HomeMy WebLinkAboutTask Order No. 10004A with T-O Engineers for Silverstone Letter of Map Revision, Phase 2 Eight Mile Creek~~iQ/~E IDIAN~-
Public IDAHO
Works Department
TO: Mayor Tammy de Weerd
1vEembcrs of the City Council
FROM: Kyle Radek, PE, CFM
Assistant City Engineer
DATE: 9/24/2009
Mdyar Tammy de Weerd
eiey Council Mambar~e
Keith Bird
Brad Hoaglun
Charles Rountree
David Zaremba
~~~~ .
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SUBJECT: Taste Order 1(}004a fnr Silverstone Letter of Map Revsic~n, Phase 2 nn
Ei~htntile Creek
RECO><4MENllED ACTION
A. Move to:
l.. Approve Task Order 10004a with TO Engineers for Silverstone Letter of Map
Revision, Phase 2 for a not-to-exceed cost of $46,359.
2. Aut.hori7e the Mayor to sign the agrcerncrit.
II.DEPARTIVIENT CONTACT PERSONS
Torn Barry, Director of Public Works 489-037?
Warren Stewart, PW E.ngineering Manager 489-0350
Kyle Radek, Asst. City Ergineer 489-0343
III. DESCRIPTION
A. Background
Between 5 and 9 years ago, development occurred in the Silverstone and Silverstone Campus
Subdivisions which affected the lloodplain o1'Eightmile Creek. A subsequent study to determine
new Base Flood Elevations (BFIa} for development revealed that the previous development
caused Banc Flood llevations to rise more than what is allowed by the National Flood Insurance
Program (hiFIP). FEMA, who regulates this program has directed the City to provide updated
mapping through a Letter oi'Niap Revision (LOMB).
Page 1 of 3 p +
B. Yroposcd I'ro•cct
This project will complete the engineering work required to complete and suhmit the I.,OMK to
PLMA. This work includes aerial mapping, hydraulic analysis, building the submittal, and
coordination with FEMA. Upon completion, this project will provide correct floodplain
mapping far the area and keep us in good standing in the 1~'FIP.
C. Consultant Selection
"f'he consultant selected for this project was the same consultant used for the first phase of this
L,OMR submittal. This consultant was chosen for phase 1 because they had been involved in the
development of the BEFs that originally identified the problem.
1V. IMYAC"I'
A. Strategic Impact:
This activity aligns with our department's vision of conserving and protecting our natural
resources and property through sound floodplain management.
B. Service/Delivery Impact:
"This prvject will satisfy the City's duty to manage floodplain development according to NFIP
ntles and allow it to remain in good standing in the program which will guarantee the availability
of flood insurance to residents.
C_. Fiscallmpact:
Project Costs
Consultant Agreement
Total
Time and Materials Not-to-cYCeed $46,159
Time and Materials Not-to-exceed $46,359
Project Funding
Project will be funded comprehc;nsive surface water program.
V. AL`l'1/RNA'I'1VES
A. `1'he City could choose not to submit a LOMB. This would likely result in FEMA
putting the City on probation in the NF1P. Policy holders would pay an additional
charge o.f $SU on their insurance premium.
B. The City could attempt to get the developers who trade the changes to the
floodptain to pay for the study and submit the changes. With the circumstances of
the problem development and our current code, it is unlikely that the City would
make much progress in this effort.
Prrb e 2 of .)
VL. T'1NIE CONSTRAINTS
'I'bis problem was identified and shared with FCMA in 20G8. We have been making progress on
the rnap revision since then, but if we are not dilibent in our efforts, FBMA could put the City on
probation. Cornplction of this work in the next 4 months should satisfy [')/MA.
VTT. LIST OF ATTACHI<TF,NTS
A. Consultant Agreement
Approved for Counci I Agenda:
Tom Barry, Director of Public Works
llatc
Pogo 3 of 3
Task Order No. 10(104-A
Scope of Work
Completion of Letter of Map Revision (LOMB) Subnritial
rlood Study of 1?ight Mile Creek
Silverstone and Silverstone Campus Subdivision Areas
Client: City of Meridian
Consuhant: T-O Engineers, Inc.
September 23, 2009
Pu nsc
-'~-----
T-0 Engineers completed a flood study un Eight Mile Creek in a cooperative effort between the
Kevin Spencer Company and the C{ty of Meridian in June 2008, referred to herein as the `'2008
study". '['he 2008 study dernonstratcs higher 100-year base flood elevations compared to the
existing FI~.1VIA maps. The higher flood elevations result from improvements to Overland Road,
tiling of Eight Mile Creek south of Overland Road, and installation of culverts at South Jade Way
and South Topaz Way. The City intends to submit the 2008 study, with modifications as necessary,
as a Letter of Map Revision (I ,OMB) to FF;MA for approval and implementation of the modified
base flood elevations into the effective F1:MA maps and H'lood Insurance Study.
The preceding Task Order No. 10004 is complete with the major work efforts being: development
of a duplicate effective HEC-BAS mode] from the existing I [EC-2 hardcopy model data, extension
of the 2008 study upstream, collection of additional survey data to better define the extents of
Hooding, and creation ofa hydraulic model of the S00-year event.
Additional complexities arose that were not foreseen in development of the scope of work I'or
Task Order No. 10004. "tire issues include: additional upstream extension of the study to
accomplish tic-in, differences in computational methods betwcc;n HEC'-2 and HF,C-R1S at
Overland Road, development of a revised profile baseline to limit revisions to the F1S profile
coordinates, discovery of the potential for the updated flood elevations to produce extended
flooding in the southwest corner of the Silverstone area and further west across Eagle Road.
1'he purpose of this scope of work for "l'ask Order No. 10004-A is to finish the LOMB application
and submit to }~'IiMA. T`lie submittal will address the issues encountered during [,ask Order No.
10004 and incorporate solutions into the LOMB submittal.
Scope cif Work
1) Aerial Mapping
Obtain aerial mapping to define extent of flooding to the south and west of the original flood study
area. FF,MA requires topographic work maps and it is mire cast effective to complete aerial
mapping compared to additional survey between previously completed model cross sections along
with manual reconstruction of planimetric features (roads, buildings, sidewalks, hcrrrrs, etc.) tiY~rn
raw survey data. Mapping effort includes setting control and aerial tarfets by survey, analysis of
aerials, creation of digital surface, creation of contour map, and integration. into project database
fhis scope includes mapping west toward the Ninemi le Creek drainage divide in view of the
likelihood of Hooding west across Eagle Road.
2) Analysis
Rcvicw aerial mapping between surveyed cross sections For supplementary flow paths around
culverts, especially Jade Way, and refine model accordingly. Review aerial mapping for extent
and elevation of high ground in the Siiverstonc area and Hooding to the south and west at
Golds#one Way and Eagle Road. Complete mapping of floodplain lirttits.
2} FEMA strbmittal forms.
Update 2008 report narrative and graphics. Discuss issues and solutions arising tFom Task Order
No. 10004 in narrative. Produce modified FEMA maps and water surface profiles in Flood
Insurance Study, Develop FEMA LOMR Forms, assemble F>/MA required digital submittals,
compile submittal package.
3} Submittal Coordination
Review LOMk submittal with City. Provide City with digital version of LOMR submittal
including H1~X'-RAS model and mapping of floodplain (as submitted to FF.1V1A) conformed to Ada
County coordinates for City to include in GIS database. Submit LOMB application to Ada County
for review and community acknowledgement. Submit to I~ EMA. Review 1~ F,MA approved LO~VIR
lbr accuracy.
~) Potential Coordination tiv~ith FEMA to Approve L01~1R
The LOMB submittal will be developed with quality control to comply with generally known
F1rMA requirements. however, it is typical for FF,MA to request additional data or analysis of
specific details during the LOMB approval process. Specific requests posed by FEMA cannot be
anticipated at this stage ot'scopiug. Therefore, a budget amount of $5,000.00 is established for this
potential work item based on two days oI'analysis and coordination with PEMA, and t<vo days of
revisior>,ire-submittal oFrelevant portions of the modes and mapping.
Fee
The fee for completing scope iterrn #1 through #5 is anot-to-exceed amount ol'$4G,359.00. The
Fee is based on what is known and reasonably foreseeable but no guarantee is expressed that the
scope is all inclusive and that no other items/tasks he required tTrroughout the process. No
payments will be made for work above the agreed amount without written authorization.
A preliminary budget estimate of $40K for the LOMR work was provided to the City in ,lanuary
2009. Task Order No. 10004 was authorized for S20K with an anticipated additional $20K to
complete engineering efforts for the I,OMR. "Task Order 1~Io. 10004-A ltas an estimated Fee of
$4GK and is comprised of $20K for mapping and related survey cl'forts not anticipated in the
January 2009 estimate and $2Gk Ior the remaining engineering to address the additional items and
complete the T,OMR subrttittal.
Assumptions and Exclusions
T'he following assumptions arc incorporated from Task Order No. I0004 and updated herein.
Additional services may be required if the assumptions do not remain valid in the process of
completing the work. Additional or excluded services may be added by amendment of the
agreement.
() It is assumed FEMA will accept termination of the LOMB at the north edge of Overland Road
with a known differential in flood elevations north (downstream) of Overland Road. Flood
elevations higher than FEMA regulatory values were revealed in a separate site-specific study for
lands north of Overland Road previously completed by Consultant. The submittal ro FEMA will
characterize the relative insensitivity of the flood. elevations at Overland Road (and upstream) to
the flood c;lcvations downstream of Overland E~oad as a proposed basis for FEMA approval. The
City reviewed this finding and proposed submittal approach to retain FEMA values north of
Overland tZoad for purposes ol~mapping continuity with FIrMA Region X staff on December 19,
2008. At that time, FEMA did not object to the approach.
2) It is assumed the City will not enter into a joint LOMB submittal with landowners north of
Overland Road to extend the flood study downstream.
3) It is assumed that the flood study of conceptual improvements to I-84 and Eagle Road completed
by Connecting Idaho Partners {CIY) is not submitted to FrMA by CIY, the City of Meridian or as a
joint submittal with this proposed scope of work.
4) It is assumed submittal fees, if required by FNMA, would be paid directly by the City to FEMA
5) ]t is assumed that nn new fill or development will occur within the limits of the; flood study after
beginning work on the mapping, the submittal and during the FEMA approval process. Any such
till may require revision ofthc study.
6) Ada County will not require revision of the flood study as a condition o}'the County signing the
Community Ack»owledgement fomt.
7) "Fhe City will obtain permission to strrvcy on private property
8) P>r1v1A has established regulatory Flows for 8-Mile and 5-Mile Creeks and those (low were
used in the 2008 study. It is assumed that FEMA will not require a hydrologic study Co modify the
flows.
9j 7'he Narnpa and Meridian Irrigation District does not have review or approval authority over the
LOMR submittal. and neither the City or County will request comment from the District.
10} No floodway will be delineated nn Eight Mile Creek. 'l'he cut•rent FEMA maps do not
designate a floodway on tight lVtile Creek and the 2flOR study area has been platted as a
subdivision. Property within the contcntplated extension of the 2008 study will be subject to City
or County requirements for proposed development to demonstrate limitations of base flood
elevation surcharges to less than one toot.
I I) The City will lead coordination efforts with FEMA including confirmation of receipt of
submittal, estahlish a FEMA case nwnber and contact person, inquiries as to status of FEMA
review and approval.
12) City will develop landowner location, contact summary and FEMA required flood elevation
notification letters for properties atFected by 2008 study.
CITY OF MERIDIAN
BY: .~~~r7rr l,~c-~-~-K.1.e.~~
TAMMY~d WEERD, MAYOR
Dated: 10 - i,_- ~9 ~~,~~
T-O Engineers, Inc.
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BY: Steven E. Holt, 8`t3cretary
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Attest:
SEAL
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JAY E L. HOLMAN, CITY CL~ ,q T ts't • Q,2'\,:
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~''%„ COUNTY • \\~.~.
Approved as to Content
BY:
KEITH TTS,~ URC ASING AGENT
Dated: ~~ ~ ~ ~~
Approved as to Form
CITY ATTORNEY
Department Approval
BY:
NAME:
TITLE:
Dated:
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