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TIMBERLINE CHURCH PROPERTY ODP - ODP210003 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT
TIMBERLINE CHURCH ODP MASTER DRAINAGE STUDY CITY OF FORT COLLINS, COLORADO Martin/Martin, Inc. Project No.: 20.0336 June 30, 2021 Prepared For: Timberline Church 2908 South Timberline Road Fort Collins, Colorado 80525 Prepared By: Martin/Martin, Inc. 12499 West Colfax Avenue Lakewood, Colorado 80215 303.431.6100 Principal-in-Charge: Scott E. Paling, PE Project Manager: Melyssa C. Hartzell, PE Project Engineer: Tom Ogren, EIT II TABLE OF CONTENTS I. GENERAL LOCATION AND EXISTING SITE INFORMATION ..................................................................... 1 A. General Location ............................................................................................................................... 1 B. Existing Site information ................................................................................................................... 1 II. MAJOR DRAINAGE BASIN DESCRIPTION ............................................................................................... 2 A. Overall Basin Description .................................................................................................................. 2 B. Master Planning Improvements ....................................................................................................... 2 C. Existing Drainage Facilities ................................................................................................................ 3 III. FLOODPLAIN INFORMATION ................................................................................................................. 4 IV. PROJECT DESCRIPTION .......................................................................................................................... 4 V. PROPOSED DRAINAGE FACILITIES ......................................................................................................... 4 A. General Concept ............................................................................................................................... 4 B. Proposed Drainage Patterns ............................................................................................................. 6 C. Detention Basin and Outlet Design ................................................................................................... 9 D. Area to be Serviced ........................................................................................................................... 9 E. Low Impact Design (LID).................................................................................................................... 9 F. Potential Impacts .............................................................................................................................. 9 G. Conveyance of Minor and Major Stormwater .................................................................................. 9 VI. CONCLUSION ....................................................................................................................................... 10 A. Master Plan Conformance .............................................................................................................. 10 B. Criteria Compliance ......................................................................................................................... 10 REFERENCES .............................................................................................................................................. 101 APPENDICES Appendix A - Maps 1. Vicinity Map 2. FEMA FIRM Map 3. Fort Collins Flood Hazard Map 4. NRCS Soils Map 5. USFW Wetlands Mapper 6. ECS Report Feature Delineations Appendix B - Hydrologic Calculations 1. Development Imperviousness Assessment 2. Rational Calculations Appendix C - Supporting Documents 1. Geotechnical Report 2. Foothills Basin Map 3. Pinecone PUD Drainage Plan 4. Ft. Collins IDF Curves 5. Relevant Ft. Collins Criteria Appendix D - Drainage Plans 1. 2007 Report Drainage Plan 3. ODP Drainage Map I. GENERAL LOCATION AND EXISTING SITE INFORMATION A. General Location The Timberline Church ODP (hereafter referred to as “PROJECT”) site is located at 2908 Timberline Road in Fort Collins, Colorado 80525. The PROJECT lies within the Tract A and Lots 1, 2, and 5 of the Timberline Church PUD. Specifically, in the West half of Section 29, Township 7 North, Range 68 West of the 6th Principal Meridian, City of Fort Collins, Larimer County, State of Colorado. The overall site is 37.21 acres and consists of three general areas: the main Timberline Church and associated parking lot, the Colorado State University (CSU) property, and the Timberline Housing development area. The CSU property will be transferred to Timberline Church concurrently with the Timberline Housing Project. The PROJECT is bound to the north and east by apartment complexes associated with the Rigden Farm development, to the south by the Foothills Channel and Rendezvous Trail, and to the west by Timberline Church and parking lot. Adjacent major roadways around the PROJECT site include South Timberline Road to the west and Custer Drive to the north. A vicinity map is provided in Figure 1. Figure 1: Timberline Church and Attainable Housing Vicinity Map B. Existing Site information The existing site consists of Timberline Church, several single-story CMU buildings, native grasses, existing asphalt drives and parking areas, concrete sidewalks, an existing water quality and detention pond (Detention Pond 211), and a drainage swale. The overall site generally slopes from the northwest to the southeast at 1%. The Timberline Church and associated parking lot is conveyed via existing storm infrastructure overland flow to the southeast and into and a drainage swale that discharge into Detention Pond 211. The CSU property overland flows to the southeast undetained directly into the Foothills Channel. The Timberline Housing Project site drains through curb and gutter, storm inlets and storm pipe, or overland flow into Detention Pond 211. Detention Pond 211 releases through two outlet structures into the Foothills Channel. The PROJECT is located within the Foothills Master Drainage Basin. II. MAJOR DRAINAGE BASIN DESCRIPTION A. Overall Basin Description The PROJECT lies entirely within the Foothills Basin which is generally bound by Taft Hill, Ziegler, Horsetooth, and Drake Road. The Foothills Basin is mostly developed with commercial and mixed use residential. The basin drains from west to east through open channels and storm infrastructure to the Fossil Creek Reservoir Inlet Ditch (FCRID). Site changes developed by the PROJECT are anticipated to have no adverse impacts and are considered to be negligible. Additionally, the PROJECT is anticipated to comply with the intended land use of the Foothills Basin. A vicinity map of the Foothills Basin is provided in Figure 2. Figure 2: Foothills Basin Vicinity Map B. Master Planning Improvements A Master Plan for the Foothills Basin was completed in 1981. In 1994, the Pinecone PUD Overall Drainage Plan by Lidstone and Anderson, Inc. divided the PROJECT site into two Major Basins: 59, 60. In this report Basin 60 discharged into the channel undetained, while Basin 59 was slightly detained. Total releases from the site were limited to 97 cfs. In 1999, the Timberline Church site was further developed, as outlined in “Final Drainage and Erosion Control Study for Timberline Church,” by Northern Engineering Services, Inc., dated December 3, 1999. Water quality was provided by means of an extended detention facility (Detention Pond 211). Improvements limited discharge from the detention facility to 20 cfs. The 1999 Report also included an additional outfall to Foothills Channel and provided an overall site impervious design value based on future development plans. In 2007, the Final Drainage and Erosion Control Study for Timberline Church by Northern Engineering was developed for major developments to the site (hereafter referred to as “2007 REPORT”). This report utilized a “beat-the-peak” methodology to establish a new allowable site release of 82 cfs. The 2007 final drainage study also sub divided Basin 60 into Basins 60 and Basin 960; where the original Basin 60 consists of the Timberline Church Site and Basin 960 consists of the parcels currently owned by CSU. Refer to the Appendix for the 2007 REPORT Drainage plan and the current Existing Drainage Plan analyzed with the PROJECT. Peak flows for existing basins were not calculated as part of an existing site analysis. A drainage report titled “Timberline Attainable Housing Drainage Report City of Fort Collins, Colorado” by Martin/Martin, Inc. has been developed concurrently with this report to discuss the Timberline Housing improvements, modifications to Detention Pond 211, and proposed storm infrastructure on site (hereafter referred to as “HOUSING REPORT”). Updates triggered by the development of the PROJECT are discussed in Section 6. C. Existing Drainage Facilities 1. Detention Pond 211 Per the 2007 REPORT, Detention Pond 211 consists of three hydraulically connected sections: swale, north, and south ponds. For the remainder of this report, when referring to Detention Pond 211, it will imply the composition of these three sections. Detention Pond 211 is located along the east extents of the site. Recently surveyed topography was used in the development of the existing pond’s stage-storage curve, further discussed in the HOUSING REPORT. Updates triggered by the development of the Timberline Housing Project and considerations of potential future conditions are discussed in Section 5. Based on the 2007 REPORT, Detention Pond 211 historically outfalls to the Foothills Channel. 2. Foothills Channel The existing Foothills Channel runs from the south west to the east along southern extents of the property and discharges directly to Fossil Creek Reservoir Inlet Ditch. Future conditions outlined by this ODP are anticipated to have no adverse impacts and are considered to be negligible. 3. Fossil Creek Reservoir Inlet Ditch The existing Fossil Creek Reservoir Inlet Ditch runs north to south and discharges directly to Fossil Creek Reservoir. Future conditions outlined by this ODP are anticipated to have no adverse impacts and are considered to be negligible. III. FLOODPLAIN INFORMATION The Flood Insurance Rate Map Number 08069C1000F Panel 1000 of 1420, dated December 19, 2006, shows that the proposed development is not located within the 100-year floodway area. The FEMA FIRMETTE Map is included in the Appendix. According to the City of Fort Collins, the Foothills Channel is considered a High Risk Floodway. The floodway limits remain within the channel. Because the channel and existing detention pond are hydraulically connected, there is a possibility of back flow into the pond when the Foothills Channel WSEL is higher than the WSEL in the detention facility. A map showing the Fort Collins Floodway is included in the Appendix. IV. PROJECT DESCRIPTION The PROJECT is north of the Pinecone development and west of the Rigden Farm development. The proposed development associated with the Timberline Housing Project is described in the HOUSING REPORT and includes the construction of seven multi-family residential units, private drives and parking lots, and utility infrastructure necessary to service the proposed buildings over 9.1 acres of the overall 38.21 Timberline Church area. Potential future improvements include potential mixed-use development within the CSU parcel areas, and potential mixed-use development north of the main church within Sub-Basin C4, previously assumed as a building as part of the Phase II Improvements of the Timberline Church. The remaining site continues to remain as established in the 2007 REPORT. V. PROPOSED DRAINAGE FACILITIES A. General Concept The proposed drainage basins located on the PROJECT site consist of pavement, proposed building roof, landscaped areas, sidewalk and paved walking paths, paved parking lots, an extended detention pond, and a drainage swale. The PROJECT is comprised of seven Major Basins (Bains A, B, C, D, E, F, and G) that are discussed in Section 5.2. The HOUSING REPORT further divides Basin F, as it was developed by the HOUSING PROJECT. The HOUSING REPORT also includes additional discussion about drainage facilities that have been designed to improve Stormwater Quality and in accordance with Chapter 7 - Water Quality of the City of Fort Collins Stormwater Criteria Manual. The balance of the existing site remaining undisturbed will maintain existing drainage ways to the existing detention pond prior to discharging offsite to the Foothills Channel. The 2007 REPORT was reviewed against the as-built condition of the site. When reviewing the 2007 REPORT, it was noted that there were several basins that had slightly different areas based on current conditions than what was reported in the 2007 REPORT. It was determined that these differences were negligible and are related to accuracy of measurements. The corrected sub-basin areas are shown below in Table 1 (The naming of each Sub-Basin in this comparison was held constant to the 2007 REPORT). Various City of Fort Collins design criteria has been updated since the development of the 2007 REPORT and construction of the church. Where comparisons were made, like criteria was utilized to maintain consistency. Specifically, the rational analysis used the current value of 2% for landscaped areas where the overall site imperviousness assessment compared the conditions utilizing the 2007 REPORT landscape impervious value of 0%. The corrected runoff coefficients are shown below in Table 1. Sub-Basin Sub-Basin Area (AC) Sub-Basin Area (AC) C2 C100 Q2 (CFS) Q100 (CFS) A1 6.39 6.37 0.83 1.00 12.22 51.16 A2 0.31 0.31 0.94 1.00 0.83 3.09 A3 2.16 2.13 0.75 0.93 3.91 17.09 A4 0.08 0.08 0.95 1.00 0.22 0.79 B1 1.69 1.72 0.84 1.00 3.27 13.55 B2 0.90 0.86 0.9 1.00 2.07 7.96 B3 1.71 0.48 0.95 1.00 1.29 4.75 B4 1.35 1.33 0.91 1.00 3.34 12.81 B5 0.04 0.02 0.95 1.00 0.06 0.21 C1 3.31 3.33 0.89 1.00 6.96 27.3 C2 0.09 1.27 0.91 1.00 3.19 12.26 C3 1.82 1.71 0.95 1.00 4.63 17.01 C4 2.10 2.17 0.95 1.00 5.88 21.63 D1 7.65 7.93 0.69 0.86 8.55 37.4 D2 0.89 0.80 0.92 1.00 2.02 7.67 E1 2.26 2.31 0.27 0.33 1.76 7.67 OS-1 3.06 3.02 0.88 1.00 5.45 21.63 OS-2 1.43 1.41 0.88 1.00 2.55 10.11 TOTAL 37.25 37.25 0.66 0.92 68.20 274.09 Note: Black values are area assessments based on current conditions and proposed future developments and Red values are from the 2007 REPORT Table 1: Composite Site Imperviousness Summary As this ODP assumes property transfer of the CSU parcels to Timberline Church, the total site area was increased to include the full property for Sub-Basin OS-2 (the 1.41 acres within OS-2 from the 2007 study cuts off the southern portion of the parcel). A comparison of the total site areas in the associated drainage studies are summarized in Table 2 below. Value ODP 2007 REPORT Site Area (acres) 37.86 37.25 Table 2: Composite Site Comparison The design approach (beat the peak) of the Detention Pond 211 was not changed. Minor infilling into the pond will occur with the PROJECT resulting in a slight decrease of storage capacity. This reduction is offset by enlarging the pond in different areas discussed further in the HOUSING REPORT. B. Proposed Drainage Patterns Runoff patterns established in the 2007 report are intact. The HOUSING REPORT establishes the drainage patterns and facilities necessary to convey and treat runoff generated by and conveyed through the HOUSING PROJECT. As discussed in HOUSING REPORT, several sub- basins were updated from the 2007 REPORT. The affected basins (A1, A2, A3, B3, B4, C2, D1, D2, E1, and E2) were revised with new basin names. Several sub-basins established in the 2007 report have been grouped into Basin F with this ODP. 1. Major Basins Descriptions Basin A - Basin A consists of mainly the southern existing church parking lot and an existing courtyard on the west side of the existing Timberline Church. Additionally, Basin A contains a portion of Timberline Road and parking lot drives. Basin A is located in the central portion of the PROJECT and does not include any development modifications. Basin A has increased in size from the 2007 report (to 6.53 acres from 6.39 acres) due to a portion of Timberline Road shown within CSU Parcel 2 (Sub-Basin E2 -2007 Report Sub-Basin OS-2). As CSU Parcel 2 develops, it is unlikely that Timberline Road runoff will be routed through the site. Therefore, this area has been wrapped into Sub-Basin A1, following current drainage patterns. Stormwater runoff developed within Basin A drains overland and is captured by curb and gutter directed towards Design Point A1. Existing grated inlets at Design Point A1 collect and route runoff to Detention Pond 211. Basin B - Basin B consists of the south central existing church parking lot. Basin B is located in the central portion of the PROJECT and does not include any development modifications. Stormwater runoff developed within Basin B drains overland and is captured by curb and gutter directed towards Design Point B1 and B2. Existing inlets at Design Points B1 and B2 collect and route runoff to Detention Pond 211. Basin C - Basin C consists of the existing Church roof and east portion of the existing church parking lot. Sub-Basin C4 (2.10 acres) is included within Basin C, is currently undeveloped landscaped area and is intended to be improved in the future as a mixed- use development with an overall imperviousness established at 91-percent. This Sub- Basin was analyzed in the 2007 Report as a future Phase 2 building. No modifications to the 2007 drainage design for Sub-Basin C4 are proposed. As the 2.10 acres within Sub- Basin C4 develop, rooftop runoff and site flows should be directed towards Design Point 4, with an existing 24” storm sewer intended to collect and route flows to Detention Pond 211. Detention Pond 211 accommodates the full development of Sub-Basin C4 at 91-percent imperviousness for water quality and 100-year detention volumes. Future development within Sub-Basin C4 will need to comply with current site-specific City of Fort Collins LID and water quality regulations. Stormwater runoff developed within Basin C is collected via roof drains and existing storm sewer and is routed to Design Point C1. The Timberline Housing site routes this storm sewer to Detention Pond 211. Basin D - Basin D consists fully of the northern existing church parking lot. There are no development modifications within Basin D. Stormwater runoff developed within Basin D drains overland and is captured by curb and gutter and routed to Design Point D1 and directly to Pond 211 via existing swales. Basin E - Basin E consists of the two CSU parcels that will be developed in the future as mixed use and a private drive connection to Timberline Road. Basin E1 (2007 Report Sub-Basin OS-1) has decreased in size from 3.02 acres to 1.96 acres to reflect developable area and terminate at the private drive. Basin E2 (2007 Report Sub-Basin OS-2) has increased in size from 1.41 acres to 2.99 acres to include the full extents of the parcel (the 1.41 acres within OS-2 from the 2007 study cuts off the southern portion of the parcel) and has removed area with Timberline Road as detailed in the Basin A description. Basin E was not considered to be tributary to Detention Pond 211 by the Pinecone PUD and 2007 REPORT and, if developed, will be required to provide detention and water quality per the City of Fort Collins criteria. Stormwater runoff will need to be captured by future storm infrastructure and treated for on-site for water quality and detention before discharging to the Foothills Channel via storm outfall at Design Point E2. Basin E is historically tributary to the Foothills Channel. Basin F - Basin F consists of Timberline Housing development area and is further sub divided and detailed within the HOUSING REPORT. This basin is located along the eastern extent of the PROJECT. Basin F absorbed basins previously established in the 2007 REPORT. Stormwater runoff is captured by storm infrastructure proposed with the HOUSING PROJECT via overland flow directed towards grated inlets. The design point for Basin F is Design Point F1 located at a storm outfall proposed by the HOUSING PROJECT at the south mid-easterly extents of this Basin. This Basin is tributary to Detention Pond 211. Basin G - Basin G consists fully of Detention Pond 211. This basin is located on the eastern extents of the PROJECT. Basin G (2007 Report Sub-Basin E1) has decreased in size from 2.31 acres to 1.61 acres to reflect areas developed by Timberline Housing. Basin G, Detention Pond 211 is historically tributary to the Foothills Channel. See Figure 1 for a Sub-Basin Routing Map and Table 3 for a summary of the updated ODP Runoff conditions. 3 Figure 1: Sub-Basin Routing Map Basin PROPOSED ODP SUB- BASIN ID 2007 SUB-BASIN ID AREA OR SURFACE CHARACTERISTIC IMPACTED BY PROJECT (Y/N) ODP DESIGN POINT AREA (ACRES) IMP. (%) C2 C100 Q2 (CFS) Q100 (CFS) A1 A1, E1, E2 Y A1 6.53 83% 0.74 0.88 10.50 43.56 A4 A4 N A2 0.08 90% 0.73 0.83 0.16 0.62 A - 6.61 83% 0.74 0.88 10.66 44.18 B1 B1 N B1 1.69 92% 0.82 0.92 3.24 12.68 B2 B2 N B2 0.90 91% 0.81 0.92 1.89 7.47 B5 B5 N B5 0.04 100% 0.89 0.96 0.10 0.37 B - 2.63 92% 0.82 0.92 5.23 20.52 C1 C1 Y C1 3.31 92% 0.82 0.92 6.31 24.68 C4 C4 Y C4 2.10 91% 0.74 0.84 3.94 15.58 C3 C3 Y C3 1.82 90% 0.74 0.83 3.37 13.19 C - 7.23 91% 0.78 0.87 13.62 53.45 D1 D1 Y D1 7.40 57% 0.52 0.76 5.97 30.42 E1 1.96 Y E1 1.96 90% 0.95 1.00 4.29 15.73 E2 2.99 Y E2 2.99 90% 0.95 1.00 6.54 24.02 E - 4.94 90% 0.95 1.00 10.83 39.75 *F A2, A3, B3, B4, C2, D2, E1 Y F1 7.46 73% 0.63 0.80 12.99 57.97 G E1 Y G1 1.60 3% 0.07 0.52 0.29 7.61 SITE COMPOSITE: 37.86 76% 0.69 0.84 59.59 253.90 *Refer to the Timberline attainable Housing Drainage Report, dated June 2, 2021, by Martin/Martin, Inc. for sub-basin descriptions and routing within the overall basin. All flows within and tributary to Basin F are tributary to Basin G for water quality and detention. Table 3: Summary of Basins 3 Per the drainage patterns developed in the 2007 REPORT, the overall site has to remain under an overall composite percent imperviousness of 80%. The ODP, including future development plans is in compliance with the 2007 report. As future parcels are developed, each site will have to be reevaluated to confirm compliance with the drainage conditions established in this ODP and the current City of Fort Collins Stormwater Criteria. C. Detention Basin and Outlet Design The HOUSING REPORT includes modifications to Detention Pond 211 to provide water quality and 100-year detention for added impervious area. While Detention Pond 211 has capacity for the future development within Sub-Basin C4 as established in the 2007 REPORT, it is likely Sub-Basin C4 will have to provide site specific water quality features meeting current City of Fort Collins Stormwater and LID Criteria. The two CSU parcels, Basins E1 and E2 are not tributary to Detention Pond 211 and outfall directly to Foothills Channel. Basins E1 and E2 will need to provide on-site water quality and detention, meeting current City of Fort Collins Stormwater Criteria when those parcels are developed. D. Area to be Serviced No runoff patterns were modified by this ODP. Runoff patterns established in the 2007 report are intact. The HOUSING REPORT establishes the drainage patterns and facilities necessary to convey and treat runoff generated by and conveyed through the HOUSING PROJECT. E. Low Impact Design (LID) The HOUSING PROJECT design includes the implementation of a variety of LID features into the drainage design. The HOUSING REPORT is anticipated to utilize bioretention (rain gardens), grass swales, underground filtration, and treatment train. Further discussion of design and methodology is provided in the HOUSING REPORT. Any future development within Sub-Basins C4 and Basin E will need to comply with current City of Fort Collins stormwater and LID requirements when developed. F. Potential Impacts Based on the 2007 REPORT and the Overall Drainage Plan for the Pinecone ODP, there are no known impacts from off-site basins on the Timberline Church site. This ODP is not expected to impact any zoning land use plans that are adopted by the City of Fort Collins. G. Conveyance of Minor and Major Stormwater The proposed drainage system is designed in accordance with the CRITERIA and the MANUAL. Per the CRITERIA, the 2-year and 100-year design storm events were considered as the minor and major storm events, respectively. The Rational Method was used to estimate the minor and major storm runoff generated in the proposed and existing conditions. On-site flows tributary to Detention Pond 211 will be captured by roof drains, storm inlets, or via overland flow into rain gardens or directly into Detention Pond 211. Basin E is anticipated to remain tributary to the Foothills Channel. VI. CONCLUSION A. Master Plan Conformance This report has taken into account the results and recommendations of the previous PUD developed in the 2007 REPORT for Timberline Church and the Overall Drainage Plan for the Pinecone ODP. Proposed infrastructure is anticipated to provide local benefits from both a stormwater quantity and quality perspective. B. Criteria Compliance This report has been prepared in compliance with the CRITERIA, MANUAL, and the City of Fort Collins Municipal Code, Section 3.4.3 Water Quality. The proposed drainage design is consistent with both existing and developed conditions. REFERENCES A. “City of Fort Collins Municipal Code”, Latest revision. B. “City of Fort Collins Stormwater Criteria Manual”, Latest revision. C. “Geotechnical Engineering Report”, Terracon Consultants, Inc May 5, 2021. D. “Urban Drainage and Flood Control District Drainage Criteria Manual Vol. 1, 2 and 3”, Wright- McLauglin Engineers, Latest revision. E. “Final Drainage and Erosion Control Study for Timberline Church”, Northern Engineering Services, Inc., May 9, 2007. F. “Final Drainage and Erosion Control Study for Timberline Church”, Northern Engineering Services, Inc., December 3, 1999. G. “Overall Drainage Plan for the Pinecone ODP”, Lidstone & Anderson, March 7, 1995. H. “Timberline Attainable Housing Drainage Report City of Fort Collins, Colorado” by Martin/Martin, Inc., June 2, 2021. APPENDIX A MAPS 1000 ft N➤➤N © 2021 Google © 2021 Google © 2021 Google Rigden Farm Timberline Church Foothills C h a n n el Foothills Channel Rendezvous Trail APPROXIMATE SITE LOCATION National Flood Hazard Layer FIRMette 0 500 1,000 1,500 2,000250 Feet Ü SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT SPECIAL FLOOD HAZARD AREAS Without Base Flood Elevation (BFE) Zone A, V, A99 With BFE or DepthZone AE, AO, AH, VE, AR Regulatory Floodway 0.2% Annual Chance Flood Hazard, Areas of 1% annual chance flood with average depth less than one foot or with drainage areas of less than one square mileZone X Future Conditions 1% Annual Chance Flood HazardZone X Area with Reduced Flood Risk due to Levee. See Notes.Zone X Area with Flood Risk due to LeveeZone D NO SCREEN Area of Minimal Flood Hazard Zone X Area of Undetermined Flood HazardZone D Channel, Culvert, or Storm Sewer Levee, Dike, or Floodwall Cross Sections with 1% Annual Chance 17.5 Water Surface Elevation Coastal Transect Coastal Transect Baseline Profile Baseline Hydrographic Feature Base Flood Elevation Line (BFE) Effective LOMRs Limit of Study Jurisdiction Boundary Digital Data Available No Digital Data Available Unmapped This map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standards The flood hazard information is derived directly from the authoritative NFHL web services provided by FEMA. This map was exported on 2/12/2021 at 4:14 PM and does not 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. This map image is void if the one or more of the following map elements do not appear: basemap imagery, flood zone labels, legend, scale bar, map creation date, community identifiers, FIRM panel number, and FIRM effective date. Map images for unmapped and unmodernized areas cannot be used for regulatory purposes. Legend OTHER AREAS OF FLOOD HAZARD OTHER AREAS GENERAL STRUCTURES OTHER FEATURES MAP PANELS 8 B 20.2 The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location. 1:6,000 105°2'33"W 40°33'6"N 105°1'56"W 40°32'39"N Basemap: USGS National Map: Orthoimagery: Data refreshed October, 2020 4,514 752.3 Timberline Housing - Ft. Collins Flood Hazards This map is a user generated static output from the City of Fort Collins FCMaps Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. City of Fort Collins - GIS 572.0 1: WGS_1984_Web_Mercator_Auxiliary_Sphere Feet572.00286.00 Notes Legend 3,430 City Floodplains City High Risk - Floodway City High Risk - 100 Year City Moderate Risk - 100 Year City Limits NearMap Logo United States Department of Agriculture A product of the National Cooperative Soil Survey, a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local participants Custom Soil Resource Report for Larimer County Area, ColoradoNatural Resources Conservation Service February 12, 2021 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/ portal/nrcs/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/? cid=nrcs142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface....................................................................................................................2 Soil Map..................................................................................................................5 Soil Map................................................................................................................6 Legend..................................................................................................................7 Map Unit Legend..................................................................................................8 Map Unit Descriptions..........................................................................................8 Larimer County Area, Colorado......................................................................10 73—Nunn clay loam, 0 to 1 percent slopes.................................................10 74—Nunn clay loam, 1 to 3 percent slopes.................................................11 References............................................................................................................13 4 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 5 6 Custom Soil Resource Report Soil Map 448815044882304488310448839044884704488550448863044887104488790448815044882304488310448839044884704488550448863044887104488790496660 496740 496820 496900 496980 497060 497140 496660 496740 496820 496900 496980 497060 497140 40° 32' 59'' N 105° 2' 22'' W40° 32' 59'' N105° 2' 1'' W40° 32' 38'' N 105° 2' 22'' W40° 32' 38'' N 105° 2' 1'' WN Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 150 300 600 900 Feet 0 45 90 180 270 Meters Map Scale: 1:3,190 if printed on A portrait (8.5" x 11") sheet. Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Unit Polygons Soil Map Unit Lines Soil Map Unit Points Special Point Features Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit Gravelly Spot Landfill Lava Flow Marsh or swamp Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip Sodic Spot Spoil Area Stony Spot Very Stony Spot Wet Spot Other Special Line Features Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Background Aerial Photography 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 15, Jun 9, 2020 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Aug 11, 2018—Aug 12, 2018 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. Custom Soil Resource Report 7 Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 73 Nunn clay loam, 0 to 1 percent slopes 24.5 97.7% 74 Nunn clay loam, 1 to 3 percent slopes 0.6 2.3% Totals for Area of Interest 25.1 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, Custom Soil Resource Report 8 onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Custom Soil Resource Report 9 Larimer County Area, Colorado 73—Nunn clay loam, 0 to 1 percent slopes Map Unit Setting National map unit symbol: 2tlng Elevation: 4,100 to 5,700 feet Mean annual precipitation: 14 to 15 inches Mean annual air temperature: 48 to 52 degrees F Frost-free period: 135 to 152 days Farmland classification: Prime farmland if irrigated Map Unit Composition Nunn and similar soils:85 percent Minor components:15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Nunn Setting Landform:Terraces Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Parent material:Pleistocene aged alluvium and/or eolian deposits Typical profile Ap - 0 to 6 inches: clay loam Bt1 - 6 to 10 inches: clay loam Bt2 - 10 to 26 inches: clay loam Btk - 26 to 31 inches: clay loam Bk1 - 31 to 47 inches: loam Bk2 - 47 to 80 inches: loam Properties and qualities Slope:0 to 1 percent Depth to restrictive feature:More than 80 inches Drainage class:Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat):Moderately low to moderately high (0.06 to 0.20 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Calcium carbonate, maximum content:7 percent Maximum salinity:Nonsaline (0.1 to 1.0 mmhos/cm) Sodium adsorption ratio, maximum:0.5 Available water capacity:High (about 9.1 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 4e Hydrologic Soil Group: C Ecological site: R067BY042CO - Clayey Plains Hydric soil rating: No Custom Soil Resource Report 10 Minor Components Heldt Percent of map unit:10 percent Landform:Terraces Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Ecological site:R067BY042CO - Clayey Plains Hydric soil rating: No Wages Percent of map unit:5 percent Landform:Terraces Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Ecological site:R067BY002CO - Loamy Plains Hydric soil rating: No 74—Nunn clay loam, 1 to 3 percent slopes Map Unit Setting National map unit symbol: 2tlpl Elevation: 3,900 to 5,840 feet Mean annual precipitation: 13 to 17 inches Mean annual air temperature: 50 to 54 degrees F Frost-free period: 135 to 160 days Farmland classification: Prime farmland if irrigated Map Unit Composition Nunn and similar soils:85 percent Minor components:15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Nunn Setting Landform:Terraces Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Parent material:Pleistocene aged alluvium and/or eolian deposits Typical profile Ap - 0 to 9 inches: clay loam Bt - 9 to 13 inches: clay loam Btk - 13 to 25 inches: clay loam Bk1 - 25 to 38 inches: clay loam Bk2 - 38 to 80 inches: clay loam Custom Soil Resource Report 11 Properties and qualities Slope:1 to 3 percent Depth to restrictive feature:More than 80 inches Drainage class:Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat):Moderately low to moderately high (0.06 to 0.20 in/hr) Depth to water table:More than 80 inches Frequency of flooding:None Frequency of ponding:None Calcium carbonate, maximum content:7 percent Maximum salinity:Nonsaline to very slightly saline (0.1 to 2.0 mmhos/cm) Sodium adsorption ratio, maximum:0.5 Available water capacity:High (about 9.9 inches) Interpretive groups Land capability classification (irrigated): 2e Land capability classification (nonirrigated): 3e Hydrologic Soil Group: C Ecological site: R067BY042CO - Clayey Plains Hydric soil rating: No Minor Components Heldt Percent of map unit:10 percent Landform:Terraces Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Ecological site:R067BY042CO - Clayey Plains Hydric soil rating: No Satanta Percent of map unit:5 percent Landform:Terraces Landform position (three-dimensional):Tread Down-slope shape:Linear Across-slope shape:Linear Ecological site:R067BY002CO - Loamy Plains Hydric soil rating: No Custom Soil Resource Report 12 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/national/soils/?cid=nrcs142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ home/?cid=nrcs142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 13 United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/ nrcs/detail/soils/scientists/?cid=nrcs142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/? cid=nrcs142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf Custom Soil Resource Report 14 Timber line - Housing Source: Esri, Maxar, GeoEye, Earthstar Geographics, CNES/Airbus DS,USDA, USGS, AeroGRID, IGN, and the GIS User Community Wetlands Estuarine and Marine Deepwater Estuarine and Marine Wetland Freshwater Emergent Wetland Freshwater Forested/Shrub Wetland Freshwater Pond Lake Other Riverine June 1, 2021 0 0.1 0.20.05 mi 0 0.15 0.30.075 km 1:7,218 This page was produced by the NWI mapperNational Wetlands Inventory (NWI) This map is for general reference only. The US Fish and Wildlife Service is not responsible for the accuracy or currentness of the base data shown on this map. All wetlands related data should be used in accordance with the layer metadata found on the Wetlands Mapper web site. Timberline Housing Ecological Characterization Study A-3 Figure A-3. Field-delineated features. APPENDIX B HYDROLOGIC CALCULATIONS Project Timberline Housing ODP Project #20.0336 Date 6/29/2021 Title Existing Conditions Assessment Surface C I Asphalt/Concrete 0.95 100 Gravel 0.50 40 Roofs 0.95 90 Sandy Soil 0.15 0 Clayey Soil 0.25 0 Sub-Basin Sub-Basin Area (AC) Sub-Basin Area (AC) C2 C100 Q2 (CFS) Q100 (CFS) A1 6.39 6.37 0.83 1.00 12.22 51.16 A2 0.31 0.31 0.94 1.00 0.83 3.09 A3 2.16 2.13 0.75 0.93 3.91 17.09 A4 0.08 0.08 0.95 1.00 0.22 0.79 B1 1.69 1.72 0.84 1.00 3.27 13.55 B2 0.90 0.86 0.9 1.00 2.07 7.96 B3 1.71 0.48 0.95 1.00 1.29 4.75 B4 1.35 1.33 0.91 1.00 3.34 12.81 B5 0.04 0.02 0.95 1.00 0.06 0.21 C1 3.31 3.33 0.89 1.00 6.96 27.3 C2 0.09 1.27 0.91 1.00 3.19 12.26 C3 1.82 1.71 0.95 1.00 4.63 17.01 C4 2.10 2.17 0.95 1.00 5.88 21.63 D1 7.65 7.93 0.69 0.86 8.55 37.4 D2 0.89 0.80 0.92 1.00 2.02 7.67 E1 2.26 2.31 0.27 0.33 1.76 7.67 OS-1 3.06 3.02 0.88 1.00 5.45 21.63 OS-2 1.43 1.41 0.88 1.00 2.55 10.11 TOTAL 37.25 37.25 0.66 0.9 68.2 274.09 Notes: Black values are area assessments based on current conditions and proposed future developments Red values are from the 2007 REPORT Surface Characteristics (From 2007 Report) PROJECT INFORMATION PROJECT NAME: PROJECT NO: DESIGN BY: REVIEWED BY: JURISDICTION: REPORT TYPE: DATE: C2 C5 C10 C100 % IMPERV 0.06 0.16 0.26 0.51 2% 0.73 0.75 0.77 0.83 90% 0.89 0.90 0.92 0.96 100% 0.73 0.75 0.77 0.83 90% 37.86 0.69 0.84 75.6% AREA (ACRES) C2 C5 C10 C100 7.46 0.63 0.80 72.6% Timberline Housing 20.0336 TEO MCH ASPHALT/CONCRETE F DRIVES AND WALKS TOTAL SITE COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS Ft. Collins ODP 06/29/21 JURISDICTIONAL STANDARD COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS ROOF LANDSCAPE SUB-BASIN COMPOSITE 6/29/2021 10:28 AM COMPOSITE_C-VALUES G:\LOVATO\20.0336-Timberline Housing\ENG\DRAINAGE\Calculations\Rational Calculations (Non-UDFCD)_ODP.xlsm AREA (ACRES) C2 C5 C10 C100 5.37 0.89 0.90 0.92 0.96 100% 1.16 0.06 0.16 0.26 0.51 2% 6.53 0.74 0.77 0.80 0.88 82.6% AREA (ACRES) C2 C5 C10 C100 0.08 0.73 0.75 0.77 0.83 90% 0.08 0.73 0.75 0.77 0.83 90.0% AREA (ACRES) C2 C5 C10 C100 1.55 0.89 0.90 0.92 0.96 100% 0.14 0.06 0.16 0.26 0.51 2% 1.69 0.82 0.84 0.87 0.92 91.9% AREA (ACRES) C2 C5 C10 C100 0.82 0.89 0.90 0.92 0.96 100% 0.08 0.06 0.16 0.26 0.51 2% 0.90 0.81 0.83 0.86 0.92 90.9% AREA (ACRES) C2 C5 C10 C100 0.04 0.89 0.90 0.92 0.96 100% 0.04 0.89 0.90 0.92 0.96 100.0%SUB-BASIN COMPOSITE PERCENT IMPERVIOUSNESS B1 ASPHALT/CONCRETE LANDSCAPE SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS B2 ASPHALT/CONCRETE LANDSCAPE SUB-BASIN COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS B5 ASPHALT/CONCRETE SUB-BASIN COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS A1 ASPHALT/CONCRETE LANDSCAPE SUB-BASIN COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS A4 ROOF SUB-BASIN COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS REFER TO THE TIMBERLINE ATTAINABLE HOUSING DRAINAGE REPORT DATED JUNE 2, 2021 BY MARTIN/MARTIN, INC. FOR SUB-BASIN DESCRIPTIONS AND ROUTING WITHIN THE OVERALL BASIN. ALL FLOWS WITHIN AND TRIBUTARY TO BASIN F ARE TRIBUTARY TO BASIN G FOR WATER QUALITY AND DETENTION. 6/29/2021 10:28 AM COMPOSITE_C-VALUES G:\LOVATO\20.0336-Timberline Housing\ENG\DRAINAGE\Calculations\Rational Calculations (Non-UDFCD)_ODP.xlsm AREA (ACRES) C2 C5 C10 C100 3.03 0.89 0.90 0.92 0.96 100% 0.28 0.06 0.16 0.26 0.51 2% 3.31 0.82 0.84 0.86 0.92 91.7% AREA (ACRES) C2 C5 C10 C100 0.06 0.89 0.90 0.92 0.96 100% 1.76 0.73 0.75 0.77 0.83 90% 1.82 0.74 0.75 0.77 0.83 90.3% AREA (ACRES) C2 C5 C10 C100 0.17 0.89 0.90 0.92 0.96 100% 1.93 0.73 0.75 0.77 0.83 90% 2.10 0.74 0.76 0.78 0.84 90.8% COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS C4 ASPHALT/CONCRETE ROOF SUB-BASIN COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS C3 ASPHALT/CONCRETE ROOF SUB-BASIN COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS C1 ASPHALT/CONCRETE LANDSCAPE SUB-BASIN COMPOSITE AREA (ACRES) C2 C5 C10 C100 4.08 0.89 0.90 0.92 0.96 100% 3.28 0.06 0.16 0.26 0.51 2% 0.04 0.73 0.75 0.77 0.83 90% 7.40 0.52 0.57 0.63 0.76 56.5% AREA (ACRES) C2 C5 C10 C100 1.96 0.95 0.00 0.00 1.00 90.0% AREA (ACRES) C2 C5 C10 C100 2.99 0.95 0.00 0.00 1.00 90.0% AREA (ACRES) C2 C5 C10 C100 1.60 0.07 0.00 0.00 0.52 90.0% 37.86 0.69 0.84 75.6% G SUB-BASIN COMPOSITE TOTAL SITE COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS PERCENT IMPERVIOUSNESS PERCENT IMPERVIOUSNESS SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS PERCENT IMPERVIOUSNESS D1 ASPHALT/CONCRETE LANDSCAPE ROOF SUB-BASIN COMPOSITE E2 SUB-BASIN COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS E1 SUB-BASIN COMPOSITE SUB-BASIN SURFACE CHARACTERISTICS COMPOSITE RUNOFF COEFFICIENTS REFER TO THE TIMBERLINE ATTAINABLE HOUSING DRAINAGE REPORT DATED JUNE 2, 2021 BY MARTIN/MARTIN, INC. FOR SUB-BASIN DESCRIPTIONS AND ROUTING WITHIN THE OVERALL BASIN. ALL FLOWS WITHIN AND TRIBUTARY TO BASIN F ARE TRIBUTARY TO BASIN G FOR WATER QUALITY AND DETENTION. BASIN TO BE FUTURE MIXED USE ASSUMED AS COMMERCIAL INDUSTRIAL TO BE CONSERVATIVE. C2 = 0.95*1 = 0.95 C100=0.95*1.25 = 1.00 BASIN TO BE FUTURE MIXED USE ASSUMED AS COMMERCIAL INDUSTRIAL TO BE CONSERVATIVE. C2 = 0.95*1 = 0.95 C100=0.95*1.25 = 1.00 CALCULATED BY:JOB NO:CHECKED BY:PROJECT:DATE:Is Project Urban? YesAREA LENGTH SLOPEtiLENGTH SLOPE VEL.ttCOMP.TOT. LENGTH SLOPE IMPtc tcac ft ft/ft min ft ft/ft fps min tc ft ft/ft % First DP min(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)(16) (17)F F1 0.63 7.46 90 0.0200 6.40.00 0.0 6.4 90.0 0.02 72.6% 6.4A1 A1 0.77 6.53 150 0.0150 6.4 720 0.0210 20 2.90 4.1 10.5 870.0 0.02 82.6% 16.0 10.5A4 A4 0.75 0.08 25 0.0200 2.5 215 0.0100 20 2.00 1.8 4.3 240.0 0.0190.0% 12.4 5.0B1 B1 0.84 1.69 360 0.0200 7.1 200 0.0100 20 2.00 1.7 8.8 560.0 0.02 91.9% 11.9 8.8B2 B2 0.83 0.90 200 0.0200 5.5 125 0.0100 20 2.00 1.0 6.5 325.0 0.02 90.9% 11.5 6.5B5 B5 0.90 0.04 10 0.0200 0.90.00 0.0 0.9 10.0 0.02 100.0% 5.0C1 C1 0.84 3.31 375 0.0250 6.7 255 0.0100 20 2.00 2.1 8.8 630.0 0.02 91.7% 12.4 8.8C3 C3 0.75 1.82 200 0.0200 7.10.00 0.0 7.1 200.0 0.02 90.3% 7.1C4 C4 0.76 2.10 200 0.0200 6.90.00 0.0 6.9 200.0 0.02 90.8% 6.9D1 D1 0.57 7.40 140 0.0140 10.1 1365 0.0100 20 2.00 11.4 21.5 1505.0 0.01 56.5% 29.8 21.5E1 E1 0.95 1.96 50 0.0200 1.5 900 0.0100 20 2.00 7.5 9.0 950.0 0.01 90.0% 17.6 9.0E2 E2 0.95 2.99 50 0.0200 1.5 900 0.0100 20 2.00 7.5 9.0 950.0 0.01 90.0% 17.6 9.0G G1 0.07 1.60 25 0.0250 6.90.00 0.0 6.9 25.0 0.03 90.0% 6.9*Velocity (V) = CvSw0.5TABLE 6-2*Table 6-2, UDFCD (V.1), Chapter 6, Page 6-5in which: Cv = Conveyance Coefficient (See Table Above)Sw = Watercourse Slope (ft/ft)TEOMCH06/29/21INITIAL/OVERLANDTIME OF CONCENTRATION SUMMARYTRAVEL TIME20.0336Timberline HousingSTANDARD FORM SF-2(RATIONAL METHOD PROCEDURE)REMARKStc CHECK (URBANIZED BASINS)Type of Land SurfaceConveyance Coefficient, CvNearly Bare Ground10Grassed Waterway155Short Pasture and Lawns7Paved Areas and Shallow Paved Swales20Heavy Meadow2.5Tillage / FieldBASINDESIGN POINTC5CvDATASUB-BASINTIME (ti)(tt)TOC6/29/2021 10:25 AMG:\LOVATO\20.0336-Timberline Housing\ENG\DRAINAGE\Calculations\Rational Calculations (Non-UDFCD)_ODP.xlsm*REFER TO THE TIMBERLINE ATTAINABLE HOUSING DRAINAGE REPORT DATED JUNE 2, 2021 BYMARTIN/MARTIN, INC. FOR SUB-BASIN DESCRIPTIONS AND ROUTING WITHIN THE OVERALL BASIN.ALL FLOWS WITHIN AND TRIBUTARY TO BASIN F ARE TRIBUTARY TO BASIN G FOR WATER QUALITYAND DETENTION.** CALCULATED BY:TEOJOB NO:20.0336CHECKED BY:MCHPROJECT:Timberline HousingDATE:06/29/21DESIGN STORM:2-YEARONE-HR PRECIP:0.82(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)F F1 7.46 0.63 6.4 4.70 2.59 12.99A1 A1 6.53 0.74 10.5 4.83 2.17 10.50A4 A4 0.08 0.73 5.0 0.06 2.78 0.16B1 B1 1.69 0.82 8.8 1.39 2.33 3.24B2 B2 0.90 0.81 6.5 0.73 2.58 1.89B5 B5 0.04 0.89 5.0 0.04 2.78 0.10C1 C1 3.31 0.82 8.8 2.71 2.32 6.31C3 C3 1.82 0.74 7.1 1.34 2.51 3.37C4 C4 2.10 0.74 6.9 1.55 2.53 3.94D1 D1 7.40 0.52 21.5 3.85 1.55 5.97E1 E1 1.96 0.95 9.0 1.86 2.31 4.29E2 E2 2.99 0.95 9.0 2.84 2.31 6.54G G1 1.60 0.07 6.9 0.11 2.54 0.290.950.95I.Return Period: 2-YEAR 5-YEAR 10-YEAR 100-YEARDepth In Inches: 0.82 1.00 1.40 2.86*Equation 5-1, UDFCD (V.1), Chapter 5, Page 5-9*Rainfall Intensity:In Which: I = Rainfall Intensity (Inches Per Hour)P1 = 1-Hour Point Rainfall Depth (Inches)tc = Time Of Concentration (Minutes)STANDARD FORM SF-3STORM DRAINAGE SYSTEM DESIGN(RATIONAL METHOD PROCEDURE)CxA (AC)I (IN/HR)Q (CFS)REMARKSAREA (AC)RUNOFF COEFFtc (MIN)BASIN DESIGN POINTDIRECT RUNOFFTOTAL RUNOFFtc (MIN)S(CxA) (AC)I (IN/HR)Q (CFS)2-YEAR6/29/2021 10:25 AMG:\LOVATO\20.0336-Timberline Housing\ENG\DRAINAGE\Calculations\Rational Calculations (Non-UDFCD)_ODP.xlsm***REFER TO THE TIMBERLINE ATTAINABLE HOUSING DRAINAGE REPORT DATED JUNE 2,2021 BY MARTIN/MARTIN, INC. FOR SUB-BASIN DESCRIPTIONS AND ROUTING WITHIN THEOVERALL BASIN. ALL FLOWS WITHIN AND TRIBUTARY TO BASIN F ARE TRIBUTARY TOBASIN G FOR WATER QUALITY AND DETENTION. CALCULATED BY:TEOJOB NO:20.0336CHECKED BY:MCHPROJECT:Timberline HousingDATE:06/29/21DESIGN STORM:100-YEARONE-HR PRECIP:2.86(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)F F1 7.46 0.80 6.4 5.97 9.04 57.97A1 A1 6.53 0.88 10.5 5.75 7.58 43.56A4 A4 0.08 0.83 5.0 0.06 9.70 0.62B1 B1 1.69 0.92 8.8 1.56 8.14 12.68B2 B2 0.90 0.92 6.5 0.83 8.99 7.47B5 B5 0.04 0.96 5.0 0.04 9.70 0.37C1 C1 3.31 0.92 8.8 3.04 8.11 24.68C3 C3 1.82 0.83 7.1 1.51 8.75 13.19C4 C4 2.10 0.84 6.9 1.76 8.83 15.58D1 D1 7.40 0.76 21.5 5.62 5.41 30.42E1 E1 1.96 1.00 9.0 1.96 8.05 15.73E2 E2 2.99 1.00 9.0 2.99 8.05 24.02G G1 1.60 0.52 6.9 0.83 8.84 7.611.001.00Return Period: 2-YEAR 5-YEAR 10-YEAR 100-YEARDepth In Inches: 0.82 1.00 1.40 2.86*Equation 5-1, UDFCD (V.1), Chapter 5, Page 5-9*Rainfall Intensity:In Which: I = Rainfall Intensity (Inches Per Hour)P1 = 1-Hour Point Rainfall Depth (Inches)tc = Time Of Concentration (Minutes)BASIN DESIGN POINTDIRECT RUNOFFTOTAL RUNOFFtc (MIN)S(CxA) (AC)I (IN/HR)Q (CFS)REMARKSAREA (AC)RUNOFF COEFFtc (MIN)STANDARD FORM SF-3STORM DRAINAGE SYSTEM DESIGN(RATIONAL METHOD PROCEDURE)CxA (AC)I (IN/HR)Q (CFS)100-YEAR6/29/2021 10:25 AMG:\LOVATO\20.0336-Timberline Housing\ENG\DRAINAGE\Calculations\Rational Calculations (Non-UDFCD)_ODP.xlsm***REFER TO THE TIMBERLINE ATTAINABLE HOUSING DRAINAGE REPORT DATED JUNE 2,2021 BY MARTIN/MARTIN, INC. FOR SUB-BASIN DESCRIPTIONS AND ROUTING WITHIN THEOVERALL BASIN. ALL FLOWS WITHIN AND TRIBUTARY TO BASIN F ARE TRIBUTARY TOBASIN G FOR WATER QUALITY AND DETENTION. Project Timberline Housing ODP Project #20.0336 Date 6/29/2021 Title Composite Site Assessment Basin PROPOSED ODP SUB- BASIN ID 2007 SUB- BASIN ID AREA OR SURFACE CHARACTERISTIC IMPACTED BY PROJECT (Y/N) ODP DESIGN POINT AREA (ACRES)IMP. (%) C2 C100 Q2 (CFS) Q100 (CFS) A1 A1, E1, E2 Y A1 6.53 83% 0.74 0.88 10.5 43.56 A4 A4 N A4 0.08 90% 0.73 0.83 0.16 0.62 A 6.61 83% 0.74 0.88 10.66 44.18 B1 B1 N B1 1.69 92% 0.82 0.92 3.24 12.68 B2 B2 N B2 0.90 91% 0.81 0.92 1.89 7.47 B5 B5 N B5 0.04 100% 0.89 0.96 0.10 0.37 B 2.63 92% 0.82 0.92 5.23 20.52 C1 C1 N C1 3.31 92% 0.82 0.92 6.31 24.68 C4 C4 N C4 2.10 91% 0.74 0.84 3.94 15.58 C3 C3 N C3 1.82 90% 0.74 0.83 3.37 13.19 C 7.23 91% 0.78 0.87 13.62 53.45 D1 Y D1 7.40 57% 0.52 0.76 5.97 30.42 E1 OS-1 Y E1 1.96 90% 0.95 1.00 4.29 15.73 E2 OS-2 Y E2 2.99 90% 0.95 1.00 6.54 24.02 E 4.94 90% 0.95 1.00 10.83 39.75 A2, A3, B3, B4, C2, D2, E1 Y F1 7.46 73% 0.63 0.80 12.99 57.97 E1 Y G1 1.60 3% 0.07 0.52 0.29 7.61 37.86 76% 0.69 0.84 59.59 253.90 SITE COMPOSITE: *REFER TO THE TIMBERLINE ATTAINABLE HOUSING DRAINAGE REPORT DATED JUNE 2, 2021 BY MARTIN/MARTIN, INC. FOR SUB-BASIN DESCRIPTIONS AND ROUTING WITHIN THE OVERALL BASIN. ALL FLOWS WITHIN AND TRIBUTARY TO BASIN F ARE TRIBUTARY TO BASIN G FOR WATER QUALITY AND DETENTION. *F G D1 - - - - APPENDIX C SUPPORTING DOCUMENTS REPORT COVER PAGE Geotechnical Engineering Report __________________________________________________________________________ Timberline Apartments Fort Collins, Colorado May 5, 2021 Terracon Project No. 20215032 Prepared for: Tetrad Property Group, LLC Fort Collins, Colorado Prepared by: Terracon Consultants, Inc. Fort Collins, Colorado T r o u t m a nParkPond SpringCreekDr a g o n f l y P o n d Heron PondNew Mercer DitchWa r ren L a k e FossilCreekReservoirInletPle a s ant V alley an d LakeCanalSprin g C reek Larim er CountyCanal#2 S p r i n g C r e e kParkPond W o o d w a r dGoverno rPond P arkwoodLakeP r o s p e c t P o n d #2North Larim er County Canal #2 O a k R i dg eFederalBld gPond H a r m onyReservoir G o l d e nMeadow sPond Canvasback Pond Foothills Channel R o l l a n dMoorePond F t C o l l i n sGolfCoursePond A v e r yPond S pr i n g Creek SherwoodLateral L a k eSherwoodCachela Poudr eRiverCanal #2 New Mercer DitchNew M erce r Ditch B i g P o n d W e s t M i l n eP o n d Larimer County Canal #2O a k R i d g eFederalBld gPond Dixon C anyonLa teralC o n f l u e n c e a n d W i g e o n Po n d s E a s t M i l n e P o n d FOOTHIL LS BASIN K FOO THILLS BASIN APPROXIMATE PROJECT LOCATION 960 14.22 XX XX 60 14.22 XX XX FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 8 Table 3.4-1. IDF Table for Rational Method Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) 5 2.85 4.87 9.95 39 1.09 1.86 3.8 6 2.67 4.56 9.31 40 1.07 1.83 3.74 7 2.52 4.31 8.80 41 1.05 1.80 3.68 8 2.40 4.10 8.38 42 1.04 1.77 3.62 9 2.30 3.93 8.03 43 1.02 1.74 3.56 10 2.21 3.78 7.72 44 1.01 1.72 3.51 11 2.13 3.63 7.42 45 0.99 1.69 3.46 12 2.05 3.50 7.16 46 0.98 1.67 3.41 13 1.98 3.39 6.92 47 0.96 1.64 3.36 14 1.92 3.29 6.71 48 0.95 1.62 3.31 15 1.87 3.19 6.52 49 0.94 1.6 3.27 16 1.81 3.08 6.30 50 0.92 1.58 3.23 17 1.75 2.99 6.10 51 0.91 1.56 3.18 18 1.70 2.90 5.92 52 0.9 1.54 3.14 19 1.65 2.82 5.75 53 0.89 1.52 3.10 20 1.61 2.74 5.60 54 0.88 1.50 3.07 21 1.56 2.67 5.46 55 0.87 1.48 3.03 22 1.53 2.61 5.32 56 0.86 1.47 2.99 23 1.49 2.55 5.20 57 0.85 1.45 2.96 24 1.46 2.49 5.09 58 0.84 1.43 2.92 25 1.43 2.44 4.98 59 0.83 1.42 2.89 26 1.4 2.39 4.87 60 0.82 1.4 2.86 27 1.37 2.34 4.78 65 0.78 1.32 2.71 28 1.34 2.29 4.69 70 0.73 1.25 2.59 29 1.32 2.25 4.60 75 0.70 1.19 2.48 30 1.30 2.21 4.52 80 0.66 1.14 2.38 31 1.27 2.16 4.42 85 0.64 1.09 2.29 32 1.24 2.12 4.33 90 0.61 1.05 2.21 33 1.22 2.08 4.24 95 0.58 1.01 2.13 34 1.19 2.04 4.16 100 0.56 0.97 2.06 35 1.17 2.00 4.08 105 0.54 0.94 2.00 36 1.15 1.96 4.01 110 0.52 0.91 1.94 37 1.16 1.93 3.93 115 0.51 0.88 1.88 38 1.11 1.89 3.87 120 0.49 0.86 1.84 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 9 Figure 3.4-1. Rainfall IDF Curve – Fort Collins FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 1.0 Overview 1.1 Storm Runoff Determination Page 1 1.0 Overview This Chapter presents information that is specific to the City of Fort Collins and may be a significant deviation from the information presented in the UDFCD Manuals. Utilizing UDFCD methodologies for hydrology calculations may not be accepted by FCU. 1.1 Storm Runoff Determination The runoff analysis for a development must be based on the proposed land use for that area. Contributing runoff from upstream areas must be based on the existing land use and the topographic characteristics of those areas. All runoff calculations, requirements and assumptions must be based on the Master Drainage Plan for the area that is being developed. Natural topographic features are the basis of location for drainage easements and future runoff calculations. Average land slopes may be utilized in runoff computations unless better data is available. The drainage facilities designed must be able to handle the design flows with minimal erosion damage to the system. 1.2 Design Storm Frequencies All drainage system design and construction must take into consideration three separate and distinct drainage problems. The first is the eightieth (80th) percentile storm event or the rain event for which 80% of all rain events have an equal or smaller depth of rain. This storm event is often referred to as the “water quality storm” and is used to design water quality components of storm drainage systems. The second is the “minor storm” or “initial storm”, which is the 2-year storm in the City of Fort Collins. This is the storm that has a probability of occurring, on the average, once every two (2) years, or one that has a fifty percent (50%) probability of exceedance every year. The third is the “major storm”, which is the 100-year storm in the City of Fort Collins. This is the storm that has a probability of occurring, on the average, once every one hundred (100) years, or one that has a one percent (1%) probability of exceedance every year. RUNOFF CALCULATIONS BOTH THE 2-YEAR AND THE 100-YEAR STORM EVENTS MUST BE INCLUDED IN ALL DRAINAGE SYSTEM ANALYSES AND REPORTS FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.2 Runoff Coefficients Page 4 3.2 Runoff Coefficients Runoff coefficients used for the Rational Method are determined based on either overall land use or surface type across the drainage area. For Overall Drainage Plan (ODP) submittals, when surface types may not yet be known, land use shall be used to estimate flow rates and volumes. Table 3.2-1 lists the runoff coefficients for common types of land uses in the City. Table 3.2-1. Zoning Classification - Runoff Coefficients Land Use Runoff Coefficient (C) Residential Urban Estate 0.30 Low Density 0.55 Medium Density 0.65 High Density 0.85 Commercial Commercial 0.85 Industrial 0.95 Undeveloped Open Lands, Transition 0.20 Greenbelts, Agriculture 0.20 Reference: For further guidance regarding zoning classifications, refer to the Land Use Code, Article 4. For a Project Development Plan (PDP) or Final Plan (FP) submittals, runoff coefficients must be based on the proposed land surface types. Since the actual runoff coefficients may be different from those specified in Table 3.2-1, Table 3.2-2 lists coefficients for the specific types of land surfaces. FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.3 Time of Concentration Page 6 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 (years) Frequency Adjustment 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 The next step to approximate runoff using the Rational Method is to estimate the Time of Concentration, Tc, 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: 𝐓𝐓𝐜𝐜=𝐓𝐓𝐢𝐢+𝐓𝐓𝐭𝐭 Equation 5-3 Where: Tc = Total Time of Concentration, minutes Ti = Initial or Overland Flow Time of Concentration, minutes Tt = Channelized Flow in Swale, Gutter or Pipe, minutes 3.3.2 Overland Flow Time Overland flow, Ti, can be determined by the following equation: 𝐓𝐓𝐢𝐢=𝟏𝟏.𝟖𝟖𝟖𝟖(𝟏𝟏.𝟏𝟏−𝐂𝐂𝐂𝐂𝐂𝐂𝐟𝐟)√𝐋𝐋√𝐒𝐒𝟑𝟑 Equation 3.3-2 Where: C = Runoff Coefficient, dimensionless Cf = Frequency Adjustment Factor, dimensionless L = Length of Overland Flow, feet S = Slope, percent CXCF PRODUCT OF CXCF CANNOT EXCEED THE VALUE OF 1 OVERLAND FLOW LENGTH L=200’ MAX IN DEVELOPED AREAS L=500’ MAX IN UNDEVELOPED AREAS FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 3.0 Rational Method 3.4 Intensity-Duration-Frequency Curves for Rational Method Page 8 Table 3.4-1. IDF Table for Rational Method Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) Duration (min) Intensity 2-year (in/hr) Intensity 10-year (in/hr) Intensity 100-year (in/hr) 5 2.85 4.87 9.95 39 1.09 1.86 3.8 6 2.67 4.56 9.31 40 1.07 1.83 3.74 7 2.52 4.31 8.80 41 1.05 1.80 3.68 8 2.40 4.10 8.38 42 1.04 1.77 3.62 9 2.30 3.93 8.03 43 1.02 1.74 3.56 10 2.21 3.78 7.72 44 1.01 1.72 3.51 11 2.13 3.63 7.42 45 0.99 1.69 3.46 12 2.05 3.50 7.16 46 0.98 1.67 3.41 13 1.98 3.39 6.92 47 0.96 1.64 3.36 14 1.92 3.29 6.71 48 0.95 1.62 3.31 15 1.87 3.19 6.52 49 0.94 1.6 3.27 16 1.81 3.08 6.30 50 0.92 1.58 3.23 17 1.75 2.99 6.10 51 0.91 1.56 3.18 18 1.70 2.90 5.92 52 0.9 1.54 3.14 19 1.65 2.82 5.75 53 0.89 1.52 3.10 20 1.61 2.74 5.60 54 0.88 1.50 3.07 21 1.56 2.67 5.46 55 0.87 1.48 3.03 22 1.53 2.61 5.32 56 0.86 1.47 2.99 23 1.49 2.55 5.20 57 0.85 1.45 2.96 24 1.46 2.49 5.09 58 0.84 1.43 2.92 25 1.43 2.44 4.98 59 0.83 1.42 2.89 26 1.4 2.39 4.87 60 0.82 1.4 2.86 27 1.37 2.34 4.78 65 0.78 1.32 2.71 28 1.34 2.29 4.69 70 0.73 1.25 2.59 29 1.32 2.25 4.60 75 0.70 1.19 2.48 30 1.30 2.21 4.52 80 0.66 1.14 2.38 31 1.27 2.16 4.42 85 0.64 1.09 2.29 32 1.24 2.12 4.33 90 0.61 1.05 2.21 33 1.22 2.08 4.24 95 0.58 1.01 2.13 34 1.19 2.04 4.16 100 0.56 0.97 2.06 35 1.17 2.00 4.08 105 0.54 0.94 2.00 36 1.15 1.96 4.01 110 0.52 0.91 1.94 37 1.16 1.93 3.93 115 0.51 0.88 1.88 38 1.11 1.89 3.87 120 0.49 0.86 1.84 FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5) 4.0 SWMM 4.1 Input Parameters Page 11 Table 4.1-2. Land Use - Percent Impervious Land Use Percent Impervious (%) 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: For further guidance regarding 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 Surface Type Percent Impervious (%) 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 APPENDIX D DRAINAGE PLANS LEASING OFFICES TIMBERLINE ROAD(R.O.W. VARIES)EXISTINGTIMBERLINECHURCHBUILDING 6BUILDING 5BUILDING 3BUILDING 2BUILDING 1BUILDING 7BUILDING 4FOOTHILLS CHANNELA1B1B2C1C4C3B5A4D1F1G1WATER QUALITYAND DETENTIONPONDCSU PARCEL 1FUTURE MIXED USECSU PARCEL 2FUTURE MIXED USEPRIVATE DRIVEFUTURE MIXED USEDEVELOPMENTTIMBERLINEHOUSING36" FESTRIPLE TYPE 16 VALLEY INLET10' TYPE R INLET36" FES34"X53" FES26"x45" FESSINGLE TYPE 16 VALLEY INLETDOUBLE TYPE 16 VALLEY INLETSINGLE TYPE 16 VALLEY INLETTRIPLE TYPE 16 VALLEY INLETFOOTHILLS CHANNEL10' TYPE R INLET10' TYPE R INLET10' TYPE R INLETE2E1OWNER:DATE:SHEET TITLE:OWNER:DATE:SHEET TITLE:CHECKED BY:DRAWN BY: TIMBERLINE CHURCH ODP 2908 S TIMBERLINE RD, FORT COLLINS, CO 80525TIMBERLINE CHURCH2908 S TIMBERLINE RD,FORT COLLINS, CO 80525(970) 482-4387XXXX 6/30/2021 SUBMITTAL 244 North College Avenue #130Fort Collins, Colorado 80524P 970.409.3414www.norris-design.comNOT FORCONSTRUCTIONMARTIN/MARTINC O N S U L T I N G E N G I N E E R S12499 WEST COLFAX AVENUELAKEWOOD, COLORADO 80215303.431.6100MARTINMARTIN.COM811TIMBERLINE CHURCH O.D.P.A PARCEL OF LAND LOCATED IN THE WEST HALF OF SECTION 29,TOWNSHIP 7 NORTH, RANGE 68 WEST OF THE 6TH PRINCIPAL MERIDIANCITY OF FORT COLLINS, COUNTY OF LARIMER, STATE OF COLORADOODP 2ODP DRAINAGE MAPFOOTHILLSCHANNELG(POND)E1E2FD1A1A4C1C4C3B1B5B2