HomeMy WebLinkAbout01-10-2007TO:
Members of the Sebastian Cil ouncil
FROM:
Al Minner, City Manager
RE:
COLLIER CREEK UPDAj
V
DATE:
Wednesday, January 10,
Enclosed for your review is an update concerning the Collier Creek Canal project. The review
has been prepared by Dave Fisher and provides information on the project permitting process as
well as some changes that have been made in the design scheme.
While the basic scheme remains the same, being rip -rap side slopes, the width, cross section and
construction methods have changed slightly. These changes were a result of answering
questions and concerns from SJRWMD in their initial reviews and comments providing over
summer 2006.
At this time, CDM has resubmitted the plans for further review and we are hopeful that SJRWMD
will finish their staff review shortly enabling a final hearing and permitting from the SJRWMD
Board. Upon receiving the final permit, we are optimistic that project bidding will take place in a
March — June time frame with construction starting in July 2007.
Also for you information, the City was informed that a $500,000 grant may be awarded for use on
this project. As always, if you have questions on this or any other matter, please feel free to
contact me at your earliest convenience.
Status Update: Collier Creek Stormwater Retrofit Project
5 January 2007 / D. Fisher
Following is an update status report regarding the Collier Creek Stormwater Retrofit Project,
multi -million dollar project calling for dredging and slope stabilization of the Collier Canal wet
detention facility.
Nature of the Collier Canal System and Project Objectives
Collier Canal is major part of the City's existing stormwater management system and the
major collector of stormwater runoff from the roads and residential properties located in
the Sebastian Highlands Unit #2 and Unit #4, a total tributary basin of approximately 850
acres (approximately 750 acres of which is residential to both the northeast and to the
southwest of the canal). There is a significant flow control structure (aka The Collier
Creek Dam) at the north end of the canal adjacent to Hardee Park with a controlling
elevation of 15.5 ft NGVD. Flow from the structure northward is through a relatively
narrow, natural riparian system that discharges directly into the South Prong of the St.
Sebastian River which itself discharges into the Indian River Lagoon. Flow from tributary
ditches discharges directly into Collier Canal.
The Collier Canal system is an approximately 6000-ft long, linear -dredged canal that
varies in width from 80 ft to 100 ft. Since its construction in the 1960s, no continual
maintenance dredging program has been performed on the canal. This lack of
maintenance has resulted in severe deposition and erosion problems that have led to a
degradation of both in -canal and discharge water quality. In addition, there is extensive
bulkhead failure occurring along much of the perimeter of the canal. The continuous
erosion and deposition has resulted in an existing condition more characteristic of a
shallow linear detention pond rather than the originally intended deepwater canal system.
The existing canal bottom, not recently dredged or maintained, varies between elevations
10.0 to 13.0 ft feet NGVD. The project calls for dredging the canal to a depth of 8.5 feet
NGVD which will increase the permanent pool volume and result in a reduction of mass
loading of nutrients and suspended solids to the ecosystem of the St. Sebastian River
and the Indian River Lagoon.
Both the St. Sebastan River and the Indian River Lagoon, for their protection and
improvement, are now subject to established regulatory objectives for total maximum
daily loads (TMDLs) and pollutant load reduction goals (PLRGs). Accordingly, the
proposed dredging and slope stabilization in Collier Canal has two main specific
objectives:
1. To provided baseline water quality improvement by removal of approximately 33,000
CY of accumulated sediments which will deepen the canal by an average of
approximately three feet and provide an increase in the all-important system
residence time to 9.5 days from the existing 5.2 days, an increase of more than 80
percent.
2. To stabilize failing seawall and side slope situations thereby preventing additional
erosion of the adjacent land into the canal.
5 Jan 07 / DWF
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Status Update: Collier Creek Stormwater Retrofit Project
5 January 2007 / D. Fisher
Design:
The basic design of the Collier Canal Retrofit Project has evolved since late 2004 / early 2005
through identification and discussion of environmental and regulatory concerns, extensive
public input, and a continuous ongoing evaluation of City and project objectives and financial
parameters. The resulting project design, represented in current permitting application
documents, is characterized by:
Retrofitting existing canal perimeter bulkheads with fabric and stone rip -rap with 3:1 side
slopes and dredging the canal to lower the bottom elevation several feet to increase the
permanent pool storage volume. Side slopes will be clad with rip -rap that go up to but
not beyond the original existing seawalls (instead of to the property lines generally behind
the existing walls in most locations as originally planned). All locations will get rip -rap
treatment but in some locations with badly deteriorated seawall, the bulkheads will be
replaced for structural purposes (perhaps 2-5 locations). The rip -rap will be installed from
the top of slope to elevation 13.5 NGVD, two feet below the normal water surface level.
Where the existing seawall has failed beyond repair, it will be entombed in the canal.
A wading bird habitat at Hardee Park with some existing wading bird habitat remaining on
the south end of the canal near CR-512.
A construction / dredging plan that can be done in phases based on available funding
with the first phase likely being done from CR-512 northward to the Fleming Street
bridge, the second phase being done between the Fleming Street bridge and the Barber /
Lake Street bridge, and the final phase, if called for, northward from the Barber / Lake
Street bridge to the control structure. There is a minimal amount of work to be done at
the control structure on the north end, mainly replacing existing gauges and providing
some control over the level / configuration of the boards in the structure. There will be a
temporary spoil area in Hardee Park during construction for dewatering of the majority of
the dredged material prior to reuse in the project and/or further disposal at approval sites.
5 Jan 07 / DWF
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Status Update: Collier Creek Stormwater Retrofit Project
5 January 2007 / D. Fisher
Permitting:
The initial SJRWMD permit application reflecting all input and design up to that date was
submitted in March 2006. The formal response from SJRWMD in April 2006 requested
further information in nine (9) specific areas:
1. Archaeological / historical resources impact;
2. Definition of surface waters acreage and impact;
3. Amount of proposed dredging and material to be removed;
4. Prevention of erosion and slumping during low water conditions;
5. Construction / dredging plan;
6. Dewatering and turbidity control plan;
7. Sediment analysis;
8. Details of the then proposed plan to use a pipeline for the pumping of sediments to a
SJRWMD containment area;
9. Impacts to fish, wildlife, and wading bird habitat.
After further extended discussion and review, public input, evaluation of changed conditions,
and further assessment and articulation of City objectives, the response to that SJRWMD
request for additional information was filed on 14 December 2006. It reflects the following.
1. Awaiting comments from State Division of Historical Resources.
2. Based on the SJRWMD definition that surface waters are defined from top of bank to
top of bank, there are approximately 13.6 acres of dredging and/or fill impacts to
surface waters. Wading bird habitat issues have been revisited and surveyed further;
impact now estimated to be 0.65 acres and to be mainly accommodated at Hardee
Park location.
3. The existing canal varies in depth but it will be dredged to a depth of approximately
8.5 feet NGVD, about five feet below normal surface water elevation.
4. A new slope stability analysis pertaining to revised plans recommends not lowering
the water level of the canal more than 1-2 feet in a gradual drawdown when
constructing new slopes and associated work. Groundwater levels behind the
slope(s) will need to be monitored and restrictions will be required regarding how far
the canal water level can be lowered.
5. Construction means and methods are to be determined by the contractor subject to
prior engineering approval. Note, however, the type of drawdown restrictions in item
(4) directly above and that dredged material will be brought to Hardee Park for
separation and dewatering prior to any reuse in the project and/or further disposal at
approved sites. Hardee Park will be designed and permitted as a temporary
containment area.
6. A detailed dewatering and turbidity control plan will provide guidelines, procedures,
and methods for contractor to follow for protection of sensitive downstream systems
and prevention of state water quality violations. See item (5) directly above.
7. A sediment analysis in included in an attached geotechnical report which indicates
the samples did not contain contaminant compounds above lab method detection
limits with the exception of total barium, total chromium, total lead, and total
petroleum hydrocarbons none of which exceed residential or leachability -based Soil
Cleanup Target Levels.
8. City no longer proposes pumping material through a pipeline to a dredge material
containment area owned by SJRWMD. Schedule, cost, and further permitting
requirements preclude going any further with this previously proposed option.
9. As noted above, SJRWMD recommends City utilize Hardee Park to create 0.65 acre
of new wading bird habitat in a newly vegetated littoral wetlands zone there. Also,
there is an additional 0.46 acre of existing wading bird habitat that will be preserved
and enhanced.
5 Jan 07 / DWF
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Status Update: Collier Creek Stormwater Retrofit Project
5 January 2007 / D. Fisher
Construction
Based on permitting approval (currently expected by end March 2007), we currently
anticipate soliciting construction bids in the March — June time period with contract award
and construction beginning by July 2007. Depending on how many phases to be
undertaken in the first contract (itself likely determined by construction bid pricing and
funding available), the entire project schedule (all phases) is currently expected to be in
the range of 18 months.
Financial
The current budget amount allocated to the Collier Creek Stormwater Retrofit Project is
approximately $3.5 million. The original amount allocated was approximately $1.44
million but was increased to take into account the lack of any homeowner assessment for
the project as was originally anticipated at the time of overall program bond funding.
The Collier Creek Stormwater Retrofit Project is the single largest project in the city's
Stormwater Capital Improvement Program and other projects and grant opportunities
have been evaluated and amended to reflect the needs and the large weighted value of
the Collier Creek project within the overall program. Some major factors in this approach
are:
City revisiting and deciding to cancel long-term plans for an additional curb -and -
gutter program in the Sebastian Highlands basin served by the Collier Creek
Canal. This decision enabled design revisions to the Collier Creek Canal project
that result in a less expensive and less intrusive project while also reducing the
amount of stormwater enhancement "credits" originally called for by a future
curb -and -gutter program.
• City deciding to not go forward at this time with any plan for City sanitary sewer
and/or potable water system. This decision avoided additional project expense
that may have been needed to address such concerns.
• Cutting back on the extent and depth of the improvements to the Collier Canal to
reduce costs as well as to address come citizen concerns regarding possibly
more intrusive design / construction measures.
• Requesting the transfer of a recent prospective $500,000 grant to the Collier
Creek Project from the Twin Ditches project to enable City to take full benefit of
the grant.
• Working with SJRWMD to minimize the cost of any "mitigation" required by the
project. We expect to know the level of that prospective mitigation cost soon and
also expect it to be significantly lower than the current conservative budget
estimate for same.
• Temporarily holding back the start of some of the other stormwater capital
improvement projects until more is known about the actual financial needs of the
Collier Creek project.
5 Jan 07 / DWF
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