HomeMy WebLinkAbout05-15-2012 c3 silt removal various locationscounci l
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C I T Y O F S A N L U I S O B I S P O
FROM :
Jay D . Walter, Director of Public Work s
Prepared By :Dan Van Beveren, Senior Civil Enginee r
SUBJECT : SILT REMOVAL — VARIOUS LOCATIONS, SPECIFICATION NO . 91065
RECOMMENDATION
1.Approve plans and specifications for Silt Removal —Various Locations, Specification No . 91065 .
2.Authorize staff to advertise for bids .
3.Authorize the City Manager to award the contract if the lowest responsible bid is within th e
Engineer's Estimate of $250,000 .
4.Approve the transfer of $285,000 from the Master Silt Removal account to the project account .
DISCUSSIO N
Backgroun d
The City's creeks contain locations where sediment collects over time and requires removal t o
facilitate storm flow . This project consists of the removal of accumulated sediment from th e
following five locations : 1) San Luis Obispo Creek at the Marsh Street Bridge, 2) Prefumo Creek a t
Los Osos Valley Road, 3) Prefumo Creek at Madonna Road, 4) San Luis Obispo Creek at the Wate r
Reclamation Facility, and 5) San Luis Obispo Creek at the confluence of Prefumo Creek . Sedimen t
has accumulated in these five locations over the past several years and needs to be removed in orde r
to restore drainage capacity . A detailed description of each of these locations follows .
Site #1 : San Luis Obispo Creek at the Marsh Street Bridge
The portion of San Luis Obispo Creek beneath the Marsh Street Bridge is a location where the cree k
makes a gradual sweeping curve . During periods of heavy flow, sedimentation accumulates alon g
the inside of this curve . As a result, several feet of material has been deposited along the wester n
portion of the creek beneath the bridge . Sediment has been removed from this location every fe w
years in order to maintain the capacity of the creek channel at this critical location, which flood s
during significant storm events . This sediment removal work was last done in 2007 .
Site #2 : Prefumo Creek at Los Osos Valley Roa d
The portion of Prefumo Creek between Los Osos Valley Road and Laguna Lake is a location wher e
the creek slope flattens and sediment accumulates as the water in the creek slows down prior t o
entering Laguna Lake . Sedimentation has been removed from this location every few years in orde r
to maintain the capacity of the creek channel and to help prevent the accumulated sediment fro m
migrating into the lake . This sediment removal work was last done in 2006 .
Site #3 : Prefumo Creek at Madonna Roa d
Immediately downstream from Laguna Lake, Prefumo Creek crosses under Madonna Road and
continues in a southerly direction . Over the years, silt has accumulated within the main channel o f
the creek and the presence of this silt now causes standing water to remain for several weeks afte r
Meeting Dat e
May 15, 2012
Item Number
C3
C3-1
Silt Removal - Various Locations (91065)Page 2
each rain event . The removal of sediment from this location will minimize the problem of standin g
water. There are no records of silt removal work previously being done at this location .
Site #4 : San Luis Obispo Creek at the Water Reclamation Facilit y
Adjacent to the Water Reclamation Facility, San Luis Obispo Creek contains a secondary bypas s
channel which is parallel to the main creek channel . This bypass channel is above the main channe l
and is only utilized following heavy storms, when the water level in the creek rises . During thes e
heavy flows, sediment is deposited along the bypass channel . Every few years, the bypass channe l
needs to be cleared of sediment in order to restore its flood carrying capacity . Sediment was las t
removed from this location in 2004 .
Site #5 : San Luis Obispo Creek at the Prefumo Creek Confluenc e
At the location where San Luis Obispo Creek joins Prefumo Creek ; north of Los Osos Valley Road ,
another bypass channel carries storm water during heavy storms, and like the other locations, tend s
to collect sediment over time . Sediment was last removed from this location in 2007 .
Regulatory Permittin g
Due to the locations of these projects within the creek system, work must be scheduled for the late
summer or early fall - the time of year when the water in the creeks is lowest, and when work ca n
be performed without impacting the flowing water within the creeks . As such, scheduling thes e
projects around this limited construction timeline requires advance planning in both the design an d
regulatory permitting work .
All five of these project locations require regulatory permits from the California Department of Fis h
and Game, the California Regional Water Quality Control Board, and the U .S Army Corps of
Engineers . As of April 20, 2012, the necessary permits from the Army Corps of Engineers are still
pending, but permits from all of the other agencies have been received . Based on recent discussion s
with staff from the Army Corps of Engineers, indications are that the City will receive the necessar y
Army Corps Engineers permits in time for the scheduled construction start in September 2012 . The
recommended action will allow the project to be advertised now so that construction may begin i n
September . In the event that the Army Corps of Engineers permits are not received within thi s
timeline, the project will have to be postponed until 2013 .
CONCURRENCE S
The City's Community Development Department issued a Mitigated Negative Declaration for thi s
project in July 2011 . All mitigation measures identified in this environmental document have bee n
incorporated into the project specifications prior to advertisement .
FISCAL IMPACT
The 2011-13 Financial Plan, Appendix B, page 3-185, identifies $250,000 of construction funding
in 2011-12, and an additional $280,000 in 2012-13 . The source of these budgeted funds is the San
Luis Obispo County Flood Control and Water Conservation District Zone 9 program which oversee s
and provides funding for flood control improvements located within the San Luis Obispo Cree k
watershed . All construction expenses associated with this project will be reimbursed by the County as
part of its Zone 9 flood control program.
C3-2
Silt Removal –Various Locations (91065)Page 3
The project budget is detailed in the following table .
Construction :
$250,00 0
Construction Contingencies :
$25,00 0
Total for Construction :
$275,00 0
Misc . Construction Costs (Printing, Materials Testing, Etc .)
$10,00 0
Staff recommends transferring $285,000 from the Master Silt Removal account in support of thi s
project . Currently, there is $299,488 available in the master account . There is sufficient funding to
support this request. Additional funding of $280,000 has been allocated in the 2012-13 fiscal yea r
and will become available July 1, 2012 .This funding will be used for other identified locations of silt
removal .
Fiscal Impact Summary
Balance in Construction Phase as of 4120112 Proposed Chang e
2012 Silt Removal - Various Locations (91065)-285,000 285,00 0
Master Silt Removal Account (90581)299,488 14,488 (285,000)
Total 299,488 299,488 -
ATTACHMEN T
Map of Five Silt Removal Location s
AVAILABLE FOR REVIEW IN THE COUNCIL OFFIC E
Plans and Special Provisions for Silt Removal – Various Locations, Specification No . 9106 5
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