Patton Reservoir Replacement Project

1100 Arden Road, Pasadena, CA


The applicant, Brown and Caldwell, on behalf of the property owner, California American Water Company, has submitted a Modification to Conditional Use Permit #4804 to allow the replacement of the existing Patton Reservoir with a new circular prestressed concrete reservoir.

Patton Reservoir was built in the 1920’s. Over the years, the reservoir has had minor upgrades and repairs, but the overall water storage capacity and reservoir design remains unchanged. Patton Reservoir currently has a capacity of 540,000 gallons, with the potable water stored within the reservoir serving California America Water customers and fire hydrants within the adjacent City of San Marino. The existing reservoir is a partially buried rectangular basin measuring 110 feet by 110 feet, with a 3.5 foot graded and paved berm surrounding it. The buried portion of the basin has sloped side walls with a concrete berm surrounding it. The existing reservoir’s steel trussed roof, which is supported by wood posts, stands 4.5 feet above the berm.

Due to its age, the reservoir cannot adequately supply current demand and provide adequate fire suppression water storage capacity. Additionally, the deteriorated reservoir structure does not meet present earthquake design requirements. The project applicant is proposing to replace the existing Patton Reservoir to increase water storage capacity, increase supply reliability, and correct structural deficiencies.

The proposed replacement circular reservoir would be located on the same footprint as the existing reservoir and have an internal diameter of 107 feet.  A new similar berm is proposed around the replacement reservoir, and the replacement reservoir would measure 12 feet above the top of the berm.  The proposed capacity of the new reservoir is 940,000 gallon.  The new reservoir would continue to have a mild-sloped roof design (similar to the existing reservoir roof) and would be painted Hunter Green in color.

The proposed project would only replace the reservoir and would not require any additional infrastructure/changes within the site or modifications to the purpose of the existing facility.


An Initial Study was prepared for the project and concluded that there will be less than significant impacts on the environment with the incorporation of mitigation measures; a Mitigated Negative Declaration has therefore been prepared. Possible impacts on Vibration and Tribal Cultural Resources were identified in the Initial Study.

Comments on the Initial Study and Mitigated Negative Declaration may be received in writing between Wednesday, November 24, 2021 and Wednesday, December 15, 2021; and in writing at future public hearings considering these documents. Please submit comments in writing by 5:00 PM on November 22, 2021, to the attention of Beilin Yu, Senior Planner, Planning & Community Development Department, Planning Division, Current Planning Section, 175 North Garfield Avenue, Pasadena, California, 91101; or via email to If you wish to challenge the Initial Study and Mitigated Negative Declaration in court, you may be limited to raising those issues that your or someone else raised at any public hearing where these documents were considered.





Date:   Wednesday, December 15, 2021

Time:  5:30 pm

Place: Please see the Hearing Officer agenda for instructions on how to access the meeting via webcast. The meeting agenda will be posted on December 10, 2021 at

CASE MANAGER: Beilin Yu, Senior Planner
PHONE: (626) 744-6726