20130323 SCJ Cmt Ltr 11272013 i
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SC�1 �LLIANCE
CONSULTING SERVICES
November 27, 2013
Karen Bennett
City of Yelm
105 Yelm Avenue West
Yelm,WA 98597
Re: Prairie Park Stormwater Review
SCJ Project#0490.03
Dear Karen:
We have received and addresses/commented on the peer review comments from Parametrix. Below
are SCJ Alliance responses to comments for the Prairie Park Stormwater Renovations project.
Our comments are as follows:
1. GN-01—Please revise note 9.A under SCJ Alliance General Erosion Control Notes to read "No more
than 100 feet" per City of Yelm Development Guidelines Section, 6.160.D.
We have changed the callout to reflect 100'.
2. DT-01, SD Sheets—Please provide a Construction Entrance Detail (per City of Yelm Civil Plan
Checklist), and show where construction entrances will be located on the plans.
During project discussions with the City, this comment was waived by the City staff due to the site
already being paved. No revisions were made.
3. SD Sheets—Please provide existing topography, as well as spot elevations of proposed grading plan
at each site to ensure adequate drainage.
During project discussions with the City, this comment was waived by the City staff. No revisions
were made.
4. SD Sheets—The same linetype is used for different features in the base map, making it difficult to
determine existing conditions. Please revise base map for clarity, and add existing features to
Legend.
During project discussions with the City, this comment was waived by the City staff. No revisions
were made.
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5. SD Sheets—Please check all pipe length labels. According to Note 5 under SCJ Alliance Storm
Drainage Notes, pipe lengths are called out from center of structure to center of structure. This
does not appear to be consistent in the plans.
We have reviewed and revised the pipe lengths as requested.
6. SD Sheets—Please revise structure labels to include SD pipe invert, diameter, and direction.
We have reviewed and revised stormwater labels as requested.
7. SD—Please add/revise callouts to more clearly explain which SD pipes and structures are to remain,
and those that are not to be plugged.
We have reviewed and revised stormwater labels as requested.
8. SD Sheets—Please revise infiltration gallery detail so that filter fabric is wrapped around all sides of
gallery.
We have shown filter fabric on all sides of the gallery.
9. SD Sheets—Please revise infiltration gallery detail so that the space between the top of the filter
fabric and the finished grade refer to the provided restoration detail.
We have revised our"pavement restoration"detail to be a "trench restoration"detail. During
discussions with City it was agreed that COY detail4-10 was typical for public rights-of-ways not
private improvements. We have not added the detail to the plans.
10.SD-01—Please revise Trench Restoration detail so that cement conc. pavement layer is in accordance
with City of Yelm Standard Detail 4-10,Trench-Pavement Restoration Detail.
We have revised our"pavement restoration"detail to be a "trench restoration"detail. During
discussions with City it was agreed that COV detail4-10 was typical for public rights-of-ways not
private improvements. We have not added the detail to the plans.
11.SD-02 and SD-03—Please revise Pavement Restoration detail so that Class B ACP layer is in
accordance with City of Yelm Standard Detail 4-10,Trench-Pavement Restoration Detail.
We have revised our"pavement restoration"detail to be a "trench restoration"detail. During
discussions with City it was agreed that COY detail4-10 was typical for public rights-of-ways not
private improvements. We have not added the detail to the plans.
12. Drainage Report—Stormwater Treatment was not addressed in the 1992 DOE Manual in a manner
that is consistent with current State of Washington standards. The computations should be revised
to follow the 2012 Stormwater Management Manual for Western Washington as prepared by
Department of Ecology.
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�.�- November 27, 2013
+ Page 3 of 3
We have revised our stormwater calculations to reflect the City's request to meet the 2012 DOE
Manual. We have increased the size of infiltration galleries to accommodate the greater predicted
duration of stormwater flows. The peak flow is reduced using WWHM therefore we have not
modified the sizing of the Aqua-Swirl treatment devices. Please see attached stormwater report for
calculations.
13. Plans/Drainage Report—A Tributary Area Map should be provided depicting both the entire
drainage area that is being removed from the Prairie Park Development.
A tributary area map has been added to the stormwater report.
14. Plans/Drainage Report—Existing pre-development contours of the Prairie Park development should
be provided as assurance that the bottom elevation of each infiltration gallery is below any fill that
have been placed during construction.
During project discussions with the City, this comment was waived by the City staff. We have not
added the contours to the plans;however the plans do have a requirement for the contractor to
verify that the bottom of the gallery is installed in native material.
15. Drainage Report p.4—Rationale for the statement"The proposed infiltration trenches will not
contain perforated pipe" should be provided.
We have revised the design to include perforated pipe throughout the gallery.
Please contact me at 360-352-1465 or email at jim�@sclalliance.com if you have any questions.
Respectfully,
SCJ Alliance
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ames Gibson, PE
` Project Manager
Enclosure(s): Drainage Report
Plans
N:\Projects\490 Margaret Clapp\490-03 Prairie Park Stormwater System Revisions for Fay Fuller Building\Correspondence\To\L-2013-1127
Bennett.doc
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