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Blonm, Page 2, (}1/25b6 2. The infiltration rate used in the modeiing is 2 in/hr. Ii should be noted �ha� t12e maxiar�tt�aa infiltration rate recommended in the Minnesota Stormwater Manual is 1.6 in/ht' fox gravel�y soils. The soi� borings indicate that the onsite soils wi�h the greatest infiltration capacity are saa�ds w�ie�. �ave a Maa�ual recom�nended in�ltration rate o�'f}.8 i�/%r. Based nn soil bo�ings in t�.e in�il�:ratian areas these arates cou�.d be revise�t. 3. Tlxe details indicate that aggregate less ihan 3 znches will t�e used to pravide bedding for the perforated pipes. The speci�ications should fi�rther indica�e thai aggregate with fines should nat be used as i'ines vcrill clog t�te systerz� and prevent infil�ratian. RATE CONTROL Peak dischurge Yates foY develapment,s inust he at or� b�low existing �^ates fo� the 2, 10, and l00 year starin events. T�e su�rr�it�ed information indicates that rates will be below predevelo�ment rates for pro�aased conditions. It should be noted, however, ihat infiltration rates are still questionaiale, �s�ecially in the area of the northeast perforated pipes w�ere no soil boring data has bean �rovided. �f infilira�ion rates For the perfc�rated pipe areas are deernec� acceptab�e, the site aneets CRWD rate co�trol criteria. VOLUME CONTRQL Developments and redevelopments must �educe runaff volurrces in the amount equivalent to an inch nf runaff from the impervious areas af the site. ,Stormwater must be p�etreated befa�e discharging in infiltration areas to maintain long-term viability of the infiltratian area. Wzth a Z in/hr in�l�ration ra�e, ��e HydrnCAD mn�eling indica�es that for a 2-yr sta� event, z�are t�a� double the volume requirec� to �e infiltrated of 4,335 cubic feet will be in�ltrated zn t%e narthw�st area alone where soi� borings have verified that the in-sit�a soils will promote an��tz'at�an, I�in�ltration rates for the perforated pip� areas are de�rn�d acceptahle, i�e site wi11 rneet CRWD valurn� co�trol criteria. WATER QUALITY Developments and redevelopments nzust incorporate effective non point sou�^ce pollutian reduction BMPs to achieve 90% snlid �enioval. Credits will be given far the volume of wate� inf ltrated. Based on a P8 ra�odel deve�oped by EOR, tk�e sxte will ac��e�e a� �e�.st 90% solzd �e�nova� through onsite infil�ration. Thearef4are, the site �eets CRWD watear quality critearia. FLOODZIVG A structu�e's lowest floor elevation naust be 2 feet ahove the �OO yea� high �vater level af the adjacent ponds and wate� bodies. TI�e high r�vater �evel of the underground storage pip�s as at �east two feei be�c�w t�e first floox elevaiion o�the proposed hnmes. However, if the houses have basernents, �he high water ievel of ihe p�pes wi11 be abave the basernent flaor eievaiinn. rt shnuld be veri�ed �y the ap�licant tk�at tlai� does not pose any flooding coneerns, especially for �he northeast and northwest lots adjacezat to the lar�e p�rforated pipe areas. ii as unknawn at th�s time if the site meets CRWD "Dur mission is to protect, rnanage, and i�nprove the water resources of the Capital Region Watershed l�istrict. "