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<br /> j. Site Descri tion: Ex�stin Conditions
<br /> � � � The project location is bounded by an alley to the west, 39'�St to the south, and
<br /> y� � � Burlington Northem R.O.W. to the east, near the intersection of 29`� St and Smith Ave in
<br /> �`, � f�•' North Everett, in the SE '/, of the SW % of Section 29, T29N,RSF;. The azea has been
<br /> {a ,� e;;tensively developed for industriai uses, including much of the project site. The project
<br /> � �� site is a gravel, heavily overgrown with blackberry bushes, to the south of an existing
<br /> ,� -`''�.wazehouse and pazking area. The site was graded and filled in the past, creating a slope
<br /> � v� t`� from west to east, with a steep embankment along the east property line that drops down
<br /> �, �� to die Burlington No�thern R.O.W.. The Snohomish County Soil Survey shows that Lhe
<br /> �. G' <;; soil type for the project azea is Everett Gravelly Sandy Loam, which has excellent
<br /> � infiltration chazacte�stics. However since the site had fil] material placed on it in the
<br /> (�'`j ""� �� past, a geotechnical report by Earch Consultants Inc.reveals that the soil type underlying
<br /> � ,r�, , ,..
<br /> r� ..., the project site is actually silty sand and sandy silt fill material, whic�has poor
<br /> �+ infiltration characteristics.
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<br /> ,� �� II. Site Description• Pro�osed Develo�ment
<br /> � � �
<br /> ~(�,� ,,,y^ The propased development is to construct a new building with a 6,000 sf footprint and an
<br /> �� t'� '`�--. , approximately S,SQO sf asphalt azea. At sometime in the future the nro e
<br /> '� Y_'� expect:;to pave the remaining 0.68 ac of his property. Hence,when sizpng�e�er .
<br /> � ` L. �`" retention/detention(R/D) facilities, 0.84 ac of impervious area was used for the
<br /> � �� �ti calculations. Storm water runoff from the a�:r halt azeas will be routed to a catch basin in
<br /> ' the north ea;t corner of the ro e The i! •.off is then conve ed throu a retention�.n t,,�
<br /> P P rtY• y �
<br /> � � � pipe, then a wetpond, and finally to a detention pipe.
<br /> ' � ,�1, �— ��'f �� '��� �
<br /> C The minim m cr��nP i ,n,f,nP�����N,�calculated as 704 cf usin � L�,�
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<br /> � � � Sectiun 3-3.6.1 of the City of Evcrett Stormwate;Management Mani:al. The reten6on � "
<br /> pipe is 56 ft of four foot diameter 14 gage Cb1P with 3 x 1 inch ccrrugations. There is a S�IZ�M
<br /> � �j three foot high baffle�l5 ft&om the inlet side of the vault,dividing the retention i e into
<br /> � two cells of 26%and 76%of the retained vo]ume. P P YG��lUl� iS
<br /> � � From the retention pipe, storm water is conveyed to a wetpond. The wetpond has been1 n �l,Y .
<br /> C� � sized to retain 15%of the siY month storm under developed conditions. The wetpond has V��
<br /> dimensions of 25 ft x 6 ft x 2 ft, with a storage volume of 300 cf. Wedand vegetatioi�, �
<br /> � ' � such as cattails and hardstem bulrsh,will be planted to a density of one plant per 2.25 sf. 1
<br /> � Ruaoff from the asphalt areas that exceeds the six month sto ��L` mi�
<br /> � �' both the retent�on pipe and wetpond to a detendon pipe. Runoff from th plr posed �u Or /Y�/Y��
<br /> � j structure will be routed directly to the detention pipe. The detention pipe has been sized � � '
<br /> � ��Q to detain runofffrom the entue site, 0.84 ac,and discharge at rates of 50% of the riva V'(''�rjl,Q i�1
<br /> � � year and 100%of the 10 and 100 year events under pre-developed conditions. The
<br /> � �_ detention pipe is 73 ft of seven foot diameter 14 guge CMP with 3 x lin comigations. �`��
<br /> ` Including a safety factoc of 50% for a 100% impervious site, the detention pipe exceeda )
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