AGENDA
ITEM
18 AGENDA
CALEXICO California ITEM
WHERE CALIFORNIA AND MEXICO MEET
18 CITY COUNCIL
AGENDA STAFF REPORT
DATE: October 15, 2025
TO: Mayor and City Council
APPROVED BY: Benjamin Martinez, City Manager fE 3 FOR CM.
REVIEWED BY: Karla Chaparro, Finance Director Je
PREPARED BY: Jesus Villegas, Public Works Director/City Engineer SUBJECT: Authorize Public Works Department to Advertise Request for Proposals (RFP) for Engineering Design Services to Replace the Existing Gaseous Chlorine Feed System with a Liquid Hypochlorite Feed System at Water Treatment Plant and Eastside Water Reservoir.
Recommendation:
It is recommended that the City Council authorize the Public Works Department to Advertise Request for Proposals for Engineering Design Services to Replace the Existing Gaseous Chlorine Feed System with a Liquid Hypochlorite Feed System at Water Treatment Plant and Eastside Water Reservoir, due to the current system exceeding its 10-year useful life.
Background:
The City of Calexico owns and operates a Water Treatment Plant ("WTP") and Eastside Water Reservoir ("EWR"), which provide its residents with its potable water. The water supply received by both the WTP and EWR comes from the Colorado River through the Imperial Irrigation District's ("IID") All-American canal. The City's WTP has a design capacity of 14 Million Gallons per Day ("MGD"), with an average daily demand of 7-8 MGD and a current peak flow of 9 MGD.
The EWR has a design capacity of 6 MGD, with an average daily demand of 1.25 MGD.
Both the WTP and EWR currently rely on gaseous chlorine water disinfection, which cleans the water prior to the distribution throughout the supply system. Said chlorine gas, although effective, comes with its share of risks and hazards. Chlorine is described by the Clean Air Act (40 CR 7412) as a hazardous air pollutant, which means that the storage and handling of the material is subject to very stringent measures to help prevent any leak that might endanger nearby population. In the case of the City of Calexico, the Water Treatment Plant is located adjacent to residential and commercial areas, schools, and the Calexico International Border, whereas the Eastside Water Reservoir is located adjacent to residential areas, underscoring the importance of following to the best safety standards and maintenance, to avoid any leaks that could harm our community.
The City's current chlorine gas equipment was installed in 2010, with a ten (10) year useful lifespan. Most of the system is comprised with Schedule 80 PVC, which has been conveying highly concentrated chlorine solution through the pipes, thus affecting the structural integrity of the pipes and, therefore, requests immediate maintenance to eliminate the risk of cracks and leaks on fittings.
Given that the whole system is past its useful life, and that the main components of the system need repair, a retrofit of the entire chlorine system is already required at this moment, to ensure that the WTP will continue to operate safely, to protect staff, citizens at both sides of the border, and the environment, as well as maintaining compliance with rigorous Federal and State regulations.
Due to the fact that this type of water disinfection system requires much more attention, effort and care to operate because of the dangers posed by the handling and storage of chlorine, many municipalities have opted to convert their Gaseous Chlorine Feed System to a Liquid Chlorine (12.5% Bulk Sodium Hypochlorite) Feed System. This represents two main points; first, since less agencies require the maintenance for the gas chlorine system, it has become increasingly expected quality of water delivered to their citizens.
Discussion and Analysis:
As it currently stands, the City of Calexico is in a pivotal time, with the opportunity to upgrade its already existing infrastructure, whether by updating its current Gaseous Chlorine Feed System, or switch to newer technology by installing a Liquid Hypochlorite (12.5% Bulk Sodium Hypochlorite) Feed System.
The Water Treatment Plant relies on heavy 2,000 Ibs. (pounds) tanks to supply the chlorine to the disinfection system. The Eastside Water Reservoir relies on 150 Ibs. (pounds) tanks to supply the chlorine to the disinfection system. They are bought in bundles of three (3) approximately six (6) times a year. With this information, the approximate yearly total spent on the current chlorine system, is broken down as follows:
- Number of 2,000 Ibs tanks bought in a year is 30 at $1.55 a pound = 2,000 Ibs x 30 tanks × $1.55 a pound = $93,000.00
- Number of 150 Ibs tanks bought in a year is 18 at $6.11 a pound = 150 Ibs x 18 tanks x $6.11 a pound = $16,497.00
- Total yearly dollar amount of chlorine gas = $93,000.00 + $16,497.00 = $109,497.00 2 However, several additional expenses shall be taken into consideration, including both the physical maintenance of the equipment, it also includes the permit procurement from the State of California, which is as follows:
- California Accidental Release Prevention (CalARP) Program = $18,000.00 every five (5) years, roughly $3,600.00 per year.
- Certified Unified Program Agency (CUPA) Annual Permit = $5,000.00 every (1) year.
The regular maintenance covers the following:
- Annual Chlorine System Maintenance at both the WTP and EWR = $50,000.00 per (1) year.
- Annual Quantitative Fit Testing = $1,800.00 per (1) year. - Replacement of Scrubbers at WTP and EWR = $152,000.00 every ten (10) years, roughly $15,200.00 per year.
- Due to the current configuration of the loading/unloading station for the chlorine gas tanks at the WTP, the process takes too much staff time (estimated):
Three (3) laborers at $25.00 for 3 hours, 6 times a year = $1,350.00 • Two (2) operators at $39.00 for 3 hours, 6 times a year = $1,404.00 • Total staff time = $1,350.00 + $1,404.00 = $2,754.00
The total yearly cost including the permits and maintenance is:
$3,600.00 + $5,000.00 + $50,000.00 + $1,800.00 + $15,200.00 + $2,754.00 = $78,354.00 And adding both the cost of the chlorine gas and the cost of permits and maintenance is:
00$109,497.00 + $78,354.00 = $187,851.00
The benefits of a Liquid Hypochlorite Feed System can't be overstated. Due to the fact that sodium hypochlorite is not listed by the U.S. Code of Regulations as a hazardous air pollutant, unlike chlorine, the Water Treatment Plant will be subject to less regulations and oversight, eliminating the necessity of keep training the staff, keeping records and attending inspections, on a regular basis, related to the storage and use of a hazardous air pollutant. Based on current trends from both our WTP and EWR, the amount of 12.5% bulk sodium hypochlorite (liquid chlorine) needed is of 52,250 gallons, at $2.7748 per gallon, gives an approximate yearly total of $144,983.30.
The maintenance for this system will not be as stringent as for the chlorine one, since sodium hypochlorite is not as corrosive.
Comparing the current yearly cost of the Gaseous Chlorine System of $187,851.00, against the anticipated yearly cost of the Liquid Chlorine (Sodium Hypochlorite) System of $144,983.30, the conversion will reduce the costs of the WTP and EWR.
Given the above-referenced information, the City has the following two (2) options to address the maintenance of both the WTP and EWR Chlorine Facility's:
3 Option No. 1 - Retrofit the Chlorine Facility's at the WTP and EWR CONS:
1. High risk of potential liability
2. Spillage/release requires 3-mile radius evacuation
3. Limited staffing and equipment in the Calexico Police and Fire Department Hazmat Team
4. Operation and maintenance cost:
a. Certified Unified Program Agency (CUPA) Annual Permit ($5,000 per year) b. CUPA California Accidental Release Prevention Program/Risk Management Consultant ($18,000 every 5 years)
c. Annual Chlorine System Maintenance at WTP and EWR ($50,000 per year) d. Annual Quantitative Fit Testing ($1,800 per year)
e. Replacement of Scrubbers at WTP and EWR ($152,000 every 10 years)
5. Anticipated renovation cost of the current Gaseous Chlorine Feed System at both the WTP and EWR = $3,500,000.00.
Option No. 2 - Convert Gaseous Chlorine Feed System to Liquid Hypochlorite Feed System at the WTP and EWR
PROS
1. Reduce risk of potential liability
2. Eliminate a 3-mile radius evacuation in case of a chlorine gas spillage/release.
3. Significant savings in operation and maintenance costs.
4. Anticipated cost of Liquid Hypochlorite Feed System at the WTP and EWR = $1,500,000.00.
City staff is recommending that the City Council authorize the Public Works Department to advertise Request for Proposals for Engineering Design Services for Chlorine Conversion Project - Gaseous Chlorine Feed System to Liquid Hypochlorite Feed System at Water Treatment Plant and Eastside Water Reservoir. If this item is approved by the City Council, the tentative schedule for this project will be as follows:
Description Date
Advertisement October 21, 2025
Proposal Due Date November 11, 2025 at 2:00p.m.
City Council Contract Review (Approval if December 03, 2025 applies)
Fiscal Impact:
-Capital Improvement Program Budgeted Item for FY 2025-2026 Estimated Advertisement
Fund No. 516-90-987-56000-000 $1,500.00
Total $1,500.00
4 Coordinated With:
City Manager's Office.
Finance Department.
Public Works Department.
Attachments):
N/A