Stantec Consulting Services Inc.
1340 Treat Boulevard Suite 525, Walnut Creek CA 94597-7984 March 4, 2024
Attention: Mr. Kevin Werner
City Administrator/City Engineer
259 N. Wilma Ave.
Ripon, CA 95366
Dear Mr. Werner,
Reference: Well 9 Evaluation and Condition Assessment Proposal Stantec is pleased to submit this proposal to evaluate the condition of Well 9 and its reported capacity issues as reported by City of Ripon (the City) staff. According to the Well Data Sheet for Well 9, the original capacity of the well, when constructed in 1989, was around 1500 gallons per minute (gpm). Recent monitoring by City staff indicates that this capacity has dropped to approximately 500 gpm. The well is fairly shallow at only 202 feet deep, contains 30 feet of well screen (170 to 200 feet bgs), and has a 165- foot sanitary seal. Additionally, the static water level was reported to be 40.3 feet in December of 1989, when the well was constructed. Known water quality issues at the site include arsenic at about two times the maximum contaminant level (MCL), which is treated prior to introduction to the City’s potable system.
Additional water quality issues found at other (former or active) well locations include nitrate and salinity.
Due to the capacity and water quality issues at Well 9, the City has requested that the well be further evaluated for the following:
Can improvements to the current well be made to increase capacity; Could the well be converted to non-potable water service; Could drilling a new well at the existing site produced enough water to justify the cost of treatment as a potable source; and,
Could a new well be drilled that potentially eliminates the need for costly treatment, to be used as a potable source.
Task 1: Test Boring and Zone Water Quality Testing ($167,145) Stantec proposes to contract directly with a C-57 licensed well drilling contractor to drill a 600-foot test boring at the Well 9 site to support the design of a new production well. Information collected during drilling will include lithologic, geophysical, and aquifer grain size analysis necessary for the design of the future well’s screen interval, screen slot size, and gravel pack. Additional, up to three zones samples are proposed to assess water quality targeting intervals below 200 feet and the Corcoran Clay (if present).
Stantec will assist in the collection of samples for Title 22 water quality analysis. A general outline of the test boring program and assumptions is as follows and was used in the solicitation of bids from C-57 licensed well drillers, a summary of which is provided in Table 1:
Exhibit A
March 4, 2024
Mr. Kevin Werner
Reference: Well 9 Evaluation and Condition Assessment Proposal
50 foot 32‐inch diameter conductor with 10.3 Sack sand‐cement seal 600 foot in minimum 12-inch boring
Geophysical logs (long, short, point, resistivity; lat or guard log; SP, and natural gamma) Borehole deviation survey
Zone Sampling Assuming 3 zones (unit cost per zone sample) o Zones to be developed for a minimum of 6 hours of active development (airlifting/pumping) and until turbidity is less than 100 NTU
o 20 foot screen section
o Pumping/airlifting ~25 to 50 gpm
o Gravel Packed
o Sealed above and below zone with 20 to 30 feet of bentonite o Monitor flow and volume of water pumped from each zone o Monitor water levels in zone and annulus for potential short circuiting Transport Cuttings and initial drilling fluids to WWTF approximately 1 mile from the site for disposal. Development water can be disposed of to pump to waste line or sanitary sewer, near site. Potable water available at the site for drilling.
Abandon boring according to SJ County requirements (to be reamed at a later date if test results are favorable).
Based on the fee estimates provided above, Altamont Water Well and Pump was selected as the preferred well drilling contractor. During drilling, Stantec will provide field services that include logging lithologic samples in accordance with the Unified Soils Classification System every 5 to 10 feet of drilling and at changes in lithology. Stantec will also collect up to 10 samples of aquifer samples for grain size analysis, including laboratory analysis of the samples. Following the completion of the test boring and collection of lithologic and geophysical data, Stantec will design the zone water quality testing program for up to three zones, monitor development, and will coordinate the collection of samples for Title 22 water quality analysis. The samples will be analyzed by the City’s contracted laboratory.
Table 1: Summary of Test Boring Bids
Well Driller Stantec Field
and Technical
Services
Bid Cost Total Driller
Cost (w/
Stantec 10%
Markup)
Altamont Water Well and Pump
$16,500
$136,950 $150,645
Nor-Cal Pump and Well Drilling $233,110 $256,421
Roadrunner Drilling $310,900 $341,990
Maggiora Bros. Drilling Inc. $342,750 $377,025
Task 2: Well 9 Condition Assessment and Test Boring Technical Memorandum ($15,000) To further evaluate Well 9, Stantec proposes to conduct a limited duration pumping test to assess aquifer properties and identify it current efficiency. Following the pumping test, the City’s pump contractor will March 4, 2024
Mr. Kevin Werner
Reference: Well 9 Evaluation and Condition Assessment Proposal
remove the pump from Well 9 and perform a downhole video log. Stantec will be present during video logging to guide/assure pertinent aspects of the well are captured. The information obtained from the pumping test and video log will be used to document the current condition of the interior of the well casing and screen and provide recommendations to whether further well rehabilitation is warranted. If well rehabilitation is recommended, Stantec will provide a discussion on the means and methods for completing the work.
In addition to the Well 9 evaluation, Stantec will provide an assessment of whether another well could be drilled on-site through review of City well construction, geophysical logs, and water quality data. These data will be used to assess if a well of sufficient capacity may be feasible at the site and if alternate screening is plausible in reducing or eliminating the need for arsenic treatment. If construction of a new well is feasible, a test boring program that includes depth specific zone water quality testing will be developed to further evaluate the design of a future well.
Based on the finding above, Stantec will prepare a Well 9 Condition Assessment that includes the following:
Results of the well pumping test analysis, including an assessment of well efficiency, and aquifer properties.
Summary of well video logging and a visual evaluation of the condition of the interior of the well. Evaluate alternatives to restore well capacity including:
o Well rehabilitation.
o Drill new well at the site.
o Abandon well as potable source for non-potable uses.
Summary of testing boring and zone water quality testing including recommendations regarding the viability of a future water supply well.
Task 3: Preparation of Well Design and Technical Specifications ($11,000) If the lithologic and water quality data collected from the test boring support moving forward with a new well at the site, Stantec will prepare the well design and technical specifications for bidding purposes, including the bid form. Stantec will prepare the technical specifications and bid form in a manner that is consistent with the City’s preferred format so that the City can incorporate them into a full bid package for contractor bidding. Stantec bid support services and well construction management/monitoring services can be provided as a separate contract following design.
Assumptions and Limitations: The City to contract directly with a well pump contractor to remove the existing pump and to obtain a downhole video of the existing Well 9. City of Ripon staff to assist in the operation of Well 9 to perform pumping test with water being discharged to its pump to waste facilities. This scope includes Stantec contracting with a well driller for the test boring and water quality zone testing design however does not include laboratory fees for zone water quality samples, which according to City staff are to be provided by the City’s existing contracted laboratory. Stantec will however support during water quality sampling and provide the subcontract physical laboratory services for aquifer grain size analysis. Per our discussion with City Staff, proposal assumes that City is responsible for compliance with the California Environmental Quality Act (CEQA), if applicable.
March 4, 2024
Mr. Kevin Werner
Reference: Well 9 Evaluation and Condition Assessment Proposal
Stantec proposes to perform the above scope for a fee not to exceed $193,145, billed on a time and material basis. If this scope and fee is acceptable, Stantec will prepare a contract for authorization by the City for your review. If you have any questions regarding the content of this proposal, please do not hesitate to contact me at 925.699.8012 or via email at [email protected].
Regards,
Stantec Consulting Services Inc.
Thomas Butler PG, CHG, CEG
Senior Hydrogeologist/Geochemist
Phone: 925-296-2126
[email protected]
Kevin Werner PE
City Administrator/City Engineer
Phone: 209-599-2108
[email protected]
cc: James Pease, City of Ripon
City of Ripon Authorization