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Home My WebLink AboutGrading Plans - 03/09/2020Accepted 3/9/2020 WL � I NORTH ERN ENGINEERING Drainage Memo — 327 North Loomis Avenue Date: January 20, 2020 Project: 327 North Loomis Avenue Fort Collins, CO Attn: Stormwater Staff City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, CO 80521 Stormwater Staff: Project No. 1714-001 This letter serves to document the proposed drainage impacts of a proposed single-family home at 327 North Loomis Avenue in Fort Collins, Colorado. Project Overview The project proposes to scrape off the existing 1-story home located on the property and replace it with a single-family home with a larger footprint and basement. Existing Site The existing site functions as a"B" Lot, with drainage from the lot draining from the home out to the side lot lines, which then convey the drainage to both the front and back of the lot. Existing grades in the front yard range between 2%-3%, and grades in the back of the home vary between 0.5% and 3%. In addition to the existing home, the existing lot consists of detached shed and concrete entry walk. The remainder of the site is Kentucky Bluegrass lawn, with small landscaping beds and mature trees. The total existing impervious area for the lot is 1,084 sf. Proposed Site The proposed site will continue to function as a`B' Lot, with drainage from the new residence being directed to the side lot lines, and then to both the front and back of the lot via existing "swales" along the lot line. Existing grades outside of our improvements will remain unchanged. The proposed home is located roughly in the same location as the existing home. The existing shed will be replaced in the same location as a slightly larger shed. Window wells are proposed on either side of the building to provide emergency egress from the basement. The total proposed impervious area for the lot is 2,075 sf. This is an increase of 991 sf. The increase in runoff as a result will be negligible, and no adverse impacts to adjacent properties are anticipated. Detention Since the impervious area increases less than 1000 sf, no detention is required for the site. FORT COLLINS: 301 North Howes Street, Suite 100, 80521 � 970.221.4158 GREELEY: 820 8t" Street, 80631 � 970.395.9880 � WEB: www.northernengineering.com � I NORTH ERN ENGINEERING Water Qualitv Water Quality for the site is provided by releasing concentrated flows from the roof into the landscaped areas allowing stormwater runoff to infiltrate into surrounding soils. Stormwater unable to infiltrate is slowly passed through vegetated areas, further removing stormwater contaminates before stormwater leaves the property. An exhibit has been provided to illustrate the existing and proposed impervious areas. Please feel free to contact us if you have any questions. Sincerely, �P��.��F� . •;..o� sco� u-,_ s ' "= 45018 �'" �, '• 1/zo/zo •' �,� o,�'•., ,.•'�� .S��NAL E�G� Frederick S. Wegert, PE Project Engineer FORT COLLINS: 301 North Howes Street, Suite 100, 80521 � 970.221.4158 GREELEY: 820 8t" Street, 80631 � 970.395.9880 � WEB: www.northernengineering.com EXISTING PROPOSED .. I . EXISTING SHED � � PROPOSED SHED � '� �_ � — I � � _ '. I w EXISTING � � � � x � � � 1 H HOUSE m N � PROPOSED HOUSE cn w` . I �� O > � � � —-— O W I � o Q J 2 Q - _ - 2 x x �I I EXISTING FENCE �I, I . . EXISTWG FENCE �I SURFACE %IMPERV. IMPERV. SURFACE %IMPERV. IMPERV. NREA (SF) AREa (SF) aREH (SF) I AREA (SF) ROOFTOP 1,026 iW% 1,026 ROOFTOP 1,155 I iW% I 1.'!55 GONGRETE 58 1004fi 58 CONCRETE 320 100% I 320 ASPHALT 0 100°b 0 PAVERS 0 50% 0 GRAVEL 0 50% 0 �N��W 159 0% I 0 WEIL LAN�SCAPE 3,812 Ob 0 LANOSCAPE 2662 Q% 0 rora�s aaee TOTAL= 1,084 TOTn�s aaee TOTAL= 2,075 � EXISTING VS. PROPOSED NORTHERN 827 N. LOOMIS AVENUE IMPERVIOUS AREA E N G I N E E R I N G FORr co�uNs �,��„wa COLORADO F~wECEar ic=w� e„_ o�._ oR�,��- DR-1 e. e*s��.., _ .�on.e �� JANUARY20-2020 171q-0p1 � �i > w J 3Q i � NORTH LEGEN�: �w�P�s�c� ;..�p.� .,�W� m. .xa�zEo,.o.,��>..,,s O E.�„�� o. ��.,�N .� ._��.�E „� .Ao,� �� .��a�,=«no� .A - s.�� NE ��wE� �,, � NOTES. c� a e i.,�� r �x..rHs. e� F+o> .o �x .w. cno� ro-w .ni.�wi�i.. � FlNis�cr, aoo� a.��Ar,oN= s�ow� � - ,n .Iv i.below. noCallce City of Fort Collins, Colorado IITIISTY PLAN APPROVAL � �.� �:� �� ar: � �e� m:� �� : � �� m: � � P�-.� �� zc� :,: � z '-- w� ' =W � �(((yyy z G w W �, � � fn c Q � c � � � Z � o Q O � � Z � N M Snect G12