HomeMy WebLinkAboutDTS-07-024 - Emergency Repairs, Lower Laurel Creek WatercourseL
Ki REPORT
Development& L
Technical Services
Report To:
Councillor Christina Weylie, Chair of Development and
Technical Services Committee
Date of Meeting:
February 19, 2007
Submitted By:
D. Mansell, Director of Engineering
Prepared By:
G. MacDuff, Manager of Development Engineering
Ward(s) Involved:
Ward 2
Date of Report:
January 29, 2007
Report No.:
DTS 07-024
Subject:
Emergency Repairs, Lower Laurel Creek Watercourse
RECOMMENDATION:
That Council authorize Engineering Services to tender the emergency repairs on the Lower
Laurel Creek watercourse with said tender and total costs to be brought back to Council for
approval.
BACKGROUND:
In 2001, Council approved a Lower Laurel Creek slope stabilization project for a section of the
Laurel Creek watercourse immediately behind the Bridgeport Grand Hotel. This slope
stabilization work addressed significant erosion problems along an outside bend of the main
channel of Laurel Creek, and consisted of the placement of several layers of armourstone, as
well as some additional geotechnical materials on the slope face itself. At the time of these
works, the remaining downstream section, which consisted of gabion baskets (stone filled wire
mesh "baskets") showed no indications of instability, and accordingly, remained in-place.
In December of 2006, Operations staff identified that the remaining section of gabions between
the 2001 works and Carisbrook Drive supporting the easterly embankment of Laurel Creek had
abruptly collapsed, and significant erosion of the remaining embankment was occurring. The
collapse resulted in more than two-thirds of the gabion wall completely sliding into the main
channel of the watercourse, forming a blockage within the main channel itself (see attached).
After preliminary review, Engineering staff determined that immediate repair of the wall failure
would be necessary to avoid further risk to persons/property/bridge, and accordingly under the
provisions of the Purchasing Policy, retained Stantec Consulting Limited to prepare a restoration
plan for the affected area. Engineering staff have also liaised with the Grand River Conservation
Authority (GRCA) and obtained their concurrence that immediate repairs are necessary; failure
to initiate repairs prior to peak spring runoff periods would (potentially) result in further risk to the
public, as well as impacts to the natural watercourse (Grand River).
Furthermore, preliminary review indicates that the westerly gabion wall structure is becoming
unstable, and poses a failure risk as well. As such, we will be addressing the failure of the
easterly embankment and the potential failure of the westerly bank.
It is our intent to continue a similar armourstone wall design on the remaining section of the
watercourse from the limit of the works undertaken in 2001 to the confluence of the watercourse
with the Grand River. The total approximate length of the easterly bank is 35m, with the westerly
bank comprising approximately 35m.
FINANCIAL IMPLICATIONS:
No budget provision currently exists for these works, estimated to cost $700,000. Staff
proposes that the capital out of current portion be funded through an increased allocation from
the Hydro Capital Investment Reserve Fund to the capital pool and that the growth-related
portion be funded through Development Charges as follows:
C/C $630,000
DC $ 70,000
Total $700,000
Note: This is a pre-tender estimate of total project cost. Actual tender amounts may
differ due to the nature and timing of the works.
The projected opening balance for the Hydro Capital Reserve Fund is $2,271,000 in 2007.
$1,570,000 has been notionally allocated to fund the increased costs of the Hanson Avenue
Twin Pad, leaving $701,000 available for other purposes in 2007.
CONCLUSION:
In order to protect persons /property /bridge and the natural environment, immediate emergency
repairs are necessary on the Lower Laurel Creek watercourse. Due to the presence of a warm
water fishery (Grand River), this work must be completed within a very narrow window of
opportunity. As any impact to the watercourse should be minimized, the repair cannot be staged
or deferred. As such, we request that Council authorize the tendering of this work with the final
costs and funding approach to be brought back to Council for approval following the close of the
tender.
D. Mansell, P. Eng. George MacDuff, CET
Director of Engineering Manager of Development Engineering
Affected Area