HomeMy WebLinkAbout07-10-2018 Item 11 - Silt Removal 2018 Meeting Date: 7/10/2018
FROM: Daryl Grigsby, Director of Public Works
Prepared By: Violeta Esparza-Reniere, Engineer III
SUBJECT: SILT REMOVAL 2018
RECOMMENDATIONS
1. Approve Plans and Specifications Silt Removal 2018, Specification No. 91523; and
2. Authorize staff to advertise for bids; and
3. Authorize the City Manager to award the construction contract of up to $120,000 to the lowest
responsible bidder.
DISCUSSION
Background
The City’s creeks contain locations where sediment collects over time and requires removal to
facilitate storm flow. Without proper and routine maintenance, channel flow capacities decrease,
and the surrounding properties become more susceptible to flooding. This project consists of the
removal of accumulated sediment from Prefumo Creek between Los Osos Valley Road and
Laguna Lake.
Project Site: Prefumo Creek, in between Los Osos Valley Road and Laguna Lake
Prefumo Creek between Los Osos Valley Road and Laguna Lake experiences sediment deposits
because the creek slope flattens and water velocity decreases. If addressed early enough,
sediment can be removed from the creek prior to migration into Laguna Lake. Therefore, the
accumulated sediment needs to be removed periodically to maintain creek capacity and prevent
the sediment from migrating into Laguna Lake.
Roughly six feet of sediment, or approximately 1,320 cubic yards, was deposited since the last
silt removal project completed in 2015. This sediment , as well as exotic invasive vegetation, will
be removed by this project . Areas along the creek that are disturbed during construction will be
revegetated to reduce erosion and protect the creek banks. All existing trees will be protected.
This project will restore Prefumo Creek’s flow capacity and reduce the likelihood of sediment
transfer into Laguna Lake.
Regulatory Permitting
Due to the location of this project within the creek system, work must be scheduled for late
summer or early fall – the time of year when the water in the creeks is lowest, and when work
can be performed with reduced likelihood of imp acts to adjacent wildlife. As such, scheduling
these projects around this limited construction timeline requires advanced planning, design, and
regulatory permitting work.
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The project requires regulatory permits from the California Department of Fish and Wildlife, the
California Regional Water Quality Control Board, and the U.S. Army Corps of Engineers. As of
June 18, 2018, t he California Department of Fish and Wild life permit is still pending but permits
from all of the other listed agencies have been r eceived. Based upon recent correspondence with
the City’s environmental consultant, indications are that the remaining permit will be received in
time for the scheduled construction start in September 2018.
Construction Timing
By authorizing this project for advertisement and allowing the City Manager the authority to
award a contract up to $120,000, the City may be able to complete this work before the end of
2018. The recommended action will allow the project to be advertised now so that a construction
contract may be awarded w ithin the construction window limited by the regulatory permits.
Delegating the City Manager authority to award a contract up to $120,000, greater than the
Engineer’s Estimate of $82,350, will ensure that if bids are returned higher than the estimate that
the project can move forward without delay. If the City is ultimately not successful in obtaining
a California Department of Fish and Wildlife permit to allow for construction work to be
completed this year, all bids will be rejected, and the project will be rebid next year.
ENVIRONMENTAL REVIEW
The City’s Community Development Department has issued an Addendum to Initial Studies /
Mitigated Negative Declaration ER#1-11 for this project. All required mitigation measures
identified in this environmental document have been incorporated into the project specifications.
FISCAL IMPACT
The 2017-19 Financial Plan, pages E2-18 and E2-19, identifies the silt removal project with a
construction budget of $102,000 in 2017-18 and $100,000 in 2018-19 to support this and other
silt removal projects. With the 2018-19 allocation, a total of $311,000 will be available in the Silt
Removal Master Account . The funding source for this work is provided by the San Luis Obispo
County Flood Control and Water Conservation District Zone 9, which will reimburse the City for
actual costs incurred up to $311,000, though this silt removal project is not projected to exceed
$120,000
Due to the short construction window, the strategy is to allow the City Mana ger to award the
contract to the lowest responsible bid up to the amount of $120,000. The total project estimate
including contingency cost is $96,100; this request to award up to $120,000 allows for flexibility
to accommodate bids that may come in over the engineer’s estimate and still construct during the
tight construction window.
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Total Project Estimate: $82,350
Contingencies:$8,250
Monitoring $5,000
Printing and Misc:$500
Total Project Estimate $96,100
Silt Removal Budget $311,000
Remaining Balance after Project:$214,900
Silt Removal 2018, Specification #91523
ALTERNATIVE
Deny authorization to advertise and award. The City Council may choose not to authorize
project advertisement. This is not recommended since postponing this project until a later date
decrease the capacity of the creek, increase sediment migration into Laguna Lake, and increases
the risk of flooding in neighboring residential area.
Attachments:
a - Council Reading File - 91523 Silt Removal 2018 Plans
b - Council Reading File - 91523 Silt Removal 2018 Specifications
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