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STORIINATHR SITB PLAN JUNE 32, 200� <br />u�a�rLarngnLANE rn�r r, <br />POTENTIAL PROI3LEAtS <br />Thc downstrcam system appcars to havc adcquatc capaciry �i�ith no advcrsc impacts tu thc <br />adjacent properlics. <br />Sediment discharge from thc site should '�e minimal duc to the vault that is proposed for thc site. <br />Tltere were no observed sediment discharges from the downstmam properties. <br />Streambank erosion should not be a probiem, as the dctention faciliticsproposed for thc site will <br />restrict Qie release of stonnwatcr runoff to the cxisting rates. The downstream channel appears to <br />bc adequatcly stabalized by the cxisting vegetation. <br />]�o dischargc of storm�vatcr to thc groundwatcr is proposed. <br />No spills or discl�arge of priority pollutants are anticipated from this residential de�clopment <br />Past Dakota Way on the downstrcam reconissance, an area of concern was located. It appcars <br />thcre might bc a faulty septic systcm. City staff was notified to investigate on t1Yir own. <br />Prevention and Source Control will be addresscd in Section VI of tUis repori. <br />UPS'TREA�1 I3ASIN <br />Tlie upstrcam Uasi� tributa.ry to thc wctland corridor has been analysed to dctcmiinc the rcquircd <br />culvert size to be placed under the road�vay at thc wetland crossings. 'Che cul�er[ has also been <br />sized to allow for fish passage. The Fish Passage Guidelines: CtJvert L�stal(ations from section <br />1[I-2.3.4 of the DOS Manua( were uscd in dic dcsign of the culvert. The design has been based <br />upon die requiremenls, as listed in Tablc III-2.S Pish Passage Dcsign Criteria for Culvert <br />Installation. Tltese requirements are as following: <br />1. Q10°o should not exceed 4 Ws dvough the culvcrt. Q10% for a 2 yr 24 hr storn less <br />than 44 cfs is equal to dic 2 yr 24 hr stonn event. In this case the rivo year 24 i;r storm <br />is 16 cfs. Therefore Q10% = the 2 yr 24 hr stonn. <br />2. The pipc bottom sliould be countersunk Uy a minimum of 20°% of the height of dic <br />culvcrt. <br />3. Minimum flow depth shali be 0.3 ft. <br />RUNOFF CALCULATION: <br />Thc upstrcam basin consists of approximatcly 140 acres north of the site, from \Vest <br />Casino Ruacl, south. Tlie tributary area has been detcnnined from die Snohomish County <br />acrial mapping and feld invcstigation along �vith input from die City of Everett This <br />basin includes a largc portion of dte N�altcr E Hall Golf Course. No cuh�erts werc evident <br />under West Casino Road. The design flow rate assumes that new cicvclopment will meet <br />the rcyuirements of the City of Everett Stomiwater Management �ianunl or the DOE <br />Dcsign Manual. <br />Land Usc CN Area (acl <br />Impervious 98 40.0 <br />Grass 86 100.0 <br />� so,.,,ai�.������.e�is•�so��dm�-o�ayr�coieina�aos�oae�oac�memrssPw�iedomooc DWH/srm <br />