HomeMy WebLinkAboutMINUTES - 05031988 - 2.6 TO: BOARD OF SUPERVISORS, AND AS GOVERNING BOARD OF CONTRA
COSTA COUNTY FLOOD CONTROL AND WATER CONSERVATION
DISTRICT
FROM: J. MICHAEL WALFORD, PUBLIC WORKS DIRECTOR
DATE: May 3 , 1988
SUBJECT: San Pablo Creek Drainage
Specific Request(s) or Recommendation(s) & Background &
Justification
I. RECOMMENDATION
1. ACCEPT the attached report prepared by the Flood Control
District staff entitled "Preliminary Study Report on San
Pablo Creek Watershed Downstream of San Pablo Reservoir. "
2 . DIRECT the Flood Control District to commence the
engineering and the California Environmental Quality Act
(CEQA) process for amending the Drainage Area 73 adopted
plan to include needed improvements on San Pablo, Appian,
Castro and Wilke Creeks.
3 . DIRECT the Community Development Director, Zoning
Administrator and County Planning Commission to pay special
attention to the hydrology impact of all new development in
Drainage Area 73 in light of the issues identified in the
above report and to require the implementation of
mitigation measures by all developments adding impervious
surfaces. The amount of work shall be equivalent to at
least $0. 15 per square foot of new impervious surface.
Continued on attachment: X yes Signature:
Recommendation of County Administrator
Recommendation of Board Committee
Approve Other:
Signature(s) :
Action of Board on: May 3 , 1988
Approved as Recommended X Other
, Vote of Supervisors I HEREBY CERTIFY THAT THIS IS
A TRUE AND CORRECT COPY OF AN
X Unanimous (Absent ) ACTION TAKEN AND ENTERED ON
Ayes: Noes: THE MINUTES OF THE BOARD OF
Absent: Abstain: SUPERVISORS ON DATE SHOWN.
Attested May 3 , 1988
Orig. Div. :Public Works (FC) PHIL BATCHELOR,
cc: County Administrator CLERK OF THE BOARD
County Counsel OF SUPERVISORS AND
Community Development Dir. COUNTY ADMINISTRATOR
Public Works
Flood Control
Accounting
MFK:md
BO:21.t4
By
DEPUTY CLERK
II. FINANCIAL IMPACT
The cost of the engineering and CEQA work indicated above is
estimated to be $50, 000.
III. REASONS FOR RECOMMENDATION/BACKGROUND
An overview on the adequacy of the major natural creeks serving
Drainage Area 73 downstream of San Pablo Reservoir is provided in
the attached report. Continued urbanization is causing the
various inadequacies in these creeks to become a larger, more
frequent problem.
It is recommended that the District complete the necessary.
.engineering and CEQA process to provide data for use by the Board
and the City Councils of Richmond and San Pablo to determine if
the adopted plan for Drainage Area 73 should be expanded to
address the inadequacies in these creeks. In the interim, it is
proposed that all new development in the watershed be required to
participate in the necessary mitigation of the accumulative
hydrology impact.
IV. CONSEQUENCES OF NEGATIVE ACTION
Action to eliminate the noted problems in these natural creeks
will not occur.
PRElZMINARY STUDY REPORT ON
SAN PABID CREEK wAamrnim
DOWNSTREAM OF
SAN PABID RESERVOIR
Prepared by
CONTRA COSTA COUNTY FLOOD CICNT SOL
AND
WATER CONSERVATION DISTRICT
March 21, 1988
1 These categories will be used throughout the report to assist in
understanding the issues, the: possible solutions, and who should
pay for the solutions.
Natural Creek Capacity:
The natural creeks have varying degrees of capacity. With a few
exceptions, San Pablo Creek above Interstate 80 has adequate
capacity to contain the 100-year storm event. The points of
inadequate capacity are generally the result of inadequate road
crossings, or where urbanization has occurred below the top of
creek bank. Three road crossings known to be inadequate are La
Honda Road, D'Avila Way, and the Kennedy Grove entrance road.
Downstream of Interstate 80 the exact limits of inadequate
channel have not been established. The Corps of Engineers is
currently evaluating the San Pablo creek flood plain in this area.
Upon completion of their study, in approximately one year, they
will establish the limits for the channel having insufficient
capacity and the adjacent urbanized area subject to flooding from
the creek.
Appian Creek is believed to be inadequate along most of its length
downstream of Valley View Road. A capacity study of this creek
has not been performed by the CCCFCD. Over the years various
segments of the creek have been improved and spot analysis by
private engineers have been performed to substantiate the adequacy
of these improvements.
3
Castro Creeks. The natural erosion process presents two major
1 problems. First, the erosion moves sediment downstream depositing
it in areas where the creek has adequate capacity and slow flow
velocities. This erosion-sedimentation process will have a severe
impact upon the future maintenance costs for the Corps of
Engineers improvements being constructed in the North Richmond
area.
Second, the erosion process creates creek bank instability and
ultimately bank failure. This in turn causes a personal property
loss by the adjacent property owner. The loss at times can be
severe if improvements have been built too close to the natural
creek. Unfortunately, along the creeks being discussed,
urbanization has encroached significantly upon the natural creek
area. Over the, years, significant property losses have occurred,
and it is anticipated that these losses will continue to occur.
The increase in upstream urbanization will increase the volume of
discharge and the frequency of higher discharges than are
currently experienced. This will result in more creek bank
failures . How much responsibility should these upstream
developments bear in preventing these bank failures? Should they
be responsible for the property owners who have built or purchased
homes too close to the natural creek? The developments, through
the California Environmental Quality Act (CEQA) , have some shared
responsibility with the property owners along these creeks.
5
San Pablo Creek Phase I Corps of Engineers Improvements:
r
This plan of improvement involves the construction of San Pablo
Creek channel improvements, to convey the 100-year storm event,
from the railroad tracks at Giant Highway to the Bay. The
improvements are currently under construction by the Corps of
Engineers, and they should be completed by 1990. The estimated
cost for the work is $8, 000, 000 of which approximately $1, 800, 000
is a local cost. To date, $1, 300, 000 of the local cost has been
funded by a 1983 assessment district formed by property owners in
the flooded area being protected by the new improvements. It is
proposed that some of the $500, 000 shortfall in funding be covered
by the established Drainage Area 73 drainage fee.
San Pablo Creek Phase II Corps of Engineers Improvements:
This plan involves the construction of San Pablo Creek channel
improvements, from the railroad tracks upstream to the point where
the Corps of Engineers determines that the natural creek has
sufficient capacity to contain the 100-year storm event. The
scope of these improvements and their cost have not yet been
determined. Also, the method for funding the local cost share has
not been determined. Similar to the Phase I improvements, these
improvements will probably require a local assessment district
covering the flood area and a share of the Drainage Area 73
drainage fees. Drainage Area 73 was formed in 1982 , to fund a
portion of the local cost share for the Corps of Engineers'
7
future development where applications have not even been prepared.
Each development should be held ' responsible for meeting this
requirement.
WHO PAYS? HOW MUCH DO THEY PAY?
Approximately 80% of the watershed is urbanized? Should the
remaining 20% be required to finance the solutions for all of the
problems? The answer is no. However, the new developments should
be required to pay at least their fair share, and in some
instances, more than their faire share where the identified
adverse impacts from the developments demand mitigation.
The 1983 Engineer's Report for Drainage Area 73 estimates that
approximately 20, 000, 000 square feet of impervious surface would
be added to the watershed during the next twenty to thirty years.
It is recommended that consideration be given to increasing the
present drainage fee to $0. 20 per square foot of impervious
surface. This amount would be split to provide $0. 10 per square
foot for the downstream Corp of Engineers' improvements and $0 . 10
per square foot for upstream improvements, to eliminate
inadequate reaches of creek and to provide grade control
structures to slow down the erosion process and the velocity of
creek flows. If implemented within the next four months, the
$0. 10 fee would raise approximately $1, 500, 000 for improvement
upstream of Interstate 80.
9
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