HomeMy WebLinkAbout07.a. (Revised) Joint Walnut Creek/Grayson Creek Levee Rehabilitation ProjectJoint Walnut Creek/Grayson Creek
Levee Rehabilitation
Project
Danea Gemmell
Planning and Development
Division Manager
CCCSD
Item No. 7.a.
February 18, 2016
Paul Detjens
Senior Engineer/
Program Manager
CCCFCWCD
REVISED
~40-Year Flood Event near
Pacheco Creek
2013 Study Identified up to
$146M in Potential Damages
Influent Pumps located below grade Final/Standby Effluent Pumps located
below the Pump & Blower Building
Background
2005-2006
•Major storm events lead to overtopping of levees near Pacheco Creek (~40 year
event)
2007
•Flood Control District (FCD) Project to desilt Walnut Creek Channel
•FCD Interim Levee Project to raise western levee of WC Channel/Grayson Creek
April
2013
•Board accepts Integrated Regional Water Mgmt Plan (IRWMP) for Prop 1E Grant
•Joint Project with FCD to raise levee with 25% share ($550K)
June
2013
•Notice of unsuccessful Prop 1E Grant
July
2013
•Enterprise Committee presented w/FCD request to split project with 50% share (or
$1.1M) w/ potential to reduce costs with soil import program on Kiewit property
•Staff received direction to proceed with plan on Kiewit property
June
2014
•Adopted FY2014-15 CIP (DP 3741) includes Walnut Creek Channel /Grayson Creek
Levee Rehabilitation Project ($620K)
Existing Capital Project (DP7341)
•Priority Ranking: High
•CIB Program: Treatment Plant
•Lead Agency: FCD
•Total Project Cost: $2.2M
•District Cost Share: 50%
•Current Protection: <100 yrs
•Proposed Protection: 500 yrs
Project Location
USACE Flood Protection Standard
is 100-Year w/ 3-ft Freeboard
Pre 2007 2007 - 2018 Post 2018
<<<100 Year Protection
? Freeboard
~100-Year Protection
1 to 3 -ft Freeboard
500-Year Protection
3-ft Freeboard
Project Scope
•Increase embankment to 500 year Flood Projection
with 3-ft Freeboard
•Expected 6’ to 8’ ROW transaction to FCD at
minimal costs (possible ROW trade of property)
•Relocate/Replace fence to bottom of slope
•Soil import operation to stockpile & secure
25,000 cy of fill to minimize project costs
•FCD planning a separate project to desilt Walnut
Creek Channel
Water Surface Modeling Results
Proposed Levee Modifications
Location
#
Location
Description
Current
Freeboard for
100-Year Flood
(feet)
Proposed
Freeboard for
500-Year Flood
(feet)
Proposed Levee
Elevation
Increase
(feet)
1 Basin B /
Walnut Creek
Channel
1.5 3.0 3.0
2
Near
Confluence of
Walnut and
Grayson
Creeks
3.7 3.0 1.8
3 Headworks /
Grayson Creek 2.1 3.0 2.2
Project Benefits
•Levees will meet current levee protection
standards (100 Year with 3-foot of freeboard)
•Levee will meet 500-Year Protection and
accommodate 16-inches of sea level rise
•Levee will protect $150M+ of existing treatment
plant assets
•Increased protection of overall plant site and
personnel
•Increased protection from catastrophic failures,
plant shutdowns, extended shutdowns,
emergency discharge of untreated wastewater
Level of Protection Summary
Level of
Protection
Average
Levee
Raising on
Grayson
Creek
Average
Levee
Raising on
Walnut Creek
Total
Estimated
Project Cost
(2013)
100-Yr with 3.0
Freeboard
1.6 ft 0.9 ft $1,860,000
200-Yr with 3.0
Freeboard
1.9 ft 1.2 ft $1,939,000
500-Yr with 3.0
Freeboard (*)
2.5 ft 2.9 ft $2,005,000
Agreement Terms
•50%-50% split between CCCSD and FCD with
estimated $2.2M project cost
•Both agencies will share in import soil savings
•Budget approved by both parties with Quarterly
review of expenditures to monitor costs
•Budget includes staff costs for CCCSD & FCD
Flood Control District’s Role
•Lead agency
•Obtain permits,
approvals,
entitlements & CEQA
•Manage utility
relocations
•Produce design
documents
•Bid project
•Construction inspection and management
CCCSD’s Role
•Lead 25,000 cy soil
import for operation at
Kiewit property
•Provide survey &
ROW support
•Review design and
bid documents
•Coordinate access &
fence relocation
District Staff Recommends
The Board of Directors authorize the General
Manager to execute an agreement with the Contra
Costa County Flood Control and Water
Conservation District for implementing the joint
Walnut Creek/Grayson Creek Levee
Rehabilitation Project with a Not-to-Exceed
Amount of $1.1 million for the District’s Share
Questions Questions