Project Overview
The City of Dinuba, through the California State Water Resources Control Board’s Proposition 1 Groundwater Sustainability Grant Program, will perform a planning study that will investigate options to clean up and/or prevent the spread of certain pollutants in the City’s municipal groundwater supply. The pollutants include nitrates from agricultural fertilizer and municipal wastewater; the soil fumigant dibromochloropropane (DBCP); and another constituent of soil fumigants, 1,2,3-Trichloropropane (TCP). These pollutants occur in the region’s shallow aquifers as a result of widespread land use and wastewater management practices that were generally considered acceptable but over time, have resulted in groundwater degradation.
The study will identify options for projects that can be funded under future implementation grants to aid in assuring a more secure and higher quality water supply for City residents, and to serve as an example of projects that can be undertaken to protect and improve public drinking water supplies in similar agricultural settings. The total cost of the study will be approximately $1.97 million, and the grant is for $1.77 million, with the balance being provided by the City as a local match consisting of both labor and cash payments.
Project Objectives
The Dinuba Wellfield RI/FS objectives are to identify, evaluate and prioritize implementation project options that cleanup or prevent pollution of drinking water aquifers by controlling contaminant migration, cleaning up the aquifers over time, and/or decreasing contaminant loading. Options that will be evaluated include making modifications to the way the City’s municipal wells are operated, modifying the wellfield, implementing groundwater recharge projects or implementing measures to decrease the amount of nitrate loading to groundwater. These projects, if successful, would enhance the sustainability and resilience of local water supplies, protect water quality and improve it over time, and decrease long-term treatment costs.
Overlapping Programs
The Dinuba Wellfield RI/FS will study potential implementation project options that fall within the Proposition 1 program by protecting or cleaning up contamination in drinking water aquifers, while at the same time exploring alternatives that help compliance with other State programs. These include coordination of aquifer protection and cleanup with treatment engineering approaches at the surface, and exploring practical aquifer cleanup solutions under the recently adopted Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) program that is being implemented by the Central Valley Regional Water Quality Control Board to address salt and nitrate impacts to shallow aquifers from historical agricultural land uses. The recharge project alternatives would also contribute to sustainable groundwater management by helping to stabilize falling groundwater levels.
Stakeholder Advisory Group
The City of Dinuba is forming a Stakeholder Advisory Group (SAG) to provide an opportunity for community members, industry, and local water agency representatives to provide input into how the success of the project will ultimately benefit the City of Dinuba and surrounding communities.
To become a part of the SAG, email tbarton@ppeng.com for more information. Meeting times, dates and locations will be posted as they are scheduled.
Second Quarterly Stakeholder Advisory Group Meeting for Wellfield RI/FS Project.
Where: Online via video conference.
Meeting Objective: This second quarterly meeting included discussion on a project review, field sampling, supply well profiling, refinement of subsurface stratigraphy, groundwater flow modeling, major project deliverables, and schedule and upcoming milestones.
Download PowerPoint Presentation
Third Quarterly Stakeholder Advisory Group Meeting for Wellfield RI/FS Project
Where: Online via video conference.
Meeting Objective: This SAG quarterly meeting included an update on the remedial investigation.
Download PowerPoint Presentation
Fourth Quarterly Stakeholder Advisory Group Meeting for Wellfield RI/FS Project
Where: Online via video conference
Meeting Objective: This SAG quarterly meeting provided the Stakeholder Advisory Group with an overview of the DRAFT Dinuba Refined Model Technical Memorandum and the DRAFT Feasibility Study Report for the City of Dinuba Wellfield RI/FS Project.
SAG Presentation Power Point PDF
Youtube video link to: https://youtu.be/-ePuPCBIXHI
Past Video Recordings of SAG Meetings: https://youtube.com/playlist?list=PL0cp-bmvpC6pycQs8yFAEy3fwfWMeWDmW
Public Outreach Meetings
If you were unable to attend the City of Dinuba’s Wellfield Remedial Investigation/Feasibility Study (RI/FS) Project Public Outreach Meeting on Thursday, January 20, 2022, the Power Point presentation (available in English and Spanish) and recorded video of the meeting have been posted online.
The City entered into Grant Agreement No. SWRCB-D1912528 (Grant Agreement) with the California State Water Resources Control Board (State Water Board), Division of Financial Services to identify, evaluate, and prioritize an implementable project that optimizes wellfield activity to prevent the spread of nitrate, the soil fumigant 1,2-dibromo-3-chloropropane (DBCP), and another constituent of soil fumigants, 1,2,3-trichloropropane (1,2,3-TCP) contamination within the drinking water aquifer that underlies the City. Implementation project alternatives that were considered included measures to modify the City’s wellfield, modify wellfield operations, increase non-potable water use, and implement recharge projects in the wellfield area.
This meeting provided an overview of the Dinuba Wellfield RI/FS Project, a discussion on the objectives, goals and benefits of the project, a review of the project timelines, and provided the public with an opportunity for comments and questions. Please feel free to share this information with others who may have an interest in the project.
Meeting Presentation & Video Links:
- Public Outreach Meeting Video: https://youtu.be/Td7a_0rMr1Q
- Presentation Power Point: https://www.dinuba.org/images/2022/2022-0120-Dinuba-Public-Outreach-Presentation.pdf
- Presentación de PowerPoint en español: https://www.dinuba.org/images/2022/Spanish-Dinuba-Public-Outreach-Presentation.pdf
Remedial Investigation Report
Per Grant Agreement Task 7.2 Prepare a Remedial Investigation (RI) Report, the Final RI Report is provided for your review. The RI Report describes the data compilation, field data collection, data evaluation methods and findings that were used to address the data needs and update the conceptual understanding of the aquifer system in accordance with the Workplan. The following RI tasks were completed:
- Existing data were compiled and evaluated to develop a conceptual understanding of aquifer conditions and contaminant distribution to inform development of a numerical groundwater flow and solute transport model.
- Supplemental groundwater level and quality data were collected and integrated into the conceptual understanding.
- Groundwater flow and contaminant concentration profiling of select City public supply wells was conducted to assess vertical gradients and flow, and the interactions of the wells with the aquifer system, and to ascertain the vertical distribution of contaminants near the wells.
- The results of the data compilation and investigation efforts were used to update the current understanding of the aquifer system, groundwater occurrence and flow, and contaminant occurrence and behavior in the vicinity of the Dinuba Water Service Area and develop a refined conceptual framework for future analysis (hydrogeologic conceptual model).
- The updated and refined hydrogeologic conceptual model was used to define the layering, aquifer parameters, groundwater budget and flows, contaminant distribution and contaminant transport parameters for a numerical groundwater flow and solute transport model. The groundwater flow model will be described in the Groundwater Modeling Technical Memorandum (To be submitted under separate notice).
- The RI Report also includes a description of deviations from the Workplan per Grant Agreement Task 7.1.1.
The City of Dinuba Final RI Report is now available for review. The following files are available for download:
- Text, tables, and figures in pdf file
- Appendix A – Field Notes
- Appendix B – Well Construction Data
- Appendix C – Well Completion Reports
- Appendix D – Well Profile Test Reports
- Appendix E – Analytical Results
- Appendix F – Contaminant Concentration Trends
- Appendix G – Data Quality Reviews and Laboratory Reports
- Appendix H – Drawdown near RCR Well 1 During Profile Test
- Appendix I – National Stormwater Calculator Reports
- Appendix J – Technical Memorandum, Dinuba Refined Dinuba Refined Model Development and Calibration
Dinuba Refined Model Development and Calibration Technical Memorandum
The City of Dinuba entered into Grant Agreement No. SWRCB D1912528 (Grant Agreement) with the California State Water Resources Control Board, Division of Financial Assistance to implement the Dinuba Wellfield Remedial Investigation/Feasibility Study (RI/FS) Project (Dinuba Wellfield Project). The Dinuba Wellfield Project is being completed in accordance with the process described in the Dinuba Wellfield RI/FS Workplan (Workplan).
Per Grant Agreement Task 8.2 Prepare a Groundwater Solute Transport Modeling Technical Memorandum (Tech Memo), the Final Tech Memo is Appendix J of the Final RI Report. The Tech Memo includes the following information:
- 2.1 Modeling details and results including model development, model calibration, sensitivity analysis, and an evaluation of the effectiveness of alternatives to achieve remedial action objectives.
- 2.2 Description of the conceptual understanding on which the model is based, how the model simulates components of the natural system, and the underlying assumptions and limitations.
The City of Dinuba Refined Model Development and Calibration Tech Memo is now available for review. The document is Appendix J of the Final Remedial Investigation Report.
- Appendix J – Technical Memorandum, Dinuba Refined Dinuba Refined Model Development and Calibration
Dinuba Final Feasiblity Study Report
The City of Dinuba entered into Grant Agreement No. SWRCB D1912528 (Grant Agreement) with the California State Water Resources Control Board, Division of Financial Assistance to implement the Dinuba Wellfield Remedial Investigation/Feasibility Study (RI/FS) Project (Dinuba Wellfield Project). The Dinuba Wellfield Project is being completed in accordance with the process described in the Dinuba Wellfield RI/FS Workplan (Workplan).
Per Grant Agreement Task 9.2 Prepare a Feasibility Study Report, the Feasibility Study Report must include, at a minimum, the following:
9.2.1 Summary of the Project area’s history, geology, hydrogeology, surface water, local land use, previous investigations, and remedial actions.
9.2.2 Summary of the nature and extent of constituents of concern including nitrate, DBCP, and 1,2,3-TCP in groundwater. Include types of contaminants, concentrations detected, and vertical and lateral extent of the contamination.
9.2.3 Summary of the contaminant properties and transport based on soil and aquifer properties.
9.2.4 Remedial action objectives that the proposed implementation projects will achieve, and the feasibility evaluation criteria used in the analysis.
9.2.5 Description of the remedial action alternatives evaluated.
9.2.6 Evaluation of the remedial action alternatives based on screening analysis, modeling, and engineering evaluation.
9.2.7 Estimated total of approximate life cycle costs and estimated schedule for each cleanup alternative evaluated.
9.2.8 Description of the rationale for selecting the preferred alternative(s).
9.2.9 Preliminary design and construction cost estimate(s) for the preferred alternatives.
9.2.10 Recommendations for additional studies and investigations in the Project area to support future implementation projects.
The City of Dinuba Final Feasibility Study Report is now available for review. The following files are available for download:
- Text, tables, and figures in pdf file
- Appendix A and B pdf files