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File #: 1945-2019    Version: 1 Name:
Type: Afternoon Administrative Report Status: Agenda Ready
File created: 6/20/2019 In control: CITY COUNCIL
On agenda: 11/19/2019 Final action: 11/19/2019
Title: Lake Hennessey and Milliken Reservoir Watershed Water Quality Monitoring
Attachments: 1. ATCH 1 - Hennessey and Milliken Reservoir Watershed Study Hydrology, 2. ATCH 2 - Maps of Watershed Sample Sites, 3. ATCH 3 - List of Water Quality Parameters, 4. ATCH 4 - Implementation of Water Quality Sampling & Analysis Plan
To: Honorable Mayor and Members of City Council

From: Philip Brun, Utilities Director

Prepared By: Joy Eldredge, Deputy Utilities Director

Lake Hennessey and Milliken Reservoir Watershed Water Quality Monitoring


Authorize the Utilities Director to execute a Memorandum of Understanding with Napa County for Water Quality Monitoring of the Lake Hennessey and Milliken Reservoir Watersheds.

The City and County have a shared interest in gathering additional data to learn how land use changes in the Hennessey and Milliken watersheds might impact the drinking water in the related lake and reservoir. The City owns the Lake Hennessey Reservoir and the Milliken Reservoir which serve as municipal drinking water supplies for the residents and businesses of Napa, and over 2,000 customers in unincorporated Napa County. The Hennessey watershed drainage area is composed of approximately 34,000 acres reaching as far north as Angwin. Of this total area, the City owns just 2,822 acres. The Milliken watershed drainage area is comprised of 6,200 acres of which the City owns nearly 2,200 acres. Both watersheds are located in the unincorporated area of the County; thus, the County establishes zoning and land use laws, and processes land use permits for private development, on these important lands.

On June 20, 2017 the County and City entered into a Memorandum of Understanding (MOU) regarding a study of the watersheds that would be cost shared equally.

On September 26, 2017 the City Council and County Board of Supervisors approved a professional services agreement with Systech to develop a calibrated watershed analysis risk management framework (WARMF) model simulating hydrology and water quality, develop a water quality sampling and analysis plan, and provide a tool which the City and County can use for watershed management on an ongoing basis. The WARMF model combines the physical characteristic...

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