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HomeMy WebLinkAboutGrading Plans - 08/25/2023PROJECT NO. 2052-001 ATTENTION: Stormwater Department City of Fort Collins 700 Wood Street Fort Collins Colorado 80521 Dear City Staff: C 1�:: This letter memo accompanies the submittal for the Teft Acres, por Tract 12, 3235 Moore Ln. Grading Plan dated August 17, 2023. Specificalfy, this letter report serves to document the drainage impacts associated with the proposed developments. The proposed development consists of the addition of a new accessory building (barn) and an adjacent patio on a 1.45-acre residential fot. The total impervious footprint for both the proposed barn and the patio is 1,472 sf. The proposed Grading Plan for the addition of the barn and patio allows for the lot drainage to remain substantially unchanged and follow existing drainage patterns. A swale is proposed north of the proposed barn which will route runoff from the proposed barn to the west where it will enter the historic drainage pattern. The historic drainage pattern, for the area within the limits of disturbance, is that runoff will overland ffow east to northwest where it will initially enter a swale along the lot line that runs east to west. From that swale the runoff wilf be conveyed to another swale that runs south to north afong the back of the lots within Teft Acres. south to north swale will convey the runoff to Spring Creek. The runoff off the front of the lot remains unchanged. The proposed barn is increasing the total impervious by 2%. This 2% increase in area results in an increase in runoff during the 100-year event by 0.26 cfs (see attached Rationaf Cafcs). This increase in 0.26 cfs is negligible and will have no adverse impacts on downstream infrastructure. Additionally, there are no structures between the proposed barn discharge location and Spring Creek. A regional drainage map has also been included to show the conveyance from the proposed barn to Spring Creek. For additional information please refer to the Grading Plan dated August 24, 2023. Please feel free to contact me if you have any questions. Sincerely, NORTHERN ENGINEERING SERVICE, INC. � �- �`�'---. � ��p,p0 �°� �� p �: ���� �� � ��— ` � Jacob O'Banion, EI Project Engineer NORTHERNENGINEERING.COM � 970.221.4158 FORT COLLINS � GREELEY BLAINE MATHISEN, PE Project Manager DRAINAGE MEMO: 3235 Moore Lane DATE: August 24, 2023 Grading/Stormwater Plan Accepted PROJECT: Teft ACres, por TYaCt 12, 3235 MoOre Ln. IBuilding Permit Released� Accepted by: sagenbroad Fort Collins, CO 80526 Date: 08/25/2023 Attachments: 1. Rational Calculations 2. 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