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C. 12

To:	Board of Supervisors
From:	Julia R. Bueren, Public Works Director/Chief Engineer
Date:	February 7, 2017

Contra

Costa

County

Subject:

APPROVE the Garin Ranch Basin & Heron Park Basin Low-flow Channel Improvements Project & related actions under CEQA, Brentwood area. (District III)

APPROVE	OTHER
RECOMMENDATION OF CNTY ADMINISTRATOR	RECOMMENDATION OF BOARD COMMITTEE

Action of Board On: 02/07/2017

APPROVED AS RECOMMENDED

OTHER

Clerks Notes:

VOTE OF SUPERVISORS

AYE:

John Gioia, District I Supervisor
Candace Andersen, District II Supervisor
Diane Burgis, District III Supervisor
Karen Mitchoff, District IV Supervisor
Federal D. Glover, District V Supervisor

Contact:

Leigh Chavez, 925-313-2366

I hereby certify that this is a true and correct copy of an action taken and entered on the minutes of the Board of Supervisors on the date shown.
ATTESTED: February 7, 2017
David Twa,

BY:	, Deputy

RECOMMENDATION(S):

APPROVE the Garin Ranch Basin and Heron Park Basin Low-flow Channel Improvements Project (Project), and AUTHORIZE the Chief Engineer, or designee, to advertise the Project, Brentwood area. [County Project No.7571-6D8178, DCD-CP#16-46] (District III).


DETERMINE the Project is a California Environmental Quality Act (CEQA), Class 15301(b) Categorical Exemption, pursuant to Article 19, Section 15301(b) of the CEQA Guidelines, and

RECOMMENDATION(S): (CONT'D)

DIRECT the Director of Conservation and Development to file a Notice of Exemption with the County Clerk, and AUTHORIZE the Chief Engineer or designee to arrange for payment of a $25 fee to Conservation and Development for processing, and a $50 fee to the County Clerk for filing the Notice of Exemption.

FISCAL IMPACT:

100% Drainage Area 52C Funds

BACKGROUND:

The purpose of the project is to improve the drainage of Garin Ranch and Heron Park Basins to reduce or eliminate ponding and mosquito breeding habitat. Garin Ranch Basin consists of a north and south basin connected by an existing double concrete box culvert under Redhaven Street. The basins are considered “off-line basins” since they do not collect creek flows; only piped storm drainage from residential neighborhoods. The basins contain low-lying grassy vegetation that is regularly maintained.

The proposed improvements generally consist of excavating a low-flow area along the bottom of each basin beginning at the existing basin pipe inlets that flow into the basins, traveling through the basins, and ending at the existing concrete outfall structures that exit the basins.

In each of the basin areas, the low-flow area will be graded to drain the basin through the existing concrete outfall structure. It will be lined with filter fabric leaving excess filter fabric on each side. One or more four to six inch diameter fabric-wrapped perforated PVC pipes will be placed on the bottom over a layer of drain rock. The low-flow area will then be backfilled with permeable drain rock over the wrapped perforated pipe and the excess filter fabric will be wrapped over the top. Additional drain rock will be placed on top so that no filter fabric is exposed.

The low-flow areas will be trapezoidal in shape with 1:1 side slopes and be between six and 14 feet wide and one to two feet deep. The length of the low-flow area at Garin Ranch Basin will be approximately 2,445 feet and Heron Park Basin 890 feet.

Cleanouts will be installed approximately 250 feet apart along the perforated pipe and low-flow areas. The existing riprap protection located at the pipe outfalls will be filled in with permeable drain rock. All work will be contained within the existing basins.

The project is a covered activity under the East Contra Costa County Habitat Conservation/Natural Community Conservation Plan (HCP/NCCP) as “Activities in the Urban Development Area”. The project will follow applicable HCP/NCCP Avoidance and Minimization Measures to minimize impacts to covered species and water quality. In addition, HCP/NCCP fees will be paid to the Conservancy as appropriate prior to the start of construction. A nesting bird survey will be conducted prior to work if the project is constructed during nesting bird season (February 1 to August 31). Real Property transactions, including temporary right-of-way may be necessary to support construction of this project. General Plan Conformance has been received from the City of Brentwood.

CONSEQUENCE OF NEGATIVE ACTION:

Delay in approving the project may result in a delay of design, construction, and may jeopardize funding.