HomeMy WebLinkAbout05/04/1999, C10 - ANDREWS/CONEJO STORM DRAINAGE IMPROVEMENTS. SPECIFICATION NO. 99704B council
AD agenda Report N.6�
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CITY OF SAN LUIS OBISPO
FROM: Michael D.McCluskey,Public Works Direc 6r
Prepared by: Jeff van den Eikhof,Engineering Assistant VV
SUBJECT: Andrews/Conejo Storm Drainage Improvements.
SpecificationNo.99704B
CAO RECOMMENDATION:
1. Approve plans and specifications for"Andrews/Conejo Storm Drainage Improvements."
2. Authorize staffto advertise for bids for"Andrews/Conejo Storm Drainage Improvements."
3. Authorize CAO to award contract if lowest responsible bid is within budget
4. Appropriate $77,200 from the unappropriated balance of the General Fund to the project
account.
DISCUSSION:
In March of 1995,storms hit San Luis Obispo causing severe damage to several areas around town.
One area hit particularly hard were several homes on Conejo Drive. A rock catcher located in a
stream bed directly above the homes was overwhelmed by rock and debris carried by the runoff.
Once the rock catcher was plugged,the water began to flow around the structure and through the
properties below. Significant damage occurred to the homes located at 1717 and 1739 Conejo
Drive.
Litigation ensued,and on July 13, 1998 the City of San Luis Obispo settled with the owners of the
above properties for the amount of$100,000. In the settlement,the City also agreed to include
within the 1998/1999 City of San Luis Obispo Public Works Budget an amount designated to
construct a drainage system which would reduce the probability of future flooding problems.
The Council directed staff to prepare a preliminary engineer's estimate for construction of the
project. The engineer's estimate was$250,000,plus$30,000 for modifications to the existing rock
catcher. Then,Council directed Staff to begin design of the stone drainage system.
Calculations done by Staff in 1982 showed that the existing drainage system was not up to current
design standards. The newly designed system will divert the excess runoff before it reaches the
existing system. The combination of the existing and the new systems will more than triple the
drainage capacity of this area,and exceed the current design storm requirements.
As designed,the drainage system consists of two inlet structures located directly above the existing
rock catcher. The inlets will be located out of the direct debris flow. When the rock catcher begins
to backup,water will flow into the inlets. The water will then be piped down a drainage easement .
on 1451 Andrews to Andrews Street. Then down Andrews Street to an outlet structure located on
the northeast side of the Andrews Footbridge at San Luis Obispo Creek.
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Council Agenda Report—Andrews/Conejo Storm Drainage Project: Spec.#99704B
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During the design phase, engineering calculations showed that the required pipe size exceeded
original estimates. Other design problems included underground utility conflicts and exiting above
the creek level. These constraints necessitated the use of two 900mm(36in)pipes running parallel,
instead a of single larger pipe.
Due to the nature of the project, a Biological Assessment and a Cultural Resource Investigation
were required for the Initial Study and Agency permits.
The Cultural Resource Investigation identified the house located at 1451 Andrews Street as the
Andrews Adobe. Historical records indicate that in 1800 the adobe structure was built by mission
Indians for use by the Mayordomo of the Mission. The entire project area falls within the original
holdings of Mission San Luis Obispo. Asa result of these findings,it has been recommended that a
Registered Professional Archaeologist monitor all trenching and excavation activities within the
project area
The Biological Assessment identified the stream bed at 1451 Andrews as emergent wetlands. The
project area at San Luis Creek was identified as a migratory path for steelhead trout. Marginal
habitat for the California red-legged frog was identified approximately 50 meters downstream from
the project site in San Luis Creek. No frogs were found during the biological assessment. As part
of the mitigation measures, a formal consultation has been initiated with the National Marine
Fisheries,and an approved environmental monitor must be retained to monitor all stream and creek
construction activities.
CONCURRENCES:
The Community Development Department has granted a Mitigated Negative Declaration. Permits
are in the process of being issued by regulatory agencies.
Staff will not send the project out to bid until all of the permits have been received.
FISCAL IMPACT
This project was budgeted for in the 1997-99 Financial Plan,Appendix B, page 113,as part of a
settlement agreement due to the Carl Hysen, et al, v. City of San Luis Obispo ruling. The
original budgeted amount was$250,000,plus$30,000 for modifications to the existing rock
catcher. During the Summer of 1998,the existing rock catcher was modified at a cost of
$10,000.
Andrews Street was originally scheduled for resurfacing during the Fall 1998 resurfacing
program. It was postponed until completion of this project. Andrews Street will be resurfaced in
conjunction with this project. Funding for resurfacing will come from the Pavement
Maintenance Budget
Due to unforeseen environmental issues and pipe sizing issues, the estimated construction costs
exceeded the originally budgeted amount by $77,200, which will require a supplemental
appropriation from the General Fund Reserves in an equal amount
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Council Agenda Report—Andrews/Conejo Storm Drainage Project: Spec. #99704B
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The bulk of the increased costs are related to the pipe itself. Significant utility crossings
combined with the need to keep the pipe high as it enters the creek, resulted in a shift from a
single pipe, original budget concept, to two parallel pipes. This increases material costs as well
as the width of the trench and associated costs. A smaller increase in the project cost is due to
requirements in the environmental review for archeological and biological construction
monitoring.
Estimated Construction Cost
Engineer's Estimate $350,600
Contingencies(10%) _ $35,000
Subtotal $385,600
Archaeological Monitor $4,000
Environmental Monitor $2,000
Total Construction Estimate39$ 1,600
Amount Funded by Pavement Maintenance Budget
$44,400
Balance of Construction Funds Available $270,000
Amount of Funds Deficient ($77,200)
ATTAC)E M ENTS:
Vicinity Map
Project Specifications and Drawings are available in the Council Office for review
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