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HomeMy WebLinkAboutSOUTH COLLEGE STORAGE - FDP - FDP170019 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTFINAL DRAINAGE REPORT South College Storage Fort Collins, Colorado August 8, 2017 Prepared for: Brandon Grebe GYS LLC Real Estate / Development / Consulting Prepared by: 301 North Howes Street, Suite 100 Fort Collins, Colorado 80521 Phone: 970.221.4158 Fax: 970.221.4159 www.northernengineering.com Project Number: 1269-002  This Drainage Report is consciously provided as a PDF. Please consider the environment before printing this document in its entirety. When a hard copy is absolutely necessary, we recommend double-sided printing. August 8, 2017 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 RE: Preliminary Drainage Report for South College Storage Dear Staff: Northern Engineering is pleased to submit this Final Drainage Report for your review. This report accompanies the PDP submittal for the proposed South College Storage. This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual (FCSCM). We understand that review by the City is to assure general compliance with standardized criteria contained in the FCSCM as well as maintaining the overall Master Drainage Plan set forth by the City. If you should have any questions as you review this report, please feel free to contact us. Sincerely, NORTHERN ENGINEERING SERVICES, INC. Nicholas W. Haws, PE Blaine Mathisen Vice President Project Engineer South College Storage Preliminary Drainage Report TABLE OF CONTENTS I. General Location and Description ............................................................................... 1 A. Location ............................................................................................................................................. 1 B. Description of Property ..................................................................................................................... 1 C. Floodplain.......................................................................................................................................... 3 II. drainage basins and sub-basins .................................................................................. 3 A. Major Basin Description .................................................................................................................... 3 B. Sub-Basin Description ....................................................................................................................... 3 III. drainage DESIGN CRITERIA ...................................................................................... 4 A. Regulations........................................................................................................................................ 4 B. Four Step Process .............................................................................................................................. 4 C. Development Criteria Reference and Constraints ............................................................................ 5 D. Hydrological Criteria ......................................................................................................................... 6 E. Hydraulic Criteria .............................................................................................................................. 6 F. Floodplain Regulations Compliance .................................................................................................. 6 G. Modifications of Criteria ................................................................................................................... 6 IV. drainage FACILITY DESIGN ....................................................................................... 7 A. General Concept ............................................................................................................................... 7 B. Specific Details .................................................................................................................................. 8 V. CONCLUSIONS ........................................................................................................ 9 A. Compliance with Standards .............................................................................................................. 9 B. Drainage Concept .............................................................................................................................. 9 References ....................................................................................................................... 10 APPENDICES: APPENDIX A – Hydrologic Computations APPENDIX B – Hydraulic Computations B.1 – Storm Sewers B.2 – Inlets B.3 – Detention Facilities APPENDIX C – Water Quality Design Computations APPENDIX D – Erosion Control Report APPENDIX E – Soils Resource Report South College Storage Preliminary Drainage Report LIST OF TABLES AND FIGURES: Figure 1 - Aerial Photograph ................................................................................................. 1 Figure 2 - Proposed Site Plan ............................................................................................... 2 Figure 3 - Fort Collins Floodplains ......................................................................................... 3 MAP POCKET: Historic Drainage Exhibit Proposed Drainage Exhibit South College Storage Preliminary Drainage Report 1 I. GENERAL LOCATION AND DESCRIPTION A. Location 1. Vicinity Map Figure 1 - Aerial Photograph 2. South College Storage is in a tract of land in southeast quarter of Section 11, Township 6 North, Range 69 West of the 6th P.M., City of Fort Collins, County of Larimer, State of Colorado. 3. The project site is located at the northwest corner of Skyway Drive and College Avenue. 4. Currently the existing site has minimal storm infrastructure to convey runoff. Historically, the site sheet flows east towards Collage Ave. and is collected in an existing 30” FES at a low point along the western property line. From there the flow is conveyed via 30” RCP pipe east. The project site also has an existing drainage ditch running north to south near the southwest corner of the site. This ditch will be relocated to the west eventually but that will be associated with the future development to the south, the property owned by Trilby Holdings Group LLC. B. Description of Property 1. South College Storage is approximately 13.00 net acres. 2. The runoff generated from the project sheet flows west to east. The runoff generated in the southwest corner of the site will be collected and conveyed by the existing drainage ditch that runs north to south. The remaining portion of the site all sheet flows towards an existing 30” FES that will collect and convey the flows offsite towards Fossil Creek. The design engineers will maintain these existing flow patterns. South College Storage Preliminary Drainage Report 2 3. According to the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey Skyways Storage consists of several native soil types. Most the site (70.0 percent) consists of Kim-Thedalund loams, 3 to 15 percent slopes, which falls into Hydrologic Soil Groups B. Kim loam, 3 to 5 percent slopes, is roughly 18.1% of the site and falls into Hydrologic Soil Group B. Fort Collins loam consists of 10.7% and falls into Hydrologic Soils Group C. The remaining 1.3% of the site is made up of Midway clay loam, 5 to 25 percent slopes, which falls into Hydrologic Soils Group D. 4. The proposed development will clear all the existing vegetation along the newly proposed private drive aisle, building location, and associated parking lots (Tract A). South College Storage will not be modifying any of the area to the west of the private drive aisle (Outlot B). The area to the west will be regraded and modified during the ditch realignment, which will take place when the property to the south begins to develop. Additionally, South College Storage will try to minimize the limits of disturbance to the east of the proposed parking lots and building (Tract B). Water quality will be provided on-site by use of rain gardens and surrounding green space. South College Storage will be detaining the 100-yr event and releasing at the historic 2-yr event. However, South College Storage will be bypassing regional flows through the site. This is discussed in more detail within Section IV. Figure 2 - Proposed Site Plan 5. There is currently an existing drainage ditch that runs south to north and is located near the southwest corner of the Outlot A. This ditch will be rerouted to run parallel along the western property line when the property to the south of the South College Storage begins development. 6. The project site is within a General Commercial (CG) Zoning District. The proposed use is permitted as a use within this zone district. South College Storage Preliminary Drainage Report 3 C. Floodplain 1. The property does not lie within a plottable FEMA floodplain. However, according to FIRM Panel 08069C1000F for Larimer County, dated December 19th, 2006, this tract lies in an area of minimal flood hazard, Zone X. 2. Additionally, the project does not lie within a City floodplain either. Figure 3 - Fort Collins Floodplains II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin Description 1. South College Storage straddles the boundary between the Mail Creek Basin and the Fossil Basin. South College Storage has been design in accordance with the Fossil Creek Master Drainage Plan. B. Sub-Basin Description 1. South College Storage has historically conveyed all the generated runoff via overland flow from west to east, to a low point adjacent to College Avenue where it is captured by an existing flared end section. These flows will bypass the detention and water quality amenities being proposed for South College Storage and head directly to the existing flared end section adjacent to College Avenue. 2. Historically, the total amount of flow passing through the project site from the west (H3 and OS1) is 2.19 cfs for the Historic 2-year, and 11.05 cfs for the Historic 100- year. These flows are being captured by a Type C Inlet (near the intersection of Skyway Drive and Mars Drive). From there the runoff is conveyed via 18” RCP pipe under Mars Drive and enters a swale that will route the runoff to the existing flared end section adjacent to College Avenue. South College Storage Preliminary Drainage Report 4 3. For a more in depth analysis for the areas within the property boundary three basins were delineated; H1, H2, and H3. These basins were delineated in a way that would correspond with the proposed basins, in order to accurately determine the max allowable release rate for South College Storage site specifically. 4. Basin H1 is the area directly to the west of the College Avenue, where the existing flared end section is located (Outlot B in the proposed plat). Basin H1 is 100% landscaping and this basin will remain, for the most part, completely untouched when South College Storage is constructed. There will be some minor grading along the western portion of the basin as well as two separate swales cut during the construction but the imperviousness will remain the same. 5. Basin H2 corresponds to the area that will be being developed for South College Storage as well as half of the Mars Drive expansion. Basin H2 historically has been 100% landscaping with a Historic 2-year flowrate of 1.84 cfs. This flowrate was used to help determine our max allowable release rate from our site. More information on the max allowable release rate will be discussed further on in Section IV. 6. Basin H3 is the area to the west of the project site and east of the existing property boundary (Outlot A in the proposed plat). There is currently a ditch running northwest to southeast across this basin. However, this ditch will be reconstructed to run north to south parallel to the western property line when this area is eventually developed. For analysis purposes, it was assumed that this ditch is constantly full so any flow generated from this basin will flow east towards the ultimate design point of the existing flared end section in Basin H1. All flow generated in Basin H3 will bypass South College Storage. 7. Basin OS1 is the only offsite basin entering our site. The flow is generated by a small portion of landscaping to the west of Basin H3. Flow from OS1 enter Basin H3 and then follow the conveyance path that Basin H3 uses. 8. Currently, at the intersection of College Avenue and Skyway Drive there is a 2’ Curb Chase that is conveying runoff from Skyway to the existing flared end section in Basin H1. South College Storage is going to replace that 2’ Curb Chase with a 10’ Type R inlet to help convey any flows that are currently going through that curb chase to their historic location. 9. There are no known drainage studies for this associated project site. 10. A more detailed description of the project’s proposed drainage patterns follows in Section IV.A.4., below. 11. A full-size copy (11” x 17”) of the Historic Drainage Exhibit can be found in the Map Pocket at the end of this report. III. DRAINAGE DESIGN CRITERIA A. Regulations There are no provisions outside of FCSCM being proposed with South College Storage. South College Storage is releasing at a reduced Historic 2-year rate, providing adequate WQCV, and also meeting the LID standards set forth by the FCSCM. B. Four Step Process The overall stormwater management strategy employed with the South College Storage project utilizes the “Four Step Process” to minimize adverse impacts of urbanization on South College Storage Preliminary Drainage Report 5 receiving waters. The following is a description of how the proposed development has incorporated each step. Step 1 – Employ Runoff Reduction Practices Several techniques have been utilized with the proposed development to facilitate the reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the current use by implementing multiple Low-Impact Development (LID) strategies, including: Reducing the sites footprint as much as possible and limiting the amount of land being disturbed to the west and east of the site within the property boundary. Routing flows, to the extent feasible, through a Rain Garden to aid in the removal of pollutants from the runoff. Providing on-site detention to increase time of concentration, promote infiltration and reduce loads on existing storm infrastructure. 100% of Basin M (which will be described in Section IV will receive its water quality from a Rain Garden. Please see Section IV for further explanation of drainage patterns and LID treatment. Additionally, a map indicating how these areas were calculated is included in Appendix C. Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with Slow Release The efforts taken in Step 1 will facilitate the reduction of runoff and provide the necessary BMPs required for water quality. A majority of the stormwater that is generated on the project site will be routed into a rain garden. For the portion of the site that is unretainable it will be flowing slowly over a large grass buffer as it makes its way to the existing flared end section. Step 3 – Stabilize Drainageways As stated in Section I.B.5, above, there is a major drainageway within the property boundary. However, South College Storage is downstream of this drainageway and will not cause any adverse impacts on the existing drainageway. As previously noted, this drainageway will be getting rerouted when Outlot A gets developed. This drainageway will get moved to the west and align parallel with the western property boundary. Additionally, while this step may not seem applicable to South College Storage, the proposed project indirectly helps achieve stabilized drainageways nonetheless. Once again, site selection has a positive effect on stream stabilization. By repurposing an undeveloped, under- utilized site, combined with LID, the likelihood of bed and bank erosion is greatly reduced. Furthermore, this project will pay one-time stormwater development fees, as well as ongoing monthly stormwater utility fees, both of which help achieve citywide drainageway stability. Step 4 – Implement Site Specific and Other Source Control BMPs. South College Storage includes a three story building with an associated drive aisle, all of which will require the need for site specific source controls including: A localized trash collection system through use of individual bins stored internally. C. Development Criteria Reference and Constraints 1. There are no known drainage studies for the existing property. 2. There are no known drainage studies for any adjacent properties that will have any effect on the South College Storage project. South College Storage Preliminary Drainage Report 6 3. The subject property is essentially an "in-fill" development project, as the site is surrounded by currently developed properties. As such, several constraints have been identified during the course of this analysis that will impact the proposed drainage system, including: Mars Drive will need to tie into the existing elevation of Skyway Drive at the intersection. Existing vegetation to the east and west of the project site will be preserved. The existing grades at the project site are too steep to develop on so these grades will be modified but historic drainage patterns will be maintained. D. Hydrological Criteria 1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations associated with this development. Tabulated data contained in Table RA-7 has been utilized for Rational Method runoff calculations. 2. The Rational Method has been employed to compute stormwater runoff utilizing coefficients contained in Tables RO-11 and RO-12 of the FCSCM. 3. The Rational Formula-based Modified Federal Aviation Administration (FAA) procedure has been utilized for detention storage calculations. 4. Two separate design storms have been utilized to address distinct drainage scenarios. The first event analyzed is the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The second event considered is the “Major Storm,” which has a 100-year recurrence interval. 5. No other assumptions or calculation methods have been used with this development that are not referenced by current City of Fort Collins criteria. E. Hydraulic Criteria 1. As previously noted, the subject property historically drains towards a flared end section located adjacent to College Avenue via overland flow. 2. All drainage facilities associated with the South College Storage project are in accordance with the criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District’s (UDFCD) Urban Storm Drainage Criteria Manual. 3. As stated in Section I.C.1, above, the subject property is not located within any regulatory floodplain. 4. The South College Storage project does not propose to modify any natural drainageways. F. Floodplain Regulations Compliance 1. As previously mentioned, all structures are located outside of any FEMA 100-year or City floodplain, and thus are not subject to any floodplain regulations. G. Modifications of Criteria 1. The proposed South College Storage development is not requesting any modification to the current criteria. South College Storage Preliminary Drainage Report 7 IV. DRAINAGE FACILITY DESIGN A. General Concept 1. The main objectives of the South College Storage drainage design is to maintain historic drainage patterns, and ensure no adverse impacts to downstream properties or existing downstream infrastructure. 2. As previously mentioned, there is off-site flows entering onto the project site. 3. A list of tables and figures used within this report can be found in the Table of Contents at the front of the document. The tables and figures are located within the sections to which the content best applies. 4. The South College Storage project is composed of four major drainage basins, designated as Basins E1, M, W1, and OS.1. The drainage patterns for each major basin are further described below. Basin E1 Basin E1 is the exact same basin as the previously discussed historic basin, Basin H1. However, due to such steep grades some additional grading will occur on the western edges of this basin to eliminate the need for landscaping walls. There will also be two new swales cut in within Basin E1 to help better convey runoff from the off-site flows and the released flows to the existing flared end section adjacent to College Avenue. Basin M Basin M corresponds to all the detainable area associated with the development of South College Storage and half of Mars Drive. Basin M is further subdivided into seven (10) sub-basins, designated as Basins M1, M2, M3.a, M3.b, M3.c, M4,M5, M6, M7 and M8. Sub-basin M1 is composed of the private drive aisle and wraps around the eastern side of the proposed building. Sub-basin M2 consists of the sidewalk along the east side of Mars Drive as well as the western section of the private drive aisle adjacent to the west side of the building. Sub-basins M3.a, M3.b, and M3.c correspond to portions of the roof that will be conveyed to the drive aisle via down spouts. Sub-basin M4 is composed of the southern private drive aisle and a small portion of landscaping area adjacent to the building. Sub-basin M5 corresponds to the area designated for the Rain Garden as well as the onsite detention pond. Sub-basin M6 is affiliated with a portion of the east side of Mars Drive between a local high and low point. Sub-basin M7 is affiliated with a portion of the west side of Mars Drive between a local high and low point. Sub-basin M8 corresponds to a small portion of Mars Drive that will be entering the site via a curb chase. All the flow generated within Basin M will be treated via Rain Garden and detained on site and released at a reduced Historic 2-year flow towards the existing flared end section. Flows generated in Basin M will be collected by roof leaders and inlets located within Mars Drive as well as inlets within the private drive aisles. Basin W1 Basin W1is essentially the same basin as the historic basin H3. There is currently a drainage ditch running from northwest to southeast across the southern 1/3 of the basin. Runoff generated in this basin will bypass the South College Storage project site South College Storage Preliminary Drainage Report 8 via a Type C Inlet and 18” RCP and it will be conveyed via swales to the existing flared end section in Basin E1. Basin OS.1 Basin OS.1 is within the South College Storage project site but because of steep slopes and lack of existing storm infrastructure it is uncatchable and therefore will be sheet flowing offsite undetained and untreated. Basin OS.1 consists of a small portion of the paved intersection of Mars Drive and Skyway Drive as well as the landscaping areas on the backside of the private drive aisles. Because this area is leaving the site undetained the developed 100-year flow rate associated with Basin OS.1 (1.21 cfs) will be subtracted from the Historic 2-year flow rate from Basin H2 (1.84 cfs) for the allowable release rate (1.84 – 1.21 = 0.63 cfs). B. Specific Details 1. The main drainage problem associated with this project site is the deficiency of water quality present, and lack of existing stormwater infrastructure on the South College Storage site. The proposed site will mitigate these issues by instituting the following water quality devices and stormwater structures: The runoff generated from Basin M will be routed to a designed Rain Garden. All runoff generated from the proposed building roof will be routed to a designed Rain Garden as well. The runoff generated from Basin M will be routed to a detention pond. The remaining runoff generated from Basin OS.1 is routed across landscape areas. A 18” RCP will help convey the flows associated with the neighborhood to the west through the South College Storage site into landscape areas. 2. The allowable release rate was established by calculating the historic 2-year peak runoff rate of the project area and reducing it by the 100-year peak runoff rate of the offsite flows associated with the South College Storage project area, resulting in an overall release of 0.63 cfs (Basin H2 = 1.84 cfs; Basin OS.1 = 1.21 cfs  1.84 – 1.21 = 0.63 cfs) 3. Detention Pond and Water Quality Calculations Rain Garden M Rain Garden M was sized for the 12-hour Water Quality Capture Volume (WQCV). Calculations for Rain Garden M, based on characteristics of Basin M, indicate a WQCV of 2462 cu. ft. The total WQCV provided is 2897 cu. ft. at a water surface elevation of 5024.25 feet. All storm events above the water quality storm will overtop the emergency spillway and be conveyed to the detention pond to the south. Detention Pond M The modified FAA method was used to quantify the required detention volume. Calculations for Detention Pond M, based on characteristics of Basin M and Basin OS.1 and an adjusted release rate of 0.63 cfs, indicate a detention volume of 38,145 cu. ft. The 100-year water surface elevation in Detention Pond M is at an elevation of 5024.15 feet. Detention Pond M will not be providing any additional water quality because Rain Garden M is treating the whole site and conveying the treated runoff to the Detention Pond. An Emergency Spillway has been set at the 100-year elevation just above the proposed outfall location. In the event that the South College Storage Preliminary Drainage Report 9 outlet structure is compromised runoff will be conveyed through the emergency spill way and flow east towards the existing flared end section adjacent to College Avenue. The top of the pond along the remaining sides of the pond is set at an elevation of 5025.38. Therefore, more than a foot of freeboard has been provided on all the other sides of the detention pond. V. CONCLUSIONS A. Compliance with Standards 1. The drainage design proposed with South College Storage project complies with the City of Fort Collins’ Stormwater Criteria Manual. 2. The drainage design proposed with the South College Storage project complies with the City of Fort Collins’ Master Drainage Plan for the Fossil Creek Basin. 3. There are no regulatory floodplains associated with the South College Storage development. 4. The drainage plan and stormwater management measures proposed with the South College Storage development are compliant with all applicable State and Federal regulations governing stormwater discharge. B. Drainage Concept 1. The drainage design proposed with this project will limit potential damage associated with its stormwater runoff. South College Storage will detain based on characteristics of Basin M at a reduced allowable release rate. Water quality will be provided in Rain Garden M which is considered an LID treatment. South College Storage Preliminary Drainage Report 10 References 1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities, November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services. 2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No. 174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code. 3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007. 4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service, United States Department of Agriculture. 5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008. APPENDIX A HYDROLOGIC COMPUTATIONS CHARACTER OF SURFACE: Runoff Coefficient Percentage Impervious Project: Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: Asphalt ……....……………...……….....…...……………….………………………………….0.. 95 100% Date: Concrete …….......……………….….……….………………..….………………………………… 0.95 90% Gravel ……….…………………….….…………………………..……………………………….0.. 50 40% Roofs …….…….………………..……………….…………………………………………….. 0.95 90% Pavers…………………………...………………..…………………………………………….. 0.40 22% Lawns and Landscaping Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0% Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year Cf = 1.00 Basin ID Basin Area (s.f.) Basin Area (ac) Area of Asphalt (ac) Area of Concrete (ac) Area of Roofs (ac) Area of Gravel (ac) Area of Pavers (ac) Area of Lawns and Landscaping (ac) 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient Composite % Imperv. H1 209401 4.81 0.000 0.000 0.000 0.000 0.000 4.81 0.25 0.25 0% H2 177381 4.07 0.000 0.000 0.000 0.000 0.000 4.07 0.25 0.25 0% H3 179543 4.12 0.000 0.000 0.000 0.130 0.000 3.99 0.26 0.26 1% OS1 67342 1.55 0.000 0.000 0.000 0.000 0.000 1.55 0.25 0.25 0% TOTAL 633667 14.55 0.000 0.000 0.000 0.130 0.000 14.42 0.15 0.15 0% DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I. 10-year Cf = 1.00 June 9, 2017 **Soil Classification of site is Clay Loam** Page 1 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\C-Values Overland Flow, Time of Concentration: Project: South College Storage Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S ½ Velocity (Swale Flow), V = 15·S ½ NOTE: C-value for overland flows over grassy surfaces; C = 0.25 Is Length >500' ? C*Cf (2-yr Cf=1.00) C*Cf (10-yr Cf=1.00) C*Cf (100-yr Cf=1.25) Length, L (ft) Slope, S (%) Ti 2-yr (min) Ti 10-yr (min) Ti 100-yr (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) Length, L (ft) Slope, S (%) Velocity, Rational Method Equation: Project: South College Storage Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: h1 H1 4.81 20 20 19 0.25 0.25 0.31 1.61 2.74 5.84 1.93 3.29 8.77 h1 H2 4.07 16 16 15 0.25 0.25 0.31 1.81 3.08 6.62 1.84 3.14 8.42 h1 H3 4.12 27 27 24 0.26 0.26 0.32 1.39 2.37 5.09 1.47 2.51 6.76 h1 OS1 1.55 32 32 30 0.25 0.25 0.31 1.26 2.14 4.56 0.49 0.83 2.20 Area, A (acres) Intensity, i2 (in/hr) 100-yr Tc (min) DEVELOPED RUNOFF COMPUTATIONS C100 Design Point Flow, Q100 (cfs) Flow, Q2 (cfs) 10-yr Tc (min) 2-yr Tc (min) C2 Flow, Q10 (cfs) Intensity, i100 (in/hr) Basin(s) B. Mathisen June 9, 2017 Intensity, i10 (in/hr) Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 C10 Q = C f ( C )( i )( A ) Page 3 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Direct-Runoff CHARACTER OF SURFACE: Runoff Coefficient Percentage Impervious Project: South College Storage Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: B. Mathisen Asphalt ……....……………...……….....…...……………….………………………………….. 0.95 100% Date: June 9, 2017 Concrete …….......……………….….……….………………..….………………………………… 0.95 90% Gravel ……….…………………….….…………………………..……………………………….. 0.50 40% Roofs …….…….………………..……………….…………………………………………….. 0.95 90% Pavers…………………………...………………..…………………………………………….. 0.40 22% Lawns and Landscaping Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0% Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year C f = 1.00 100-year C f = 1.25 Design Point Basin IDs Basin Area (s.f.) Basin Area (ac) Area of Asphalt (sq ft) Area of Asphalt (ac) Area of Concrete (sq ft) Area of Concrete (ac) Area of Roofs (sq ft) Area of Roofs (ac) Area of Gravel (sq ft) Area of Gravel (ac) Area of Pavers (ac) Area of Lawns and Landscaping (ac) 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient 100-year Composite Runoff Overland Flow, Time of Concentration: Project: South College Storage Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S ½ Velocity (Swale Flow), V = 15·S ½ NOTE: C-value for overland flows over grassy surfaces; C = 0.25 Is Length >500' ? C*Cf (2-yr Cf =1.00) C*Cf (10-yr Cf =1.00) C*Cf (100-yr Cf =1.25) Length, L (ft) Slope, S (%) Ti 2-yr (min) Ti 10-yr (min) Ti 100-yr (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) Length, L (ft) Slope, Rational Method Equation: Project: South College Storage Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: h1 H1,H2,H3,OS1 14.55 21 21 16 0.25 0.25 0.32 1.59 2.71 6.30 5.8 9.9 28.9 os H3, OS1 5.67 23 23 17 0.26 0.26 0.32 1.51 2.58 6.10 2.2 3.7 11.1 C100 Intensity, i2 (in/hr) Intensity, i10 (in/hr) Intensity, i100 (in/hr) COMBINED DEVELOPED RUNOFF COMPUTATIONS B. Mathisen June 9, 2017 Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 Design Point Basin(s) Area, A (acres) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) Flow, Q2 (cfs) Flow, Q10 (cfs) Flow, Q100 (cfs) C2 C10 Q = C f ( C )( i )( A ) Page 6 of 23 D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Comb-Direct-Runoff South College Storage DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q100 (cfs) h1 H1 4.81 0.25 0.31 20.0 18.6 1.93 8.77 h1 H2 4.07 0.25 0.31 16.0 14.8 1.84 8.42 h1 H3 4.12 0.26 0.32 26.5 24.5 1.47 6.76 h1 OS1 1.55 0.25 0.31 31.9 29.6 0.49 2.20 DESIGN POINT BASIN ID TOTAL AREA (acres) C10 C100 10-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q100 (cfs) h1 H1,H2,H3,OS1 14.55 0.25 0.32 20.8 16.3 5.82 28.89 os H3, OS1 5.67 0.26 0.32 22.8 17.2 2.19 11.05 Page 7 of 23 D:Historic \Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\SUMMARY-TABLE CHARACTER OF SURFACE: Runoff Coefficient Percentage Impervious Project: South College Storage Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: B. Mathisen Asphalt ……....……………...……….....…...……………….………………………………….0.. 95 100% Date: Concrete …….......……………….….……….………………..….………………………………… 0.95 90% Gravel ……….…………………….….…………………………..……………………………….0.. 50 40% Roofs …….…….………………..……………….…………………………………………….. 0.95 90% Pavers…………………………...………………..…………………………………………….. 0.40 22% Lawns and Landscaping Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0% Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year C f = 1.00 100-year C f = 1.25 Basin ID Basin Area (s.f.) Basin Area (ac) Area of Asphalt (ac) Area of Concrete (ac) Area of Roofs (ac) Area of Gravel (ac) Area of Pavers (ac) Area of Lawns and Landscaping (ac) 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient 100-year Composite Runoff Coefficient Composite % Imperv. E1 209401 4.81 0.000 0.000 0.000 0.000 0.000 4.81 0.25 0.25 0.31 0% M1 21177 0.49 0.428 0.000 0.000 0.000 0.000 0.06 0.87 0.87 1.00 88% M2 11126 0.26 0.179 0.028 0.000 0.000 0.000 0.05 0.82 0.82 1.00 80% M3.a 12920 0.30 0.000 0.000 0.297 0.000 0.000 0.00 0.95 0.95 1.00 90% M3.b 5090 0.12 0.000 0.000 0.117 0.000 0.000 0.00 0.95 0.95 1.00 90% M3.c 18010 0.41 0.000 0.000 0.413 0.000 0.000 0.00 0.95 0.95 1.00 90% Overland Flow, Time of Concentration: Project: South College Storage Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S ½ Velocity (Swale Flow), V = 15·S ½ NOTE: C-value for overland flows over grassy surfaces; C = 0.25 Is Length >500' ? C*Cf (2-yr Cf =1.00) C*Cf (10-yr Cf =1.00) C*Cf (100-yr Cf =1.25) Length, L (ft) Slope, S (%) Ti 2-yr (min) Ti 10-yr (min) Ti 100-yr (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) Length, L (ft) Slope, Rational Method Equation: Project: South College Storage Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: h1 E1 4.81 20 20 19 0.25 0.25 0.31 1.61 2.74 5.84 1.93 3.29 8.77 m1 M1 0.49 5 5 5 0.87 0.87 1.00 2.85 4.87 9.95 1.20 2.05 4.84 m2 M2 0.26 5 5 5 0.82 0.82 1.00 2.85 4.87 9.95 0.60 1.02 2.54 m1 M3.a 0.30 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.80 1.37 2.95 m4 M3.b 0.12 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.32 0.54 1.16 m2 M3.c 0.41 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 1.12 1.91 4.11 m4 M4 0.33 5 5 5 0.81 0.81 1.00 2.85 4.87 9.95 0.77 1.32 3.32 m5 M5 1.09 5 5 5 0.26 0.26 0.33 2.85 4.87 9.95 0.81 1.39 3.55 m6 M6 0.29 5 5 5 0.76 0.76 0.94 2.85 4.87 9.95 0.63 1.07 2.73 m7 M7 0.24 5 5 5 0.89 0.89 1.00 2.85 4.87 9.95 0.61 1.04 2.38 m8 M8 0.12 5 5 5 0.83 0.83 1.00 2.85 4.87 9.95 0.27 0.46 1.15 h1 W1 4.12 26 26 24 0.28 0.28 0.35 1.42 2.42 5.15 1.62 2.76 7.34 h1 OS1 0.44 13 13 12 0.31 0.31 0.39 1.98 3.39 7.16 0.27 0.46 1.21 DEVELOPED RUNOFF COMPUTATIONS C100 Design Point Flow, Q100 (cfs) Flow, Q2 (cfs) 10-yr Tc (min) 2-yr Tc (min) C2 Flow, Q10 (cfs) Intensity, i100 (in/hr) Basin(s) B. Mathisen August 3, 2017 Intensity, i10 (in/hr) Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 C10 Area, A (acres) Intensity, i2 (in/hr) 100-yr Tc (min) Q = C f ( C )( i )( A ) Page 3 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Direct-Runoff CHARACTER OF SURFACE: Runoff Coefficient Percentage Impervious Project: South College Storage Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: B. Mathisen Asphalt ……....……………...……….....…...……………….………………………………….. 0.95 100% Date: August 3, 2017 Concrete …….......……………….….……….………………..….………………………………… 0.95 90% Gravel ……….…………………….….…………………………..……………………………….. 0.50 40% Roofs …….…….………………..……………….…………………………………………….. 0.95 90% Pavers…………………………...………………..…………………………………………….. 0.40 22% Lawns and Landscaping Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0% Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year C f = 1.00 100-year C f = 1.25 Design Point Basin IDs Basin Area (s.f.) Basin Area (ac) Area of Asphalt (sq ft) Area of Asphalt (ac) Area of Concrete (sq ft) Area of Concrete (ac) Area of Roofs (sq ft) Area of Roofs (ac) Area of Gravel (sq ft) Area of Gravel (ac) Area of Pavers (ac) Area of Lawns and Landscaping (ac) 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient 100-year Composite Runoff Overland Flow, Time of Concentration: Project: South College Storage Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S ½ Velocity (Swale Flow), V = 15·S ½ NOTE: C-value for overland flows over grassy surfaces; C = 0.25 Is Length >500' ? C*Cf (2-yr Cf =1.00) C*Cf (10-yr Cf =1.00) C*Cf (100-yr Cf =1.25) Length, L (ft) Slope, S (%) Ti 2-yr (min) Ti 10-yr (min) Ti 100-yr (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) Length, L (ft) Slope, Rational Method Equation: Project: South College Storage Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: h1 E1, M1, M2, M3, M4, M5, M6, M7, W1, OS1 13.00 15 15 10 0.38 0.38 0.48 1.87 3.19 7.72 9.3 15.9 48.0 m4 M1-M4 and M8 2.02 5 5 5 0.87 0.87 1.00 2.85 4.87 9.95 5.0 8.5 20.1 m5 M1, M2, M3, M4, M5, M6, M7, M8 3.64 5 5 5 0.68 0.68 0.85 2.85 4.87 9.95 7.0 12.0 30.7 COMBINED DEVELOPED RUNOFF COMPUTATIONS B. Mathisen August 3, 2017 Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 Design Point Basin(s) Area, A (acres) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) Flow, Q2 (cfs) Flow, Q10 (cfs) Flow, Q100 (cfs) C2 C10 C100 Intensity, i2 (in/hr) Intensity, i10 (in/hr) Intensity, i100 (in/hr) Q = C f ( C )( i )( A ) Page 6 of 23 D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Comb-Direct-Runoff South College Storage DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q100 (cfs) h1 E1 4.81 0.25 0.31 20.0 18.6 1.93 8.77 m1 M1 0.49 0.87 1.00 5.0 5.0 1.20 4.84 m2 M2 0.26 0.82 1.00 5.0 5.0 0.60 2.54 m1 M3.a 0.30 0.95 1.00 5.0 5.0 0.80 2.95 m4 M3.b 0.12 0.95 1.00 5.0 5.0 0.32 1.16 m2 M3.c 0.41 0.95 1.00 5.0 5.0 1.12 4.11 m4 M4 0.33 0.81 1.00 5.0 5.0 0.77 3.32 m5 M5 1.09 0.26 0.33 5.0 5.0 0.81 3.55 m6 M6 0.29 0.76 0.94 5.0 5.0 0.63 2.73 m7 M7 0.24 0.89 1.00 5.0 5.0 0.61 2.38 m8 M8 0.12 0.83 1.00 5.0 5.0 0.27 1.15 h1 W1 4.12 0.28 0.35 25.9 23.7 1.62 7.34 h1 OS1 0.44 0.31 0.39 13.5 12.2 0.27 1.21 DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q100 (cfs) h1 E1, M1, M2, M3, M4, M5, M6, M7, W1, OS1 13.00 0.38 0.48 15.0 10.5 9.31 48.04 m4 M1-M4 and M8 2.02 0.87 1.00 5.0 5.0 4.99 20.08 m5 M1, M2, M3, M4, M5, M6, APPENDIX B HYDRAULIC COMPUTATIONS B.1 – Storm Sewers B.2 – Inlets B.3 – Detention Facilities APPENDIX B.1 STORM SEWERS APPENDIX B.2 INLETS Project: Inlet ID: Gutter Geometry (Enter data in the blue cells) Maximum Allowable Width for Spread Behind Curb TBACK = 7.5 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.250 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013 Height of Curb at Gutter Flow Line HCURB = 6.00 inches Distance from Curb Face to Street Crown TCROWN = 25.0 ft Gutter Width W = 2.00 ft Street Transverse Slope SX = 0.020 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX = 25.0 25.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 6.0 inches Allow Flow Depth at Street Crown (leave blank for no) check = yes MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs Version 4.04 Released November 2016 ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) South College Storage Inlet A2 UD-Inlet_Inlet A2.1.1.xlsm, Inlet A2.1.1 6/15/2017, 11:00 AM Design Information (Input) MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 3.00 3.00 inches Number of Unit Inlets (Grate or Curb Opening) No = 1 1 Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 6.0 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) = N/A N/A feet Width of a Unit Grate Wo = N/A N/A feet Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) = 5.00 5.00 feet Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10 Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60 Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67 Low Head Performance Reduction (Calculated) MINOR MAJOR Depth for Grate Midwidth dGrate = N/A N/A ft Depth for Curb Opening Weir Equation dCurb = 0.33 0.33 ft Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.77 0.77 Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00 Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition) Qa = 5.4 5.4 cfs Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 0.6 2.6 cfs CDOT Type R Curb Opening INLET IN A SUMP OR SAG LOCATION Version 4.04 Released November 2016 H-Vert H-Curb W Lo (C) Lo (G) Wo WP CDOT Type R Curb Opening Override Depths UD-Inlet_Inlet A2.1.1.xlsm, Inlet A2.1.1 6/15/2017, 11:00 AM Project: Inlet ID: Gutter Geometry (Enter data in the blue cells) Maximum Allowable Width for Spread Behind Curb TBACK = 7.5 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.250 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013 Height of Curb at Gutter Flow Line HCURB = 6.00 inches Distance from Curb Face to Street Crown TCROWN = 25.0 ft Gutter Width W = 2.00 ft Street Transverse Slope SX = 0.020 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX = 25.0 25.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 6.0 inches Allow Flow Depth at Street Crown (leave blank for no) check = yes MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs Version 4.04 Released November 2016 ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) South College Storage Inlet A3 UD-Inlet_Inlet A3.xlsm, Inlet A2.1.2 6/15/2017, 11:02 AM Design Information (Input) MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 3.00 3.00 inches Number of Unit Inlets (Grate or Curb Opening) No = 1 1 Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 6.0 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) = N/A N/A feet Width of a Unit Grate Wo = N/A N/A feet Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) = 5.00 5.00 feet Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10 Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60 Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67 Low Head Performance Reduction (Calculated) MINOR MAJOR Depth for Grate Midwidth dGrate = N/A N/A ft Depth for Curb Opening Weir Equation dCurb = 0.33 0.33 ft Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.77 0.77 Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00 Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition) Qa = 5.4 5.4 cfs Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 0.6 2.2 cfs CDOT Type R Curb Opening INLET IN A SUMP OR SAG LOCATION Version 4.04 Released November 2016 H-Vert H-Curb W Lo (C) Lo (G) Wo WP CDOT Type R Curb Opening Override Depths UD-Inlet_Inlet A3.xlsm, Inlet A2.1.2 6/15/2017, 11:02 AM Grass Type Limiting Manning's n A 0.06 B 0.04 C 0.033 D 0.03 E 0.024 Analysis of Trapezoidal Grass-Lined Channel Using SCS Method NRCS Vegetal Retardance (A, B, C, D, or E) A, B, C, D or E C Manning's n (Leave cell D16 blank to manually enter an n value) n = see details below Channel Invert Slope SO = 0.0300 ft/ft Bottom Width B = 10.00 ft Warning 01 Left Side Slope Z1 = 0.04 ft/ft Warning 01 Right Side Slope Z2 = 0.25 ft/ft Check one of the following soil types: Soil Type: Max. Velocity (VMAX) Max Froude No. (FMAX) Non-Cohesive 5.0 fps 0.60 Cohesive 7.0 fps 0.80 Paved N/A N/A Minor Storm Major Storm Max. Allowable Top Width of Channel for Minor & Major Storm TMAX = 42.00 42.00 feet Max. Allowable Water Depth in Channel for Minor & Major Storm dMAX = 1.32 1.32 feet Allowable Channel Capacity Based On Channel Geometry Minor Storm Major Storm MINOR STORM Allowable Capacity is based on Depth Criterion Qallow = 103.7 103.7 cfs MAJOR STORM Allowable Capacity is based on Depth Criterion dallow = 1.32 1.32 ft Water Depth in Channel Based On Design Peak Flow Design Peak Flow Qo = 2.2 11.0 cfs Water Depth d = 0.41 0.56 feet Version 4.04 Released November 2016 AREA INLET IN A SWALE South College Storage Inlet B2 Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management' Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management' Choose One: Non-Cohesive Cohesive Paved UD-Inlet_Inlet B2.xlsm, Inlet B2 6/15/2017, 1:43 PM Version 4.04 Released November 2016 AREA INLET IN A SWALE South College Storage Inlet B2 Inlet Design Information (Input) Type of Inlet Inlet Type = Angle of Inclined Grate (must be <= 30 degrees) θ = 0.00 degrees Width of Grate W = 3.00 feet Length of Grate L = 3.00 feet Open Area Ratio ARATIO = 0.70 Height of Inclined Grate HB = 0.00 feet Clogging Factor Cf = 0.50 Grate Discharge Coefficient Cd = 0.84 Orifice Coefficient Co = 0.56 Weir Coefficient Cw = 1.81 MINOR MAJOR Water Depth at Inlet (for depressed inlets, 1 foot is added for depression) d = 1.41 1.56 Total Inlet Interception Capacity (assumes clogged condition) Qa = 16.9 17.8 cfs Bypassed Flow, Qb = 0.0 0.0 cfs Capture Percentage = Qa/Qo = C% 100 100 % Warning 01: Sideslope steepness exceeds USDCM Volume I recommendation. Warning 02: Depth (d) exceeds USDCM Volume I recommendation. CDOT Type C (Depressed) CDOT Type C (Depressed) UD-Inlet_Inlet B2.xlsm, Inlet B2 6/15/2017, 1:43 PM Weir Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Jun 15 2017 Existing 2' Curb Chase (Skyway and College) Rectangular Weir Crest = Sharp Bottom Length (ft) = 2.00 Total Depth (ft) = 0.50 Calculations Weir Coeff. Cw = 3.33 Compute by: Known Depth Known Depth (ft) = 0.50 Highlighted Depth (ft) = 0.50 Q (cfs) = 2.355 Area (sqft) = 1.00 Velocity (ft/s) = 2.35 Top Width (ft) = 2.00 0 .5 1 1.5 2 2.5 3 Depth (ft) Existing 2' Curb Chase (Skyway and College) Depth (ft) -0.50 -0.50 0.00 0.00 0.50 0.50 1.00 1.00 Length (ft) Weir W.S. Project: Inlet ID: Gutter Geometry (Enter data in the blue cells) Maximum Allowable Width for Spread Behind Curb TBACK = 10.0 ft Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.050 ft/ft Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.018 Height of Curb at Gutter Flow Line HCURB = 6.00 inches Distance from Curb Face to Street Crown TCROWN = 25.0 ft Gutter Width W = 2.00 ft Street Transverse Slope SX = 0.023 ft/ft Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft Street Longitudinal Slope - Enter 0 for sump condition SO = 0.028 ft/ft Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013 Minor Storm Major Storm Max. Allowable Spread for Minor & Major Storm TMAX = 15.0 15.0 ft Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 6.0 inches Allow Flow Depth at Street Crown (leave blank for no) check = yes MINOR STORM Allowable Capacity is based on Spread Criterion Minor Storm Major Storm MAJOR STORM Allowable Capacity is based on Spread Criterion Qallow = 19.7 19.7 cfs Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management' Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management' Version 4.04 Released November 2016 ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm) (Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread) South College Storage Inlet C2 UD-Inlet_Inlet C2.xlsm, Inlet C2 6/15/2017, 1:52 PM Design Information (Input) MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a') aLOCAL = 3.0 3.0 inches Total Number of Units in the Inlet (Grate or Curb Opening) No = 2 2 Length of a Single Unit Inlet (Grate or Curb Opening) Lo = 5.00 5.00 ft Width of a Unit Grate (cannot be greater than W, Gutter Width) Wo = N/A N/A ft Clogging Factor for a Single Unit Grate (typical min. value = 0.5) Cf-G = N/A N/A Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1) Cf-C = 0.10 0.10 Street Hydraulics: OK - Q < Allowable Street Capacity' MINOR MAJOR Total Inlet Interception Capacity Q = 2.4 2.4 cfs Total Inlet Carry-Over Flow (flow bypassing inlet) Qb = 0.0 0.0 cfs Capture Percentage = Qa/Qo = C% = 100 100 % CDOT Type R Curb Opening INLET ON A CONTINUOUS GRADE Version 4.04 Released November 2016 CDOT Type R Curb Opening UD-Inlet_Inlet C2.xlsm, Inlet C2 6/15/2017, 1:52 PM 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Capacity (cfs) Head (ft) Nyloplast 30" Dome Grate Inlet Capacity Chart Weir Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Monday, Jun 5 2017 Design Point m8 Rectangular Weir Crest = Sharp Bottom Length (ft) = 2.00 Total Depth (ft) = 0.50 Calculations Weir Coeff. Cw = 3.33 Compute by: Known Q Known Q (cfs) = 1.13 Highlighted Depth (ft) = 0.31 Q (cfs) = 1.130 Area (sqft) = 0.61 Velocity (ft/s) = 1.84 Top Width (ft) = 2.00 0 .5 1 1.5 2 2.5 3 Depth (ft) Design Point m8 Depth (ft) -0.50 -0.50 0.00 0.00 0.50 0.50 1.00 1.00 Length (ft) Weir W.S. Weir Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Monday, Jun 12 2017 20' Curb Cut Rectangular Weir Crest = Sharp Bottom Length (ft) = 20.00 Total Depth (ft) = 0.50 Calculations Weir Coeff. Cw = 3.33 Compute by: Known Q Known Q (cfs) = 22.06 Highlighted Depth (ft) = 0.48 Q (cfs) = 22.06 Area (sqft) = 9.57 Velocity (ft/s) = 2.30 Top Width (ft) = 20.00 0 2 4 6 8 10 12 14 16 18 20 22 24 Depth (ft) 20' Curb Cut Depth (ft) -0.50 -0.50 0.00 0.00 0.50 0.50 1.00 1.00 Length (ft) Weir W.S. Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Aug 3 2017 Design Point M4 Triangular Side Slopes (z:1) = 10.00, 10.00 Total Depth (ft) = 0.85 Invert Elev (ft) = 5024.25 Slope (%) = 1.29 N-Value = 0.020 Calculations Compute by: Known Q Known Q (cfs) = 26.10 Highlighted Depth (ft) = 0.77 Q (cfs) = 26.10 Area (sqft) = 5.93 Velocity (ft/s) = 4.40 Wetted Perim (ft) = 15.48 Crit Depth, Yc (ft) = 0.85 Top Width (ft) = 15.40 EGL (ft) = 1.07 0 2 4 6 8 10 12 14 16 18 20 22 Elev (ft) Depth (ft) Section 5023.50 -0.75 5024.00 -0.25 5024.50 0.25 5025.00 0.75 5025.50 1.25 5026.00 1.75 Reach (ft) APPENDIX B.3 DETENTION FACILITIES Pond No : m5 100-yr 0.85 5.00 min 38627 ft3 3.64 acres 0.887 ac-ft Max Release Rate = 0.63 cfs Time (min) Ft Collins 100-yr Intensity (in/hr) Inflow Volume (ft3) Outflow Adjustment Factor Qav (cfs) Outflow Volume (ft3) Storage Volume (ft3) 5 9.950 9236 1.00 0.63 189 9047 10 7.720 14331 0.75 0.47 284 14048 15 6.520 18156 0.67 0.42 378 17778 20 5.600 20792 0.63 0.39 473 20319 25 4.980 23112 0.60 0.38 567 22545 30 4.520 25173 0.58 0.37 662 24511 35 4.080 26509 0.57 0.36 756 25753 40 3.740 27772 0.56 0.35 851 26921 45 3.460 28904 0.56 0.35 945 27959 50 3.230 29981 0.55 0.35 1040 28941 55 3.030 30937 0.55 0.34 1134 29803 60 2.860 31856 0.54 0.34 1229 30627 65 2.720 32821 0.54 0.34 1323 31498 70 2.590 33657 0.54 0.34 1418 32239 75 2.480 34529 0.53 0.34 1512 33017 80 2.380 35346 0.53 0.33 1607 33739 85 2.290 36135 0.53 0.33 1701 34434 90 2.210 36924 0.53 0.33 1796 35128 95 2.130 37564 0.53 0.33 1890 35674 100 2.060 38242 0.53 0.33 1985 36257 105 2.000 38984 0.52 0.33 2079 36905 110 1.940 39616 0.52 0.33 2174 37442 115 1.890 40349 0.52 0.33 2268 38081 120 1.840 40989 0.52 0.33 2363 38627 *Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2. A = Tc = Project Location : Design Point C = Design Storm DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF Input Variables Results Required Detention Volume Fort Collins, Colorado Project Title Date: Project Number Calcs By: Client Pond Designation Invert Elevation Water Quality Volume 100-yr Detention Volume Total Pond Volume Min Sc D = Depth between contours (ft.) A1 = Surface Area lower contour (ft 2 ) t A2 = Surface Area upper contour (ft 2 ) Area/Row No. of Rows 5019.80 59.27 0.10 1.98 1.98 0.0000 5020.00 678.12 0.20 62.52 64.50 0.0015 5020.20 1179.73 0.20 183.49 247.99 0.0057 5020.40 2877.45 0.20 393.31 641.29 0.0147 5020.60 4043.70 0.20 688.82 1330.11 0.0305 5020.80 5274.32 0.20 929.08 2259.19 0.0519 5021.00 6576.08 0.20 1182.65 3441.84 0.0790 WQCV 5021.20 7734.75 0.20 1429.52 4871.36 0.1118 5021.40 8662.38 0.20 1638.84 6510.20 0.1495 5021.60 9151.41 0.20 1781.16 8291.35 0.1903 5021.80 9557.17 0.20 1870.71 10162.06 0.2333 5022.00 9968.95 0.20 1952.47 12114.53 0.2781 5022.20 10386.77 0.20 2035.43 14149.96 0.3248 5022.40 10810.61 0.20 2119.60 16269.55 0.3735 5022.60 11240.48 0.20 2204.97 18474.52 0.4241 5022.80 11676.37 0.20 2291.55 20766.07 0.4767 5023.00 12118.30 0.20 2379.33 23145.40 0.5313 5023.20 12566.25 0.20 2468.32 25613.72 0.5880 5023.40 13020.23 0.20 2558.51 28172.23 0.6467 5023.60 13480.24 0.20 2649.91 30822.15 0.7076 5023.80 13946.28 0.20 2742.52 33564.67 0.7705 5024.00 14418.35 0.20 2836.33 36401.00 0.8357 5024.20 14896.44 0.20 2931.35 39332.35 0.9029 Total Vol 5024.40 15380.56 0.20 3027.57 42359.92 0.9724 5024.60 15870.70 0.20 3125.00 45484.92 1.0442 5024.80 16366.89 0.20 3223.63 48708.55 1.1182 5025.00 16869.10 0.20 3323.47 52032.02 1.1945 5025.20 17377.33 0.20 3424.52 55456.54 1.2731 Elevation Depth Volume WQCV 5020.84 1.14 0.0573 100-yr Detention 5024.15 4.45 0.8870 Overall Detention 5024.15 4.45 0.8870 Circular Perforation Sizing Dia (in.) 1 Pond M 0.05 13 0.0573 ac-ft 5019.70 ft Pond M Volume Project Title Date: Project Number Calcs By: Client Pond Designation Q = 0.63 cfs C = 0.607 Q = Release Rate (cfs) Eh = 5024.11 ft C = Discharge Coefficients (unitless) Ei = 5019.17 ft Aa = Area Allowed of Opening (ft2) g = Gravity (32.2 ft/s2) 0.05819 ft2 Eh = High Water Surface Elevation (ft) 8.379304 in2 Ei = Elevation of Outlet Invert (ft) H = Height of Opening (in.) R = Inner Radius of Outfall Pipe (in.) Δ = Top of Plate to Center of Pipe (in.) S = Arc Length of Open Area (in.) Ac = Area of Opening (in2) θ = Angle of Plate on Pipe to Center Pipe (radians) Calculated Area of Opening (Ac) Design Height of Opening (H) Proposed Outfall Pipe Diameter 8.16 sq. in. B. Mathisen August 3, 2017 Aa = 1-1/2 in 12 in Branden Grebe 1269-002 South College Storage Pond M [ ( ( ) ) ] 2 2 R Sin S R R S K − = QCA = 2 g ( E h − E i ) S = R θ ( ) ( R ) Cos R Cos → = ∆ 2 = ∆ 2 −1 θ θ Ac = π R 2 − K APPENDIX C WATER QUALITY DESIGN COMPUTATIONS Project Title Date: Project Number Calcs By: Client Pond Designation 0.8 WQCV = Watershed inches of Runoff (inches) 60.00% a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = Iwq/100) 0.189 in A = 3.64 ac V = 0.0573 ac-ft 2496.34 cu. ft. V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) South College Storage August 3, 2017 1269-002 B. Mathisen Brandon Grebe Rain Garden M Drain Time a = i = WQCV = Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event 0.189 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 WQCV (watershed inches) Total Imperviousness Ratio (i = Iwq /100) Water Quality Capture Volume 6 hr 12 hr 24 hr 40 hr WQCV = a ( 0.91 i 3 − 1 . 19 i 2 + 0 . 78 i ) WQCV = a ( 0.91 i 3 − 1 . 19 i 2 + 0 . 78 i ) V * A 12 WQCV   Sheet 1 of 2 Designer: Company: Date: Project: Location: 1. Basin Storage Volume A) Effective Imperviousness of Tributary Area, Ia Ia = 60.0 % (100% if all paved and roofed areas upstream of rain garden) B) Tributary Area's Imperviousness Ratio (i = Ia /100) i = 0.600 C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.19 watershed inches (WQCV= 0.8 * (0.91* i 3 - 1.19 * i 2 + 0.78 * i) D) Contributing Watershed Area (including rain garden area) Area = 158,427 sq ft E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = cu ft Vol = (WQCV / 12) * Area F) For Watersheds Outside of the Denver Region, Depth of d6 = 0.43 in Average Runoff Producing Storm G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 2,494.3 cu ft Water Quality Capture Volume (WQCV) Design Volume H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft (Only if a different WQCV Design Volume is desired) 2. Basin Geometry A) WQCV Depth (12-inch maximum) DWQCV = 12 in B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft (Use "0" if rain garden has vertical walls) C) Mimimum Flat Surface Area AMin = 1663 sq ft D) Actual Flat Surface Area AActual = 2382 sq ft E) Area at Design Depth (Top Surface Area) ATop = 3288 sq ft F) Rain Garden Total Volume VT = 2,835 cu ft (VT = ((ATop + AActual ) / 2) * Depth) 3. Growing Media 4. Underdrain System A) Are underdrains provided? B) Underdrain system orifice diameter for 12 hour drain time i) Distance From Lowest Elevation of the Storage y = 0.5 ft Volume to the Center of the Orifice ii) Volume to Drain in 12 Hours Vol12 = 2,494 cu ft iii) Orifice Diameter, 3/8" Minimum DO = 1.53 in Sheet 2 of 2 Designer: Company: Date: Project: Location: 5. Impermeable Geomembrane Liner and Geotextile Separator Fabric A) Is an impermeable liner provided due to proximity of structures or groundwater contamination? PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW THE LINER IF THE SUBGRADE IS ANGULAR 6. Inlet / Outlet Control A) Inlet Control 7. Vegetation 8. Irrigation A) Will the rain garden be irrigated? Notes: Design Procedure Form: Rain Garden (RG) B. Mathisen Northern Engineering August 3, 2017 South College Storage Rain Garden M Choose One Choose One Choose One Sheet Flow- No Energy Dissipation Required Concentrated Flow- Energy Dissipation Provided Plantings Seed (Plan for frequent weed control) Sand Grown or Other High Infiltration Sod Choose One YES NO YES NO RainGardens_BMP-Basin M.xlsm, RG 8/3/2017, 2:49 PM APPENDIX D EROSION CONTROL REPORT South College Storage Final Erosion Control Report A separate Erosion and Sediment Control Plan (along with associated details) has been included with the FDP submittal. It should be noted, however, that any such Erosion and Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of the BMPs depicted, and additional or different BMPs from those included may be necessary during construction, or as required by the authorities having jurisdiction. It shall be the responsibility of the Contractor to ensure erosion control measures are properly maintained and followed. The Erosion and Sediment Control Plan is intended to be a living document, constantly adapting to site conditions and needs. The Contractor shall update the location of BMPs as they are installed, removed or modified in conjunction with construction activities. It is imperative to appropriately reflect the current site conditions at all times. The Erosion and Sediment Control Plan shall address both temporary measures to be implemented during construction, as well as permanent erosion control protection. Best Management Practices from the Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways and inlet protection at proposed storm inlets. Vehicle tracking control pads, spill containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site restrooms shall also be provided by the Contractor. Grading and Erosion Control Notes can be found on Sheets C0.01 of the Utility Plans. The Utility Plans also contain a full-size Erosion Control Plan as well as a separate sheet dedicated to Erosion Control Details. In addition to this report and the referenced plan sheets, the Contractor shall be aware of, and adhere to, the applicable requirements outlined in any existing Development Agreement(s) of record, as well as the Development Agreement, to be recorded prior to issuance of the Development Construction Permit. Also, the Site Contractor for this project will be required to secure a Stormwater Construction General Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division – Stormwater Program, before commencing any earth disturbing activities. Prior to securing said permit, the Site Contractor shall develop a comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE requirements and guidelines. The SWMP will further describe and document the ongoing activities, inspections, and maintenance of construction BMPs. APPENDIX E Soils Resource Report MAP POCKET HISTORIC DRAINAGE EXHIBIT PROPOSED DRAINAGE EXHIBIT S S S S VAULT ELEC ELEC T S B M CABLE D VAULT ELEC C V.P. V.P. V.P. V.P. F E S S SS SS H Y D X X X X X X X S S S S S VAULT ELEC ELEC T S B M CABLE D VAULT ELEC C V.P. V.P. V.P. V.P. F E S S SS SS H Y D VAULT ELEC ELEC T S B M CABLE D VAULT ELEC V.P. V.P. V.P. V.P. V.P. V.P. F E S ST H Y D X X X X X X X X X X X X X X X X X X X X X X X X X X X X X OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU OHU X X X X X X X X X X X X ELEC LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD LOD UD m5 (16.0:1) (11.8:1) (15.7:1) (15.7:1) (17.2:1) (15.7:1) (10.3:1) (13.1:1) (10.8:1) m4 m2 m1 h1 OS HISTORIC FLOWS FROM NEIGHBORHOOD TO THE WEST EXISTING FLARED END SECTION DETENTION POND M 100-YEAR ELEV. = 5024.12 FT. TOTAL VOLUME = 38,158 CU. FT. RAIN GARDEN M SKYWAY DRIVE (80' R.O.W.) MARS DRIVE SOUTH COLLEGE AVENUE (ROW VARIES) INLET INLET EXISTING DRAINAGE WAY m7 m6 M1 W1 E1 OS1 M2 M3.a M4 M5 M6 M7 INLET (REPLACED 2' CURB CHASE) M8 m8 M3.c M3.b 20' CURB CUT OUTFALL No. Revisions: By: Date: REVIEWED BY: C. Snowden DESIGNED BY: DRAWN BY: SCALE: DATE: 06.21.2017 PROJECT: 1269-002 Sheet of 21 SOUTH COLLEGE STORAGE These drawings are instruments of service provided by Northern Engineering Services, Inc. and are not to be used for any type of construction unless signed and sealed by a Professional Engineer in the employ of Northern Engineering Services, Inc. NOT FOR CONSTRUCTION REVIEW SET 301 North Howes Street, Suite 100 Fort Collins, Colorado 80521 E NGINEER ING N O R T H E RN PHONE: 970.221.4158 www.northernengineering.com C7.00 DRAINAGE EXHIBIT CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE, OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES. CALL UTILITY NOTIFICATION CENTER OF COLORADO Know what'sbelow. Call before you dig. R City Engineer Date Date Date Date Date Stormwater Utility Parks & Recreation Traffic Engineer Date Water & Wastewater Utility City of Fort Collins, Colorado UTILITY PLAN APPROVAL Environmental Planner CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE, OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES. CALL UTILITY NOTIFICATION CENTER OF COLORADO Know what'sbelow. Call before you dig. R City Engineer Date Date Date Date Date Stormwater Utility Parks & Recreation Traffic Engineer Date Water & Wastewater Utility City of Fort Collins, Colorado UTILITY PLAN APPROVAL Environmental Planner City Engineer Date Date Date Date Date Stormwater Utility Parks & Recreation Traffic Engineer Date Water & Wastewater Utility City of Fort Collins, Colorado UTILITY PLAN APPROVAL Environmental Planner 1. REFER TO THE "FINAL DRAINAGE REPORT FOR SOUTH COLLEGE STORAGE" BY NORTHERN ENGINEERING, DATED June 21, 2017 FOR ADDITIONAL INFORMATION. NOTES: EXISTING INLET GRATE EXISTING DECID. TREE EXISTING CONIF. TREE EXISTING LIGHT POLE EXISTING STUMP EXISTING CURB/GUTTER FLOWLINE A2 a3 4:1 79.45  HP SLOPE PROPOSED OVERLAND FLOW DIRECTION CONCENTRATED FLOW DIRECTION EXISTING STORM DRAIN FUTURE CURB AND GUTTER PROPOSED STORM DRAIN DRAINAGE BASIN PROPOSED CONTOUR PROPOSED FLOWLINE ELEVATION EXISTING CONTOUR DRAINAGE BASIN MINOR/MAJOR COEFF. DESIGN POINT DRAINAGE BASIN ID DRAINAGE BASIN AREA EXISTING OVERLAND FLOW DIRECTION RUNOFF SUMMARY TABLE: FOR DRAINAGE REVIEW ONLY NOT FOR CONSTRUCTION LEGEND: NORTH ( IN FEET ) 0 1 INCH = 40 FEET 40 40 80 120 ST 21 DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q100 (cfs) h1 E1 4.81 0.25 0.31 20.0 18.6 1.93 8.77 m1 M1 0.50 0.87 1.00 5.0 5.0 1.24 5.00 m2 M2 0.26 0.82 1.00 5.0 5.0 0.60 2.54 m1 M3.a 0.30 0.95 1.00 5.0 5.0 0.80 2.95 m4 M3.b 0.12 0.95 1.00 5.0 5.0 0.32 1.16 m2 M3.c 0.41 0.95 1.00 5.0 5.0 1.12 4.11 m4 M4 0.33 0.81 1.00 5.0 5.0 0.77 3.32 m5 M5 1.09 0.26 0.33 5.0 5.0 0.81 3.55 m6 M6 0.29 0.71 0.89 5.0 5.0 0.59 2.58 m7 M7 0.22 0.88 1.00 5.0 5.0 0.56 2.21 m8 M8 0.12 0.78 0.98 5.0 5.0 0.26 1.13 h1 W1 4.12 0.27 0.34 26.0 23.8 1.58 7.27 h1 OS1 0.44 0.31 0.39 13.5 12.2 0.27 1.21 PROPOSED UNDERDRAIN UD PROPOSED CURB AND GUTTER X X X X X X X S GATEWAY CENTER DR. POLARIS DR. AURORA WAY CONSTELLATION DR. h1 OS SKYWAY DR. COLLEGE AVE. OS1 H3 H2 H1 EXISTING DRAINAGE EXHIBIT FORT COLLINS, CO E NGINEER ING N O R T H E RN 06.15.2017 D:\PROJECTS\1269-002\DWG\DRNG\1269-002_EX-DRNG.DWG SOUTH COLLEGE STORAGE RUNOFF SUMMARY TABLE: A2 a3 EXISTING CONCENTRATED FLOW DIRECTION EXISTING CONTOUR DRAINAGE BASIN MINOR/MAJOR COEFF. DESIGN POINT DRAINAGE BASIN ID DRAINAGE BASIN AREA EXISTING OVERLAND FLOW DIRECTION LEGEND: DESIGN POINT BASIN ID TOTAL AREA (acres) C2 C100 2-yr Tc (min) 100-yr Tc (min) Q2 (cfs) Q100 (cfs) h1 H1 4.81 0.25 0.31 20.0 18.6 1.93 8.77 h1 H2 4.07 0.25 0.31 16.0 14.8 1.84 8.42 h1 H3 4.12 0.26 0.32 26.5 24.5 1.47 6.76 h1 OS1 1.55 0.25 0.31 31.9 29.6 0.49 2.20 Design Procedure Form: Rain Garden (RG) B. Mathisen Northern Engineering August 3, 2017 South College Storage Rain Garden M Choose One Choose One 18" Rain Garden Growing Media Other (Explain): YES NO RainGardens_BMP-Basin M.xlsm, RG 8/3/2017, 2:49 PM     = 12 hr Elevation (ft) n 1/4 0.059 sq-in Surface Area (ft2) Total Outlet Area 0.65 sq. in. South College Storage 8/3/2017 1269-002 B. Mathisen Brandon Grebe 0.8870 ac-ft 0.8870 ac-ft Required Area Per Row Total Vol. (ac-ft) Total Vol. (ft3) Incremental Vol. (ft3) Incremental Depth (ft) Calc. Depths ( ) 3 * * 1 2 1 2 D A A A A V = + + 1269-002 South College Storage Project Number : Project Name : Detention Pond M Page 1 of 1 1269-002_FAAModified Method.xls M7, M8 3.64 0.68 0.85 5.0 5.0 7.03 30.69 Page 7 of 23 D:\Projects\Historic 1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\SUMMARY-TABLE S (%) Velocity, V (ft/s) Tt (min) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) h1 E1, M1, M2, M3, M4, M5, M6, M7, W1, OS1 Yes 0.88 0.88 1.00 875 3.20% 8.3 8.3 3.8 650 1.50% 2.45 4.4 400 5.50% 4.69 2.3 15 15 10 m4 M1-M4 and M8 Yes 0.88 0.88 1.00 150 6.00% 2.8 2.8 1.3 350 5.00% 4.47 1.3 0 N/A N/A 5 5 5 m5 M1, M2, M3, M4, M5, M6, M7, M8 Yes 0.88 0.88 1.00 150 6.00% 2.8 2.8 1.3 120 0.50% 1.41 1.4 0 N/A N/A 5 5 5 COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS B. Mathisen August 3, 2017 Design Point Basin IDs Overland Flow Gutter/Pipe Flow Swale Flow Time of Concentration (Equation RO-4) ( ) 3 1 1 . 87 1 . 1 * S C Cf L Ti = − Page 5 of 23 D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Comb-Tc-10-yr_&_100-yr Coefficient Composite % Imperv. h1 E1, M1, M2, M3, M4, M5, M6, M7, W1, OS1 566325 13.00 68209 1.57 3269 0.08 36020 0.83 0 0 0 10.53 0.38 0.38 0.48 18% m4 M1-M4 and M8 87887 2.02 41922 0.96 1495 0.03 36020 0.83 0 0 0 0.08 0.87 0.87 1.00 86% m5 M1, M2, M3, M4, M5, M6, M7, M8 158427 3.64 60567 1.39 2305 0.05 36020 0.83 0 0 0 1.24 0.68 0.68 0.85 60% COMBINED DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS **Soil Classification of site is Sandy Loam** 10-year Cf = 1.00 Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I. Page 4 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Comb-C-Values S (%) Velocity, V (ft/s) Tt (min) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) h1 E1 No 0.25 0.25 0.31 495 5.50% 20.0 20.0 18.6 N/A N/A N/A N/A N/A 20 20 19 m1 M1 No 0.87 0.87 1.00 150 6.00% 2.9 2.9 1.3 350 5.00% 4.47 1.3 N/A N/A N/A 5 5 5 m2 M2 No 0.82 0.82 1.00 15 25.00% 0.7 0.7 0.2 120 0.50% 1.41 1.4 N/A N/A N/A 5 5 5 m1 M3.a No 0.95 0.95 1.00 N/A N/A N/A 35 100.00% 20.00 0.0 N/A N/A N/A 5 5 5 m4 M3.b No 0.95 0.95 1.00 N/A N/A N/A 35 100.00% 20.00 0.0 N/A N/A N/A 5 5 5 m2 M3.c No 0.95 0.95 1.00 N/A N/A N/A 35 100.00% 20.00 0.0 N/A N/A N/A 5 5 5 m4 M4 No 0.81 0.81 1.00 30 2.00% 2.4 2.4 0.8 120 8.00% 5.66 0.4 N/A N/A N/A 5 5 5 m5 M5 No 0.26 0.26 0.33 75 25.00% 4.6 4.6 4.3 N/A N/A N/A N/A N/A 5 5 5 m6 M6 No 0.76 0.76 0.94 25 2.00% 2.6 2.6 1.2 150 0.50% 1.41 1.8 N/A N/A N/A 5 5 5 m7 M7 No 0.89 0.89 1.00 25 2.00% 1.6 1.6 0.7 150 0.50% 1.41 1.8 N/A N/A N/A 5 5 5 m8 M8 No 0.83 0.83 1.00 25 2.00% 2.0 2.0 0.7 140 1.40% 2.37 1.0 N/A N/A N/A 5 5 5 h1 W1 No 0.28 0.28 0.35 355 1.40% 25.9 25.9 23.7 N/A N/A N/A N/A N/A 26 26 24 h1 OS1 No 0.31 0.31 0.39 100 1.60% 12.6 12.6 11.4 120 1.40% 2.37 0.8 N/A N/A N/A 13 13 12 DEVELOPED TIME OF CONCENTRATION COMPUTATIONS Gutter/Pipe Flow Swale Flow Design Point Basin Overland Flow B. Mathisen August 3, 2017 Time of Concentration (Equation RO-4) ( ) 3 1 1 . 87 1 . 1 * S C Cf L Ti = − Page 2 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Tc-10-yr_&_100-yr M4 14533 0.33 0.261 0.006 0.000 0.000 0.000 0.07 0.81 0.81 1.00 80% M5 47459 1.09 0.000 0.019 0.000 0.000 0.000 1.07 0.26 0.26 0.33 2% M6 12642 0.29 0.210 0.000 0.000 0.000 0.000 0.08 0.76 0.76 0.94 72% M7 10439 0.24 0.218 0.000 0.000 0.000 0.000 0.02 0.89 0.89 1.00 91% M8 5031 0.12 0.095 0.000 0.000 0.000 0.000 0.02 0.83 0.83 1.00 82% W1 179487 4.12 0.143 0.016 0.000 0.000 0.000 3.96 0.28 0.28 0.35 4% OS1 19010 0.44 0.032 0.006 0.000 0.000 0.000 0.40 0.31 0.31 0.39 9% TOTAL 566325 13.00 1.566 0.075 0.827 0.000 0.000 10.53 0.30 0.30 0.38 18% DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I. 10-year Cf = 1.00 August 3, 2017 **Soil Classification of site is Clay Loam** Page 1 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\C-Values S (%) Velocity, V (ft/s) Tt (min) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) h1 H1,H2,H3,OS1 Yes 0.88 0.88 1.00 875 3.20% 8.3 8.3 3.8 1500 1.00% 2.00 12.5 N/A N/A 21 21 16 os H3, OS1 Yes 0.88 0.88 1.00 1230 2.80% 10.3 10.3 4.7 N/A N/A N/A N/A 23 23 17 COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS B. Mathisen June 9, 2017 Design Point Basin IDs Overland Flow Gutter/Pipe Flow Swale Flow Time of Concentration (Equation RO-4) ( ) 3 1 1 . 87 1 . 1 * S C Cf L Ti = − Page 5 of 23 D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Comb-Tc-10-yr_&_100-yr Coefficient Composite % Imperv. h1 H1,H2,H3,OS1 633667 14.55 0.00 0.00 0.00 0.00 0.00 0.00 5650.00 0.13 0.00 14.42 0.25 0.25 0.32 0% os H3, OS1 246885 5.67 0.00 0.00 0.00 0.00 0.00 0.00 5650.00 0.13 0.00 5.54 0.26 0.26 0.32 1% COMBINED DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS **Soil Classification of site is Sandy Loam** 10-year Cf = 1.00 Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I. Page 4 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Comb-C-Values V (ft/s) Tt (min) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) h1 H1 No 0.25 0.25 0.31 495 5.50% 20.0 20.0 18.6 N/A N/A N/A N/A N/A 20 20 19 h1 H2 No 0.25 0.25 0.31 335 6.00% 16.0 16.0 14.8 N/A N/A N/A N/A N/A 16 16 15 h1 H3 No 0.26 0.26 0.32 355 1.40% 26.5 26.5 24.5 N/A N/A N/A N/A N/A 27 27 24 h1 OS1 Yes 0.25 0.25 0.31 875 3.20% 31.9 31.9 29.6 N/A N/A N/A N/A N/A 32 32 30 DEVELOPED TIME OF CONCENTRATION COMPUTATIONS Gutter/Pipe Flow Swale Flow Design Point Basin Overland Flow B. Mathisen June 9, 2017 Time of Concentration (Equation RO-4) ( ) 3 1 1 . 87 1 . 1 * S C Cf L Ti = − Page 2 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Tc-10-yr_&_100-yr