11325 19TH AVE SE 2018-01-01 MF Import

Erich O. Tietze & pssoc. 2067750236 P. 03 . I � . t � - '—MEMO (continued) ]framei, Ch &Ma 0. Inc. '• � ' Perhaps the areas designated as biofiltratton swales should be marked in the e1d prior i - ko grading for bullding pads,parking lots,and traffic lanes. � � 5. The design of swales number one and two mises some questzons. For�exa le, there appeats to be 760 feet of swale depzcted on the plans, while the applicant dai 239 feet of swale. It is difficult to unde�stand how the system will work without rvater ollng at the "Y" created by the intersection of the two swales. Tn addition, is the pplicant counting the same swale twice? From the informaHon provided in the table of Bio8ltratlon Swale Data, it appears that there is actually 239 feet of swalg, alth ugh it is not depicted on the drawings. If the swale is to be eounted twice, the s'wale ould be � proportionately larger downstream frpm the "Y". � ' 6. With regard to the planting schedule for the wet pond. We recommend a mix f species rather than a monoculture in facilities of this type. Ivlany of the spede� reco ended in the table of Additional Vegetation for Biofiltiation Stvafes, found on the me plan sheet, would be approprtate for planting on the edges of wet ponds. ' I , Erosion Co�lrol P(an " ; .� The erosion control plan depicted on Sheet 1 of 1 has some issues that need to be a ressed. Specifically: � ; , 1. T,he ditches that are shown on the south side of the site traverse through the d line of several of the majoz trees that are to be preserved. Essent[ally, the'drip ' e of a ' ' �� coniferrnu tree does not represent t�e extent of root growth, CeneraUy spea 'ng, the � � root ball extends up to two times the diameter of the drip llne. The trees wlll robably ' �j�` not survive such treatmeat., or may be severely weakened, posing a futu e saEety hazard, { � . � 2. Straw bale check dams, shown tluoughout the ditch system on the site, are no oriously � ineffective. when used as check dams because of poor placement, maintena ce, and deterioration. Other methods acceptable to the City of fiverett Departaient Public „ �� Works should be considered. In additlon, a achedule of maintenarice s uld be lnduded for all check dams, sumps, and erosion control faciliries. { 3. The outfall for the perforated ptpe on the sediment pond should rest atop � bed f gravel �a� or straw to minimize the formation of riwlets. Some provision for m�inte nce, as , Q;�" well aa a schedule, should be provided. 4. Once the rockeries are constructed on site, where will water be conveyed? �Ch►ce uilding , pads are constructed, and rockedes are in place, how will water traverse t{�e sit 'I'here will still be problems wtth erosion once the site has been graded. An idga of ow site water will be conveyed once the preliminary grading is accomplished would heIpful and may serve tq circumvent erosion and sedimentation problems before they o cur. ; , � _ ± �^ 7 � i Page 2 �