04-0180 Stormwater flooding 060906
City of Yelm
Community Development Department
105 Yelm Avenue West
P.O. Box 479
Yelm, WA 98597
June 12, 2006
Erling Birkland, Director of Facilities
Yelm Community Schools
PO Box 476
Yelm, WA 98597
RE: Ridgeline Junior High School – Stormwater System Review
Rocky:
The City of Yelm has reviewed the Ridgeline Jr. High School Stormwater System Hindcast & Revised Design Analysis prepared by Edward Wiltsie, P.E. and dated May 25, 2006, along with a
‘clarification’ letter prepared by Robert Tauscher, P.E. and dated May 31, 2006, and accepts the report as meeting the City’s requirement that Yelm Community Schools and Jerome W. Morrissette
& Associates show that the construction of the stormwater system in a high groundwater area will not significantly increase the base flood elevation and impact the ‘downstream’ properties
in Hawks Landing.
The scope of the report submitted by Mr. Wiltsie goes well beyond the very specific question asked by the City of Yelm and includes construction of the athletic track, softball field,
and stormwater pond. The report also does not specifically examine the pre-existing site conditions at the time the Ridgeline School was permitted. While including this superfluous
analysis in the report makes it much more difficult to answer the very specific question asked by the City of Yelm, I find it is possible to conclude that there is no significant impact
on the Hawk’s Landing subdivision attributable to the stormwater system, with the following findings.
The recommendations of the report relating to construction of a swale alone the raised grade track will be required. While it appears that this requirement is related to the construction
of the athletic fields rather than the stormwater system, the report does not contain sufficient analysis to support this conclusion and the construction of the swale is required unless
a supplemental report is prepared which is limited to the original scope requested by the City of Yelm.
The analysis does not support the recommendations relating to the drainage basin outside the project site based on the scope requested by the City of Yelm. However, to be clear on this
point, the clarification letter submitted by Robert
Tauscher on May 31, 2006, which states that the only recommendation of JWMAA are recommendation relating to the construction of a swale near the track needs to be stamped and signed
by either Mr. Tauscher or Mr. Wiltsie. If this is not possible, a new report limited to the scope originally identified by the City of Yelm will be required.
The City of Yelm contacted Jerome W. Morrissette and Associates prior to the approval of the civil engineering plans regarding the potential for high groundwater at the site.
The Hawks landing subdivision was fully constructed prior to the submission of any land use permits, civil engineering plans, or building permits to the City of Yelm by Yelm Community
Schools, and was an existing condition when Ridgeline Junior High School was being permitted.
Community Development Department
Respectfully,
Jim Gibson, P.E.
Development Review Engineer
c. Jerome W. Morrissette, P.E. JWMAA
Bob Tauscher, P.E. JWMAA
Ed Wiltsie, P.E. JWMAA