HomeMy WebLinkAbout05/06/1997, 7 - FLOOD MANAGEMENT PLAN, PHASE 1 SPECIFICATION NO. 96-05A council "'°° fay 6, 1997
j acEnaa REpoat
C I T Y OF SAN LUIS OBISPO
FROM: Michael McCluskey,Public Works Director
Prepared By: Wayne Peterson,City Engineer
SUBJECT: Flood Management Plan,Phase 1
Specification No.96-05A
CAO RECOMMENDATION
Receive report from consultant and conceptually endorse giving first preference to bio-engineered
channels or bio-technical approaches to bank stabilization.
DISCUSSION
The City has been required by the Corps of Engineers to prepare a Flood Management Plan for the
creek systems throughout the San Luis Obispo drainage basin in order to demonstrate that the methods
chosen to maintain the creeks and repair damaged creek bank were within guidelines established by the
Federal Government. Currently the City cannot receive permits for work in the creeks from the Corps
of Engineers because of the Corps and Regional Water Quality Control Board staff's dissatisfaction
with the methods used and results of past creek maintenance work.
On December 3' , the City Council authorized the CAO to award a contract of up to $80,000 to
Questa Engineering Corporation for the preparation of Phase 1 work on the Flood Management Plan.
The scope of work was reviewed by staff of Zone 9, Regional Water Quality Control Board and
Army Corps of Engineers. Because of the need to accomplish the repair work before additional winter
storms caused further damage the Corps and City agreed to conduct the study in two phases. The fust
phase was a study of the reaches of the creek where the damages needed to be repaired now. The
second phase will look at the entire drainage basin. The first phase of the study is a model for the 2nd
phase. The second phase will have additional information included such as design standards and
methods for sizing structures in our water shed based on our increased knowledge of the rainfall rate,
runoff, and characteristics of the watershed that we did not have 20 years ago when the Nolte Master
Plan was completed.
The first draft of "Draft Stream Corridor Management Plan for San Luis Obispo Creek", one of several
documents that will eventually be submitted as a part of the Phase 1 work, was received by staff in
early April. Staff of the City,County,and State and Federal agencies have been reviewing the draft and
making suggestions for change. The report is primarily an informational document. It summarizes the
existing conditions and resources of the creek system. It also provides guidelines on how to conduct
specialized hydraulic design engineering to stabilize creek banks in ways that are the least
environmentally damaging.
The consultant wants to report his findings to the City council and seek concurrence of the City Council
that the City will be willing to commit to a different policy of stream bank maintenance than was
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Council Agenda Report-Flood Management Plan-Phase 1 Report;No.96-05A
Page 2
followed in the recent past. The consultant is here to explain what these new policies would look like,
their benefits,and their costs.
With Council's approval of the concepts embodied in the report the consultant will be able to complete
Phase 1 and city staff will be able to contract with Questa Engineering to prepare the plans and
specifications and apply for the permits necessary to repair the creek banks at the 9 points in the City
and the one point in the County,the police pistol range, that were damaged during the heavy rains of
the winter of 1995. Some of these projects will eventually be paid for by FEMA and some by Zone 9.
It is important that the consultant be able to persue these projects so that the repairs can be completed
prior to winter 1997-8.
FISCAL IMPACT
Approving the recommended guidelines tonight will have no direct general fund impact. However,
approval will allow design of projects following the guidelines to proceed and construction to occur
this fall. Sourse of funding for the projects is planned to come from FEMA and Zone 9.
Attachment:
Letter from Jeff Peters,Questa Engineering,April 23, 1997
Introduction Section Phase 1 Report Draft/April4, 1997
Copy of Draft Report in Council Reading file.
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4-24-1997 3:29AM FROM r. 2
April 23, 1997
Nor.Wayne Peterson
City Engineer
City of San Luis Obispo
955 Morro Street
San Luis Obispo, CA 93401
SuT: Report on San Luis Obispo Creek
Dear Mr.Peterson:
Several areas along San Luis Obispo Creek suffered significant damage from the severe
flooding events of the winter of 1995-96, and to a lesser extent the high creek flows of this
past winter. Severe bank erosion has damaged storm drainage culverts where they discharge
into the creek,and threaten City property and public and private improvements elsewhere.
notably the ponds at the City's wastewater treatment plant site.
Normally, the City would apply to various State and Federal agencies for approval to
construct bank stabilization structures such as wire gabion baskets and rock rip-rap on an
individual project basis as a series of separate permits. Since work would be required in the
creekbed,potentially affecting riparian wetlands and waters of the U.S.,permits are required
from the U.S.Army Corps of Engineers,the Central Coast Regional Water Quality Control
Board. and California Department of Fish and Game. If any endangered species are
threatened by work,the permit has to be coordinated with the U.S.Fish and Wildlife Service.
Changes in stream flow direction due to stabilization Work are often difficult to predict
without specialized hydraulic engineering studies. Stabilization measures, particularly those
that utilize"hard"structures such as concrete walls or cemented rock, can have unforseen
consequences resulting in bank erosion can be passed downstream.Some downstream effects
from prior stabilization projects have occurred within San Luis Obispo Creek.
Unless projects are engineered carefully, the result of such unintended consequences,
downstream, could over time, result in the nearly complete lining of a creek system,
displacing valuable riparian and aquatic habirat.
Because of these concerns.the regulatory agencies have requested that the City consider all
the bank protection and other creek management problems together as one project, assess
impacts and develop mitigation measures cumulatively, and develop an overall plan to deal
with creek management issues in the least environmentally damaging way possible.This will
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4-24-1997 3:29AM FROM r. 3
likely mean that the City will have to make some changes to the way it has traditionally
approached bank stabilization designs and creek management and maintenance.
Based on the requests from the regulatory agencies, and under contract to the City, Questa
Engineering Corporation has developed a Stream Corridor Management Plan to address
problems on San Luis Obispo Creek. The Plan includes both guidelines on how to conduct
the specialized hydraulic design engineering,as well as recommendation on how to stabilize
banks at specific sites in the least environmentally damaging way.
Much of the report is advisory or informational to the City Council. It summarizes the
existing hydrologic conditions and biological resources of the creek,as well as inventorying
the management problems and opportunities for enhancement and restoration along the creek
corridor. These are shown and prioritized in the report. Extensive opportunities are
recognized for creek enhancement,including enhancement of the fishery.
The report also examines various alternative approaches for bank stabilization and.repair.
These range from traditional"hard"approaches such as grouted rock and concrete structures,
rip-rap and gabions to "soft" approaches that utilize purely vegetative measures such as
hydroseeding, use of biodegradable fiber erosion control blankets.
Based on detailed hydrologic analysis of the creek system, the report recommends an
integrated or biotechnical approach to bank stabilization. Such an approach represents a
change in the way the City has dealt with bank erosion in the pact. The recommended
approach requires more detailed and rigorous geomorphic and hydrologic analysis of the
creek,and places a greater emphasis on inclusion of native perennial woody plants to provide
stabilization and erosion protection.
Beyond the informational items, the reports request that the City commit to a specific
detailed hydraulic design procedure for planning bank stabilization projects, as well as a
more environmentally sensitive approach to flood control channel design and preventative
maintenance, wherever possible.
Section 5.5 of the report (p. 64,.40' paragraph) requests that the City commit to a policy
giving first preference to bioengineered channels or bio-technical approaches to bank
stabilization. In approving this report, San Luis Obispo will be one of the first cities in
California to officially adopt as a policy, a method of bank stabilization that is aesthetically
attractive and biologically sensitive and beneficial.
The report also serves as the basis for future project permit streamlining. As long as the
projects adhere to the principals, design concepts, and procedures outlined in the report,
separate Corps of Engineers approval on an individual project basis will not be needed. The
City will provide the Corps with a Notification and Description of the proposed projects and
request a Notice to Proceed. A Memorandum of Understanding may also be possible with
the California Department of Fish and Game for a 1601 Streambed Alteration Agreement
and, under certain conditions, for expedited review by the Central Coast Regional Water
4-24-1997 3:30An�1 FkCiM r. ..
Quality Control Board for a Section 401 Water(duality Certification.
The report also presents conceptual designs for repair of 9 individual sites which the City has
submitted a request to FEMA for reimbursement funding. The City will still need to review
and approve Plans and Specifications for each project,including the repair sites.
We look forward to discussing the draft report with the City,County and permitting agencies.
In the interim,we would be pleased to answer any questions that arise.
Sincerely,
Jeffrey Peters,P.E.
Principal
JP/cw
Clef.:96132L.21
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1.0 INTRODUCTION
Background
Many segments of San Luis Obispo Creek(SLO Creek) haveon-going problems involving flooding
and bank instability, and will require active management. Management actions may consist of channel
sediment removal, vegetation control, and riparian enhancement repair of existing failing bank
protection structures,and construction of new bank protection and flood control improvements. Most
of these management actions will require some form of approval or permitting from the U.S. Army
Corps of Engineers, Central Coast Regional Water Quality Control Board (Regional Board), and
California Department of Fish and Game(DFG) (collectively Regulatory Agencies).
Channel modification, vegetation management, and stream bank stabilization projects can have
significant impacts on channel hydraulics, water quality, and biological resources. Unless designed
and maintained correctly, such projects can have unintended, unwanted effects downstream.
Armoring a stream bank can, in some circumstances, translate energy and bank erosion problems
downstream. The result of such improperly designed and unintended actions spiraling downstream
could eventually lead to the complete lining of a streamway, with attendant losses in riparian habitat
and aquatic values.Because of these concerns, the Regulatory Agencies have requested preparation
of a comprehensive Stream Corridor Management Plan for SLO Creek that will form the basis for
future project planning, decision making and permitting. Through informal scoping meetings and
discussions, the Regulatory Agencies collectively have requested a plan that:
1. Is based on a thorough inventory of resources and an understanding of the extent and cause of
problems.
2. Addresses the underlying causative factors, preferably at a watershed level.
3. Includes a detailed geomorphic and hydraulic analysis as the basis for sound engineering design.
4. Incorporates fluvial geomorphic principles in a"managed, natural channel design".
5. Creates a design basis that does not move problems downstream.
6. Minimizes impacts to wetlands and biological resources, preferably through the use of"soft"
vegetative approaches.
7. Includes mitigation in the design so that there is no net loss of wetlands, fisheries and aquatic
habitat or riparian resources.
8. Enhances and restores, where possible, these resources.
This is the first in a series of reports that complies with the requests from the Regulatory Agencies,
and forms the framework for the design phase. The next report will present a Design Concept Plan,
based on comments and input from the agencies on the information in the first report. The Design
Concept Report will provide the basis for subsequent preparation of Plans and Specifications.
Questa Engineering Corporation 1 96132Phasel/April 4, 1997
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Study Objectives and Regulatory Requirements
This report presents the results of our inventory and analysis of the existing geomorphic and
hydrologic conditions, and biological resources of a portion of SLO Creek, located within the City
of San Luis Obispo, California (Figure 1-1). Alternatives are reviewed and recommendations are
made that can form the basis for preparation of subsequent plans, management programs, and site
designs.
The principal portion of the study area is SLO Creek at the southwest end of the City of San Luis
Obispo, extending from Los Osos Valley Road to the Marsh Street Bridge. Short segments of Stenner
and Prefumo Creeks are also included, as well as a segment of the main stem of SLO Creek above
Cuesta Park to the Highway 101 crossing.
There are significant stream corridor management issues within the study area. These issues include:
r (1) periodic flooding; (2) degraded riparian habitat; (3) low aquatic habitat values and degraded
fishery resources; and, of particular focus in this study(4) extensive areas of stream bank instability
and in-channel sediment accumulation.
The extent and probable causes of the management problems are addressed first. The results of the
inventory and analysis are then used to develop and screen stream corridor management alternatives,
including alternative bank stabilization approaches. A preferred alternative is then proposed, along
with Design Criteria. Plans and enhancement and stabilization designs (Design Concept Plan) will
then be developed, based on the selected or preferred alternative.
A Technical Advisory Committee(TAC) composed of representatives from the City, County, select
Resources and Regulatory Agencies, and other interested individuals and groups are providing
guidance in selection and development of the preferred stream corridor management approaches.
Most members of the TAC also sit as an advisory committee to the Zone 9 geographic area(SLO
Creek watershed) of the County Flood Control District.
This report and the subsequent Design Concept Plan will then be submitted to the U.S. Army Corps
of Engineers as a supporting document for application for an Individual Section 404 Wetlands Fill
Permit for any identified Phase I projects. The reports will also be used as background information
in submittals to the Central Coast Regional Board for application for a Section 401 Water Quality
Certification(or waiver)associated with the Section 404 wetlands fill permit application and for the
required CEQA/NEPA documentation. A separate Streambed Alteration Agreement must also be
received from the DFG. Consultation and coordination with DFG and the U.S. Fish and Wildlife
Service(FWS)is also required because of the potential and likely presence of endangered species in
the study area. This is required under Section 9 of the Endangered Species Act.
Study Area Location, Phasing, and Work Scope
Ultimately, a Stream Corridor Management Plan, encompassing flood control, water quality, bank
stability and sedimentation, and biological resources will be prepared for the entire SLO Creek from
II its mouth to headwaters, its major tributaries, and important watershed areas.
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Questa Engineering Corporation 2 96132Phawl/Apri!4, 1997
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QUESTA ENGINEERING CORPORATION FIGURE
1220 BRICKYARD COVE ROAD STREAM CORRIDOR MANAGEMENT
PT. RICHMOND, CA 94807 PLAN FOR SAN LUIS OBISPO CREEK 1 _
Job No: 96132 Appr. J.P. Date:4/4/97 PHASE I
Because ofthe enormous scope of this overall workro
p gram and the need to complete some stream
lipcorridor management activities (principally bank stabilization) during the summer of 1997, prior to
initiation of winter rains and high flows, the work program has been divided into two phases.
Phase I (the subject of theresent study)y) is more restricted in scope and geographic area, and
addresses immediate management needs within a defined study area (Plate I). Phase II addresses
overall stream corridor management throughout the SLO Creek watershed,
including development
of hydrologic and hydraulic models, flood management, sediment management and riparian
restoration, based on comprehensive inventories and analysis, a Geographic Information System
(GIS) to house the technical inventory and management data, and design criteria handbooks and
maintenance manuals. The TAC has reviewed and approved the Phase I and H work programs. The
Phase I work program, which.is divided into Improvement Program and Repair Program components,
is as follows:
• Improvement Program. The Phase I Improvement Program provides a reach-wide
perspective of causes of stream corridor management problems (i.e., flooding, bank erosion,
sedimentation), a geographic inventory of resources and kinds of problems, a description of
corrective alternatives considered, and an identification of the recommended least
environmentally damaging solution to each kind of problem inventoried. In addition, the
Improvement Program outlines the biologic, geomorphic, and hydrologic steps, guidelines,
and analysis procedures to be used for the development of implementation plans(i.e., plans
and specifications) for addressing specific problem sites. The.Improvement Program shows
the general areas of problem types and proposed (generic) solutions; but it does.-not indicate
specific plans such as the proposed location of drop structures, gabions, etc. Public and
agency input and consensus are being provided at various points in the development of the
Improvement Program. As previously indicated, following City, Zone 9/Task Force
acceptance of the Improvement Program, and CEQA documentation,n, it will be submitted to
the Corps of Engineers and other resource and regulatory agencies as a supporting document
accompanying permit applications. .
• FEMA Repair Sites. The Repair Program and the proposed conceptual design solutions for
individual bank instability problem sites are an outgrowth of the findings and
recommendations of the Improvement Program. It consists of more detailed biologic and
hydrologic/hydraulic analysis of each of nine sites proposed to the Federal Emergency
Management Agency(FEMA) by the City in 1995 as needing immediate repair. These are
areas of significant bank instability problems where public improvements are threatened by
on-going bank erosion. All sites were seriously damaged by the 1995 winter floods along
SLO Creek.Detailed hydrologic/hydraulic analysis has been completed for each site to insure
that flow constriction, backwater effects, and downstream translation of energy and velocity
increases are minimized and considered individually and cumulatively in the design analysis,
and that biologic impacts are minimized and mitigated. The.FEMA repair sites (Plate I) are
as follows:.
— D17 -Black Adobe
— D 18 - Gold's Gym
— D19 -WWTP
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96131Phasel/Apri14, 1997
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— D59 -RRM
— D76 - Prado Street Bridge
— D94 - Hayward Lumber
— D99 - Mariposa Street
D96 a and b - Golf Course Bridge
D98 -Pistol Range
Recommendations for stream corridor improvement and management, and specific design
concepts for the nine repair sites will be provided in the forthcoming Design Concept Report.
It is anticipated that as long as the nine FEMA Repair Site projects (and any future projects
in Phase I reaches) adhere to the principles, design concepts, and procedures outlined in the
Improvement Program, including the Maintenance Element, separate'Corps of Engineers
approval on an individual project basis will not be needed. The City will provide the Corps
with a Notification and Description of the proposed projects, and a request for a Letter of
Permission. A Memorandum of Understanding may also be possible with the California
Department of Fish and Game for a 1601 Streambed Alteration Agreement and, under certain
conditions, for expedited review by the Central Coast Regional Water Quality Control Board
for a Section 401 Water Quality Certification.
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Phase I Study Area
Six stream reaches within the SLO Creek watershed comprise the Phase I study area. These reaches
consist of four reaches of SLO Creek and sections of Prefumo and Stenner Creeks. Reach names and
divisions were established by SLO Land Conservancy during their study of the hydrology and
fisheries of the creek (SLO Land Conservancy, 1996).
Reach 8 consists of a 2,000-meter stretch from the Los Osos Valley Road bridge north to the Prado
Road Bridge.Reach 9 extends from the Prado Road Bridge to the Madonna Road Bridge, a distance
of approximately 1,600 meters. Reach 10 is 1,200 meters long, extending from this bridge to the
confluence of Stenner Creek just above Marsh Street Bridge,Reach 14 lies between the Highway 101
bridge,just above Cuesta County Park and the Highway 101 bridge at the base of Cuesta Grade, a
total of approximately 2,700 meters. The Prefumo Reach is 1,000 meters long and lies between
Laguna Lake and the City limits. The Stenner Reach consists of a 700 meters stretch from the
confluence of SLO Creek to the Highway 101 Crossing.
Phase H Study Area
The Phase H study area, which will be addressed in a subsequent report, consists of the following
creek segments:
1. Remaining creeks and portions of creeks not covered in Phase I work within the City limits of the
City of San Luis Obispo; and,
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2. The following creeks in the SLO Creek drainage basin outside of the City limits.
Questa Engineering Corporation 4 96132Phasel/April 4, 1997
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Acacia Creek and tributaries for East Fork'of SLO Creek to Orcutt Road;
East Fork of SLO Creek to State Route 227;
• Prdumo Creek to a point where Prefurno Creek Road deviates from the creek alignment;
• See Canyon Creek from SLO Creek to a.point where Set Canyon Road deviates from the
creek alignment;
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• Stenner Creek from the City hmits'to a point.adjacent to.the City reservoir where the County -
maintained road ends; and,
• SLO Creek from:the Pacific Ocean to a point;where.the.Stage Coach Road above State Route
101 deviates from the creek alignment.
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