HomeMy WebLinkAboutEarth Tech # 84350 Amendment 4/29/2008EarthTech
A tgCO International Ltd. Company
September 28, 2007
Mr. David Patek
Department of Public Works
215 Church Ave
P.O. Box 1130
Oshkosh; WI 54903 -1130
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APR 2 9 2008
CITY CLERK'S:: ;=
1210 Fourier Drive P 608.836.9800
Suite 100 F 608.836.9767
Madison, WI 53717 www.earthtech.com
3 2007
PUBU
SH. w!:
Subject: Amendment Request to Stormwater Management Planning Contract
Earth Tech Project No. 84350
Dear Mr. Patek:
This letter is requesting an amendment to the scope and budget for the above referenced
project. The scope items detailed below have been reviewed by city staff and conducted under
their direction. The scope changes were necessary to comply with WDNR guidance for
compliance with NR 216 issued over the past year, and to update the analysis with data
provided by the city.
Below is a description of tasks and costs that have been, or are being conducted by Earth Tech
in conjunction with to the above referenced project. These tasks are being conducted at the
request of the city and are additional scope items to the original project contract:
Description of Additional Project Tasks
1. Change in Street Cleaning Routes / Schedules / Equipment
In September 2005 the city provided Earth Tech data on the city's street cleaning routes,
schedule, and equipment. Earth Tech created WinSLAMM files to reflect these conditions and
ran the WinSLAMM analysis to determine the TSS reduction from the initially provided street
cleaning schedule and equipment. In August 2007 the city provided Earth Tech updated
information on the street cleaning schedules and equipment and requested that the "existing
management" WinSLAMM files be revised to reflect these new conditions. Earth Tech has made
these revisions.
2. Additional Analyses for Catch Basins
Storm sewer catch basin (with sumps) information was provided to Earth Tech from the city in
September 2005. This data included the location and dimensions of all the existing catch basins
with sumps in the city. In August 2007 the city requested Earth Tech to add data to account for
existing catch basins with sumps that were installed in 2005, 2006, and 2007. The city provided
data for these years and Earth Tech added the information to the existing analysis to account for
the additional pollution control. This step required the recreation of new WinSLAMM land use
files to reflect the additional areas treated with the additional catch basins with sumps. Earth
Tech also re -ran the WinSLAMM analysis to account for the additional catch basins.
EarthTech
A fYICO International Ltd. Company
Mr. David Patek
Stormwater Plan Change Order Request
September 28, 2007
Page 2
3. Analysis of Existing Structural BMPs (wet ponds)
In September 2005 the city provided Earth Tech a spreadsheet describing each existing
stormwater pond and the data necessary to analyze the pollution control effectiveness of each
pond. This analysis was conducted by Earth Tech. In July and August of 2007 the city requested
that the methods of existing pond analysis be revised to add a graphic showing the boundary of
each pond's drainage area. Also four pond locations were added to the analysis. Earth Tech
re= evaluated the ponds with the revised approach, and re -ran the WinSLAMM analysis to
account for the additional existing pond data.
4. Re- Analysis of Base Area with WinSLAMM
In September 2005 the city provided Earth Tech GIS data sufficient to determine the areas of the
city that would be subject to the NR 151.12 regulations for new development and those
developing areas that are not subject to NR 151.12. These two classifications define geographic
areas of the city that must be included or excluded from the base level WinSLAMM. In
September 2007 additional areas of the city were discovered that were not subject to NR 151.12
and should have been included in the base level WinSLAMM analysis conducted in 2005. This
change will likely benefit the city in meeting its 20% and 40% TSS control requirements. Earth
Tech will incorporate the additional developing areas of the city not subject to NR 151.12 into the
WinSLAMM modeling and revise the current TSS loading tables to reflect these changes.
Change Order Request Costs
Task
Cost
Hrs
1. Change in Street Sweeping Routes / Schedules / Equipment
$ 2,900
34
2. Additional Analyses for Catch Basins
$ 2,500
30
3. Analysis of Existing Structural BMPs (wet ponds)
$ 2,750
31
4. Re- Analysis of Base Area with WinSLAMM
$ 1,750
22
$ 9,900
117
Thank you for you consideration of this request and please do not hesitate to contact me with
any questions at 608- 828 -8121.
Sincerely,
c
Earth Tech, Inc.
J mes A. Bachhuber
ater Resources Department Manager
cc: James Rabe; City of Oshkosh
Signed for and in behalf of the City of Oshkosh
Richard A. Wollangk, City Manager
Edward A. Nokes, City Comptroller
I hereby certify that the necessary provisions
have been made to pay the liability which will
accrue under this contract.
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