CityParkIrrigation.pdfrne.lg9v
CITY OF EDMONDS
121 5TH AVENUE NORTH • EDMONDS, WA 38020 • (425) 771-0220 • FAX (425) 771-0221
Website: www.d.edmondsma.us
DEVELOPMENT SERVICES DEPARTMENT
Planning • Building • Engineering
October 31, 2008
Brian McIntosh, Director
Edmonds Parks, Recreation & Cultural Services
700 Main Street
Edmonds, WA 98020
RE: Request for waiver per ECDC 19.10.070
1611375 th Place West, Edmonds
Dear Brian,
GARY HAAKENSON
MAYOR
We received your request for waiver to allow an irrigation system for the proposed park
at 16113 75tb Place W. The site is located in the Earth Subsidence Landslide Hazard
Area which is regulated under ECDC 19.10. Irrigation systems are specifically
prohibited in the Earth Subsidence Landslide Hazard Area as set forth in ECDC
19.10.070D unless a waiver is first obtained per ECDC 19.10.070E.
Your request for waiver was sent for peer review by our geotechnical consultant, Landau
Associates, as permitted in ECDC 19.10.070.E. It is their opinion that the information
contained in the request did not demonstrate that the requirements of ECDC 19.10.070D
were addressed. A copy of their Technical Memorandum dated October 28, 2008 is
attached for your information.
It has not been clearly demonstrated that the irrigation system will have no reasonable
likelihood of triggering or otherwise contributing any landslide hazard or earth
subsidence risk either on the subject site or in the neighboring earth subsidence or
landslide hazard area as set forth in ECDC 19.10.070E. Therefore, it is my determination
that the request for waiver for the proposed irrigation system is denied.
Sincerely,
04.
Ann Bullis, CBO
Building Official
Incorporated August 11, 1890
Sister City - Hekinan, Japan
LANDAU
1A ASSOCIATES
TECHNICAL MEMORANDUM EMM«�,WMAL RE
TO: Ann Bullis, Building Official
City of Edmonds Building Department
FROM: Dennis R. Stettler, P.E. f
DATE: October 28, 2008
RE: GEOTECHNICAL REvlEw OCT 312005
162ND STREET PARK IRRIGATION SYSTEM IBLjI ° I
EDMONDS, WASHINGTON
INTRODUCTION
This technical memorandum provides our geotechnical review continents related to the request by
the City of Edmonds Parks, Recreation & Cultural Services Department (City Paries) to waive the
requirements of Edmonds Community Development Code (ECDC) Chapter 19.10.070D.3 related to the
prohibition of irrigation systems as a part of the plans submitted to the City of Edmonds (City) Building
Official for the proposed 152°' Street Park. This geotechnical peer review was accomplished at the
request of the Building Official in accordance with Task Order No. 08-19 of Landau Associates' On -Call
Geotechnical Engineering Services Agreement with the City.
Landau Associates has previously provided review comments for the project to the City in a
technical memorandum dated May 5, 2008 for the original permit application submittal and in a technical
memorandum dated August 13, 2008 for a resubmittal of the permit application documents. In both of
those previous reviews, we pointed out that an irrigation system for the proposed park was shown on the
plans. In accordance with ECDC 19.10.070D.3, irrigation systems are prohibited within the North
Edmonds Earth Subsidence and Landslide Hazard Area (ESLHA). Irrigation systems, as well as other
surface water features with the potential to allow infiltration of storm water into the groundwater, are
prohibited because of the adverse impact of any increase in groundwater levels to overall slope stability
within this hazard area.
According to ECDC 19.10.070E, this prohibition shall apply unless the applicant "requests a
waiver based upon the written analysis of a geotechnical engineer which clearly establishes that the
proposed improvement will have no reasonable likelihood of triggering or otherwise contribute to any
landslide hazard or earth subsidence risk either on the site or in the neighboring earth subsidence or
landslide hazard area." Further, "the burden of proof shall always be upon the applicant to establish by
a clear preponderance of the evidence that no such risk will be created by the improvement. Any
geotechnical engineering report provided in any review shall consider not only the risk incurred due to or
during construction of the otherwise prohibited improvement, but also the potential impacts due to failure
130 2nd Avenue South + Edmonds, WA 98020 • (425) 778-0907 • tax (425) 778-6409 • www.landauinc_com
to maintain the improvement, damage through reasonably foreseeable events such as earthquakes or
other acts of God, or the reasonably foreseeable negligence of the owner or future owners." We have
used the stated criteria above in our review of the request for waiver.
We have received the following additional information forwarded by the City for review:
Letter to the Edmonds Building Official from Brian McIntosh, Director, Edmonds Parks,
Recreation & Cultural Services, dated October 7, 2008.
• Letter regarding Irrigation of 162"' Street Park, 76h Avenue West and 75h Place West
Walkway Improvements, Edmonds, Washington prepared by HWA Geosciences, Inc., dated
October 6, 2008.
REVIEW COMMENTS
City Parks notes that it plans to use the irrigation system only in the dry season, at the end of the
dry season all irrigation pipes would be shutoff, and an automatic flow control valve would be installed
that could sense abnormal flow beyond what is programmed and shut the irrigation system down
automatically. These are all prudent steps to limit the potential for excessive surface water to be
introduced to the site. The letter from HWA points out that a shallow trench subdrain system will be
included to remove excess water from the site. The 14WA letter alludes to the potential for the irrigation
system to leak and considers it likely that the leaking water would remain near the surface and not reduce
slope stability. However, the depth of this trench subdrain system appears to be only several feet deep
and it would probably remove some, but not all excess water that could potentially infiltrate_ The HWA
letter also qualifies their opinion on the provision that the irrigation system is properly maintained.
The proposed flow control valve and trench subdrain design elements address only the fact that
they may limit the introduction of surface water; however, the proposal of an irrigation system constitutes
an overall increase in the potential for introduction of surface water to groundwater and therefore an
increase of the potential for soil movement. Based on the specific wording of ECDC 19.10.70D, it is our
opinion that the applicant has not demonstrated that "...the proposed improvement will have no
reasonable likelihood of triggering or otherwise contribute to any landslide hazard or earth subsidence
risk.. " or has not established that "...a clear preponderance of evidence that no such risk will be created
by the improvement. "
We suggest that the planting plan for the 162" Street Park be reviewed and more
drought -tolerant planting materials be selected that are not dependent on an automatic irrigation system
for survival. We suggest that hand watering be accomplished, as necessary, until the planted materials are
initially established.
10128108 11Edmdatalproiects467417501FiteRoom\M162nd51Park-irdgalionneview_TM.doc LANDAU AssocIATES
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CLOSURE
This technical memorandum has been prepared for use by the City of Edmonds in evaluating the
request for waiver of the prohibition of an irrigation system for the City's 162nd Street Park. This
geotechnical peer review by Landau Associates does not lessen the requirements for the applicant's
geotechnical consultant and other design professionals to prepare an appropriate design for the site
conditions.
We appreciate this opportunity to be of service to the City. Please contact us if you have any
questions, or if we may be of further service.
DRShgm
10728/08 \1Edrndatalpro;ects1074115"ileRoom1R1162ndStPark_IrrigationReview TM.doc LANDAU AssOCIATES
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CITY OF EDMONDS
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Ann Bullis, Building Offeial.
City of Edmonds
Ih
11.15. Averiue North
Edmonds, V+>r.11,.'98020
Dear Ms..13ulli:s,
GARY € AAKENSON
MAYOR
October 7, 2008
Ploase. accept this 'letter as an official rerluest.ofwaiver in regard.to scction 19.7 0.070
D.3, the Issuance and, denial of permits. in the Edmonds City Development Code. This
section devils with the relationship of groundwater to stability within this earth subsidence
and landslide area.
The City of Edmonds Parks & Recreation. Department proposes to construct Via.
neighborhood park on. kind at 162"`' ,street $& 75"' Place West: that vas acquired by the
City in 1991, The development plans call for a.coiatrol.led irrigation system to erasure
swi,ival ofthe planned.vegetation and the small grassy area which. are very important
coMponents of this. park,
It should be noted that irrigation would talcs; place only in the dry season so 110 Water
would be added to the site when the arta is most proaie to slides. At the end of the dry
season all iir:igation pipes would be sham. off.at the meter. In addition the parrs
Departme.nt will install an "automatic: flow control valve" that senses abnormal flow
beyorid what is programmed and shuts the irrigation systema down automatically.
Ralph Bo`irwn.of E-IWA Goosciences is very familiar wi.th'this area andthe design plans
for this project and his. assessment is also attachcd.
Thank you for your consideration of this request and please: let me know if have. any
questions or need clarification.
s
Brian McIntosh, Director-
l dnaonds Parks, Recreation & Cultural Services
tk Calfa:JP'FJ.. Ci. PfSiiat.. .I..I%]90
Sister ('Uy w l:. ekin an, Japan
. .........
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INC
Attw Nfii—ffiianMcinto-sh,.
Parks & Recreation Director
RE. IRRTGATION oF 162'.'�� STREriT 11ARK
7611 AVENUE WEST AND 751rm PLACE XVL,STXVALXWAY 1-iMPROVE Nill"N'rS
E, I)IMONDS, WASHINGTON
'We, understand irrigation systcins:are prohi4ited in the Mcadoxvdale area unlcs,�a Avaiv��j, is
granted based on. [lie of the geotecho . jeal engincen. Bascxl on llic;.resutts of our
studics Of 111C SRO, OUr recommendations for dc.Mgn and construction of the proposed park, and
Oily revic\v of the Park's design, it is our mcominendation. that ti waiver big granted allowing
in,�tallation of an irrigation systema.
m
Tile curronij, dosigpi of the, patk includes installation of a Imich subdrain -,ystonl to remove excess
water= frown -the site ars weil as construction of a 1xitiressing rill to increaso flit -"Lability of tbe site.
Considering (110. clayey nature of the native soils at the site, itis likely that most water leaking
from the irrigation system would remain near the surftico where : it woold.not rQduco Slope
stability. Water seeping - bito. [lie soils ivoukl be removed by the subdrain systcm. Providing [hat
it . is Properly maintained and turned Oft during fliewet months, it is:our opinion that an inigalion
systeln care sattyly be installed and operated ontliis sitemithow increased risk oNmsl,ibdjty.
1Nfc: appreciate . 1.11e ()I . )POI-tunity is Provide hnical �ory . ices, on this prqjea.
. �cotc(,
Sincerely,
I-INVA INC,
MON. Boirum, 11X,
Geotechnical Enginocr, Principal
icc: Tani Starford, Gray & Osborne; Im,