HydroVisions | September 2020 by HydroVisions

VOLUME TWENTY-NINE SEPTEMBER 2020

V.29

2020 Fall Issue

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HYDROVISIONS is the official publication of the Groundwater Resources Association of California (GRA). GRAâ&#x20AC;&#x2122;s mailing address is 700 R Street. Suite 200, Sacramento, CA 95811. Any questions or comments concerning this publication should be directed to the newsletter editor at editor@grac. org or faxed to (916) 231-2141. The Groundwater Resources Association of California is dedicated to resource management that protects and improves groundwater supply and quality through education and technical leadership

Editor John McHugh editor@grac.org Editorial Board Adam Hutchinson David Von Aspern Tim Parker Executive Officers President Abigail Madrone West Yost Associates Tel: 530-756-5905 Vice-President R.T. Van Valer Roscoe Moss Company Tel: 323-263-4111 Secretary John McHugh Consulting Hydrogeologist Tel: 510-459-0474 Treasurer Rodney Fricke GEI Tel: 916-631-4500 Officer in Charge of Special Projects Christy Kennedy Woodward & Curran Tel: 925-627-4122 Immediate Past President Steven Phillips U.S. Geological Survey Tel: 916-278-3002 Administrative Director Sarah Erck GRA Tel: 916-446-3626

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Directors Bradley Herrema Brownstein Hyatt Farber Schreck Tel: 310-500-4609 James Strandberg Woodard & Curran Tel: 925-627-4122 Rob Gailey Consulting Hydrogeologist Tel: 415-407-8407 Murray Einarson Haley & Aldrich, Inc. Tel: 530-752-1130 Lisa Porta Montgomery & Associates Tel: 916-661-8389 Bill DeBoer Montgomery & Associates Tel: 925-212-1630 John Xiong Haley & Aldrich, Inc. Tel: 714-371-1800 John Van Vlear Newmeyer & Dillon Tel: 949-271-7127 Lyndsey Bloxom Water Replenishment District of Southern CA Tel: 562-9210-5521 To contact any GRA Officer or Director by email, go to www.grac.org/boardof-directors

2020 Fall Issue

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TABLE OF CONTENTS

President’s Message

Page 6

2020 GSA Summit

Page 8

Page 14

2021 GRA Call For Nominations

The Geochemist’s Gallery

Page 18

Newest ConjunctiveUse Version of Modflow Released by USGS

Groundwater Management in Ontario, Canada

Wells and Words

I AM GRA

Federal Corner

Scaling the Solution to

GRA’s New Corporate/ Organization Group Membership

GRA Parting Shot

Page 20

Page 34

Page 28

Page 32

Page 24

the Problem

Page 36

Page 44

Page 41

The statements and opinions expressed in GRA’s HydroVisions and other publications are those of the authors and/or contributors, and are not necessarily those of the GRA, its Board of Directors, or its members. Further, GRA makes no claims, promises, or guarantees about the absolute accuracy, completeness, or adequacy of the contents of this publication and expressly disclaims liability for errors and omissions in the contents. No warranty of any kind, implied or expressed, or statutory, is given with respect to the contents of this publication or its references to other resources. Reference in this publication to any specific commercial products, processes, or services, or the use of any trade, firm, or corporation name is for the information and convenience of the public, and does not constitute endorsement, recommendation, or favoring by the GRA, its Board of Directors, or its members. 2020 FALL

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Volume 25, 2 Special Issue Released: Contaminant Geophysics Contact: Editor-in-Chief - Geoff Pettifer – editorfasttimesnewsmagazine@gmail.com; +61407 841 098 Advertising: David Valintine - dvalintine@fugro.com Editor Vol 25, 2: Dale Werkema – Werkema.D@epa.gov FastTIMES Volume 24, 5 Special Issue on Contaminant Geophysics is available for download (from https://www.eegs.org/latest-issue). In the foreword from Vol 25, 2 Editor, Dale Werkema, writes “Our planet and our physical, biological, and societal dynamics are undergoing a significant recalibration to hopefully a more peaceful, healthy, equitable, just, and sustainable future. Just as weather patterns and storms are the result of atmospheric energy equilibration and ocean currents and waves are in a constant state of seeking equilibrium, with a concerted effort from our scientific community and other like-minded individuals, I hope these sectors of our life and this planet will move to a more peaceful state of justice and sustainability for ours and future generations. This process is, in fact, the underlying goal of contaminant studies culminating in complete remediation and protection of our natural resources for our utility and life sustaining properties. As much of contaminant remediation is to protect our planet’s unique life supporting water resources, this Special Issue of FastTIMES includes a sampling of our science’s contribution to this process. “

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PRESIDENTâ&#x20AC;&#x2122;S MESSAGE ABIGAIL MADRONE

Abigail Madrone, Business Development Director with West Yost. Throughout her 20-year career, Abigail has served and supported groundwater and water resources management through groundwater monitoring and analysis, project and program management and public outreach and education.

Our dedicated volunteers make GRA extraordinary. I continue to be impressed by our organizationâ&#x20AC;&#x2122;s ability to advance our mission and serve our members. The GRA Leadership team of volunteers including the Board, Committees and Branches is thriving in our new reality as we explore creative ways to stay engaged. We are leading the way by continuing to provide professional development and a forum for our members to expand their networks and grow their careers through regional branch meetings, networking sessions, advocacy, technical leadership, student outreach and events. Our marquee event, the 3rd Annual Western Groundwater Congress (WGC), on September 14-17, 2020, chaired by R.T. Van Valer, GRA Vice President and Director, is a must attend event for water resource and groundwater professionals. We have an amazing line-up of speakers, workshops and presentations that highlight industry leaders and groundwater management and remediation innovators. The WGC will include a student forum, GroundwaterX, where students can present their work and make introductions to career professionals. We will have many networking opportunities and facilitated events to catch-up with professional contacts and forge new connections.

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President’s Message

As we look to our future, we seek to support the next generation of GRA leaders to help guide and serve our organization at the Branch, Committee or Board level. We are a volunteer organization, and our ongoing success reflects the contributions of many. We are always looking for motivated and active GRA members to join our GRA Leadership team. It takes many inspiring, diverse and dedicated volunteers to support our Branches, committees, events and initiatives. • Get engaged with your local Branch by contacting your regional Branch President • Explore potential committee opportunities by contacting Committee Chairs • Interested in volunteering, but unsure who to contact, please reach out to me, amadrone@westyost.com If you or someone you know would be an exceptional candidate for consideration to join the GRA Board, please review the minimum criteria below and refer to the online nomination form to learn more about the process and procedures. Board member terms are for three years and will commence service January 1, 2021. GRA believes that diverse representation and participation on the Board adds significant value to the association and GRA’s relevance and effectiveness are enhanced by embracing all backgrounds. • GRA Board Nomination Minimum Qualifications • Active member of GRA at the time of nomination • Experience in a groundwater-related field • Prior role(s) in a GRA Branch, committee or other GRA activity, or like experience with a similar organization. Visit our website grac.org, engage with us on social media or check your inbox for upcoming announcements and details on these and other great events. Stay informed to the latest developments and technology though GRACasts and short courses to help advance your career. We are grateful for you, our members, sponsors, affiliates, volunteers and leaders. See you all virtually at the 3rd Annual Western Groundwater Congress!

- Abigail Madrone, 2020 GRA President

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LISA PORTA

Lisa Porta joined Montgomery & Associates as a senior water resources engineer in January 2019 and has more than 12 years of groundwater modeling and integrated water planning experience in California and the Western United States. She works in M&Aâ&#x20AC;&#x2122;s Sacramento office and is a member of the GRA Board of Directors and the Technical Committee Chair.

THE THIRD ANNUAL GSA SUMMIT - VIRTUAL 2020 is a year like no other, our water resources community is struggling to keep connected and exchange information in this new world. Just as the 2020 GSA Summit planning team finalized the agenda for a celebratory conference to be held in Sacramento, June 10 and 11, a state-wide lockdown occurred, that was going to last over two months. In the midst of uncertainty, our team quickly shifted gears and decided to keep the GSA Summit, on the same dates, with the same program and speakers, but this time, virtually, via a webconferencing platform. As a result, we were able to offer our GRA members and the water resources community a timely program on: lessons learned and reflections from the 2020 GSPs, tips and tricks on successful outreach to stakeholders, how to grapple with Sustainable Management Criteria (SMC) development and future GSP implementation.

GSA SUMMIT

THE 2020 GSA SUMMIT

Our virtual format comprised a 6-hour continuous conference on both days, with 20 min. breaks in-between each 1-hour long panel session. We also had a 1-hour lunch break including a popular trivia game (~ 30 folks participated each day).

Figure 1, approximate locations of GSAs and other local agencies in attendance. Over 130 SGMA enthusiasts from all over the state gathered virtually to connect on an important topic in California water resources management.

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LISA’S OPENING REMARKS:

TH HI

ANN

A UAL GS

“Way to adapt and make the most of the ever-changing world we’re living in right now!! Great job weaving in fun and entertainment too”.

Even though 2020 has turned into a very challenging year, we still have some great achievements to recognize and celebrate. This is, after all, the 5-year anniversary of SGMA and a huge milestone has been reached by the first set of GSPs submitted in January this year. On behalf of GRA, I would like to congratulate all of you who have worked so tirelessly over the past 2 years to achieve this. Having worked on some of these GSPs myself, I know the heavy lift that it was. So, let’s raise a virtual glass to each other to recognize all our efforts and keep the momentum going for the GSPs to be submitted in 2022! This summit was possible due to the incredible planning team! Special thanks to our six moderators, who extended extra effort to coordinate with speakers. Let’s not forget our fun squad, Emily and Lindsay, who organized two very fun trivia lunch breaks. THANK YOU TO OUR AMAZING PLANNING TEAM MODERATORS Bryce McAteer Dave Ceppos Georgina King Raphael Silberblatt Rob Gailey Sierra Ryan FUN SQUAD Emily Honn Lindsay Martien

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PLANNING COMMITTEE Abhishek Singh Adam Hutchinson Andy Rodgers Ann DuBay Lisa Hunter Marcus Trotta Mark Nordberg Matt Kennedy Pat Vellines

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The first day started with the keynote speakers. Tina Cannon Leahy made some eye-opening remarks on SGMA’s passage and her candid opinion regarding the current state of SGMA progress. She also clarified some of the grey areas of the legislation. Tina expressed her personal satisfaction with SGMA implementation and is glad that people are coming together on important groundwater management issues. Craig Altare, from DWR, and Natalie Stork, from State Water Board, gave us some insights into their work since GSPs were submitted and data and outreach assistance provided by their agencies. The extensive Q&A session was very interesting.

The Next session, Lessons Learned from 2020 GSPs, moderated by Bryce McAteer, provided a perspective from critically overdrafted basins; the four speakers shared insightful comments on what they learned from developing their GSPs and transitioning into implementation.

In the afternoon Rafi Silberblatt took us through tips on conflict resolution or how to survive your next SGMA meeting; and Dave Ceppos explained SGMAntics to us!

We had a fun happy hour to close out Day 1 – see all the happy faces!). It was great to follow up on topics with Tina and share our experiences working on SGMA projects and learning new skills. Emily and Lindsay created a great list of cocktails; someone made a Measurable Objective, and a few of us drank the Sustainability Goal cocktail. However, no one attempted to drink the Undesirable Result! Everyone had fun connecting and meeting new people.

Some of my favorite quotes from the panel: • Gary Petersen: Be transparent, following a good process is as important as the outcome • Deanna Jackson: There are some questions that cannot be answered by Google – (so true for SGMA!) • Eric Osterling: Development of SMCs were more subjective than initially thought; often times, everyone is right (or wrong), hard to find the right answer • Importance of trust during outreach and engagement process • And remember, GSPs are not perfect, they just set the stage for the entire long-term SGMA process 10 HYDROVISIONS

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On the morning of Day 2, two SMC development and overview sessions, moderated by Rob Gailey, provided technical and policy considerations of setting SMC for: interconnected surface water, land subsidence, chronic lowering of water levels and degraded water quality. Speakers drew from experiences developing the 2020 GSPs and answered tough questions from the audience. The second SMC session provided perspectives from a group of nonprofit organizations who have taken a detailed look on specific topics of the 2020 GSPs with an emphasis on underrepresented beneficial users (disadvantaged communities and groundwater dependent ecosystems) and stakeholder engagement. Public review of these GSPs revealed some important points to be considered for preparation of the plans due in 2022.

The afternoon session panels looked at GSP implementation, data gaps, and coordinating with other governmental agencies. Speakers in the first session, moderated by Georgina King, discussed how proving sustainability twenty years after GSP submission is a long-term commitment which will often require implementing a number of strategies, including filling data gaps and developing appropriate projects and actions to avoid undesirable results. Panelists examined some of these strategies and shared how GSAs have started implementing their GSPs. The closing session, moderated by Sierra Ryan, explored how GSAs, which are new governmental agencies, are going to interface and coordinate with existing government agencies, such as counties, cities, planning agencies, etc. in order to comply with SGMA. This session provided insights into various issues related to coordination and planning during GSP implementation.

GSA SUMMIT ARTICLES PUBLISHED BY MAVEN’S NOTEBOOK Click Here: Summary of Craig Altare’s presentation Click Here: Talks from the “Lessons Learned from 2020 GSPs in overdrafted basins” Click Here: SETTING SUSTAINABLE MANAGEMENT CRITERIA: IT’S EASY, ISN’T IT?

“This is the single most important conference for GSA’s and you all did an excellent job in making it happen.”

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As I reflect back on this Summit, I can’t help think that it is amazing how far we have come as a water resources community, working on SGMA projects! At the first GSA Summit, GSAs were just formed and were trying to understand the GSP regulations and identifying all the different aspects of GSP development. At our second Summit, last year, we were working hard to put finishing touches on the first set of GSPs. This Summit allows us to reflect on the first rounds of GSPs submitted and regroup on what we think we can do better moving forward into implementation. SGMA has helped push science and data management forward like never before, created new networks and provided platforms to reach out to various communities, including Native American tribes. We see the emergence of new local leaders in groundwater management and a true desire to succeed in sustainably managing surface water and groundwater for our future generations and the sake of this State’s economy. Thank you to our sponsors, moderators and to our excellent speakers; we really appreciate your time to prepare for this Summit and make yourselves available during these challenging times. Thank you to our generous sponsors and virtual exhibitors, for your support to GRA and the water resources community.

GSA SUMMIT

LISA’S CLOSING REMARKS:

Our cooperating organizations, the Association of California Water Agencies, Maven’s Notebook and the Northern California Water Association, helped us spread the word about this event and make sure that folks working on GSPs got the opportunity to participate.

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S&P Hope to see you all again in person next year, for our 4th Annual GSA Summit, which will be held in Sacramento June 9 and 10, 2021, at the original venue for this event at the Hilton in Sacramento-Arden. Until we see you again…KEEP CALM AND SGMA ON!

M&M R&P WDR CM

Construction Management Experienced construction managers and owner’s advisors provide an advocate for successful construction. Let West Yost provide the oversight every project needs.

ASR

DAVIS • CARLSBAD • IRVINE • PLEASANTON SACRAMENTO • SANTA ROSA • WALNUT CREEK

we are water 2020 FALL

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THE GEOCHEMIST’S GALLERY

WILLIAM E. (BILL) MOTZER William E. (Bill) Motzer, PHD, PG, CHG, is a somewhat retired Forensic Geochemist

Diluting Isotopes* Introduction In my previous articles of per- and poly-fluoroalkyl substances (PFAS), I discussed the chemistry of a “family” of manufactured (anthropogenic) chemicals used in products from the 1940s to the early 2000s that resist heat, oils, greases, stains, and water. Such surface-active agents were included in aqueous firefighting foams (AFFF), stain-resistant products, coating additives (i.e., polytetrafluoroethylene or PTFE also known as Teflon™), and cleaning products. Industrial uses were widespread spanning aerospace, automotive, chemical, construction, semiconductor, and textile companies. Under typical environmental conditions PFAS do not hydrolyze, photolyze, or biodegrade. Therefore, they are extremely environmentally persistent with potential to bioaccumulate and biomagnify in wildlife because they are readily absorbed upon ingestion, primarily accumulating in blood serum, kidneys, and liver. Animal toxicological studies have indicated potential developmental, reproductive, and systemic effects.

*A shorter version originally appeared in the California

Section of the American Chemical Society June 2020 issue of The Vortex: www.calacs.org.

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The Geochemist’s Gallery 2020 FALL

Background The most well-known and researched PFAS compounds are PFOA (perfluorooctanoic acid – C8HF15O2; CAS No.: 335-67-1) and PFOS (perfluorooctane sulfonic acid – C8HF17O3S; CAS No.: 1763-23-1). Within the U.S., PFOS and PFOA were the two PFAS compounds produced in the largest commercial amounts. PFOA is a perfluoralkyl carboxylate synthetically produced as a salt and its most widely produced form is the ammonium salt. PFOS is commonly used as a simple salt (such as potassium, sodium, or ammonium) or is incorporated into larger polymers. There are approximately 4,700 known PFAS compounds and these occur in almost all global environments including remote places. There are now major environmental concerns for surface-water and groundwater contamination in urban industrial areas. Health-based advisories or screening levels for PFOA and PFOS in drinking water have been developed by the U.S. Environmental Protection Agency (U.S. EPA) and state regulatory agencies, including California. Isotope Dilution Surface and groundwater sampling protocols have also been developed; analytical detection methods include high-performance liquid chromatography (HPLC) and tandem mass spectrometry (TMS). U.S. EPA analytical methods, specifically Method 533 for drinking water, can now determine 14 branched and linear isomer and 11 unique PFAS compounds. This method has detection and reporting limits in the ng/L (parts per trillion) range and because of the very low concentrations requires a precise and accurate analysis that includes isotope dilution analysis (IDA) usage. So why is IDA done and why is it important? First, IDA: (1) allows for accurate recovery correction and (2) normalizes instrument performance across different matrices. Second, and more importantly, IDA methodology allows accurately determination of the amount or quantity of an element or chemical compound by adding known amounts of an isotopically-enriched substance (either a stable or radioactive isotope) or standard to the sample to be analyzed (see Figure 1). Mixing of an isotopic standard with the sample essentially “dilutes” the sample’s isotope composition. Therefore, this is also considered as a method of internal standardization, because the standard (an isotopically-enriched form of analyte) is added directly to the sample. Additionally, unlike traditional analytical methods relying on signal intensity, IDA employs signal ratios. Therefore, IDA is regarded as one of analytical chemistry’s measurement methods having the highest metrological standing. IDA is almost exclusively used with TMS analyses for applications where a high degree of accuracy is required; however, it can also be employed with every type of MS used in different environmental analytical fields and standards (e.g., all National Metrology Institutes rely on IDA when producing certified reference materials). For high-precision analysis, IDA is applied when an analyte‘s low recovery is required. In addition to stable isotopes usage, radioactive isotopes can also be employed; this is often required in biomedical applications (e.g., in estimating blood volume).

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Because IDA involves same element isotopic measurements, differences in chemical compositions are eliminated. IDAâ&#x20AC;&#x2122;s major advantage is that during the entire analytical process including sample preparation, analyte separation, and sample enrichment, no analyte quantitative recovery is necessary once equilibration occurs between the spike and sample. Therefore, when compared to other analytical methods, IDA is more stable and less errorprone during chemical processing steps. For trace and ultra-trace analysis, different elemental species accuracy is essential. For such analyses, IDA, allows for adding one, or two, highly enriched isotope tracers or spikes (the two-spike method also known as the double-spike technique). This is accomplished by adding an element, with well-known concentrations to the sample, which is then mixed and homogenized with the solid sample or aqueous solution. Determination of the trace element concentration is then performed by measuring the change in the isotope ratios in the sample-spike mixture compared to those in the sample and highly enriched isotope tracer. So, the next time you submit a sample for PFAS analysis using IDA, remember that the returned analytical data will have greater accuracy and therefore reliability than other methods. Regulatory Update On May 27, 2020, The San Francisco Bay Region of the Regional Water Quality Control Board (SFRWQCB) issued a transmittal memorandum containing interim final environmental screening levels (ESLs) for PFOS and PFOA. The interim final ESLs are described and outlined in the SFRWQCB May 11, 2020 PFAS ESL memorandum. ESLs are generally used for soil to determine potential contaminant leaching to groundwater. The interim final ESLs for PFOA and PFOS are for guidance only and therefore their use is not mandatory and are not considered as default cleanup standards. The two memos may be downloaded here.

Figure 1: IDA basic principles require adding an isotopically altered standard to a sample (one spike method). This changes the analytes natural isotopic composition and by measuring this change one can accurately calculate the amount of the analyte present in the sample. Source

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The Geochemistâ&#x20AC;&#x2122;s Gallery

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CALL FOR NOMINATIONS FOR 2021 GRA DIRECTORS GRA is now soliciting nominations for GRA Board of Director candidates. Board member terms are for three years and will commence service January 1, 2021. The Nominations Task Force established the following criteria for nominating and selecting candidates for the final ballot that will be presented to GRA membership for voting: Minimum Qualifications for Director Nominees • Active member of GRA at the time of nomination • Experience in a groundwater-related field (i.e. staff or board members of consulting firms, public municipal or agricultural water agencies, private water companies, non-governmental organizations, resource management agencies, regulatory agencies, and groundwater sustainability agencies) • Prior role(s) in a GRA Branch, committee or other GRA activity, or like experience with a similar organization.

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Call for Nominations

Nominating Guidelines and Procedures • Directors and members of GRA may nominate themselves or another member as a prospective candidate to run for the Board • Nominations must be submitted in writing to GRA and accompanied by: • A statement from the nominee addressing the following questions: • Why are you interested in serving on the GRA Board of Directors? • What qualifications and experience do you have for serving as a Board member? • What specific skills or expertise do you bring to GRA and the GRA Board (e.g., leadership skills, fund-raising, financial management, etc.)? • What experience do you have serving on similar Boards? • What level of time commitment can you make to GRA? • Current curriculum vitae • A letter of recommendation from a current Director or Regular Member • The Nominations Task Force will review all nominations, evaluate the nominees based upon their response to the above questions and their qualifications, and will conduct interviews, if deemed necessary • The Nominations Task Force will recommend a slate of nominees to the GRA Board of Directors for approval • The approved slate of nominees will be presented to GRA membership in ballot form in accordance with GRA Bylaws. To nominate yourself, or to nominate someone else, please complete the online nomination form. Statement of Inclusivity GRA seeks to foster a community that encourages understanding, appreciation and acceptance of all persons involved in GRA membership and activities. GRA believes that broad representation and participation on the Board adds significant value to the association and that GRA’s relevance and effectiveness are enhanced by embracing diverse backgrounds. Nominations must be received no later than October 2, 2020. Should you have any questions or need additional information, please contact Sarah Erck, GRA Administrative Director at (916) 446-3626, or Steve Phillips, Nominations Task Force Chair, at (916) 917-7376.

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BY RANDALL T. HANSON, ONE-WATER HYDROLOGIC Randy Hanson, an expert in numerical modeling of groundwater flow, retired from the USGS in 2018 as a Research Hydrologist with 38 yearsâ&#x20AC;&#x2122; service. He is the president of One-Water Hydrologic based in sunny San Diego.

Recharge

NEWEST CONJUNCTIVEUSE VERSION OF MODFLOW RELEASED BY USGS

Designed for the analysis of conjunctive-use management. The California Water Science Center of the USGS just released the newest version of Modflow developed with the U.S. Bureau of Reclamation. With several decades of applications worldwide, this is the fourth major version of the Modflow-One Water Hydrologic Flow Model (MF-OWHM, version2). Development started as the brain child of Dr. Thomas Maddock III (University of Arizona) in 2004 and resulted in the PhD Dissertation of Dr. Wolfgang Schmid (2006) with related USGS development of the Central Valley Hydrologic Model (CHVM1, 2009) and the Pajaro Valley Hydrologic Model (PVHM, 2014). While many have looked at other approaches to groundwater modeling, the MF-OWHM uniquely provides a holistic approach to modeling the use and movement of all water by coupling groundwater and surface-water flow with land use and climate wrapped within a supply-and-demand framework. This simulation and analysis framework is demand driven and supply constrained, which allows modeling a broader scope of processes and related issues within conjunctive use. Most importantly, MF-OWHM provides better connections for understanding SGMA hydrologic budgets and undesirable effects including the those effectsâ&#x20AC;&#x2122; root cause(s). It facilitates analysis of: adaptation and sustainability, climate change, future or alternate development, and augmentation within conjunctive -All required under SGMA.

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Modflow

This newest and fastest Modflow-OWHM called “One Water” development was led by Dr. Scott Boyce (USGS) with Randy Hanson (One-Water Hydrologic), Ian Ferguson (USBR), Thomas Reimann (Technical University of Dresden), and Steffen Mehl (Cal-State Chico). Conjunctive use is one of the, essential metrics of sustainability, and models like MF-OWHM that consider all the water, all the time, everywhere in a watershed are able to perform this analysis by linking land, water, climate and food. From Sonoma, Napa, Salinas, and Pajaro Valleys of coastal California to the Central Valley, and from the Osage Nation, Oklahoma and South Platte, Nebraska to the transboundary conflicts of the Lower Rio Grande, model analysis provides new insights into the combined use of land and water. This paradigm has become clear in the new SGMA practitioners guide to hydrologic budgets that shows how the linkage between the demand drivers, climate and land use, need to be considered together when assessing the sustainability of all water resources. Thus, an integrated approach that couples the analysis of heads and flows allows seeing the effects and feedbacks controlling thresholds of the six undesirable results that are used to limit overexploitation and enhance sustainability by SGMA. MF-OWHM integrates physically-based flow processes—derived from MODFOW-2005—into a supply and demand framework to simulate natural and human-influenced flows. While MF-OWHM can be used to run any previous model developed with MF-2005 and other Modflow variants, there is more “under the hood” to help modelers easily go further and deeper in their analysis. As Modflow-2005 was further developed, many of the variants of Modflow resulted in isolated features in different versions. MF-OWHM brings all of these isolated features back into one modeling platform as an enhanced and improved fusion; an integrated hydrologic model (IHM). What makes MF-OWHM better than just the simulation of head-dependent flows in standard MODFLOW versions, is additional and optional simulation of coupled flow-dependent flows, and deformation-dependent flows that collectively affect conjunctive use, sustainability analysis of water resources and related undesirable results of SGMA. This new version also contains a wide range of new features and upgrades that are not available in any other variants of Modflow or other codes.

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With the most complete set of solvers, solver and performance information, error tracking, and more budget options, MF-OWHM has the features that help modelers make sense of model results. Other completely new features include a new version of the Conduit Flow Process for fractured and karst aquifers and the upcoming Surface-Water Operations Process for tightly coupled simulation of reservoirs and related reservoir operation rules. Many new innovations within the Farm Process also provide more complete linkages with climate and land use, such as water banking, salinity leaching, and fractional land use. Many new budget features also allow a broader spectrum of budgets and budget types from total and sub-regional budgets needed by SGMA to more detailed analysis of landscape, groundwater, surface-water, and climate budgets to more specific budgets of groups of wells, boundaries, or surface-water components. The MF-OWHM framework also is designed to support the concept of “self-updating” models. While many models rely on a spatial GUI framework, MFOWHM has created a new structure that separates spatial and structural framework data from temporal data structures needed for the development of “selfupdating” models. This allows the input files to be more transparent to model developers, users and reviewers, making input easier to use and update. These data streams also facilitate easier dataexchange protocols needed with water purveyors. This separation also allows automated programs to query databases, websites or spreadsheets for data to update the input files (e.g. stream flows or specified pumping rates). This automation, or selfupdating, of the input files allows for more ready use of the simulation model after its initial construction, thus increasing the longevity and value of the model.

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Modflow

This new approach across many features is essential for maintaining models and for creating alternate model versions needed for climate change, alternate development scenarios, and easy updates needed for annual SGMA budget reporting. MF-OWHM easily allows for importation of related Precipitation-Runoff models such as PRMS, HSPF, VIC, and BCM. MF-OWHM applications for climate-change analysis from downscaled and bias-corrected GCM output also reduces preprocessing needed to develop climate-change input. MF-OWHM can also be linked to land-use models the such as the USGS LUCAS model or other agro-economic models to include potential changes in land-use, vegetation, and crop distributions. Additional Guidance packages for the design, building, and analysis of the new features in MF-OWHM plus linkage tools for BCM data are also available. These are extremely important because many of these new features are not supported by commercial GUIs and represent new relationships from couplings, as well as new hierarchies of water-budget analysis needed for SGMA. Software Website: USGS Report: USGS MF-OWHM Download:

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GROUNDWATER MANAGEMENT IN ONTARIO, CANADA BY AZITA ASSADI Azita Assadi, M. Sc., P. Geo. (Canada) is a Hydrogeologist with over 20 years of consulting experience in the areas of water resources and groundwater management in Canada and internationally.

Ontario, Canada is located in both the northern and western hemisphere. We figure we have just as much to learn from Ontario’s watershed-based management practices as we do from our western statesneighbors, so we hope you’ll enjoy this excursion from our typical case studies. A History of Watershed-based Integrated Water Resources Management Integrated regional water management (IRWM), at least as a state-wide policy priority, is relatively new in California having formally been introduced in 2002 with the passage of the Regional Water Management Planning Act (SB 1672). Though IRWM is not a regulatory requirement, it is a successful management framework focused on providing grant opportunities as an incentive for the development of integrated multi-benefit management plans. IRWMs are managed by Regional Water Management Groups (California Water Code (CWC) §10539). The Canadian province of Ontario has more than 70 years of experience in watershed-based integrated management. There are 36 Conservation Authorities (CAs) located across the province that are responsible to manage the water resources of their local watershed with the goal of protecting people and sustainably conserving and restoring water resources (Figure 1). 24 HYDROVISIONS

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Conservation Authorities The CAs, legislated under the Conservation Authorities Act and administered by the Ministry of Natural Resources and Forestry (MNRF), are responsible for undertaking an Integrated Watershed Management (IWM) approach to manage impacts on water and other natural resources. Ontario’s IWM approach addresses flood and erosion control, drought, water supply management, source protection and water quality, climate change, groundwater and surface water interactions, and land use planning. Compared to California, the CAs’ purviews are equivalent to those of Regional Water Management Groups and Groundwater Sustainability Agencies. Provincial Groundwater Monitoring Network (PGMN) Key to integrated groundwater management in Ontario, is the collection of integrated data sets. The PGMN is a partnership program with all 36 CAs, Ministry of the Environment, Conservation and Parks (MECP) to collect and manage ambient groundwater level and quality information from key aquifers. The PGMN was implemented in 1999 following a drought that contributed to low water level conditions in many of Ontario’s groundwater basins. The objectives of the groundwater monitoring program are to track changes in quality and quantity over time to enable accurate assessments of the groundwater system response to hydrologic conditions and human activities and to support the development of scientifically-based policy and groundwater management programs. The PGMN is similar to the California Statewide Groundwater Elevation Monitoring (CASGEM) and Groundwater Ambient Monitoring and Assessment (GAMA) programs.

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CAs also collect surface water quality information from rivers and streams across Ontario through the Provincial (Stream) Water Quality Monitoring Network (PWQMN). Data from the PGMN, PWQMN, Ontario Geological Survey (OGS) mapping program (i.e., GIS-based databases, 3-D aquifer mapping, geophysical data, etc.), and other sources can be used as inputs to Source Water Protection Plans, water budgets, hydrologic models, water quantity risk assessments, groundwater baseline/impact assessments, and water well drilling programs. Evaluation and Permitting of Surface Water and Groundwater Use In California, the State Water Board’s Division of Water Rights permits the diversion and use of surface water to ensure beneficial uses and to protect existing downstream permit holders and environmental uses. There is no similar permit process to regulate groundwater use, and California only recently began requiring groundwater management in medium and high-priority basins under the Sustainable Groundwater Management Act (SGMA). In Ontario, water takings and transfers for surface water and groundwater are regulated under Ontario Water Resources Act (OWRA) and Ontario Regulation 387/04 (Water Taking and Transfer) administered by MECP to ensure that the water takings do not negatively affect the environment and other users and are sustainably managed to the standards of the Great Lake-St. Lawrence Basin Sustainability Water Resources Agreement. By law, anyone taking more than 50,000 liters of water per day (about 13,000 gallons per day) from the environment, including from groundwater, lakes, rivers, streams, and ponds, is required to apply for and obtain a Permit to Take Water (PTTW) from the MECP. This includes the taking of water for any use, whether it’s for municipal water supply, agriculture, remediation, commercial/ industrial, dewatering, recreational, or other purposes. Permits are not required for firefighting or other emergency purposes, for domestic use, or for farm uses not related to sales of irrigated crops. Applications for groundwater and surface water taking are categorized and reviewed by MECP, with the level of review depending on the taking volume and the anticipated risk to the existing water supply and environment; the greater the anticipated risk, the more evaluation required. Three categories have been defined to assign the level of evaluation1. Category 1 PTTWs represent the lowest risk-taking activities that are unlikely to pose adverse environmental impacts. Category 2 PPTWs are required to prepare a scoped hydrological and hydrogeological assessment in support of the application. Category 3 PTTWs have a high risk of causing adverse impacts to users or the environment and must identify short term/long term impacts in local and regional scales for each water taking event and also prepare a detailed ecological, hydrological, and hydrogeological study that assess the following sustainability criteria, that are similar to those required by California’s SGMA: • Chronic lowering of groundwater levels • The radius of influence • Reduction of storage and sustainable yield • Degraded water quality • Contamination migration • Land subsidence • Surface water depletion • and impacts on the natural ecosystem.

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If the adverse impacts are high risk and cannot be mitigated, a permit cannot be granted, even if the impacts are localized and/or short-term. To streamline the approval process for low-risk takings, the Environmental Activity and Sector Registry (EASR) was implemented by the MECP as part of a riskbased approval program for businesses to register certain activities on the EASR instead of obtaining a PTTW (typically for Category 1 takings). The EASR is a web-based public database of the eligible activities and facilities registered with the ministry. In some cases, the EASR can replace Category 2 PPTWs for taking of groundwater and/or stormwater, though a hydrogeologic assessment is still required for approval. All permit holders are required to monitor takings and implement mitigation measures to ensure no negative impacts result. Annual records are submitted to the MECP online Water Taking and Reporting System. An online map is available to the public to search for and view detailed information across Ontario on active PTTWs and EASRs. Ontarioâ&#x20AC;&#x2122;s online Data Catalogue is similar to that being deployed by the State Water Board pursuant to the Open Data Resolution to increase focus on water data management and accessibility to the public. California and Ontario both follow an integrated water management framework. In order to sustainably manage water resources and groundwater in California, creating an integrated evaluation and permitting process to regulate groundwater use in the State seems to be necessary. 1. For more information about permit application categories, requirements, and criteria, please refer to the Permit to Take Water Guide on the MECP website.

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WELLS AND WORDS BY BILL J. DEBOER, P.G., C.HG., MONTGOMERY & ASSOCIATES (DAVID W. ABBOTT, P.G., C. HG., CONSULTING GEOLOGIST)

Mr. Abbott, P.G., C.Hg., is a Geologist with 45+ years of applied experience in the exploration and development of groundwater supplies; well location services; installation and design of water supply wells; watershed studies; contamination investigations; geotechnical and groundwater problem solving; and protection of groundwater resources.

PVC Well Casing â&#x20AC;&#x201C; Heat of Hydration and Other Considerations Polyvinyl chloride (PVC) well casing is a common choice for many types of wells but there are some specific characteristics which need to be evaluated prior to its selection. This article is intended to highlight some of the things a geologist or engineer should consider when designing a well with PVC casing, but it is by no means comprehensive. Contact your well casing supplier or review some of the references included at the end of this article for more detailed information. PVC is a thermoplastic produced by combining PVC resin with various types of stabilizers, lubricants, pigments, fillers, and processing aids, often formulated to produce rigid well casing. PVC blank well casing conforms to ASTM International Standard F-480 and is available in a wide range of diameters from 2-inches to 16-inches or greater, typically in 20-foot lengths. Wall thickness is denotated as a Schedule Number (SCH), such as SCH40, or as a Standard Dimension Ratio (SDR), such as SDR17. Both refer to the thickness of the casing wall but in different terms. The SCH is a dimensionless number referring to wall thickness and defines a thickness of the pipe for a given diameter. SDR, by contrast, is defined as the ratio of the outside diameter to the wall thickness. In practical terms, a higher SCH designation will indicate a greater wall thickness, but a higher SDR designation will indicate a thinner wall thickness. This wall thickness, as with steel casing, is a critical component in a well design. 28 HYDROVISIONS

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PVC is often an excellent choice for well casing because it is chemically inert, meaning it will not corrode in the same manner as steel. It is relatively inexpensive, commercially available and can be easier and faster to install than steel. Joints are typically threaded, belled or use a spline-lock system and can be disassembled if required. However, PVC is not without its downsides. Of particular importance is an understanding of the collapse strength and the effects of heat on this particular property. The collapse strength of PVC is lower than steel and causes even further reductions in strength when elevated temperatures occur during well seal installations. PVC is a thermoplastic material, becoming plastic at high temperatures and hardening at low temperatures. It is designed to tolerate these changes repeatedly without compromising its structure. Geothermal wells notwithstanding, heat in a well is generated most significantly during construction when using a Portland based grout. As Portland cement cures it generates heat (exothermic reaction), referred to as the heat of hydration, which is transferred to the well casing. The reduction in collapse strength as a result of this heat can be significant and is defined as 0.6 psi reduction per degree Fahrenheit (F) increase above 70 degrees. The amount of temperature rise resulting from the curing of Portland cement is a factor of the grout thickness, the presence, movement and type of fluid inside the casing, and the type of Portland cement being used. Figure 1 â&#x20AC;&#x201C; Effect of grout thickness and casing diameter on peak casing temperature. (Roy C. Johnson et al, 1980, Well Grouting and Casing Temperature Increases) The thickness of the grout seal is a critical factor in determining the amount of heat generated. Hydration temperatures have been found to increase rapidly with increased grout thickness (Figure 1). One study found that a 1 1/2-inch grout thickness might result in increased temperatures on the order of 17 to 26 degrees F, or a reduction in collapse strength of 10.2 to 15.6 psi. Increasing the thickness to 3 5/8-inch results in a temperature increase of near 67-degrees F, resulting in 40.2 psi reduced collapse strength. The significance of this is clear when considering collapse strength of a nominal 6-inch diameter SCH80 casing is just 312 psi, as compared to 718 psi for 3/16-inch mild steel. Grout thickness should be considered through thoughtful well design, and by careful review of a caliper log when drilling with rotary techniques to check for areas of wash-out. PVC well casing is flexible and so must also be properly centralized in the borehole to ensure both a consistent thickness of grout and a plumb casing are maintained. A 2-inch thick grout seal has been suggested as a maximum to be used with PVC casing though thicknesses greater than this are often used without issue. In California, for example, 2-inches is the minimum required sanitary seal thickness and is often exceeded during well construction with PVC casing.

Example: 16-inch borehole with a 13.8- inch id casing k = 0.49 o Peak casing temperature about 132 F

r = inside diameter of casing, inches R = outside diameter of grout, inches K = units of inverse inch

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Increasing wall thickness (higher SCH or lower SDR), circulating water or drilling fluid through the casing, or performing multiple lifts are some techniques which have successfully been used to mitigate concerns with heat of hydration. Selection of the appropriate type of Portland cement is also important as different types generate different amounts of heat during hydration. HYDROVISIONS

Heat of hydration can additionally be mitigated by using a bentonite-based slurry in place of a Portland cement, however, readers are encouraged to review the findings of the Nebraska Grout Task Force which evaluated the effectiveness of various sealing materials. Geologists practicing in California are additionally encouraged to review the September 2015 Department of Water Resources Advisory on the subject prior to planning placement bentonite slurry seals. Collapse strength of PVC can continue to be a factor even after the well is constructed. For example, a submersible pump generates significant heat and can cause well failure if improperly sized for the well casing’s effective diameter. Increased collapse pressures can also be caused by excessive drawdown in the well, or by sudden reductions in internal pressure caused by rapid bailing. While the focus of this article is on heat and collapse strength, it is by no means the only factor contributing to the selection of PVC well casing. Cost can be another important variable for well design in terms of initial investment during construction, frequency of rehabilitation, future well modifications (i.e., inplace downhole perforating), and ultimately well destruction. PVC well casing is generally less expensive than steel. For this reason, it is commonly used in shallow monitoring wells associated with groundwater contamination sites and also for domestic wells. Check your local well standards to be sure destruction practices are the same for PVC cased wells as they would be for steel cased wells. Some areas consider these very differently, requiring a PVC well to be fully over-drilled at destruction while allowing a steel cased well to be grouted inplace. For a deep well, the cost of over-drilling to destroy it may equal or even exceed the original cost of installation. Figure 2 – Installing 6-inch diameter PVC well casing and screen in a domestic well in southern California. PVC can be a great option for many well construction projects and this author has had success with a variety of PVC well applications for monitoring wells, production wells and domestic wells (Figure 2). It can be used with PVC well screen (machine slotted or wire-wrapped) but can also be coupled to stainless steel screen. PVC casings can be a cost-effective approach to meeting a client’s objective and are widely used throughout the industry, but care should be taken when planning a well with PVC casing of any diameter.

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NGWA, 2003, Illustrated Glossary of Ground Water Industry Terms: Hydrogeology, Geophysics, Borehole Construction, and Water Conditioning, NGWA Press, Westerville, OH, 69 p. 1

2ASTM F-480-02, Standard Specifications for Thermoplastic Well Casing Pipe and Coupling Made in Standard Dimension Ratios (SDR), SCH 40 and SCH (80). 3CertainTeed (2007) Selection of PVC well casing based on hydraulic collapse considerations. Valley Forge, Pa: CertainTeed Corporation. 4Johnson, R. C., C. E. Kurt, and G.F. Dunham, Jr., 1980. â&#x20AC;&#x153;Well Grouting and Casing Temperature Increases.â&#x20AC;? Ground Water Vol. 18, No. 1, p. 7-13. 5Driscoll, F. G. 1986, Groundwater and Wells (2nd edition). St Paul, Mn: Johnson Filtration Systems. 6Water Well Standards: State of California, Bulletin 74-81, California Department of Water Resources, December 1981; and, California Well Standards, Bulletin 74-90 (Supplement to Bulletin 74-81), Draft, California Department of Water Resources, June 1991. Lackey, S.O., W. Myers, T.C. Christopherson, and J.J. Gottula, 2009. In-Situ Study of Grout Materials 2001-2006 and 2007 Dye Tests. Nebraska Grout Task Force, Lincoln, NE: University of Nebraska, October 2009. 7

California Department of Water Resources. Statewide Advisory: Sealing Materials for Water Wells, Monitoring Wells, Cathodic Protection Wells, and Geothermal Heat Exchange Wells. https:// water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/ Groundwater-Management/Wells/Files/GroutAdvisory_ay-20. pdf?la=en&hash=955DCD9F887B1C2D593726BA07972D14B7E7D4EE 8

Roscoe Moss Company. Technical Memorandum 008-1: Important Design Considerations for the Use of PVC to Construct Large-Diameter Water Wells. https://roscoemoss.com/wp-content/uploads/ techmemos/TechMemo008-1_Design_Constraints_for_PVC_Wells. pdf 9

Alameda County Water District. April 2011. Standards for the Construction, Use, Operation, Maintenance, Repair, Inactivation, or Destruction of Wells, Exploratory hole, Other Excavations, and Appurtenances. https://www.acwd.org/DocumentCenter/View/167/ ACWD-Well-Standards?bidId= 10

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The Groundwater Resources Association is comprised of a diverse group of experts in the groundwater industry and related fields. GRA unites these experts through collaboration, education and networking in an effort toward ensuring sustainable groundwater for all. WE ARE GRA!

Briana Seapy is the Water Program Supervisor for the California Department of Fish and Wildlife’s North Central Region in Rancho Cordova, CA. I am Briana Seapy and I am GRA! Despite spending a childhood chasing desert lizards under Oman’s baking sun, I maintained blissful water resource ignorance for most of my younger years. In the summers, I traveled across oceans to visit spoiling grandparents who let me and my brother play in the sprinklers, in the middle of the day, in the blistering San Joaquin Valley heat. Water conservation wasn’t so much a thing in those days. It was many years yet until I began to appreciate how (ground)water drives this world. I studied International Relations at a Boston-area college. I had vague dreams of international travel and policy work, but no real plans. During my third year of college, I studied in Jordan to reacquaint with my Middle Eastern roots. My time skipping showers to make it to the next water delivery, along with a course on Geopolitics and Water in the Middle East, threw a wrench in my life trajectory. The realities of water scarcity in Jordan were tangible, even for the affluent, and proximate millennia-old conflicts were underscored and perpetuated by water resource disparity. My eyes were open. I needed to pivot from my fuzzy dreams of diplomacy. I scrambled to brush up on science, engineering, and geospatial reasoning my senior year of college so I could go straight to graduate school and bolster a socio-political bachelor’s degree with a multidisciplinary deep dive into Water Resource Management. It was during my time at a California graduate school that I noticed a glaring similarity between California and the Middle East – they shared the same deep shade of red on global water resource scarcity/vulnerability maps. The rest is history. Or actually, it’s the present. I stayed in California and committed my career to water resource management – from Urban Water Conservation to Sustainable Groundwater Management Act (SGMA) implementation to hydropower licensing, I’ve spent the past eight years falling down the California water-rabbit hole (turns out it’s never-ending). Somewhere along the way, probably around the SGMA phase, I found GRA. I had a professional association budget of $100 from the State of California, and GRA conveniently lets State professionals join for that precise amount. I paid my dues and was delighted by each subsequent GRA conference – like the Western Groundwater Congress and the Groundwater Sustainability Agency Summit – that allowed me to connect with SGMA practitioners, message on fish and wildlife groundwater needs, and geek out on groundwater with a convivial, bright, and committed community of groundwater nerds. Each conference was a shining beacon of light on my crowded Outlook calendar, an opportunity to freshen my thinking, learn, and feel part of community that cares. A community that searches for solutions. A community that devotes itself to the long-term sustainable, practical, and informed management of an unseen, unsexy, underappreciated resource, yet one that is unimaginable to live without: groundwater.

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FEDERAL CORNER BY ANDREW SALLACH Andrew Sallach is an U.S. Public Health Service Officer assigned to US Environmental Protection Agency Region 9.

Per- and Polyfluoroalkyl Substances Several federal agencies are engaging with the National Academies of Sciences, Engineering, and Medicine to coordinate a Workshop on Federal Government Human Health Per- and Polyfluoroalkyl Substances (PFAS) Research. Aggressively addressing PFAS has been an active and ongoing priority for the entire federal family. This collaborative workshop will ensure coordination of PFAS research across the federal government. More information can be found here. The California State Water Resources Control Board is collaborating with U.S. EPA Region 9 on various analysis methods using the statewide data from PFAS source and drinking water testing. This collaboration helps to inform this state’s regulatory decisions to address sources of PFAS, and to protect public water systems in California. Data analysis can be found here. EPA’s Per- and Polyfluoroalkyl Substances (PFAS) Action Plan can be found here.

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HIGH RESOLUTION SITE CHARACTERIZATION: SCALING THE SOLUTION TO THE PROBLEM

BY RAGHAVENDRA SURIBHATLA, PHD Mr. Dr. Suribhatla is a Senior Water Resources Engineer with INTERA Incorporated and has academic and research experience in highresolution site characterization and data integration methods.

The cost of collecting high-resolution data that enables more precise characterization of contaminant distribution in the subsurface is a matter of scale. The USEPA defines High Resolution Site Characterization (HRSC) as “strategies and techniques that use scaleappropriate measurement and sample density to define contaminant distributions, and the physical context in which they reside, with greater certainty, supporting faster and more effective site cleanup”. A more detailed definition is provided by USEPA (2017) as “Subsurface investigation appropriate to the scale of heterogeneities in the subsurface which control contaminant distribution, transport and fate, and that provides degree of detail needed to understand: exposure pathways, processes affecting fate of contaminants, contaminant mass distribution and flux by phase and by media (mobile and immobile), and how remedial measures will affect the problem.”

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The key word in both HRSC definitions is â&#x20AC;&#x2DC;scaleâ&#x20AC;&#x2122;. The scale referred to here is a characteristic of the geologic setting and applicable contaminant fate and transport paradigm of the site under investigation. HRSC strategies and techniques explicitly recognize the impact of site-specific hydrogeologic heterogeneities on the vertical and horizontal variability of a plumeâ&#x20AC;&#x2122;s distribution. Because heterogeneities can exist at a multitude of scales, identifying the appropriate scale of measurement becomes a prerequisite for implementing HRSC strategies. This allows investigators to identify the tools that can achieve a resolution that captures variability at the appropriate scales that support the project objectives, such as faster, less resource-intensive remediation strategy. Defining and Understanding Scale The success of a remediation program depends on 1) accurately defining the location and dimensions of the plume in the subsurface and 2) determining the properties of the system that dictate how the plume will move. As such, the objectives of a site characterization program are to map the plume distribution and identify hydrogeologic factors that control transport. Site hydrogeology, including hydraulic and geochemical characteristics of the geologic medium, affect plume transport pathways and travel times. In particular, formations with spatially varying hydraulic and geochemical properties (subsurface heterogeneities), can have zones where a plume is concentrated and/ or transported to potential downgradient receptors. An understanding of the different scales at which subsurface heterogeneities are present, and identifying the heterogeneities that are relevant to remediation, facilitates a remedial design that targets high concentration zones and primary transport pathways within the plume and results in a more efficient and less costly corrective action. Identifying the Scale and Structure of Geologic Heterogeneities The data collection and interpretation process for HRSC implicitly involves identification of three distinct scales: 1. the scale of the problem 2. the required scale of characterization 3. the scale of measurement inherent to particular tools or methodologies During the initial investigation phase a key data collection objective is to identify the scale of the problem, i.e. the horizontal and vertical extent of a source area and/or dissolved plume. During the characterization phase, data collection objectives pertain to capturing the spatial variability in the source/plume distribution and the concentrations of individual constituents. The characterization objectives may include delineation of specific aquifer zones where most of the contaminant mass resides and identification of subsurface heterogeneities and features that control fate and transport. This scale is contrasted with the scale of the problem and is referred to as the required scale of characterization.

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Identifying the scale and structure (i.e. the connectedness and orientation of geologic heterogeneities that impact plume distribution) is the most challenging aspect of site characterization. By associating the site conceptual model with a particular geologic type setting, a scale of characterization can be initially identified. The initial scale can be validated against available outcrop data or historical studies and revised as more data are collected in the later stages of site characterization. The data collected using field tools however, have to be useful for identifying the heterogeneities. This places emphasis on understanding the scale of measurement of the particular tools (data collection methods) and their respective resolution. A clear hierarchy exists for the three distinct scales. The scale of the problem is the largest and establishes the spatial extent of required characterization. The scale of characterization is subordinate to the scale of the problem and is governed by heterogeneities and their impact on the contaminant distribution. The resolution of the HRSC tools, such as a multi-depth well, is a controllable parameter and is tailored to collect data that are representative of distinct units within the aquifer. For example, resolution can be increased by sampling at multiple depths within the zone of interest that may have significant spatial variation in contaminant concentrations. Alternatively, if a single screen is used to sample across the entire depth of the zone of interest, the resolution of the tool (e.g. the well) is low and the measurement (concentration) is not representative of the heterogeneity and can be potentially misleading. Benefits of Performing High Resolution Site Characterization HRSC, by definition, requires more data than a traditional site investigation where wells are installed as the primary tool for groundwater characterization. Sample collection and data density required to perform HRSC typically results in greater site investigation costs. However, depending on the degree of subsurface complexity and selected remedial technology, the increased site investigation cost can be offset by reduced remediation construction and operation costs because HRSC provides the detailed information on subsurface heterogeneity and contaminant fate and transport that enables more precise design and placement of remediation technologies. Compared to traditional investigation methods, the USEPA (2017) characterizes the benefits of HRSC as: â&#x20AC;˘ Improves remedial design by providing a detailed depiction of transport pathways and plume distribution. This in-turn reduces the potential for designing a remedy that will not meet remedial objectives. â&#x20AC;˘ Increases remedial efficiency by defining the specific zones to target for treatment, thus reducing the volume of groundwater requiring extraction and treatment or the volume of in-situ reagent treatments for injection. â&#x20AC;˘ Reduces project timeframes by enabling the design of remedies that target the plume more precisely and by potentially reducing the number of mobilizations needed to characterize the extent of the contamination at the site. This in turn reduces the carbon footprint of the remedial action and improves safety performance.

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