Appendix_A_22102_West_Sacramento_Drought_Relief_Well_Assessment_Final_TM_20220513.pdf

Appendix A Technical Memorandum and

Well Drillers Report

MEMORANDUM

TO: Gwyn-Mohr Tully & Jim Crowley - Zanjero

FROM: Mike Massaro, Kati Sethares, and Dave Settles – Bennett Engineering Services

DATE: May 13, 2022

SUBJECT: Assessment for Well Rehabilitation and New Wells for Supplemental Water

PROJECT: City of West Sacramento Drought Relief Study

Introduction and Setting Most of the City of West Sacramento’s groundwater wells were abandoned and destroyed when the City built the George Kristoff (formerly Bryte Bend) Water Treatment Plant (WTP) and converted their municipal water source from groundwater to Sacramento River surface water in 1988. Of the 27 wells that used to provide water to the East Yolo Community Service District, only Well 20 is still active as a standby well and used for environmental irrigation water and it is no longer plumbed into the City’s water system. Three other wells (22, 24, and 27) are still in place, but are capped and no longer equipped and have not been used in over 30 years.

The wells were originally installed between 45 and 50 years ago. (Well Driller’s Reports are in the Appendix for reference.)

The State of California is entering its third year of drought conditions. Currently, 87% of the state is in “Severe Drought” with Extreme and Exceptional Drought conditions anticipated this summer. The City’s average demand in summer is 20 mgd +. In preparation for future anticipated drought conditions, the City would like to consider groundwater as an additional source alternative to surface water treated at the Kristoff WTP. The City’s only active well (not connected to the distribution system), Well 20, can produce around 500 gpm, or about 1/3 of what a new production well is expected to produce.

This memorandum will discuss the current options for bringing inactive wells back on-line and re-integrating theminto the City’s distribution system as emergency standby options for supplemental water to meet summer demands. Site exhibits and conceptual level cost estimates will also be included.

Field Visit and Assessment

On January 27, 2022, our assessment team visited 3 locations of inactive wells to assess the condition of the City owned sites and determine what work may be required for re-equipping wells to supplement the City’s surface water supply for emergency drought conditions.

We have researched the California Department of Water Resources Well database and found the well completion reports for several of the City’s (former East Yolo CSD) old wells. We have also located some representative water quality data adjacent to the existing wells for assessment of necessary water treatment.

The well completion reports are included in the Appendix.

Well 22:

Well 22 is located between Oak Street and Harbor Blvd in West Sacramento. Well 22 has been capped and the pump and equipment removed. The site still has a steel tank that is used for storage and is integrated into the water distribution system. A new power drop, well pump, valving, and piping would be required to re-integrate this well into the distribution system. Treatment of the water would need to be determined based on water quality samples taken after a well rehabilitation effort. But chlorine injection is anticipated at a minimum for

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Zanjero – Assessment for Well Rehabilitation and New Wells for Supplemental Water TM

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The well driller’s report indicates this well was drilled in 1974 to a depth of 751 feet. The well is a 16-inch diameter screened in 5 sections from 382 ft depth to 672 ft depth. The surface seal is 270 feet deep. When first installed groundwater level was approximately 27 feet depth and the original pump produced 1,500 gpm.

Well 24:

Well 24 is located adjacent to Enterprise Blvd, west of Lake Washington, south of I-80, and east for the Prospect Slough Levee. The well has been capped and the pump and equipment removed. The site still has a steel tank that is used for storage and is integrated into the water distribution system. A new power drop, well pump, valving, and piping would be required to re-integrate this well into the distribution system. Treatment of the water would need to be determined based on water quality samples taken after a well rehabilitation effort. But chlorine injection is anticipated at a minimum for residual disinfection. We have also assumed that manganese levels may exceed secondary MCL levels and my require filtration. There is adequate room on the City owned property to build the systems necessary to re-establish Well 24. The condition of the well casing is unknown and will need to be swabbed, purged/pumped to waste, and video inspection completed to assess its viability to operate at a production level for supplemental supply.

The well driller’s report indicates this well was drilled in 1976 to a depth of 501 feet. The well is a 12 and 3/4-inch diameter screened in 4 sections from 406 ft depth to 459 ft depth. The surface seal is 230 feet deep. When first installed groundwater level was approximately 39 feet depth and the original pump produced 800 gpm.

Well 20:

Well 20 is located Well is active and has had the pump to waste piping set-up to fill an adjacent stormwater/irrigation canal. The site still has a steel tank and pressure filters that are abandoned. New valving and piping would be required to re-integrate this well into the distribution system. Treatment of the water would need to be determined based on water quality samples taken from the well. But chlorine injection is anticipated at a minimum for residual disinfection. We have also assumed that manganese levels may exceed secondary MCL levels and my require filtration. There is adequate room on the City owned property to build the systems necessary to re-establish Well 20 to the distribution system.

It was noted in the field that previous maintenance, inspection, and pump tests on well 20 yielded excess sand and grit which indicated the well casing and screen was not in ideal condition and the well had to be sleeved to control the grit. This has limited the pumping capacity of the well to an approximate capacity of 500 gpm, currently.

The well driller’s report indicates this well was drilled in 1973 to a depth of 631 feet. The well is a 16-inch diameter screened in 6 sections from 204 ft depth to 560 ft depth. The surface seal is 80 feet deep. When first installed groundwater level was approximately 23 feet depth and the original pump produced 1,600 gpm.

Table 1 – Anticipated Rehabilitation Well Capacity Well Original Capacity (gpm) Anticipated Rehabilitated

Capacity (gpm) 22 1,500 1,000 24 800 500 20 1,600 500

TOTAL 3,900 2,000

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Given the age and lack of use of the wells over time it is unlikely the wells will produce water at the same flow rates that they originally were able to. A conservative estimate for flow rates at these locations would yield around 2,000 gpm. Costs to both rehabilitate existing abandoned wells and install new wells will be discussed later.

Rehabilitation of these wells and sites is the shortest path to providing supplemental water to the City under drought conditions; however, the City will get greater capacity from a new production well. These old well sites would be viable locations for new wells, and total capacity is expected to be 5,400 gpm for 3 new wells, or approximately 1,800 gpm per new well. While 1,800 gpm is expected upon construction and startup of a new well, the actual capacity of a new well at these sites is unknown and may vary above or below the estimate. For example, assuming the capacity may vary up to 20% above or below the estimated 1,800 gpm would give a range of potential capacities anywhere between 1,500 gpm and 2,200 gpm. Well capacity will also decrease over its useful life, so variation above the estimated capacity is often limited and variation below estimated capacity is more common. Additional pump tests upon construction of a new well will be required to determine actual capacity.

Well Rehabilitation Procedures and Costs We would recommend the following procedures for evaluating and re-equipping Wells 22, 24, and 20. It should be noted that companies that do this well rehabilitation work are currently booked out 6-8 months for the scope of work detailed below.

Well Health Check Process The Well Health Check process involves a review of available well construction and operational data, an evaluation of physical parameters associated with well operation, and laboratory analysis of chemical and microbiological parameters in the well casing and the aquifer that the well draws from. The evaluation process is then followed by a series of well-specific recommendations for well rehabilitation and maintenance.

Background data includes well completion reports, e-logs, operating history, rehabilitation history, video logs, and any other available well data to understand the construction of the well and any other existing factors which could help identify potential problems. In addition, physical parameters, as discussed below, are also evaluated to determine the type and rate of plugging of the well and to assist in interpreting the laboratory analytical results after they are received.

Data Review If available, review data records associated with the well, including the following:

• Recent well videos

• Well completion reports and/or as-builts

• E-log data

• Water level data (static and pumping)

• Specific Capacity history (gpm/ft drawdown)

• Maintenance/rehabilitation history

• Recent analytical data

• Well operational history

• Any other available relevant data

Physical Parameters These parameters are related to the actual physical operation of the well and can indicate plugging trends, plugging rates, and potential damage to the well. Optimally, these parameters are best examined in terms of their trends over time to establish patterns in performance decline in the well.

• Specific Capacity

• Energy Usage (gallons per kWh)

• Sand Production

• Well Efficiency

• Water Levels (static and pumping levels)

Laboratory Analysis This portion of the Well Health Check process involves collecting two water samples over 24 hours from the well and submitting them to a laboratory that specializes in the analysis of water well issues. The first water sample is collected upon the initial start-up of the pump following 8-12 hours offline and represents the water from within the well casing. The second water sample is collected after 3-4-hours of constant pumping and represents water from the aquifer that the well draws from. Conditions can vary markedly from the casing to the aquifer, so this process can help isolate where problems are occurring and assist in determining the proper design and focus of any rehabilitation effort. Laboratory analysis is broken down into two groups of parameters, as detailed below.

Chemical Parameters Chemical parameters can indicate the conditions for formation of mineral incrustations on well screens and casing, the potential for corrosion, as well as providing an indicator of conducive conditions for bacterial growth.

As an initial snapshot of current well conditions, these parameters can help pinpoint specific issues in the well and allow for development of rehabilitation treatment protocols to address issues specific to the well.

• pH

• Alkalinity (Phenolphthalein Alkalinity, Total Alkalinity, Hydroxide Alkalinity, Carbonate Alkalinity, Bicarbonate Alkalinity)

• Total Dissolved Solids

• Conductivity

• ORP

• Langelier Saturation Index

• Hardness (Total Hardness, Carbonate Hardness, Noncarbonate Hardness)

• Calcium

• Magnesium

• Sodium

• Potassium

• Phosphate

• Chlorides

• Nitrate

• Chlorine

• Iron (Total Iron, Dissolved Iron, Suspended Iron, Resuspended Iron)

• Manganese

• Sulfate

• Silica

• Tanin/Lignin

• Total Organic Carbon

Biological Parameters Most compliance sampling of wells is directed toward the detection of coliform bacteria to protect against the presence of E. coli. However, many other types of bacteria can be present in a well, which can cause biofouling, corrosion, and potential health issues in the case of non-coliform pathogenic bacteria. Bacterial growth can be impacted by chemical conditions in the well, as well as pH and ORP. Low oxygen conditions in a well can provide a conducive environment of anaerobic bacteria growth, and this type of bacteria can often be pathogenic or corrosive. Slime-forming and iron-related bacteria can proliferate in wells and result in biofouling that can

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• Heterotrophic Plate Count

• Anaerobic Bacteria

• Sulfate Reducing Bacteria

• Fe/Mn Oxidizing Bacteria

• ATP Initial

• ATP 24 Hour

• Total Coliform

• E. Coli

• Bacterial Identification (speciation)

Data Review and Recommendations Report Once background data is reviewed, and results of the laboratory analyses are received, the results should be evaluated, and final recommendations should be presented for well rehabilitation or other corrective measures that should be undertaken to address the loss of production capacity in the wells. Recommendations would also be included for monitoring an ongoing set of key performance indicators (KPI) to track well health trends over time to schedule well maintenance and rehabilitation at optimal times over the well’s lifespan. Usually, a recommendations report would to be submitted within 30-45 days of sample submittal for laboratory analysis.

While the well health check process is often enough to identify the cause of decreased well capacity, in some cases, additional diagnostics may be required.

Pricing Including laboratory analytical expense, the cost for the Well Health Check is usually around $5,000 per well, If the well is already equipped, like Well 20. Wells 22 and 24 would need to partially rehabilitated and have a pump temporarily installed to begin the water quality analysis.

Well Rehabilitation Based on assessment results and recommendations of the Well Health Check process, a well-specific rehabilitation course of action would be developed. It is likely the rehabilitation process will consist of the following steps:

1. An initial video survey to document depth specific issues within the well and productive facture zones that may be experience plugging.

2. Brushing and swabbing to remove mineral incrustations and biofilm accumulations that may be present and contributing to well plugging.

3. Airlift of debris generated from brushing and swabbing activities.

4. As determined from the video logging, either hydrofracking with pressurized water and packers or application of a chemical-based rehabilitation approach to remove remaining mineral incrustations and/or biofilms.

5. Remove and neutralize any chemicals used in the rehabilitation.

6. Airlift any remaining debris in the well.

7. Video log to document completed well rehabilitation.

8. Disinfection of all pump parts and drop pipe before re-installing.

9. Short step pumping test to determine specific capacity of rehabbed well.

Cost per well for rehabilitation can vary widely depending on effectiveness of initial cleaning and condition of the screened sections, if still viable. The cost based on needs determined from the Well Health Check and video logs can be between $30,000 to 400,000 per well.