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Tenney Tank Replacement Project


 Click here for plans: Tenney Site Plan Revised

Background:    The Inverness Public Utility District (District) has 9 tanks in the system of which six are redwood and three are steel.  There is a total storage capacity of roughly 425,000 gallons that can supply 4 to 6 days of typical system demand for domestic potable use in normal weather conditions.  The problems specific to the redwood tanks are: 1) Seismically unsafe; 2) Leaking; 3) Producing higher chlorine demand loads; and, 4) Vulnerable to fire hazards.  The District’s Capital Improvement Program (presented in November 2016), identified the replacement of the most vulnerable tanks.

The existing Tenney water storage system is critical for the domestic drinking and life safety aspect as a fire water supply for Inverness.  The existing 10,000 and 60,000 gallon redwood tanks are referred to as Tenney Tanks #1 and #3.  (Tenney Tank #2; 10,000 gallon was removed in the 1990’s because of serious deterioration.)  Besides being in poor seismic condition, the redwood tanks exert a high chlorine demand.  The State Water Resources Control Board (SWRCB) inspection of the Tenney Tanks (conducted in June and August, 2017) documented the leaking tanks at the Tenney site.  The District is proposing to eventually replace all redwood tanks in the system.  The District can currently serve all existing and potential water meters.  This project will not be developing new connections.  The two new tanks will be situated in the same location as the prior three tanks.  The storage will increase from 80,000 to 118,000 gallons to help ensure sufficient capacity in future dry weather and drought years.

Project Description:  It is proposed to replace the original three redwood Tenney tanks with two steel tanks designed to current seismic criteria from the American Society of Civil Engineers-7 (ASCE-7) and the American Water Works Association (AWWA).  This requires a volume to allow for “sloshing” of water in the tank during a seismic event. The operating volumes will be 53,000 and 65,000 gallons. The tanks would be positioned to be roughly the same foot print and original water level elevation to maintain system pressure and fire flow capacity.  The two tanks would be installed in a phased approach by the same contractor.  Projected installation date is tentatively set for late 2018.  A new 4’ x 8’ building wooden shed (replacing the existing shed) will be constructed to house the chlorine pump and low wattage radio communications equipment.

Reason for Categorical Exemption: This project is categorically exempt under CEQA Article 19 Categorical Exemption, 15301(b)-Existing Facilities.  This Project undertakes no expansion of use by the District in providing domestic drinking water for the town of Inverness.  The project is also exempt under the California Environmental Quality Act (CEQA) Guidelines Section 15061(b)(3). The activity is covered by the general rule that CEQA applies only to projects, which have the potential for causing a significant effect on the environment. Where it can be seen with certainty that there is no possibility that the activity in question may have a significant effect on the environment the activity is not subject to CEQA.



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