The URL can be used to link to this page

Home My WebLink AboutGrading Plans - 04/20/2023C � 2 i2 Consultants, Inc. � April 17, 2023 16911 Potts Place, MEad, CO 970.217.9148 troy@i2-consultants.com Mr. Dan Mogen Development Review Engineer Grading/Stormwater Plan Accepted City of Fort Collins Utilities (Building Permit Released) 222 Laporte Avenue Accepted by: Dan Mogen Fort Collins, CO 80524 Date: 04/20/2023 RE: Drainage and Erosion Control Report for 510 Wood Street, Fort Collins, CO Dear Mr. Mogen: S 50 FT OF N 150 FT LOTS 1 AND 2, GRIFFIN'S SUB, BLK 295 West Side We are pleased to present this Drainage and Erosion Control Report for 510 Wood Street, Fort Collins, CO for your review and approval. This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual, September 2018. We look forward to your favorable review of this report. Please do not hesitate to contact our office if you have any questions. Sincerely, i2 Consultants, Inc. � Troy W. Campbell, PE Senior Project Engineer ENGINEER'S CERTIFICATION I hereby certify that this report for the final drainage design of 510 Wood Street, Fort Collins, CO was prepared by me (or under my direct supervision) in accordance with the rovisions of the Fort Collins Storm Drainage Criteria Manual for the owners thereof. �,00 RE�isT o ...��.....q . : � C ,�jq . , F` � � 4 � �: �: :W � `..04/17/2023:�'z � .. . � � S��oNA �...��c� Registered Professional Engineer State of Colorado No. 41159 (Seal) Drainage Report 510 Wood Street, Fort Collins, CO April 17, 2023 Page 2 Drainage Report 510 Wood Street, Fort Collins, CO Being the South 50' of the North 150' of Lots 1 and 2, Griffin's Subdivision Of Block 295 of the West Side Addition to the City of Fort Collins Located within the Northwest Quarter of Section 11, Township 7 North, Range 69 West of the 6th P.M. City of Fort Collins, County of Larimer, State of Colorado TABLE OF CONTENTS GENERAL LOCATION AND DESCRIPTION A. Site Location B. Description of Property II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin B. Sub-basin and Site Drainage III. DRAINAGE DESIGN CRITERIA A. Regulations B. Development Criteria Reference and Constraints C. Hydrological Criteria IV. DRAINAGE FACILITY DESIGN A. General Concept B. Specific Details Page K3 3 � 5 V. SEDIMENT, EROSION CONTROL AND STORMWATER QUALITY 7 A. Temporary Sediment and Erosion Control B. Permanent Water Quality BMPs VL CONCLUSIONS A. Compliance with Standards B. Drainage Concept 0 VII. REFERENCES 9 VIII. APPENDICIES 10 c �� i2 Consultants, Inc. Drainage Report 510 Wood Street, Fort Collins, CO April 17, 2023 Page 3 I. GENERAL LOCATION AND DESCRIPTION A. Site Location: The subject site is located in the northwest quarter of Section 11, Township 7 North, Range 69 West, of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. Furthermore, the project is north of Sycamore Street, on the east side of Wood Street. The subject site can be described as the south 50' of the north 150' of Lots 1 and 2, Griffin's Subdivision of Block 295 of the West Side Addition to the City of Fort Collins. The subject site currently contains a single-family dwelling, out-building, concrete patio/walks and landscaping. B. Description of Property: The subject site lot consists of roughly 0.10 acres. The subject site currently contains a single-family dwelling, out-building, concrete patio/walks and landscaping. The existing improvements will be removed as part of the redevelopment of the property. The subject site generally slopes from east to west at varying slopes from 0% to 1%. A portion of the site drains to the north to the adjacent property (514 Wood Street). The existing curb and gutter for Wood Street slopes from south to north. Based on existing site topography, it appears the area behind the sidewalk for Wood Street contains a series of low points and runoff is directed to the north. According to the Natural Resources Conversation Service (NRCS) Web Soil Survey, the native soil in this area is Paoli Fine Sandy Loam, 0 to 1 percent slopes (Map Unit Symbol #81), which is a Type A soil. Please refer to the NRCS soils information in the Appendix. Existing drainage facilities near or adjacent to the site include existing curb & gutter along Wood Street. II. DRAINAGE BASINS AND SUB-BASINS A. Maior Basin: This site is located within the Old Town Basin as shown on the City of Fort Collins Master Drainage Plan. This basin historically generally flows from west to east. c �� i2 Consultants, Inc. Drainage Report 510 Wood Street, Fort Collins, CO April 17, 2023 Page 4 The site is shown on FEMA panel 08069C0977G, effective 06/17/2008. The subject site is located with Zone X of the FEMA panel. B. Sub-basin and Site Drainaqe: The subject site generally slopes from east to west at varying slopes from 0% to 1%. A portion of the site drains to the north to the adjacent property (514 Wood Street). The existing curb and gutter for Wood Street slopes from south to north. Based on existing site topography, it appears the area behind the sidewalk for Wood Street contains a series of low points and runoff is directed to the north. It is i2's understanding that the subject residential site has not been studied previously in a site-specific drainage study or report. Based on existing site topography, it appears there is runoff that enters the subject site from the south and east properties, which are currently developed with single- family residences. This runoff will be conveyed through the subject site via proposed onsite swales, similar to the existing condition. The runoff will be conveyed to the Wood Street right-of-way. The drainage patterns proposed with the subject improvements are generally consistent with the existing conditions and seek to improve the current drainage for the subject property. III. DRAINAGE DESIGN CRITERIA A. Regulations: This report has been prepared in general accordance with the Fort Collins Stormwater Criteria Manual, September 2018. B. Development Criteria Reference and Constraints: The subject site is constrained by existing conditions surrounding the site, such as the developed adjacent existing Iots with flat slopes and the subject site having a lower elevation than Wood Street. Furthermore, the subject site is constrained by the existing lot lines with minimal to no slope. The subject site will drain to the existing Wood Street right-of-way and flow north. Based on existing elevations for Wood Street and the subject site, the runoff will flow from south to north, between the existing sidewalk and the east line for the Wood Street right-of-way. This generally follows the existing runoff pattern for the site. c �� i2 Consultants, Inc. Drainage Report 510 Wood Street, Fort Collins, CO April 17, 2023 Page 5 This report has been prepared in general accordance with the appropriate City criteria. C. Hvdroloqical Criteria: Fort Collins Stormwater Criteria Manual, September 2018. There are no deviations from the criteria in this report. The design storms for this project are the 2-year and the 100-year recurrence intervals. Runoff is calculated using the Rational Method since all basins are smaller than 5 acres. The Rational Method calculations are computed by the following: Q= ciA where: Q = Runoff in cubic feet per second c = Calculated runoff coefficient for design event i = Storm intensity in inches/hour A = Basin area in acres Hydrological calculations have been prepared in accordance with the Fort Collins Stormwater Criteria Manual, September 2018 as well as the USDCM. IV. DRAINAGE FACILITY DESIGN A. General Concept: The drainage patterns associated with the subject single-family residence improvements are generally consistent with the existing drainage patterns and flow. The proposed site grading generally directs runoff from east to west towards Wood Street. The estimated runoff for the site was determined using the Rational Method, as detailed above. The subject site has been divided into two (2) drainage basins. The basins have been created to direct runoff towards existing facilities. B. S�ecific Details: Basin EX Basin EX (0.10 acres) is the existing basin for the property. The existing basin currently contains a single-family dwelling, out-building, concrete patio/walks and landscaping. The existing improvements will be removed as part of the redevelopment of the property. Basin A Basin A(0.04 acres) is comprised of the southern portion of the subject site. This basin contains a portion of the residence, driveway, rear patio and landscaping. c �� i2 Consultants, Inc. Drainage Report 510 Wood Street, Fort Collins, CO April 17, 2023 The basin generally drains from east to west and flows under the proposed driveway. The runoff will be conveyed towards Wood Street. Page 6 Basin B Basin B(0.06 acres) is comprised of the northern portion of the subject site. This basin contains a portion of the residence, rear patio and landscaping. The basin generally drains from east to west and flows towards the western portion of the lot. The runoff will be conveyed towards Wood Street. A comparison between the existing and proposed conditions is provided below: Basin ID Area % 100- Yr Time of 100-year 100-year (ac.) Impervious Concentration Coefficient Runoff min cfs EX 0.10 36.1 6.0 0.56 0.53 Site A& B 0.10 54.4 5.8 0.76 0.72 The runoff for the subject site will increase by roughly 0.2 cfs. The increase is due to the larger residential footprint and concrete for the driveway and patios. The impervious area increase is approximately 860 s.f. The subject site is constrained by existing conditions surrounding the site, such as the developed adjacent existing lots with flat slopes and the subject site having a lower elevation than Wood Street. Furthermore, the subject site is constrained by the existing Iot lines with minimal to no slope. The northern lot line swale for 510 Wood Street will be shared with 514 Wood Street. The northern slope of the swale will be graded when 514 Wood Street is redeveloped. The northern lot line swale will convey runoff for both 510 and 514 Wood Street when both sites are redeveloped. The future grading for 514 Wood Street will account for and incorporate this swale. The subject site will drain to the existing Wood Street right-of-way and flow north. Based on existing elevations for Wood Street and the subject site, the runoff will flow from south to north, between the existing sidewalk and the east line for the Wood Street right-of-way. This generally follows the existing runoff pattern for the site. The proposed runoff from this site is not anticipated to have a negative impact on the existing adjacent facilities or neighboring properties. The expected runoff from the subject site should be negligible and should not impact the adjacent and overall basins. c �� i2 Consultants, Inc. Drainage Report 510 Wood Street, Fort Collins, CO April 17, 2023 Page 7 V. SEDIMENT, EROSION CONTROL AND STORMWATER QUALITY A. Temporary Sediment and Erosion Control: Several sediment and erosion control measures will be incorporated into the initial phase of construction. The initial sediment and erosion control measures to be installed shall include sediment control logs around the perimeter of the site. An initial control measure should be the installation of construction fence around the development perimeter. Furthermore, additional measures for sediment and erosion control shall consist of providing an area designated for a concrete washout area. The initial measures for sediment and erosion control shall be maintained and updated as necessary during the interim and final stages of the project. Additionally, any area that has been disturbed by construction activities and left exposed for more than fourteen (14) days, shall receive drilled seeding and straw mulch at 2 tons/acre, until permanent landscaping or ground cover has been provided. Four Step Process to Minimize Adverse Impacts of Urbanization Employing runoff reduction practices: There will be landscaping around the site and proposed impervious surfaces have been limited to the extent practice for the redevelopment of this residential lot. Implementing best management practices (BMPs): Onsite BMPs are not practical for the subject residential redevelopment. Stabilizing Streams: The runoff from the subject site drains to existing paved surfaces and facilities. Implementing site specific and other source control BMPs: Appropriate erosion and pollution control, for residential redevelopment shall be installed around the staging area as appropriate. B. Permanent Water Qualitv BMPs Not required for the subject property. Water quality is provided through minimizing directly connected impervious area (MDCIA) and the proposed landscape buffering onsite. Detention is not required for the subject property as the additional impervious area is less than 5,000 sf. Furthermore, LID is not required for the subject property c �� i2 Consultants, Inc. Drainage Report 510 Wood Street, Fort Collins, CO April 17, 2023 Page 8 vi. coNc�usioNs A. Compliance with Standards: The drainage design is in general compliance with the Fort Collins Stormwater Criteria Manual, September 2018. B. Drainaqe Concept: The runoff from this site will be conveyed by existing and proposed storm drainage improvements. The drainage design for the subject site should not negatively impact improvements downstream or the existing storm system. c �� i2 Consultants, Inc. Drainage Report 510 Wood Street, Fort Collins, CO April 17, 2023 Page 9 VII.REFERENCES 1. Fort Collins Stormwater Criteria Manual, dated September 2018. 2. Urban Drainage and Flood Control District, Drainage Criteria Manual Volumes 1, Revised August 2018, Volume 2, Revised September 2017 and the Volume 3, dated November 2010 and Updated October 2019. 3. City of Fort Collins Master Drainage Basin Map, no date. c �� i2 Consultants, Inc. Drainage Report 510 Wood Street, Fort Collins, CO April 17, 2023 Page 10 VIII.APPENDICIES ❑ Vicinity Map ❑ FEMA & Existing Geotechnical Information ❑ Hydrologic Calculations ❑ Charts and Figures c �� i2 Consultants, Inc. Vicinity Map A-1 FEMA � Existing GEotEchnical Information � �� i2 Consultants, Inc. B-1 National Flood Hazard Layer FI RMette ��: FEMA Legend 105°5'45"W 40°35'S2"N SEE FIS REPORT FOR DEfAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT � � � � Yr-�,�7�y�yp 1�l J•- Without Base Flood Elevation (BFE) •�'�.. � R�� I ��L+MFM1�1�-U4��,.��1"'� ��t i.i� ZoneA.V.A99 l �,rj -� With BPE or Depth zo�,e ne. no, aH. ve. aR �-'-..- � ��.C1t�f�� '�� SPECIALFLOOD . y ' ' � w., ,;�� NAZARD AREAS Regulatory Floodway ''�1 '"+� � 14f ,,� � },��.��#(3►i'CiR 2C�r-�$-Cpfi�+� �". � � 4 I L'��i��t' � � �'� N�"�.�''1=�.'If.y�.A1��3�1 �- T?P�.J F{�,, +1 _,�•M _ � 4,C„a ,+ f �� 0.2% Annual Chance Flood Hazard, Areas °1 '� � of 1% annual chance flood with average ( ' � depth less than one foot or with drainage ��i � � 4 ' � F � �� areas of less than one square mile zo„e x Mh ' � i �♦ s'� 7 - � �. � Future Conditions 1%Annual � � � i�� , � ! � �� `` � _ -- Chance Flood Hazard zo�,� x � � � Area with Reduced Flood Risk due to I „�� ! _ OTHER AREAS OF Levee. See Notes. zo�,e x � r�, ' � :� '� . FLOOD HAZARD Area with Flood Risk due to Leveezo„e o �. ► - �'� S{ �� ` il _ 41 � � � *' r r. � � �j w A�� NO SCREEN Area of Minimal Flood Hazard zone x �► �t �i , � � � _ � . — � Effective LOMRs M:�M w" 9� Y" �_ � « M= M�` �' - j OTHER AREAS Area of Undetermined Plood Hazard zo„e o � - � 4 a r, �� 9 r �.: �� Y � °z ` GENERAL '--' Channel, Culvert, or Storm Sewer �.- ��* � � STRUCTURES � i i t i i t Levee, Dike, or Floodwall '� 4 ' u� , �'" � � � � � � Cross 5ections with 1% Annual Chance ; i �� ( � _ ' � � _ •� � ��.s Water Surface Elevation ' � � � -� w� • - '�' R e - - - Coastal Transect t � if�' L7t FU� C� C i11T� 5 � � + �s+3� Base Flood Elevation Line (BFE) �.. � ��`�F r��irai��_F�� a� � �� +, �-., � � Limit ofStudy ��. ��' � �. � � ��,�� _� �. �� ` � --- -- � � � I u Jurisdiction Boundary �� — Coastal Transect Baseline '`�!� � � � i � OTHER _ — profile Baseline � � � � �� FEATURES Hydrographic Feature - � i . , ' � � rrra ��°,,, ;11- � � . , � �_ I � � "' ° ` ,,� _ � � " � Digital Data Available r w � t� � � a� � '�; . � . � � � � �'yR � .... r " r � � r-�� , _� _ ��_�- � � � �� 1, 000 � � 1, 500 � 1 - � _ �� " .M No Digital Data Available � y �'� MAP PANELS Unmapped g� � � The pin displayed on the map is an approximate � point selected by the user and does not represent � an authoritative property location. w � �. r � �� This map complies with FEMA's standards for the use of � h �ij � - digital flood maps if it is not void as described below. �. The basemap shown complies with FEMA's basemap ��`'�'g�'3-` �� 4 * accuracystandards " �1 *� � � The flood hazard information is derived directl from the � �' '� authoritative NFHL web services provided by FEMA. This map I� �� was exported on 1/26/2023 at 4:51 PM and does not S reflect changes or amendments subsequent to this date and time. The NFHL and effective information may change or �� - '� �-� become superseded by new data over time. �' I/ , This map image is void if the one or more of the following map � � ° elements do not appear. basemap imagery, flood zone labels, R N legend, scale bar, map creation date, community identifiers, - �`� � FIRM panel number, and FIRM effective date. Map images for � Feet 105°5'8"w 40°35'24"N unmapped and unmodernized areas cannot be used for 1:6,000 2,00� regulatory purposes. Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020 � � � 0 � �� 40° 35 38" N�— I i � g � Soil Map—Larimer County Area, Colorado (Strattion Custom Homes, Fort Collions, CO) as2z� asz�oo aszso� a9zsia I._ �� I.s� - _ _ � 1 .� � agzsz� aszszs asza� I. — �.I. -. I * agzsaz � �, B-2 0 as23as I �40° 35' 38" N � � I� � I � � [7 � � I■ I � n � � � �* � Soil Map iiiay not be valicl at this scale, - 40° 3S 3T' N� ` ' 'I I � 4� 492293 4923(b 492�07 432314 49zi21 492328 432335 3 3 � N Map Scale; 1:300 iFprinted on A la�dscape (il" x 8.5") sheet. � N Meters 0 4 8 16 24 � Feet 0 10 ZO 40 60 Map projectlon: Web Mercator Cc�mer coorcJinat�: WGS84 Edge tics: UTM Zone 13N WGS84 USbn Natural Resources Web Soil Survey � Conservation Service National Cooperative Soil Suroey 492342 49234�J 3 � :7 'v E�i � � � 40° 35' 3T' N 1/26/2023 Page 1 of 3 ^ II � � � Soil Map—Larimer County Area, Colorado (Strattion Custom Homes, Fort Collions, CO) MAPLEGEND Area of Interest (A01) Area of Interest (AOI) Soils Soil Map Unit Polygons � _� Soil Map Unit Lines 0 Soil Map Unit Points Special Point Features U Blowout "�' Borrow Pit �� Clay Spot Closed Depression Gravel Pit Graveliy Spot Landfill • Lava Flow _ Marsh or swamp ' Mine or Quarry Misceilaneous Water ' Perennial Water Rock Outcrop _�- Saiine Spot Sandy Spot = Severely Eroded Spot Sinkhole Slide or Slip oa Sodic Spot _ Spoil Area Stony Spot Very Stony Spot �• Wet Spot Other , Speciai Line Features Water Features Streams and Canals Trensportation � Rails N Interstate Highways US Routes Major Roads Local Roads Background � Aerial Photography MAP INFORMATION The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 17, Sep 7, 2022 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 2, 2021—Aug 25, 2021 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. : USbn Natural Resources Web Soil Survey 1/26/2023 � Conservation Service National Cooperative Soil Suroey Page 2 of 3 Soil Map—Larimer County Area, Colorado Map Unit Legend Map Unit Symbol 81 Totals for Area of Interest Map Unit Name Paoli fine sandy loam, 0 to 1 percent slopes Strattion Custom Homes, Fort Collions, CO B-4 Acres in AOI Percent of AOI 0.3 100.0% 0.3 100.0% USDn Natural Resources Web Soil Survey � Conservation Service National Cooperative Soil Survey 1 /26/2023 Page 3 of 3 � � � 0 � �� 40° 35 38" N�— I I.. - � � g � � � �5$$ � V [7 492300 Hydrologic Soil Group—Larimer County Area, Colorado (Strattion Custom Homes, Fort Collions, CO) 49230� 4923,4 4�232, 492328 � - y � ti L � —� � n � � � �� 5oil Map iiiay not be valicl at tli'is scale. � 40° 3S 3T' N�� ` ` � I I � 4� 492293 4923(b 492�07 432314 49zi21 3 3 � N Map Scale; 1:300 iFprinted on A la�dscape (il" x 8.5") sheet. � N Meters 0 4 8 16 24 � Feet 0 10 ZO 40 60 Map projectlon: Web Mercator Cc�mer coorcJinat�: WGS84 Edge tics: UTM Zone 13N WGS84 USbn Natural Resources Web Soil Survey � Conservation Service National Cooperative Soil Suroey 492335 452342 :�)Ryi�Cl ��.l��y] � � o B-5 492349 �� 40° 35 38 N 1- � � I � � :7 'v E�i � � � � 40° 35' 3T' N 49234,9 3 � 1/26/2023 Page 1 of 4 Hydrologic Soil Group—Larimer County Area, Colorado (Strattion Custom Homes, Fort Collions, CO) MAPLEGEND Area of Interest (A01) Area of Interest (AOI) Soils Soil Rating Polygons � A Q A/D 0 B � B/D Q C 0 C/D � D 0 Not rated or not availabie Soil Rating Lines . � A o � � C/D � D � Not rated or not availabie Water Features Streams and Canais Transportation � Rails �..i Interstate Highways US Routes Major Roads Local Roads Background � Aeriai Photography .�.i A/D ..� B �r B/D . . C . r C/D .�.♦ D .. Not rated or not availabie Soil Rating Points o A 0 A/D ■ B � B/D MAP INFORMATION The soil surveys that comprise your AOI were mapped at 1:24,000. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 17, Sep 7, 2022 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Jul 2, 2021—Aug 25, 2021 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. : � USbn Natural Resources Web Soil Survey 1/26/2023 � Conservation Service National Cooperative Soil Suroey Page 2 of 4 Hydrologic Soil Group—Larimer County Area, Colorado Strattion Custom Homes, Fort Collions, CO � Hydrologic Soil Group Map unit symbol 81 Map unit name Paoli fine sandy loam, 0 A to 1 percent slopes Totals for Area of Interest Description Rating Acres in AOI Percent of AOI 0.3 100.0% 0.3 100.0% Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff.� None Specified USDn Natural Resources Web Soil Survey 1/26/2023 � Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group—Larimer County Area, Colorado Strattion Custom Homes, Fort Collions, CO . .� � Tie-break Rule: Higher USbn Natural Resources Web Soil Survey 1/26/2023 � Conservation Service National Cooperative Soil Survey Page 4 of 4 Hydrologic Calculations � �� i2 Consultants, Inc. Runoff Coeffecients Sub-Basins Project: 510 Wood Street Location: 510 Wood Street Fort Collins, CO Project Number:1088-1 Date: 1 /31 /2023 I� Consultants, Inc. 16911 Potts Place, Mead, CO 970.2D.9148 troy@i2-consultants.com Atl calculations presented are based upon the criteria set forth in Citv of Fort Collins Storm Drainaae Desiqn Criteria 9/1 /2018 Basin EX (ac) (sq.ft) (%) Design Point Surface Improvement Area Area C I Comments EX % of site area Lawns, Sandy soil (flat <2%) 0.06 2754.0 0.15 2.00 62.6% Curb & gutter and walks 0.01 306.0 0.95 100.00 7.0°/o Paved Parking & Drives 0.00 216.0 0.95 100.00 4.9% Roofs 0.03 1124.0 0.95 90.00 25.5% Avg. 0.45 36.11 100.0% Total Area 0.10 4400.00 0.45 36.11 Basin A �BC� �Sq.ft� �%� Design Point Surface Improvement Area Area C I Comments 1 % of site area Lawns, Sandy soil (flat <2%) 0.02 730.0 0.15 2.00 46.2% Curb & gutter and walks 0.00 0.0 0.95 100.00 0.0% Paved Parking & Drives 0.01 275.0 0.95 100.00 17.4% Roofs 0.01 576.0 0.95 90.00 36.4% AVg. 0.58 51.11 100.0°/a Total Area 0.04 1581.00 0.58 51.11 Basin B (ac) (sq.ft) (%) Design Point Surface Improvement Area Area C I Comments 2 % of site area Lawns, Sandy soil (flat <Z%) 0.03 1162.0 0.15 2.00 41.2% Curb & gutter and walks 0.02 691.0 0.95 100.00 24.5% Paved Parking & Drives 0.00 0.0 0.95 100.00 0.0% Roofs 0.02 966.0 0.95 90.00 34.3% Avg. 0.62 56.18 100.0% Total Area 0.06 2819.00 0.62 56.18 Overall Site (ac) (sq.ft) (°/o) Design Point Surface Improvement Area Area C I Comments 2 % of site area Lawns, Sandy soil (flat <2%) 0.04 1892.0 0.15 2.00 43.0% Curb & gutter and walks 0.02 691.0 0.95 100.00 15.7% Paved Parking & Drives 0.01 275.0 0.95 100.00 6.3% Roofs 0.04 1542.0 0.95 90.00 35.0% Avg. 0.61 54.36 100.0% Total Area 0.10 4400.00 0.61 54.36 GI 5� 0_Imperv.xlsx\Sub-Basins 4/18/2023 TIME OF CONCENTRATION - 2-YEAR PROJECT. CALCULATED BY.� Cf = 1.00 510 Wood Street i2 Consultants, Inc. DATE. 1 /31 /2023 C-2 RURAL OR NON URBANIZED SUB-BASIN INITIAL/OVERLAND TRAVEL TIME tc CHECK FINAL REMARKS DATA TIME (To�) (t�) (URBANIZED) tc BASIN DP AREA C C�Cr Length Slope t� Length Slope R V tt tc Total L tc ID Ac Ft °/a min Ft (ftlft) Ft fps min min ft min min (0) (1) (2) (3) (4) (5) (6) (7) (8) (8a) (9) (10) (11) (12) (13) (14) EX EX 0.10 0.45 0.45 50 2.0 6.8 30 0.005 1.0 1.5 0.3 7.2 80 10.4 5.0 Use Tc = 5.0 mins A 1 0.04 0.58 0.58 30 2.0 4.2 75 0.005 1.0 1.5 0.8 5.1 105 10.6 5.1 Use Tc = 5.1 mins B 2 0.06 0.62 0.62 65 1.0 7.2 60 0.005 1.0 1.5 0.7 7.9 125 10.7 7.9 Use Tc = 7.9 mins Site 2 0.10 0.61 0.61 65 1.0 7.4 60 0.005 1.0 1.5 0.7 8.1 125 10.7 8.1 Use Tc = 8.1 mins i z z 3 Epuations: Rural/Non-urban Tov 1.87(1.1-CC f)"D^ �iz tt = L S �1/3 6�V V=CVSW0.5 (1) (2) or Fig. 3-3 Velocity V (1.4/n)*(R^2/3))*0.5) S in ft/ft, R= Area/Wetted Perimeter in ft, n= Roughness Coeff. Urbanized t� _ (U180)+10 (3) TIME OF CONCENTRATION -100-YEAR PROJECT: CALCULATED BY.� Cf = 1.25 510 Wood Street i2 Consultants, Inc. DATE: 1 /31 /2023 RURAL OR NON URBANIZED SUB-BASIN INITIAL/OVERLAND TRAVEL TIME tc CHECK FINAL REMARKS DATA TIME (To„) (t�) (URBANIZED) tc BASIN DP AREA C C'Cf Length Slope t� Length Slope R V tt tc Total L tc ID Ac Ft % min Ft % Ft fps min min ft min min i�) i�) i2) i3) i4) �5) i6) ��) i$) isa) i9) i��) ��) i�2) ��3) �14) EX EX 0.10 0.45 0.56 50 2.0 5.7 30 0.005 1.0 1.5 0.3 6.0 80 10.4 6.0 Use Tc = 6.0 mins A 1 0.04 0.58 0.73 30 2.0 3.0 75 0.005 1.0 1.5 0.8 3.9 105 10.6 5.0 Use Tc = 5.0 mins B 2 0.06 0.62 0.78 65 1.0 4.9 60 0.005 1.0 1.5 0.7 5.6 125 10.7 5.6 Use Tc = 5.6 mins Site 2 0.10 0.67 0.76 65 1.0 5.2 60 0.005 1.0 1.5 0.7 5.8 125 10.7 5.8 Use Tc = 5.8 mins i z 3 a Epuations: Rural/Non-urban Tov 1.87(1.1-CCf)`D^vz tt= L S �1/3 6�V V=CVSW0.5 (1) (2) or Fig. 3-3 velocity V (1.4/n)`(R"2/3))'`0.5) S in ft/ft, R= Area/Wetted Perimeter in ft, n= Roughness Coeff. Urbanized to = (L/180)+10 (3) G3 Rational Method DirecY Runoff - 2-YR G4 Project: 510 Wood Street Location: 510 Wood Street Fort Collins, Colorado Project Number 1088-1 Date: 1 /31 /2023 Rational Method: Q= CfCIA Q: C: C+{: I: A: 2-YEAR Design Point Basin �D EX EX 1 A 2 B 2 Site Area 0.10 0.04 0.06 0.10 I� Consultants, Inc. 16911 Potts Place, Mead. CO 970.217.9148 troy@i2-consultants.com Q: Runoff in cfs (peak) C: Runoff Coefficient Cf: Frequency Adjustment Factor I: Rainfall Intensity (in/hr) for design event A: Basin Area (acres) C 0.45 0.58 0.62 0.61 CfC 0.45 0.58 0.62 0.61 t� 5.0 5.1 7.9 8.1 I 2.85 2.83 2.41 2.39 QZ 0.13 0.06 0.10 0.15 1.3 cfs/acre 1.6 cfs/acre 1.5 cfs/acre 1.4 cfs/acre C:\Users\troy�Dropbox\12�ProjecYs\1088-1 Wood Street\DocumenCs�Drainage\510_rafionalxlss U28/2023 Rational Method Direct Runoff- 100-YR GS Project: 510 Wood Street Location: 510 Wood Street Fort Collins, Colorado Project Number 1088-1 Date: 1 /31 /2023 Rational Method: Q= CfCIA Q: C: C+{: I: A: 100-YEAR Design Point Basin ID 1 2 2 A B Site Area 0.10 0.04 0.06 0.10 I� Consultants, Inc. 16911 Potts Place, Mead. CO 970.217.9148 troy@i2-consultants.com Q: Runoff in cfs (peak) C: Runoff Coefficient Cf: Frequency Adjustment Factor I: Rainfall Intensity (in/hr) for design event A: Basin Area (acres) C 0.45 0.58 0.62 0.61 C{C 0.56 0.73 0.78 0.76 t� 6.0 5.0 5.6 5.8 I 9.31 9.95 9.57 9.44 a100 0.53 0.26 0.48 0.72 5.2 cfs/acre 7.2 cfs/acre 7.4 cfs/acre 7.2 cfs/acre C:\Users\troy�Dropbox\12�ProjecYs\1088-1 Wood Street\DocumenCs�Drainage\510_rafionalxlss U28/2023 Charts and FigurEs � �� i2 Consultants, Inc. FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) D-� 3.0 Rational Method Table 3.2-2. Surface Type - Runoff Coefficients Surface Type Runoff Coefficients Hardscape or Hard Surface Asphalt, Concrete 0.95 Rooftop 0.95 Recycled Asphalt 0.80 Gravel 0.50 Pavers 0.50 Landscape or Pervious Surface Lawns, Sandy Soil, Flat Slope < 2% 0.10 Lawns, Sandy Soil, Avg Slope 2-7% 0.15 Lawns, Sandy Soil, Steep Slope >7% 0.20 Lawns, Clayey Soil, Flat Slope < 2% 0.20 Lawns, Clayey Soil, Avg Slope 2-7% 0.25 Lawns, Clayey Soil, Steep Slope >7% 0.35 3.2.1 Composite Runoff Coefficients Drainage sub-basins are frequently composed of land that has multiple surface types or zoning classifications. In such cases a composite runoff coefficient must be calculated for any given drainage sub-basin. The composite runoff coefficient is obtained using the following formula: ,� � (c;xa; ) � _ �-� A, Where: C= Composite Runoff Coefficient C; = Runoff Coefficient for Specific Area (A;), dimensionless A; = Area of Surface with Runoff Coefficient of C;, acres or square feet n= Number of different surfaces to be considered At= Total Area over which C is applicable, acres or square feet 3.2.2 Runoff Coefficient Frequency Adjustment Factor Equation 5-2 The runoff coefficients provided in Table 3.2-1 and Table 3.2-2 are appropriate for use with the 2-year storm event. For any analysis of storms with higher intensities, an adjustment of the runoff coefficient is required due to the lessening amount of infiltration, depression retention, evapotranspiration and other losses that have a proportionally smaller effect on high-intensity storm runoff. This adjustment is �'�, ";` 3.2 Runoff Coefficients ��F�rt� ns Page 5 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) D-2 3.0 Rational Method applied to the composite runoff coefficient. These frequency adjustment factors, Cf, are found in Table 3.2-3. Table 3.2-3. Frequency Adjustment Factors Storm Return Period Frequency Adjustment (years) Factor (Cf) 2, 5, 10 1.00 25 1.10 50 1.20 100 1.25 3.3 Time of Concentration 3.3.1 Overall Equation CxCF PRODUCT OF CxCF CANNOT EXCEED THE VALUE OF 1 The next step to approximate runoff using the Rational Method is to estimate the Time of Concentration, T�, or the time for water to flow from the most remote part of the drainage sub-basin to the design point under consideration. The Time of Concentration is represented by the following equation: T�=T;+Tt Where: T� = Total Time of Concentration, minutes T; = Initial or Overland Flow Time of Concentration, minutes TL = Channelized Flow in Swale, Gutter or Pipe, minutes 3.3.2 Overland Flow Time Overland flow, T;, can be determined by the following equation: 1.87(1.1—CxCf)� T' 3� Where: C= Runoff Coefficient, dimensionless Cf = Frequency Adjustment Factor, dimensionless L= Length of Overland Flow, feet S = Slope, percent City of F�rt� ns Equation 5-3 Equation 3.3-2 OVERLAND FLOW LENGTH L=200' MAX IN DEVELOPED AREAS L=500' MAX IN UNDEVELOPED AREAS 3.3 Time of Concentration Page 6 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) D-3 Table 3.4-1. IDF Table for Rational Method Duration Intensity Intensity Intensity (min) 2'Year 10-year 100-year (in/hr) (in/hr) (in/hr) 5 2.85 4.87 9.95 6 2.67 4.56 9.31 7 2.52 4.31 8.80 8 2.40 4.10 8.38 9 2.30 3.93 8.03 10 2.21 3.78 7.72 11 2.13 3.63 7.42 12 2.05 3.50 7.16 13 1.98 3.39 6.92 14 1.92 3.29 6.71 15 1.87 3.19 6.52 16 1.81 3.08 6.30 17 1.75 2.99 6.10 18 1.70 2.90 5.92 19 1.65 2.82 5.75 20 1.61 2.74 5.60 21 1.56 2.67 5.46 22 1.53 2.61 5.32 23 1.49 2.55 5.20 24 1.46 2.49 5.09 25 1.43 2.44 4.98 26 1.4 2.39 4.87 27 1.37 2.34 4.78 28 1.34 2.29 4.69 29 1.32 2.25 4.60 30 1.30 2.21 4.52 31 1.27 2.16 4.42 32 1.24 2.12 4.33 33 1.22 2.08 4.24 34 1.19 2.04 4.16 35 1.17 2.00 4.08 36 1.15 1.96 4.01 37 1.16 1.93 3.93 38 1.11 1.89 3.87 F�rt� ns 3.0 Rational Method Duration Intensity Intensity Intensity (min) 2'Year 10-year 100-year (in/hr) (in/hr) (in/hr) 39 1.09 1.86 3.8 40 1.07 1.83 3.74 41 1.05 1.80 3.68 42 1.04 1.77 3.62 43 1.02 1.74 3.56 44 1.01 1.72 3.51 45 0.99 1.69 3.46 46 0.98 1.67 3.41 47 0.96 1.64 3.36 48 0.95 1.62 3.31 49 0.94 1.6 3.27 50 0.92 1.58 3.23 51 0.91 1.56 3.18 52 0.9 1.54 3.14 53 0.89 1.52 3.10 54 0.88 1.50 3.07 55 0.87 1.48 3.03 56 0.86 1.47 2.99 57 0.85 1.45 2.96 58 0.84 1.43 2.92 59 0.83 1.42 2.89 60 0.82 1.4 2.86 65 0.78 1.32 2.71 70 0.73 1.25 2.59 75 0.70 1.19 2.48 80 0.66 1.14 2.38 85 0.64 1.09 2.29 90 0.61 1.05 2.21 95 0.58 1.01 2.13 100 0.56 0.97 2.06 105 0.54 0.94 2.00 110 0.52 0.91 1.94 115 0.51 0.88 1.88 120 0.49 0.86 1.84 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 8 FORT COLLINS STORMWATER CRITERIA MANUAL Figure 3.4-1. Rainfall IDF Curve — Fort Collins Hydrology Standards (Ch. 5) p-4. 3.0 Rational Method io.00 __ _ _ _ _ _ � � -- -_ _---- ii i L - - - -- - - ' � '- 100-Year Storm 9�� - -� � � � I I I � �� - ---10-Yea�Sio�m � � I . . - - -; �J - -- - � � , �- . . . .- . � �. � - 2-Year Storm _I_. . -� �---- -- ._�._._'._. . ._:_._._._. . .- -. ---� ---�-- I I � i _ � I _ . . . . _ . . . I 8.00 -- ---- . - _ _ _. - I �- _ I I I I.. �I I I I.... _ ! �! j . . _�, . . . _ . _. . . . __ . _. . ._ . _ . . _ _ . _ . . �.00 _ i 'i i i- - i i i � �. i � , T , � � _ _ _r � _� _ N �.00 —. _ � i � - - � � - �- �' s.00 -.__ _ -�_ � —_.� . � � �_�_�_._ � i_ _I_ ,`, � I I I__ j l i l G � . . . . � , . -. . ._ .. . . �-I-�I_:-. .i � . _�_ ._-� -. i . .. . � 4.00 --�-. _ I I I I I i � I � ♦ _ _ _ _ l-i � i i � i 7: i _-�-:_ _i ._. _ � , - -- 3.00 . -� � � 1 I � I I . `. ��` . . � �-- � i i � i � i i i . \ . .�� . . . . \ � . ♦ ... �� ... 2.00 ��` -. _ ��y`-_ _ � �� l �� ► 1.00 I._�I . . i . I�I�.+�i _! `s` __ ___�'��-.��.�---.:��«�� _ _ - T i �I � i �� . � - . . II I I � ��.. ��..+�� - _..,�r�i ! �� 0.00 . 0 10 20 30 40 50 60 70 80 90 100 110 120 Storm Duration (minutes) c�tyof 3.4 Intensity-Duration-Frequency Curves for Rational Method ��F�rt� ns Page 9 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) �-5 : 1 � ►I ►I Table 4.1-2. Land Use - Percent Impervious Percent Impervious Land Use (%) Residential Urban Estate 30 Low Density 50 Medium Density 70 High Density 90 Commercial Commercial 80 Industrial 90 Undeveloped Open Lands, Transition 20 Greenbelts, Agriculture 2 Offsite Flow Analysis (when Land Use not defined) 45 Reference� I'or further guiciance x�egarding zoning classifications, refer to the Land Use Code, Article 4. For Final Plan (FP) submittals, impervious values must be based on the proposed land surface types. Refer to Table 4.1-3 for recommended percent impervious values. Table 4.1-3. Surface Type — Percent Impervious Percent Impervious Surface Type (%) Hardscape or Hard Surface Asphalt, Concrete 100 Rooftop 90 Recycled Asphalt 80 Gravel 40 Pavers 40 Landscape or Pervious Surface Playgrounds 25 Lawns, Sandy soil 2 Lawns, Clayey soil 2 c�tyoF F�rt�� 4.1 Input Parameters Page 11 EXISTING DRAINAGE i2 � Consultants, � I � Inc. spoz 16911 Pott�s Place � � Mead. C lorado � � � KnowwhaYsbO�OW. 970.217.9148 � � �, CBII before you tlig. �` N ._"`s I � I oi 4„5 �W xisnrvc ''aeva�os.-RFEr o ."° s�—?E �. PROPERtt y0. � �aa. LINE ' � . . . �4-�:�-.. . ' it�� . �isn � j � � CURB GUTIER . - 2� w • � y LEGENDOFSVMBOLS ANO SIOEWRLK (I � _ , �� I ! �NG�. -- EXSt� J 4 Nfi � w.:..7� o i�on-c �' - O SDENCE i E .__ _. _ � / n � 5 Nv SEwER g0p � f R C .' O OFISWINy g ' I RIGHT � J � ��. I[ FMCURAI r} nx.ar Z � � � � � �� z � - ri,oures r�I -.. _ W� Q � , � � � �. w urecr ��. ��. � W -� O �' � o- U � > u1 F' — . . � !a't5ii�'e COIICkF.�' O � J Q � .c_ / � _ . . _ . . . :. O � Z O X � oc . . . ..� Q - .�O�O.ED �O��C�aEi_ , , Q ' � � E�.iNG. ' � C NC EFE � � lL W ... — ... _ , ' i —... ...� / I OW� W � I �,� mc � soa3' . — .. .�z �r.£ ' r-� n 0 ,,}}�� ai � r � �o .,aerz s-�-atai� . . _—�--� . , - - � —�.1 Z �� E%ISiING / � � � PROPEUN / p E. So�NroO�SiRECT _._ _ �F „\ : O I I � 0 � PROPOSED DRAINAGE � �� W sooz /j I ` � NOTES I� .� 0 4RC T R I �lA i��. SE 0 T N I DIM J�' _. J �F �D Cn� �C ��LLNO �fC f iMO� T01�J._EIVT OFERP'GWNGZ. � �. J WYS. JUT� I'ALL BE DI4E�T � TO .AN��rpp�D AFCA OR � IALc�. �'.r �: S.d\/OODSIREET ' I RO CPi iiN 1 RXISTNG p I � � -' � - �I P OPERtt J. \ �1- LINE 5 �� "I BNSIN3UMMARY � � r.. �Y� "—�m' i I c FE M. E» E%ISiING BQO�� (ac) OFSCHii�irpN _ qi ^\ 9, G µT1Ek - , �% p.i0 SE,1 F%I� H SN F.,R ]. WOlJ11 51. AN� SIOE AIIC �I e .� � °. H . 4 51.1 tlAS . 6 H�SIN B � � ,. .... �a . 0�0 >ti.� _ � ° il_ 9.10 _4. i10 OOD .OVERA�91E E%ISiING I � �3 � � ,��v �I::: RIGHT OF-WAV� - � c. v. = � �i °� i °—° : � � < ° fiai . o �� o I i ° �o � g . � �� ., ,� � _..._..._ _..._.. _ � !�I ��„� , � m � , ,a�,� ,.. 1 SW3'��... ( � M1lv ' — — H�� -�� - 510 M6od11Ri! EXISII PROPERtt P -"' . �. - IJNE�' S�OWOC�sTFFET � SHEET � � � � DR-1 1 kl "�:C RCh f�Ln^n A S. JH FiCJ A�C �T aNI �MF SIJNS. v cs,o cr �i -n �� u��a�c� r n�o r o �nt[uT raa-crry cwn�.-e;. iw .,r-<,r ,.�n_i ee r�e„eo ra u ic .n co naEn oe swa�Es. � n. �aovicE �wa�E n�ouc rvcar.�E�N aRov=��v u�uE ns sr�awH. swn�E sHn�� a� �oMa�ErEo �V�2'N� T�i� R�EVLOPMENT pF 5'�4 WOO� ST3EEf. c�noauc F�.�m ,or. sio rvoo� srnEer � L�IN C� It �H :RAftEb C(N�:PCI II Cf "lf: :01 AS 9 41� �� '��i I�. W.�T�OhE S� i9Ri COLiNS. CO 5%G �5fi.n29 % pU�'CS': n�NEi1]}��M41i. �JM I � � �sc.�� o m� p�espa�k�ggdp. , �o avetl ftooh 9 0.03 1t�240 To�a��,ea C <a0000 � PROPOSEDIMPERVIOUSNESS �sp R) Sunacslrtproveman� ,o,��Aa��z��, o a ,a9zo 0 oz Pa�e �so eooi� f1VB9 o.on i .o avq. .o�elArea 0.10 a400.00 I NET INCREASE OF 862 S.F. OF IMPERVIOUS AREA LEGEND OF SYMPOlS prec o..-.. Eµ _ _-. cns � ��• ��ro�� , , — _ _ -- o� ��s F�ow o�a-�no� _.... �.,.. Ex�s,h� �o��R� o PRCPGSED CON�.RE � � PRCPGSE� D01miPG�1 �s • � Know whaYs bO�OW. �, CB��beforeyoutlig. N //II\\ i2 Consultants, Inc. 16911 Potts Place Mead. Colorado 970.217.9148 o\41159� W �,,,,, E l� � � Q 0 U �U Z � W Z W � W�Z � �Wg O F—a'p. U � J Z � O � �Q � �� w ow w N� � Z � � � O O � 0 � SHEET GR-1