‘extremes’ growing, water is often the focus — either too much or too little. That is no coincidence: climate and the hydrolog

With concerns about climate ‘extremes’ growing, water is often the focus — either too much or too little. That is no coincidence: climate and the hydrological cycle are tightly coupled, and water is essential to ecosystems and societies. But it is not just the quantity of water that matters. So does its quality.

Study to Evaluate Long-Term Trends and Variations in the Average Total Dissolved Solids Concentration in Wastewater and Recycled Water

Southern California Salinity Coalition | March 30th, 2018

This report was funded by the Southern California Salinity Coalition (SCSC). SCSC and its member agencies are dedicated to managing salinity in the water supplies, waste

This report was funded by the Southern California Salinity Coalition (SCSC). SCSC and its member agencies are dedicated to managing salinity in the water supplies, wastewater, and recycled water. Member agencies include Eastern Municipal Water District (EMWD), Inland Empire Utilities Agency (IEUA), Metropolitan Water District of Southern California (MWDSC), Orange County Sanitation District (OCSD), Orange County Water District (OCWD), San Diego County Water Authority (SDCWA), Sanitation Districts of Los Angeles County (LACSD), and Santa Ana Watershed Project Authority (SAWPA). Daniel B. Stephens & Associates, Inc. (DBS&A) performed the analysis and is submitting this technical memorandum to address the research questions posed by SCSC and its member agencies. The 2011 to 2016 drought in California, in conjunction with unprecedented statewide conservation legislation, caused several member agencies to face challenges meeting regulatory water quality standards for the salinity of discharge water from wastewater treatment plants (WWTPs). In particular, total dissolved solids (TDS) concentrations have increased, while the operation of WWTPs have remained consistent with prior years. Figure ES-1 is a typical example of TDS trends for WWTPs in Southern California.

Submittal of 2015 Agricultural Water Management Plans and Implementation of Efficient Water Management Practices Report

California Department of Water Resources (DWR) | September 22nd, 2017

Senate Bill X7-7, the Water Conservation Act of 2009 (SB X7-7), requires agricultural water suppliers who provide water to more than 25,000 irrigated acres (excluding acr

Senate Bill X7-7, the Water Conservation Act of 2009 (SB X7-7), requires agricultural water suppliers who provide water to more than 25,000 irrigated acres (excluding acreage irrigated by recycled water) to adopt and submit Agricultural Water Management Plans (AWMPs or Plans) to the Department of Water Resources (DWR) and to implement Efficient Water Management Practices (EWMPs), including two critical EWMPs: the measurement and volumetric pricing of water deliveries. These AWMPs were due by January 31, 2016. Governor Brown’s Executive Order B-29-15 required agricultural water suppliers that provide water from 10,000 to 25,000 irrigated acres to submit AWMPs by July 1, 2016. California Water Code (CWC) §10845(a) and (b) directs DWR to report on the following: • The status of adopted AWMPs • Exemplary elements of adopted plans • An evaluation of the effectiveness of implemented AWMPs in promoting efficient agricultural water management practices • Recommendations relating to proposed changes to the AWMP reporting requirements and EWMPs Additionally, CWC section 10608.48(g) directs DWR in consultation with the State Water Resources Control Board (SWRCB) to prepare and submit to the Legislature a report on: • EWMPs that have been implemented or are planned to be implemented, and • An assessment of the manner in which the implementation of an EWMP has affected and will affect agricultural operations and an estimation of water use efficiency improvements, if any. This legislative report addresses the above requirements in a single report and documents the status of AWMP submittals and the implementation of associated EWMPs or best management practices (BMPs) for those water suppliers submitting a United States Bureau of Reclamation (Reclamation) plan in lieu of a plan meeting SB X7-7 criteria.1 A table comparing the SB X7-7 EWMPs and Reclamation BMPs is in Appendix B. Further information on SB X7-7 requirements and legislative reports are available at http://www.water.ca.gov/wateruseefficiency/sb7/.

Submittal of Report – Status Report on Implementation of the California Statewide Groundwater Elevation Monitoring Program Years 2012-2015

California Department of Water Resources (DWR) | April 1st, 2016

Senate Bill X7 6 (SBX7 6) (Chapter 1, Statutes of 2009) added provisions for groundwater monitoring to Division 6 of the Water Code (Water Code § 10920 et seq.). The bil

Senate Bill X7 6 (SBX7 6) (Chapter 1, Statutes of 2009) added provisions for groundwater monitoring to Division 6 of the Water Code (Water Code § 10920 et seq.). The bill authorized the Department of Water Resources (DWR) to establish permanent, locally managed, groundwater elevation monitoring and reporting for all 515 groundwater basins identified in DWR Bulletin 118, California’s Groundwater, as shown in Figure 1. Groundwater elevation data are foundational to improving the management and sustainability of California's groundwater resources. DWR developed the California Statewide Groundwater Elevation Monitoring (CASGEM) Program to implement SBX7 6. Water Code section 12924(c) requires DWR to report the status of the CASGEM Program to the Governor and Legislature by January 1, 2012, and thereafter in years ending in “5” or “0”. This report covers calendar years 2012 through 2015. The overall purpose of the CASGEM Program is to track seasonal and long-term groundwater elevation trends in groundwater basins statewide. The Water Code directs DWR to rely on, and build upon, the many established local agency groundwater monitoring and management efforts throughout the state. DWR works cooperatively with local agencies, referred to as CASGEM “Monitoring Entities,” to collect and maintain groundwater elevation data in a manner that is readily and widely available to the public. During 2010 and 2011, the first two years of the CASGEM Program, DWR focused its efforts on initiating the CASGEM Program and ensuring that Monitoring Entities would, by January 2012, be able to submit groundwater elevation data electronically.

Subsidence (2004-2009) in and near lakebeds of the Mojave River and Morongo groundwater basins, southwest Mojave Desert, California

U.S. Geological Survey (USGS) | July 1st, 2014

Subsidence: A critical challenge to Friant-Kern canal water deliveries

Friant Water Authority | January 17th, 2018

The Friant Water Authority is facing a critical challenge right now - one that has reduced our ability to deliver water to many Friant Division Contractor’s

The Friant Water Authority is facing a critical challenge right now - one that has reduced our ability to deliver water to many Friant Division Contractor’s by nearly 60%. It is a challenge that must be met today if we are to ensure our long-term commitment to delivering high-quality, dependable water, in the amounts needed by farmers and cities in the San Joaquin Valley.

Subsidized or subsidizing? Municipal drinking water service funds in California

Utilities Policy (Elsevier) | September 29th, 2022

In the longstanding debate over efficiency and effectiveness in drinking water provision between public versus privately governed systems, one of the main contention poin

In the longstanding debate over efficiency and effectiveness in drinking water provision between public versus privately governed systems, one of the main contention points is the reasons for different bill levels imposed by city-run as compared to privately owned water systems. In this study, we examine one potential explanation for disparities in bills: whether cities use their general funds to subsidize their drinking water fund operations or vice versa. Either practice goes against “user pays” principles, as pointed out by critics of municipal operation. However, the claims have not been tested empirically at scale. We extract and analyze city water enterprise fund financial data from the California State Controller Cities Raw Data of Financial Transaction Reports to empirically assess the extent to which and reasons why interfund transfers occur in California's 267 municipally owned water utilities. We find very little evidence that substantial interfund transfers, in either direction, occur between water enterprise funds and general funds within California cities, indicating that enterprise fund control measures are generally successful. These findings suggest that with proper regulation, the municipal fund subsidy debate is essentially a distraction from the real reasons why municipal and other water provider rates differ substantially.

Subsurface Geometry of the San Andreas Fault in Southern California: Results from the Salton Seismic Imaging Project (SSIP) and Strong Ground Motion Expectations

Seismological Society of America (SSA) | August 1st, 2017

The San Andreas fault (SAF) is one of the most studied strike‐slip faults in the world; yet its subsurface geometry is still uncertain in most locations. The Salton S

The San Andreas fault (SAF) is one of the most studied strike‐slip faults in the world; yet its subsurface geometry is still uncertain in most locations. The Salton Seismic Imaging Project (SSIP) was undertaken to image the structure surrounding the SAF and also its subsurface geometry. We present SSIP studies at two locations in the Coachella Valley of the northern Salton trough. On our line 4, a fault‐crossing profile just north of the Salton Sea, sedimentary basin depth reaches 4 km southwest of the SAF. On our line 6, a fault‐crossing profile at the north end of the Coachella Valley, sedimentary basin depth is ∼2–3km∼2–3  km and centered on the central, most active trace of the SAF. Subsurface geometry of the SAF and nearby faults along these two lines is determined using a new method of seismic‐reflection imaging, combined with potential‐field studies and earthquakes. Below a 6–9 km depth range, the SAF dips ∼50°–60°∼50°–60° NE, and above this depth range it dips more steeply. Nearby faults are also imaged in the upper 10 km, many of which dip steeply and project to mapped surface fault traces. These secondary faults may join the SAF at depths below about 10 km to form a flower‐like structure. In Appendix D, we show that rupture on a northeast‐dipping SAF, using a single plane that approximates the two dips seen in our study, produces shaking that differs from shaking calculated for the Great California ShakeOut, for which the southern SAF was modeled as vertical in most places: shorter‐period (⁠T<1sT<1  s⁠) shaking is increased locally by up to a factor of 2 on the hanging wall and is decreased locally by up to a factor of 2 on the footwall, compared to shaking calculated for a vertical fault.

Subsurface water flux in California's Central Valley and its source watershed from space geodesy

American Geophysical Union (AGU) | September 29th, 2022

We combine measurements from Global Positioning System positioning and Gravity Recovery and Climate Experiment gravity to infer change in water components in Central Vall

We combine measurements from Global Positioning System positioning and Gravity Recovery and Climate Experiment gravity to infer change in water components in Central Valley and its source watershed, the Sacramento-San Joaquin-Tulare River basin better than possible with either technique separately. We find that the Central Valley has lost groundwater from 2006 to 2021 at 2.2 ± 0.7 km 3/ yr (95% confidence limits follow the “±” sign), with 2/3 of the groundwater loss occurring in the southern part of the Valley. We estimate the seasonal recharge and loss of subsurface water in the Central Valley. Comparison to a model accounting for precipitation, evapotranspiration, and river water entering and leaving the Central Valley suggests that deep groundwater may be flowing from the Sierra Nevada mountains into the Central Valley.