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Home My WebLink AboutZIEGLER TOWNHOMES (THE PARK TOWNHOMES AT FOSSIL RIDGE) - PDP/FDP - FDP160043 - REPORTS - DRAINAGE REPORTJanuary 11, 2017 FINAL DRAINAGE REPORT The Park Townhomes at Fossil Ridge Fort Collins, Colorado Prepared for: Russell Baker Manhattan Land Company, LLC 772 Whalers Way, Suite 200 Fort Collins, Colorado 80525 Prepared by: 301 N. Howes Street Suite 100 Fort Collins, Colorado 80521 Phone: 970.221.4158 www.northernengineering.com Project Number: 1124-002 PThis 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. January 11, 2017 City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 RE: Final Drainage Report for The Park Townhomes at Fossil Ridge Dear Staff: Northern Engineering is pleased to submit this Final Drainage Report for your review. This report accompanies the combined Preliminary & Final Plan submittal for the proposed The Park Townhomes at Fossil Ridge development (fka – Ziegler Townhomes). This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual (FCSCM), and serves to document the stormwater impacts associated with the proposed The Park Townhomes at Fossil Ridge housing project. We understand that review by the City of Fort Collins is to assure general compliance with standardized criteria contained in the FCSCM. If you should have any questions as you review this report, please feel free to contact us. Sincerely, NORTHERN ENGINEERING SERVICES, INC. Andy Reese Project Manager The Park Townhomes at Fossil Ridge TABLE OF CONTENTS I. GENERAL LOCATION AND DESCRIPTION ......................................................... 1 II. DRAINAGE BASINS AND SUB-BASINS ............................................................. 4 III. DRAINAGE DESIGN CRITERIA ......................................................................... 5 IV. DRAINAGE FACILITY DESIGN .......................................................................... 8 V. CONCLUSIONS............................................................................................. 12 References ............................................................................................................. 13 APPENDICES: APPENDIX A – Hydrologic Computations APPENDIX B – Hydraulic Computations APPENDIX C – Water Quality/LID Design Computations APPENDIX D – Erosion Control Report APPENDIX E – USDA Soils Report MAP POCKET: DR1 – Drainage Exhibit The Park Townhomes at Fossil Ridge Page|1 I. GENERAL LOCATION AND DESCRIPTION A. Location 1. Vicinity Map Figure 1 – Vicinity Map 2. The Park Townhomes at Fossil Ridge project site is located in the southeast quarter of Section 5, Township 6 North, Range 68 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. 3. The project site (refer to Figure 1) is bordered to the north by a single family residence with agricultural uses; to the south by McClelland’s Creek; to the east by Ziegler Road (ROW varies); and to the west by the Harvest Park Subdivision. 4. McClelland’s Creek is a major drainageway that is located adjacent to the project site. The Park Townhomes at Fossil Ridge Page|2 B. Description of Property 1. The Park Townhomes at Fossil Ridge are comprised of ±4.03 acres. 2. The site is currently occupied by the foundations of two residential buildings as well as various concrete sidewalks and gravel parking areas. Figure 2 – Aerial Photograph 3. The existing groundcover consists of grasses, concrete and gravel. The existing on-site runoff generally drains from the north-to-south across flat grades (e.g., <2.00%) into McClelland’s Creek. From there, the drainage continues through the channel to Fossil Creek Reservoir, and on to the Cache La Poudre River. 4. According to the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Soil Survey website: (http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx), the site consists primarily of Nunn clay loam (Hydrologic Soil Group C). 5. McClelland’s Creek is the only major drainageway within or adjacent to the project site. 6. The proposed development will consist of six townhome buildings containing a total of 36 single-family attached units. Other proposed improvements include: a new asphalt drive aisle, new sidewalks and new landscaping. 7. The proposed land use is single-family attached. This is a permitted use in the Low Density Mixed Use District (LMN). Project Site The Park Townhomes at Fossil Ridge Page|3 Floodplain 8. The subject property is not located in a FEMA regulatory floodplain. In particular, the project site is not located within a FEMA designated 100-year floodplain per Map Number 08069CO994F (Effective date: December 19, 2006). The project site is, however, located adjacent to a City of Fort Collins regulated McClelland’s Creek floodplain. Figure 4 – FEMA Firmette (Map Number 08069C0979H) 9. We have analyzed the City Floodplain map and cross sections for McClelland’s Creek and determined that the highest base flood elevation adjacent to the project site is 4909.19 (NAVD88) at XS #8. All buildings have been elevated 2’ above this elevation. Furthermore, the buildings all maintain a minimum of 12” between the finished floor elevation and the emergency spill elevation over Ziegler Road. Project Site The Park Townhomes at Fossil Ridge Page|4 II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin Description 1. The Park Townhomes at Fossil Ridge is located within the City of Fort Collins McClelland’s major drainage basin. Specifically, the project site is situated in the eastern third of this major drainage basin. This basin is located in south-east Fort Collins and has a drainage area of approximately 3.4 square miles and includes drainage originating near the College and Harmony intersection and draining through the Oakridge, Willow Springs, Stetson Creek and Harvest Park developments. The McClelland’s major drainage basin generally drains from northwest to southeast. Runoff from the major drainage basin drains to Fossil Creek Reservoir. B. Sub-Basin Description 1. The outfall for the project site is the existing storm line from Ziegler Road to McClelland’s Creek. 2. The existing subject site can be defined with one (1) sub-basin that encompasses the entire project site. The existing site runoff generally drains from northwest-to-southeast and into McClelland’s Creek. 3. The project site does not receive notable runoff from contiguous off-site properties. In the developed condition, some drainage from properties to the north will drain through the project site. The Park Townhomes at Fossil Ridge Page|5 III. DRAINAGE DESIGN CRITERIA A. There are no optional provisions outside of the FCSCM proposed with The Park Townhomes at Fossil Ridge. B. The overall stormwater management strategy employed with The Park Townhomes at Fossil Ridge utilizes the “Four Step Process” to minimize adverse impacts of urbanization on receiving waters. The following is a description of how the proposed development has incorporated each step. Step 1 – Employ Runoff Reduction Practices. The first consideration taken in trying to reduce the stormwater impacts of this development is the site selection itself. By choosing an already developed site with public storm sewer currently in place, the burden is significantly less than developing a vacant parcel absent of any infrastructure. The Park Townhomes at Fossil Ridge aims to reduce runoff peaks, volumes and pollutant loads from frequently occurring storm events (i.e., water quality (i.e., 80th percentile) and 2-year storm events) by implementing Low Impact Development (LID) strategies. Wherever practical, runoff will be routed across landscaped areas or through an infiltration gallery. These LID practices reduce the overall amount of impervious area, while at the same time Minimizing Directly Connected Impervious Areas (MDCIA). The combined LID/MDCIA techniques will be implemented, where practical, throughout the development, thereby slowing runoff and increasing opportunities for infiltration. Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with Slow Release. The efforts taken in Step 1 will help to minimize excess runoff from frequently occurring storm events; however, urban development of this intensity will still have stormwater runoff leaving the site. The primary water quality treatment will occur in the Bio-retention planters located in the second level courtyard. Step 3 – Stabilize Drainageways. As stated in Section I.B.5, above, the McClelland’s Creek drainage is adjacent to the subject site, however no changes to the channel are proposed with this project. While this step may not seem applicable to The Park Townhomes at Fossil Ridge, the proposed project indirectly helps achieve stabilized drainageways nonetheless. Once again, site selection has a positive effect on stream stabilization. By developing an infill site with existing stormwater infrastructure, combined with LID and MDCIA strategies, the likelihood of bed and bank erosion is 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. This step typically applies to industrial and commercial developments. C. Development Criteria Reference and Constraints 1. The subject property is not part of any Overall Development Plan (ODP) drainage study or similar “development/project” drainage master plan. 2. The site plan is constrained on one sides by a public street, on another side by McClelland’s Creek, and by existing development along the west side. An existing agricultural use borders the project to the north. The Park Townhomes at Fossil Ridge Page|6 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 The Park Townhomes at Fossil Ridge 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 Federal Aviation Administration (FAA) procedure has not been utilized for detention storage calculations since detention is not required for the project. 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. E. Hydraulic Criteria 1. The drainage facilities proposed with The Park Townhomes at Fossil Ridge project are designed in accordance with criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District’s (UDFCD) Urban Storm Drainage Criteria Manual. 2. As stated in Section I.C.1, above, the subject property is located next to a City of Fort Collins designated floodplain but is not located within the floodplain limits. F. Floodplain Regulations Compliance 1. As previously mentioned, this project is adjacent to a City of Fort Collins regulated floodplain. As a result, no floodplain regulations apply to the property. 2. Despite not being located within the floodplain, consideration has been given to the floodplain elevations as they relate to the proposed buildings and the finished floors have been elevated accordingly. G. Modifications of Criteria 1. No formal modifications are requested at this time. However, staff has determined that detention will not be required with this project as a result of the proximity to McClelland’s Creek. The Park Townhomes at Fossil Ridge Page|7 H. Conformance with Water Quality Treatment Criteria 1. City Code requires that 100% of runoff from a project site receive some sort of water quality treatment. This project proposes to provide water quality treatment through the use of an underground infiltration gallery (aka – underground chambers) located at the south end of the project, under the drive aisle. These chambers are considered an LID treatment method. Due to the physical constraints associated with an infill project of this nature and the prohibition of providing water quality facilities within the public right-of- way, the majority of the project site will receive formal water treatment, however small, narrow areas around the perimeter of the project cannot be captured. These areas tend to be narrow strips of concrete flatwork that link the building entrances to the public sidewalks as well as small planter beds between the building and public sidewalks or property lines. While these small areas will not receive formal water quality treatment, most areas will still see some treatment as runoff is directed across through the landscaped areas or across the landscaped parkways before reaching the roadway curb and gutter. I. Conformance with Low Impact Development (LID) 1. The project site will conform with the requirement to treat a minimum of 75% of the project site using an LID technique. Please see Appendix C for LID design information, table, and exhibit(s). As shown in the LID table provided in the appendix, 86.4% of the proposed site impervious area will receive LID treatment. J. Sizing of LID Facilities Infiltration Gallery 1. The Infiltration Gallery was sized by first determining the required water quality capture volume (WQCV) for Basins A1-A3, B1-B2 and C1-C4. A 12-hour drain time was used in this calculation. 2. Once the WQCV was identified, the minimum number of vaults needed to achieve the minimum WQCV was calculated. This volume includes the adjacent aggregates 3. As a result of all underground vaults being wrapped in a geofabric and the potential constriction of flows that could result from sedimentation in the fabric, the total release rate through the fabric was calculated. This rate was determined by multiplying the vault bottom square footage x 0.35 gpm. 4. A volume calculation utilizing the WQ flow rate into the chamber and the calculated release rate through the fabric was completed. The number of chambers have been increased as needed to confirm that the resulting volume is provided within the empty volume of the underground chambers. This is intended to ensure that the chambers do not become overwhelmed in the water quality storm event before “discharging” flows into the surrounding aggregates. The Park Townhomes at Fossil Ridge Page|8 IV. DRAINAGE FACILITY DESIGN A. General Concept 1. The main objective of The Park Townhomes at Fossil Ridge drainage design is to maintain existing drainage patterns, while not adversely impacting adjacent properties. 2. No notable off-site runoff passes directly through the project site. There is a small offsite flow from properties to the north that will pass through the project site once County Fair Lane has been constructed. This drainage will pass through the site without adversely affecting the townhome buildings. 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. Drainage for the project site has been analyzed using thirteen (13) drainage sub- basins, designated as sub-basins A1- A3, B1-B3, C1-C3 and D1-D2. The drainage patterns anticipated for the basins are further described below. Sub-Basin A1 Sub-basin A1 encompasses approximately 7% the total site area. This sub-basin is comprised primarily of roof area, concrete flatwork and landscaped areas. The sub- basin will drain to a swale located along the west property line and be captured by an area drain which will then convey runoff from the basin through the storm drain system and into the infiltration gallery. Flows will then proceed to the existing storm drain from Ziegler Road to McClelland’s Creek. Sub-Basin A2 Sub-basin A2 encompasses approximately 12% the total site area. This sub-basin is comprised primarily of roof area, concrete flatwork, and an asphalt drive aisle. Minor flows for the sub-basin will drain to an on-grade inlet located at the drive aisle entrance from County Fair. Larger flows will bypass the on-grade inlet and flow to a combo inlet located on the north side of County Fair Lane. Both Major and Minor flows will be directed into the storm drain system which will convey runoff from the basin into the infiltration gallery. Flows will then proceed to the existing storm drain from Ziegler Road to McClelland’s Creek. Sub-Basin A3 Sub-basin A3 encompasses approximately 6% the total site area. This sub-basin is comprised primarily of roof area, concrete flatwork and landscaped areas. The sub- basin will drain to a series of area drains which will then convey runoff from the basin through the storm drain system and into the infiltration gallery. Flows will then proceed to the existing storm drain from Ziegler Road to McClelland’s Creek. Sub-Basin B1 Sub-basin B1 encompasses approximately 8% the total site area. This sub-basin is comprised primarily of asphalt roadway and concrete walks. Flows from the sub-basin will flow to a combo inlet located on the north side of County Fair Lane and into the storm drain system which will convey runoff from the basin into the infiltration gallery. The Park Townhomes at Fossil Ridge Page|9 Flows will then proceed to the existing storm drain from Ziegler Road to McClelland’s Creek. Sub-Basin B2 Sub-basin B2 encompasses approximately 3% the total site area. This sub-basin is comprised primarily of asphalt roadway and concrete sidewalks. Flows from the sub- basin will flow to a combo inlet located on the south side of County Fair Lane and into the storm drain system which will convey runoff from the basin into the infiltration gallery. Flows will then proceed to the existing storm drain from Ziegler Road to McClelland’s Creek. Sub-Basin B3 Sub-basin B3 encompasses approximately 1% the total site area. This sub-basin is comprised primarily of asphalt roadway and concrete sidewalks. Flows from the sub- basin will flow offsite to the west to a pair of combo inlets located on the either side of County Fair Lane and into the Harvest Park Detention Pond. The flow from this basin has been calculated at 0.32 cfs in the 100-yr event, which will have a negligible impact on the overall drainage capacity and operation of the Harvest Park Stormwater Facilities. Sub-Basin C1 Sub-basin C1 encompasses approximately 11% the total site area. This sub-basin is comprised primarily of roof area, concrete flatwork and landscaped areas. The sub- basin will drain to a series of area drains which will then convey runoff from the basin through the storm drain system and into the infiltration gallery. Flows will then proceed to the existing storm drain from Ziegler Road to McClelland’s Creek. Sub-Basin C2a Sub-basin C2a encompasses approximately 12% the total site area. This sub-basin is comprised primarily of roof area, concrete flatwork, and an asphalt drive aisle. Minor flows for the sub-basin will drain to an on-grade area inlet located in the drive aisle drainage pan. Larger flows will bypass the on-grade inlet and flow to another area inlet in Sub-basin C2b. Both Major and Minor flows will be directed into the storm drain system which will convey runoff from the basin into the infiltration gallery. Flows will then proceed to the existing storm drain from Ziegler Road to McClelland’s Creek. Sub-Basin C2b Sub-basin C2b encompasses approximately 6% the total site area. This sub-basin is comprised primarily of roof area, concrete flatwork, and an asphalt drive aisle. Flows from the sub-basin will drain to an area inlet located in the drive aisle drainage pan. Bypassed flows from Sub-basin C2a will also drain to this area inlet. All flows will be directed into the storm drain system which will convey runoff from the basin into the infiltration gallery. Flows will then proceed to the existing storm drain from Ziegler Road to McClelland’s Creek. Sub-Basin C3 Sub-basin C3 encompasses approximately 9% the total site area. This sub-basin is comprised primarily of roof area, concrete flatwork and landscaped areas. The sub- basin will drain across landscaped areas and the Ziegler Road parkway and into the Ziegler Road curb and gutter. Flows will then proceed to the existing storm inlet in The Park Townhomes at Fossil Ridge Page|10 Ziegler and into the existing storm drain, which will convey flows from Ziegler Road to McClelland’s Creek. Sub-Basin C4 Sub-basin C4 encompasses approximately 3% the total site area. This sub-basin is comprised primarily of roof area, concrete flatwork and landscaped areas. The sub- basin will drain to an area drain which will then convey runoff from the basin to the existing storm drain from Ziegler Road to McClelland’s Creek. Sub-Basin D1 Sub-basin D1 encompasses approximately 12% the total site area. This sub-basin is comprised of native grasses as well as McClelland’s Creek. No improvements are proposed within this basin, and existing drainage patterns will be maintained. Runoff from the sub-basin will flow directly into McClelland’s Creek. Sub-Basin D2 Sub-basin D2 encompasses approximately 10% the total site area. This sub-basin is comprised primarily of existing asphalt roadway and new concrete sidewalks. Runoff from the sub-basin will flow to an existing combo inlet located on the west side of Ziegler Road and into the existing storm drain, which will convey flows from Ziegler Road to McClelland’s Creek. Sub-Basin OS1 Sub-basin OS1 is located directly north of the project boundary and includes approximately 500 LF of Ziegler frontage as well as portions of the adjacent property. This sub-basin is comprised primarily of asphalt roadway and concrete sidewalks and also includes several existing buildings. Flows from the sub-basin will flow to the Ziegler curb and gutter and proceed to a combination inlet located along the north side of County Fair Lane. Approximately 1.3 cfs will be captured by the inlet before the storm system reaches capacity. At that time, excess runoff from the site will pond at the inlet to a depth of 6”, at which point the ponding will crest the centerline of County Fair Lane. Runoff will again pond on the combo inlet located on the south side of County Fair Lane. Ponding depth will reach 3” before the offsite stormwater spills to the south along Ziegler Road, where it will proceed to the existing inlet in Ziegler Road. Runoff will then be directed into the existing storm drain system which will convey runoff from the inlet to McClelland’s Creek. Sub-Basin OS2 Sub-basin OS2 is located directly north of sub-basin OS1 and includes approximately 340 LF of Ziegler frontage as well as portions of the adjacent property. This sub-basin is comprised primarily of asphalt roadway and concrete sidewalks and also includes several existing buildings. The sub-basin could be included with Basin OS1, however the Harvest Park drainage report defined this basin specifically, so we have continued to show this basin separately from the other offsite basin. Flows from the sub-basin will flow to the Ziegler curb and gutter and proceed into sub-basin OS1 and C1. Once the flows have joined with the flows from Basin OS1, the flow path will be the same as that described for Basin OS1, with an ultimate outfall into McClelland’s Creek. A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of this report. The Park Townhomes at Fossil Ridge Page|11 B. Specific Details 1. Since detention is not required with this site, the existing impervious area has not been considered in determining allowable release from the property. 2. An allowable release rate was not determined for this project due to the proximity of the site to McClelland’s Creek. 3. The FAA method was not used to size the on-site detention volume for quantity detention since detention is not required. C. Sizing of LID Facilities Infiltration Gallery 1. The Infiltration Gallery was sized by first determining the required water quality capture volume (WQCV) for Basins A1-A3, B1-B2 and C1-C4. A 12- hour drain time was used in this calculation. 2. Once the WQCV was identified, the minimum number of vaults needed to achieve the minimum WQCV was calculated. This volume includes the adjacent aggregates 3. As a result of all underground vaults being wrapped in a geofabric and the potential constriction of flows that could result from sedimentation in the fabric, the total release rate through the fabric was calculated. This rate was determined by multiplying the vault bottom square footage x 0.35 gpm. 4. A volume calculation utilizing the WQ flow rate into the chamber and the calculated release rate through the fabric was completed. The number of chambers have been increased as needed to confirm that the resulting volume is provided within the empty volume of the underground chambers. This is intended to ensure that the chambers do not become overwhelmed in the water quality storm event before “discharging” flows into the surrounding aggregates. The Park Townhomes at Fossil Ridge Page|12 V. CONCLUSIONS A. Compliance with Standards 1. The design elements comply without variation, and meet all LID requirements. 2. The drainage design proposed with The Park Townhomes at Fossil Ridge complies with the City of Fort Collins Master Drainage Plan for the Old Town Basin. 3. There are no FEMA regulatory floodplains associated with The Park Townhomes at Fossil Ridge development. However, the project is adjacent to the McClelland Floodplain, which is a City Regulated floodplain. All applicable provisions within Chapter 10 of the City Municipal Code shall be adhered to. 4. The drainage plan and stormwater management measures proposed with The Park Townhomes at Fossil Ridge project are compliant with all applicable State and Federal regulations governing stormwater discharge. B. Drainage Concept 1. The drainage design proposed with this project will effectively limit potential damage associated with its stormwater runoff. The Park Townhomes at Fossil Ridge will not detain for the pervious area converted to impervious areas to release at the 2-year existing rate during the 100-year storm. 2. The Park Townhomes at Fossil Ridge development will not impact the Master Drainage Plan recommendations for the McClelland major drainage basin. The Park Townhomes at Fossil Ridge Page|13 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. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service, United States Department of Agriculture. 4. 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: The Park Townhomes Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: A. Reese 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 = 1.00 100-year Cf = 1.25 Basin ID 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. A1 0.28 0.00 0.02 0.10 0.00 0.00 0.15 0.57 0.57 0.71 41% A2 0.47 0.09 0.16 0.17 0.00 0.00 0.05 0.88 0.88 1.00 83% A3 0.22 0.00 0.03 0.09 0.00 0.00 0.10 0.64 0.64 0.80 50% B1 0.33 0.23 0.05 0.00 0.00 0.00 0.05 0.84 0.84 1.00 83% B2 0.11 0.08 0.04 0.01 0.00 0.00 -0.01 1.04 1.04 1.00 108% B3 0.03 0.02 0.01 0.00 0.00 0.00 0.01 0.80 0.80 1.00 76% C1 0.45 0.00 0.03 0.14 0.00 0.00 0.28 0.52 0.52 0.65 34% C2a 0.49 0.10 0.14 0.22 0.00 0.00 0.02 0.92 0.92 1.00 88% C2b 0.23 0.05 0.07 0.11 0.00 0.00 0.00 0.95 0.95 1.00 93% C3 0.34 0.00 0.06 0.14 0.00 0.00 0.14 0.66 0.66 0.83 53% Overland Flow, Time of Concentration: Project: The Park Townhomes Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S½ Velocity (Swale Flow), V = 15·S½ 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, V (ft/s) Tt (min) 2-yr Tc Rational Method Equation: Project: The Park Townhomes Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: Design Point Basin(s) Area, A (acres) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) C2 C10 C100 Intensity, i2 (in/hr) Intensity, i10 (in/hr) Intensity, i100 (in/hr) Flow, Q2 (cfs) Flow, Q10 (cfs) Flow, Q100 (cfs) Flow, WQ (cfs) A1 A1 0.28 6 6 6 0.57 0.57 0.71 2.67 4.56 9.63 0.43 0.73 1.93 0.21 A2 A2 0.47 5 5 5 0.88 0.88 1.00 2.85 4.87 9.95 1.19 2.03 4.71 0.59 A3 A3 0.22 5 5 5 0.64 0.64 0.80 2.85 4.87 9.95 0.41 0.70 1.78 0.20 B1 B1 0.33 7 7 6 0.84 0.84 1.00 2.60 4.44 9.31 0.72 1.24 3.10 0.36 B2 B2 0.11 6 6 5 1.04 1.04 1.00 2.76 4.72 9.95 0.33 0.56 1.14 0.16 B3 B3 0.03 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.07 0.13 0.32 0.04 C1 C1 0.45 9 9 9 0.52 0.52 0.65 2.35 4.02 8.21 0.55 0.94 2.39 0.27 C2a C2a 0.49 5 5 5 0.92 0.92 1.00 2.85 4.87 9.95 1.27 2.18 4.85 0.64 C2b C2b 0.23 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.63 1.08 2.31 0.31 C3 C3 0.34 7 7 6 0.66 0.66 0.83 2.60 4.44 9.31 0.59 1.01 2.64 0.29 C4 C4 0.13 5 5 5 0.44 0.44 0.55 2.85 4.87 9.95 0.16 0.27 0.70 0.08 D1 D1 0.40 5 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.29 0.49 1.25 0.14 D2 D2 0.46 5 5 5 0.71 0.71 0.88 2.85 4.87 9.95 0.93 1.59 4.05 0.46 OS1 OS1 2.06 6 6 6 0.39 0.39 0.49 2.67 4.56 9.63 2.16 3.70 9.76 1.08 OS2 OS2 0.41 6 6 5 0.71 0.71 0.89 2.76 4.72 9.95 0.81 1.38 3.63 0.40 DEVELOPED RUNOFF COMPUTATIONS A. Reese January 11, 2017 Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 Overland Flow, Time of Concentration: Project: The Park Townhomes Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = T i + 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 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, V (ft/s) Tt (min) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) B1 A3, B1, OS1, OS2 5.7 5.7 5.3 785 1.26% 2.24 5.8 0 0.0 0.00 N/A 11 11 11 C2b A1, A2, A3, B1, B2, C1, C2a, C2b, C4 6.1 6.1 5.8 544 0.50% 1.41 6.4 0 0.0 0.00 N/A 12 12 12 Rational Method Equation: Project: The Park Townhomes Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: B1 B1, OS1, OS2 2.47 12 12 12 0.56 0.56 0.69 38% 2.05 3.50 7.16 2.83 4.84 12.25 1.42 C2b A1, A2, A3, B1, B2, C1, C2a, C2b, C4 2.73 12 12 12 0.76 0.76 0.87 68% 2.05 3.50 7.16 4.25 7.26 17.05 2.13 Flow, WQ (cfs) COMBINED RUNOFF COMPUTATIONS A. Reese January 11, 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) Intensity, i100 (in/hr) Flow, Q2 (cfs) Flow, Q10 (cfs) Flow, Q100 (cfs) C2 C10 C100 Composite % Imperv. Intensity, i2 (in/hr) Intensity, i10 (in/hr) Q = C f ( C )( i )( A ) D:\Projects\1124-002\Drainage\Hydrology\1124-002_Rational-Calcs_Proposed.xlsx\Combined Runoff Design Point Basin ID Basin Area (ac) Composite % Imperv. 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient 100-year Composite Runoff Coefficient Flow, Q2 (cfs) Flow, Q10 (cfs) Flow, Q100 (cfs) Flow, WQ (cfs) A1 A1 0.28 41% 0.57 0.57 0.71 0.43 0.73 1.93 0.21 A2 A2 0.47 83% 0.88 0.88 1.00 1.19 2.03 4.71 0.59 A3 A3 0.22 50% 0.64 0.64 0.80 0.41 0.70 1.78 0.20 B1 B1 0.33 83% 0.84 0.84 1.00 0.72 1.24 3.10 0.36 B2 B2 0.11 108% 1.04 1.04 1.00 0.33 0.56 1.14 0.16 B3 B3 0.03 76% 0.80 0.80 1.00 0.07 0.13 0.32 0.04 C1 C1 0.45 34% 0.52 0.52 0.65 0.55 0.94 2.39 0.27 C2a C2a 0.49 88% 0.92 0.92 1.00 1.27 2.18 4.85 0.64 C2b C2b 0.23 93% 0.95 0.95 1.00 0.63 1.08 2.31 0.31 C3 C3 0.34 53% 0.66 0.66 0.83 0.59 1.01 2.64 0.29 C4 C4 0.13 24% 0.44 0.44 0.55 0.16 0.27 0.70 0.08 D1 D1 0.40 0% 0.25 0.25 0.31 0.29 0.49 1.25 0.14 D2 D2 0.46 65% 0.71 0.71 0.88 0.93 1.59 4.05 0.46 OS1 OS1 2.06 20% 0.39 0.39 0.49 0.81 1.38 3.63 0.40 OS2 OS2 0.41 65% 0.71 0.71 0.89 0.00 0.00 0.00 0.00 B1 B1, OS1, OS2 2.47 38% 0.56 0.56 0.69 2.83 4.84 12.25 1.42 C2b A1, A2, A3, B1, B2, C1, C2a, C2b, C4 2.73 68% 0.76 0.76 0.87 4.25 7.26 17.05 2.13 Rational Method Summary | Proposed Condition APPENDIX B Hydraulic Calculations Storm Drain A4 Existing Storm Drain Storm Drain A Storm Drain A8 Storm Drain A9 Storm Drain A Existing Storm Drain Storm Drain A Storm Drain A4 Storm Drain A8 Storm Drain A9 INLET CAPACITY SUMMARY Project: The Park Townhomes at Fossil Ridge By: A. Reese Date: Inlet A2 C2b Area Inlet South end of vaults Sump 100-Yr 5.89 6.04 Inlet A6-1 C2a Area Inlet North end of vaults Grade 100-Yr 1.27 5.44 Inlet A8-1 B2 Single Combo County Fair - South FL Sump 100-yr 1.14 5.80 Inlet A9 B1 Double Combo County Fair - North FL Sump 100-yr 4.81 6.20 Inlet A10 A2 Double Combo North Driveway Grade 2-yr 1.19 3.00 Design Storm Design Flow (CFS) Inlet Capacity (CFS) January 11, 2017 Inlet ID Design Point Inlet Type Location Inlet Conditio n D:\Projects\1124-002\Drainage\Inlets\1124-002_Inlet summary.xlsx Area Inlet Performance Curve: Inlet A2 Project: The Park Townhomes at Fossil Ridge Calculations By: A. Reese Design Point: C2b Governing Equations: At low flow depths, the inlet will act like a weir governed by the following equation: * where P = 2(L + W) * where H corresponds to the depth of water above the flowline At higher flow depths, the inlet will act like an orifice governed by the following equation: * where A equals the open area of the inlet grate * where H corresponds to the depth of water above the centroid of the cross-sectional area (A) The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown. However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation will cross at a certain flow depth. The two curves can be found below: If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir. Input Parameters: Type of Grate: Neenah R-3362-L Length of Grate (ft): 3.27 Width of Grate (ft): 1.86 Open Area of Grate (ft2): 2.90 Flowline Elevation (ft): 4910.130 Allowable Capacity: 50% Depth vs. Flow: Depth Above Inlet (ft) Elevation (ft) Shallow Weir Flow (cfs) Orifice Flow (cfs) Actual Flow (cfs) 0.00 4910.13 0.00 0.00 0.00 0.05 4910.18 0.17 1.74 0.17 0.10 4910.23 0.49 2.46 0.49 0.119 4910.249 0.63 2.69 0.63 Q2 0.15 4910.28 0.89 3.02 0.89 0.20 4910.33 1.38 3.48 1.38 0.25 4910.38 1.92 3.90 1.92 0.30 4910.43 2.53 4.27 2.53 0.35 4910.48 3.19 4.61 3.19 0.40 4910.53 3.89 4.93 3.89 0.45 4910.58 4.65 5.23 4.65 0.50 4910.63 5.44 5.51 5.44 0.55 4910.68 6.28 5.78 5.78 0.571 4910.701 6.64 5.89 5.89 Q100 0.60 4910.73 7.15 6.04 6.04 Inlet A2 is designed to intercept the full 2-year flow of 0.63 cfs with 1.5" of flow depth and the full 100-year flow of 5.89 cfs (DP C2b + C2a bypass) at a depth of 6.85". 0.00 1.00 2.00 3.00 4.00 5.00 6.00 Area Inlet Performance Curve: Inlet A6-1 Project: The Park Townhomes at Fossil Ridge Calculations By: A. Reese Design Point: C2a Governing Equations: At low flow depths, the inlet will act like a weir governed by the following equation: * where P = 2(L + W) * where H corresponds to the depth of water above the flowline At higher flow depths, the inlet will act like an orifice governed by the following equation: * where A equals the open area of the inlet grate * where H corresponds to the depth of water above the centroid of the cross-sectional area (A) The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown. However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation will cross at a certain flow depth. The two curves can be found below: If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir. Input Parameters: Type of Grate: Neenah R-3362-L Length of Grate (ft): 3.27 Width of Grate (ft): 1.86 Open Area of Grate (ft2): 2.90 Flowline Elevation (ft): 4911.180 Allowable Capacity: 50% Depth vs. Flow: Depth Above Inlet (ft) Elevation (ft) Shallow Weir Flow (cfs) Orifice Flow (cfs) Actual Flow (cfs) 0.00 4911.18 0.00 0.00 0.00 0.05 4911.23 0.17 1.74 0.17 0.10 4911.28 0.49 2.46 0.49 0.15 4911.33 0.89 3.02 0.89 0.190 4911.370 1.27 3.40 1.27 Q2 0.20 4911.38 1.38 3.48 1.38 0.25 4911.43 1.92 3.90 1.92 0.30 4911.48 2.53 4.27 2.53 0.35 4911.53 3.19 4.61 3.19 0.40 4911.58 3.89 4.93 3.89 0.45 4911.63 4.65 5.23 4.65 0.463 4911.643 4.85 5.30 4.85 Q100 0.50 4911.68 5.44 5.51 5.44 Inlet A6-1 is designed to intercept the full 2-year flow of 1.27 cfs with 2.25" of flow depth and the full 100-year flow of 4.85 cfs at a depth of 5.5". 0.00 1.00 2.00 3.00 4.00 5.00 6.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 Discharge (cfs) Project = Inlet ID = Design Information (Input) MINOR MAJOR Type of Inlet Inlet Type = Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 2.00 2.00 inches Number of Unit Inlets (Grate or Curb Opening) No = 1 1 Water Depth at Flowline (outside of local depression) Flow Depth = 6.0 8.0 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) = 3.00 3.00 feet Width of a Unit Grate Wo = 1.73 1.73 feet Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = 0.31 0.31 Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = 0.50 0.50 Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = 3.60 3.60 Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = 0.60 0.60 Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) = 3.00 3.00 feet Height of Vertical Curb Opening in Inches Hvert = 6.50 6.50 inches Height of Curb Orifice Throat in Inches Hthroat = 5.25 5.25 inches Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 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 2.3-3.6) Cw (C) = 3.70 3.70 Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.66 0.66 MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition) Qa = 3.9 5.8 cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED = 0.3 1.1 cfs INLET IN A SUMP OR SAG LOCATION The Park Townhomes at Fossil Ridge Inlet A8-1 (Combo Inlet - Sump) Denver No. 16 Combination H-Vert H-Curb W Lo (C) Lo (G) Wo WP UD Inlet 3.1_Inlet A8-1.xlsm, Inlet In Sump 1/11/2017, 7:18 AM Project = Inlet ID = Design Information (Input) MINOR MAJOR Type of Inlet Inlet Type = Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 2.00 2.00 inches Number of Unit Inlets (Grate or Curb Opening) No = 2 2 Water Depth at Flowline (outside of local depression) Flow Depth = 6.0 6.0 inches Grate Information MINOR MAJOR Length of a Unit Grate Lo (G) = 3.00 3.00 feet Width of a Unit Grate Wo = 1.73 1.73 feet Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = 0.31 0.31 Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = 0.50 0.50 Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = 3.60 3.60 Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = 0.60 0.60 Curb Opening Information MINOR MAJOR Length of a Unit Curb Opening Lo (C) = 3.00 3.00 feet Height of Vertical Curb Opening in Inches Hvert = 6.50 6.50 inches Height of Curb Orifice Throat in Inches Hthroat = 5.25 5.25 inches Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 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 2.3-3.6) Cw (C) = 3.70 3.70 Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.66 0.66 MINOR MAJOR Total Inlet Interception Capacity (assumes clogged condition) Qa = 6.2 6.2 cfs Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED = 0.7 4.8 cfs INLET IN A SUMP OR SAG LOCATION The Park Townhomes at Fossil Ridge Inlet A9 (Combo Inlet - Sump) Denver No. 16 Combination H-Vert H-Curb W Lo (C) Lo (G) Wo WP UD Inlet 3.1_Inlet A9.xlsm, Inlet In Sump 1/11/2017, 7:24 AM Project: Inlet ID: Design Information (Input) MINOR MAJOR Type of Inlet Type = Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') aLOCAL = 2.0 2.0 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 = 3.00 3.00 ft Width of a Unit Grate (cannot be greater than W from Q-Allow) Wo = 1.73 1.73 ft Clogging Factor for a Single Unit Grate (typical min. value = 0.5) Cf -G = 0.50 0.50 Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1) Cf -C = 0.10 0.10 Street Hydraulics: WARNING: Q > ALLOWABLE Q FOR MINOR & MAJOR STORM MINOR MAJOR Total Inlet Interception Capacity Q = 1.1 3.0 cfs Total Inlet Carry-Over Flow (flow bypassing inlet) Qb = 0.1 1.8 cfs Capture Percentage = Qa/Q o = C% = 96 63 % INLET ON A CONTINUOUS GRADE The Park Townhomes at Fossil Ridge Inlet A10 (Combo Inlet - On-Grade) Denver No. 16 Combination UD Inlet 3.1_Inlet A10.xlsm, Inlet On Grade 1/11/2017, 7:21 AM APPENDIX C WATER QUALITY/LID DESIGN COMPUTATIONS Project Summary Total Impervious Area 92,659 sf Target Treatment Percentage 75% Minimum Area to be Treated by LID measures 69,493.97 sf Infiltration Gallery/Underground Vaults Vault Volume 1,873 cf Total Vault Treatment Area 80,077 sf Total Treatment Area 80,077 sf Percent Total Project Area Treated 86.4% The Park Townhomes at Fossil Ridge On-Site LID Treatment Vault ID Total Required WQ Volume (cf) InFlow, WQ (cfs) Chamber Type Chamber Release Rate (cfs) Chamber Volume (cfs) Installed Chamber Volume (cfs) Mimimum No. of Chambers Minimum Release Rate (cfs) Required Chamber Volume by FAA Method (cf) Provided Number of Chambers Provided Release Rate (cfs) Provided Chamber Volume (cf) Total Installed Chamber Volume (cf) 1 1608 2.13 SC-740 0.024 45.90 74.90 22 0.52 1717 25 0.59 1148 1873 Vault Configuration Summary Note: "Chamber Volume" refers to the open volume within the vaults. "Installed Chamber Volume" refers to the total volume provided, including the surrounding aggregates. D:\Projects\1124-002\Drainage\LID\1124-002_Vault Summary.xlsx Chamber Dimensions SC-310 SC-740 Width (in) 34.00 51.00 Length (in) 85.40 85.40 Height (in) 16.00 30.00 Floor Area (sf) 20.16 30.25 Chamber Volume (cf) 14.70 45.90 Chamber/Aggregate Volume (cf) 29.30 74.90 Flow Rate** 0.35 gpm/sf 1 cf = 7.48052 gal 1 gallon = 0.133681 cf 1 GPM = 0.002228 cfs **Flow rate based on 1/2 of Nov 07 QMAX in Figure 17 of UNH Testing Report SC-310 SC-740 Flow Rate/chamber (cfs) 0.015724 0.023586 StormTech Chamber Data Chamber Flow Rate Conversion (gpm/sf to cfs) Chamber Flow Rate D:\Projects\1124-002\Drainage\LID\1124-002_Vault Summary.xlsx Project Title Date: Project Number Calcs By: Basin(S) 0.8 WQCV = Watershed inches of Runoff (inches) 68.00% a = Runoff Volume Reduction (constant) i = Total imperviousness Ratio (i = Iwq/100) 0.213 in A = 2.08 ac V = 0.0369 ac-ft V = Water Quality Design Volume (ac-ft) WQCV = Water Quality Capture Volume (inches) A = Watershed Area (acres) 1608 cu. ft. Drain Time a = i = WQCV = Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event The Park Townhomes at Fossil Ridge January 11, 2017 1124-002 A. Reese A1, A2, A3, B1, B2, C1, C2a & C2b 0.213 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 ÷ ø ö ç The Park Townhomes at Fossil Ridge Fort Collins, Colorado A. Reese Date: January 10, 2017 Pond No.: Vault 1 C2 WQ 0.87 Area (A)= 2.73 acres Quantity Detention 1717 ft 3 Max Release Rate = 0.59 cfs Time Time Ft.Collins WQ Intensity Q100 Inflow (Runoff) Volume Outflow (Release) Volume Storage Detention Volume (mins) (secs) (in/hr) (cfs) (ft 3 ) (ft 3 ) (ft 3 ) 5 300 1.43 3.4 1015 177 838 10 600 1.11 2.6 1575 354 1221 15 900 0.94 2.2 1999 531 1468 20 1200 0.81 1.9 2294 708 1586 25 1500 0.72 1.7 2547 885 1662 30 1800 0.65 1.5 2779 1062 1717 35 2100 0.59 1.4 2918 1239 1679 40 2400 0.54 1.3 3050 1416 1634 45 2700 0.50 1.2 3174 1593 1581 50 3000 0.46 1.1 3278 1770 1508 55 3300 0.44 1.0 3409 1947 1462 60 3600 0.41 1.0 3506 2124 1382 65 3900 0.39 0.9 3566 2301 1265 70 4200 0.37 0.9 3641 2478 1163 75 4500 0.35 0.8 3687 2655 1032 80 4800 0.33 0.8 3762 2832 930 85 5100 0.32 0.7 3816 3009 807 90 5400 0.31 0.7 3912 3186 726 95 5700 0.29 0.7 3926 3363 563 100 6000 0.28 0.7 3990 3540 450 105 6300 0.27 0.6 4040 3717 323 110 6600 0.26 0.6 4076 3894 182 115 6900 0.3 0.6 4179 4071 108 120 7200 0.25 0.6 4190 4248 -58 Vault Volume Calculation | FAA Method Project: Project Location: Calculations By: Input Variables Results Design Point APPENDIX D EROSION CONTROL REPORT The Park Townhomes at Fossil Ridge EROSION CONTROL REPORT A comprehensive Erosion and Sediment Control Plan (along with associated details) has been included with the final construction drawings. 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 and/or wattles along the disturbed perimeter, gutter protection in the adjacent roadways and inlet protection at existing and 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 Sheet C001 of the Utility Plans. The Final Utility Plans will 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 may 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 USDA SOILS REPORT 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, Colorado Ziegler Townhomes Natural Resources Conservation Service October 20, 2016 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 (http:// 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 alternative means 2 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 How Soil Surveys Are Made..................................................................................5 Soil Map..................................................................................................................7 Soil Map................................................................................................................8 Legend..................................................................................................................9 Map Unit Legend................................................................................................10 Map Unit Descriptions........................................................................................10 Larimer County Area, Colorado......................................................................12 34—Fort Collins loam, 0 to 1 percent slopes..............................................12 35—Fort Collins loam, 0 to 3 percent slopes..............................................13 36—Fort Collins loam, 3 to 5 percent slopes..............................................14 41—Garrett loam, 1 to 3 percent slopes.....................................................16 73—Nunn clay loam, 0 to 1 percent slopes.................................................17 74—Nunn clay loam, 1 to 3 percent slopes.................................................18 76—Nunn clay loam, wet, 1 to 3 percent slopes.........................................19 103—Stoneham loam, 5 to 9 percent slopes..............................................21 Soil Information for All Uses...............................................................................23 Soil Properties and Qualities..............................................................................23 Soil Qualities and Features.............................................................................23 Hydrologic Soil Group (Ziegler Townhomes)..............................................23 References............................................................................................................28 4 How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil scientists classified and named the soils in the survey area, they compared the 5 individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil- landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. Custom Soil Resource Report 6 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. 7 8 Custom Soil Resource Report Soil Map 4484100 4484300 4484500 4484700 4484900 4485100 4484100 4484300 4484500 4484700 4484900 4485100 497500 497700 497900 498100 498300 498500 498700 498900 499100 499300 497500 497700 497900 498100 498300 498500 498700 498900 499100 499300 40° 31' 4'' N 105° 1' 46'' W 40° 31' 4'' N 105° 0' 27'' W 40° 30' 25'' N 105° 1' 46'' W 40° 30' 25'' N 105° 0' 27'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 400 800 1600 2400 Feet 0 100 200 400 600 Meters Map Scale: 1:8,510 if printed on A landscape (11" x 8.5") sheet. Warning: 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: http://websoilsurvey.nrcs.usda.gov 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 Map Unit Legend Larimer County Area, Colorado (CO644) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 34 Fort Collins loam, 0 to 1 percent slopes 3.4 0.9% 35 Fort Collins loam, 0 to 3 percent slopes 24.0 6.6% 36 Fort Collins loam, 3 to 5 percent slopes 42.9 11.9% 41 Garrett loam, 1 to 3 percent slopes 1.0 0.3% 73 Nunn clay loam, 0 to 1 percent slopes 51.4 14.2% 74 Nunn clay loam, 1 to 3 percent slopes 185.8 51.5% 76 Nunn clay loam, wet, 1 to 3 percent slopes 44.4 12.3% 103 Stoneham loam, 5 to 9 percent slopes 8.1 2.2% Totals for Area of Interest 361.0 100.0% 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 Custom Soil Resource Report 10 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, 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 11 Larimer County Area, Colorado 34—Fort Collins loam, 0 to 1 percent slopes Map Unit Setting National map unit symbol: jpw7 Elevation: 4,800 to 5,500 feet Mean annual precipitation: 13 to 15 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period: 135 to 150 days Farmland classification: Prime farmland if irrigated Map Unit Composition Fort collins and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Fort Collins Setting Landform: Fans, terraces Landform position (three-dimensional): Base slope, tread Down-slope shape: Linear Across-slope shape: Linear Parent material: Alluvium Typical profile H1 - 0 to 8 inches: loam H2 - 8 to 18 inches: loam, clay loam H2 - 8 to 18 inches: loam, silt loam, fine sandy loam H3 - 18 to 60 inches: H3 - 18 to 60 inches: H3 - 18 to 60 inches: Properties and qualities Slope: 0 to 1 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 15 percent Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water storage in profile: Very high (about 26.0 inches) Interpretive groups Land capability classification (irrigated): 2e Land capability classification (nonirrigated): 3c Hydrologic Soil Group: B Ecological site: Loamy Plains (R067XY002CO) Hydric soil rating: No Custom Soil Resource Report 12 Minor Components Stoneham Percent of map unit: 6 percent Hydric soil rating: No Larim Percent of map unit: 5 percent Hydric soil rating: No Ascalon Percent of map unit: 4 percent Hydric soil rating: No 35—Fort Collins loam, 0 to 3 percent slopes Map Unit Setting National map unit symbol: 2tlnc Elevation: 4,020 to 6,730 feet Mean annual precipitation: 14 to 16 inches Mean annual air temperature: 46 to 48 degrees F Frost-free period: 143 to 154 days Farmland classification: Prime farmland if irrigated Map Unit Composition Fort collins and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Fort Collins Setting Landform: Interfluves Down-slope shape: Linear Across-slope shape: Linear Parent material: Pleistocene or older alluvium derived from igneous, metamorphic and sedimentary rock and/or eolian deposits Typical profile Ap - 0 to 4 inches: loam Bt1 - 4 to 9 inches: clay loam Bt2 - 9 to 16 inches: clay loam Bk1 - 16 to 29 inches: loam Bk2 - 29 to 80 inches: loam Properties and qualities Slope: 0 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Custom Soil Resource Report 13 Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.20 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 12 percent Salinity, maximum in profile: Nonsaline (0.1 to 1.0 mmhos/cm) Sodium adsorption ratio, maximum in profile: 0.5 Available water storage in profile: High (about 9.1 inches) Interpretive groups Land capability classification (irrigated): 2e Land capability classification (nonirrigated): 4c Hydrologic Soil Group: C Ecological site: Loamy Plains (R067BY002CO) Hydric soil rating: No Minor Components Nunn Percent of map unit: 10 percent Landform: Terraces Landform position (three-dimensional): Tread Down-slope shape: Linear Across-slope shape: Linear Ecological site: Loamy Plains (R067BY002CO) Hydric soil rating: No Vona Percent of map unit: 5 percent Landform: Interfluves Landform position (two-dimensional): Backslope, footslope Landform position (three-dimensional): Side slope, base slope Down-slope shape: Linear Across-slope shape: Linear Ecological site: Sandy Plains (R067BY024CO) Hydric soil rating: No 36—Fort Collins loam, 3 to 5 percent slopes Map Unit Setting National map unit symbol: jpw9 Elevation: 4,800 to 5,500 feet Mean annual precipitation: 13 to 15 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period: 135 to 150 days Farmland classification: Prime farmland if irrigated Map Unit Composition Fort collins and similar soils: 90 percent Custom Soil Resource Report 14 Minor components: 10 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Fort Collins Setting Landform: Terraces, fans Landform position (three-dimensional): Base slope, riser Down-slope shape: Linear Across-slope shape: Linear Parent material: Alluvium Typical profile H1 - 0 to 9 inches: loam H2 - 9 to 20 inches: loam, clay loam H2 - 9 to 20 inches: loam, silt loam, fine sandy loam H3 - 20 to 60 inches: H3 - 20 to 60 inches: H3 - 20 to 60 inches: Properties and qualities Slope: 3 to 5 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 15 percent Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water storage in profile: Very high (about 25.5 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 3e Hydrologic Soil Group: B Ecological site: Loamy Plains (R067XY002CO) Hydric soil rating: No Minor Components Ascalon Percent of map unit: 5 percent Hydric soil rating: No Kim Percent of map unit: 3 percent Hydric soil rating: No Stoneham Percent of map unit: 2 percent Hydric soil rating: No Custom Soil Resource Report 15 41—Garrett loam, 1 to 3 percent slopes Map Unit Setting National map unit symbol: jpwh Elevation: 5,200 to 6,000 feet Mean annual precipitation: 13 to 15 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period: 135 to 150 days Farmland classification: Prime farmland if irrigated Map Unit Composition Garrett and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Garrett Setting Landform: Terraces, fans Landform position (three-dimensional): Base slope, tread Down-slope shape: Linear Across-slope shape: Linear Parent material: Alluvium derived from sandstone and shale Typical profile H1 - 0 to 8 inches: loam H2 - 8 to 39 inches: sandy clay loam, sandy loam H2 - 8 to 39 inches: sandy loam H3 - 39 to 60 inches: Properties and qualities Slope: 1 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 10 percent Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water storage in profile: Very high (about 12.9 inches) Interpretive groups Land capability classification (irrigated): 2e Land capability classification (nonirrigated): 3e Hydrologic Soil Group: B Ecological site: Overflow (R049XY036CO) Hydric soil rating: No Custom Soil Resource Report 16 Minor Components Otero Percent of map unit: 10 percent Hydric soil rating: No Connerton Percent of map unit: 3 percent Hydric soil rating: No Harlan Percent of map unit: 2 percent Hydric soil rating: No 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 derived from igneous, metamorphic and sedimentary rock 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 Natural drainage class: Well drained Custom Soil Resource Report 17 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 in profile: 7 percent Salinity, maximum in profile: Nonsaline (0.1 to 1.0 mmhos/cm) Sodium adsorption ratio, maximum in profile: 0.5 Available water storage in profile: High (about 9.1 inches) Interpretive groups Land capability classification (irrigated): 3e Land capability classification (nonirrigated): 4e Hydrologic Soil Group: C Ecological site: Clayey Plains (R067BY042CO) 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: Clayey Plains (R067BY042CO) 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: Loamy Plains (R067BY002CO) Hydric soil rating: No 74—Nunn clay loam, 1 to 3 percent slopes Map Unit Setting National map unit symbol: jpxn Elevation: 4,800 to 5,600 feet Mean annual precipitation: 13 to 15 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period: 135 to 150 days Farmland classification: Prime farmland if irrigated Map Unit Composition Nunn and similar soils: 85 percent Custom Soil Resource Report 18 Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Nunn Setting Landform: Terraces, fans Landform position (three-dimensional): Base slope, tread Down-slope shape: Linear Across-slope shape: Linear Parent material: Alluvium Typical profile H1 - 0 to 10 inches: clay loam H2 - 10 to 60 inches: clay loam, clay H2 - 10 to 60 inches: Properties and qualities Slope: 1 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: High 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 in profile: 15 percent Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water storage in profile: Very high (about 18.9 inches) Interpretive groups Land capability classification (irrigated): 2e Land capability classification (nonirrigated): 3e Hydrologic Soil Group: C Hydric soil rating: No Minor Components Ulm Percent of map unit: 10 percent Hydric soil rating: No Satanta Percent of map unit: 5 percent Hydric soil rating: No 76—Nunn clay loam, wet, 1 to 3 percent slopes Map Unit Setting National map unit symbol: jpxq Elevation: 4,800 to 5,600 feet Custom Soil Resource Report 19 Mean annual precipitation: 13 to 15 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period: 135 to 150 days Farmland classification: Prime farmland if irrigated Map Unit Composition Nunn, wet, and similar soils: 90 percent Minor components: 10 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Nunn, Wet Setting Landform: Alluvial fans, stream terraces Landform position (three-dimensional): Base slope, tread Down-slope shape: Linear Across-slope shape: Linear Parent material: Alluvium Typical profile H1 - 0 to 10 inches: clay loam H2 - 10 to 47 inches: clay loam, clay H2 - 10 to 47 inches: clay loam, loam, gravelly sandy loam H3 - 47 to 60 inches: H3 - 47 to 60 inches: H3 - 47 to 60 inches: Properties and qualities Slope: 1 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Somewhat poorly drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat): Moderately low to moderately high (0.06 to 0.60 in/hr) Depth to water table: About 24 to 36 inches Frequency of flooding: Rare Frequency of ponding: None Calcium carbonate, maximum in profile: 10 percent Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Available water storage in profile: Very high (about 19.8 inches) Interpretive groups Land capability classification (irrigated): 2w Land capability classification (nonirrigated): 3s Hydrologic Soil Group: C Hydric soil rating: No Minor Components Heldt Percent of map unit: 6 percent Hydric soil rating: No Dacono Percent of map unit: 3 percent Hydric soil rating: No Custom Soil Resource Report 20 Mollic halaquepts Percent of map unit: 1 percent Landform: Swales Hydric soil rating: Yes 103—Stoneham loam, 5 to 9 percent slopes Map Unit Setting National map unit symbol: jptw Elevation: 4,800 to 5,600 feet Mean annual precipitation: 13 to 15 inches Mean annual air temperature: 48 to 50 degrees F Frost-free period: 135 to 150 days Farmland classification: Farmland of local importance Map Unit Composition Stoneham and similar soils: 85 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Stoneham Setting Landform: Benches, terraces Landform position (three-dimensional): Side slope, tread Down-slope shape: Linear Across-slope shape: Linear Parent material: Mixed alluvium and/or eolian deposits Typical profile H1 - 0 to 3 inches: loam H2 - 3 to 9 inches: clay loam, sandy clay loam, loam H2 - 3 to 9 inches: loam, clay loam, sandy clay loam H2 - 3 to 9 inches: H3 - 9 to 60 inches: H3 - 9 to 60 inches: H3 - 9 to 60 inches: Properties and qualities Slope: 5 to 9 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.60 to 2.00 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Calcium carbonate, maximum in profile: 15 percent Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm) Custom Soil Resource Report 21 Available water storage in profile: Very high (about 27.7 inches) Interpretive groups Land capability classification (irrigated): 6e Land capability classification (nonirrigated): 6e Hydrologic Soil Group: B Ecological site: Loamy Plains (R067XY002CO) Hydric soil rating: No Minor Components Kim Percent of map unit: 8 percent Hydric soil rating: No Larimer Percent of map unit: 5 percent Hydric soil rating: No Fort collins Percent of map unit: 2 percent Hydric soil rating: No Custom Soil Resource Report 22 Soil Information for All Uses Soil Properties and Qualities The Soil Properties and Qualities section includes various soil properties and qualities displayed as thematic maps with a summary table for the soil map units in the selected area of interest. A single value or rating for each map unit is generated by aggregating the interpretive ratings of individual map unit components. This aggregation process is defined for each property or quality. Soil Qualities and Features Soil qualities are behavior and performance attributes that are not directly measured, but are inferred from observations of dynamic conditions and from soil properties. Example soil qualities include natural drainage, and frost action. Soil features are attributes that are not directly part of the soil. Example soil features include slope and depth to restrictive layer. These features can greatly impact the use and management of the soil. Hydrologic Soil Group (Ziegler Townhomes) Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long- duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (A/D, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. 23 Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Custom Soil Resource Report 24 25 Custom Soil Resource Report Map—Hydrologic Soil Group (Ziegler Townhomes) 4484100 4484300 4484500 4484700 4484900 4485100 4484100 4484300 4484500 4484700 4484900 4485100 497500 497700 497900 498100 498300 498500 498700 498900 499100 499300 497500 497700 497900 498100 498300 498500 498700 498900 499100 499300 40° 31' 4'' N 105° 1' 46'' W 40° 31' 4'' N 105° 0' 27'' W 40° 30' 25'' N 105° 1' 46'' W 40° 30' 25'' N 105° 0' 27'' W N Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84 0 400 800 1600 2400 Feet 0 100 200 400 600 Meters Map Scale: 1:8,510 if printed on A landscape (11" x 8.5") sheet. Warning: Soil Map may not be valid at this scale. MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Rating Polygons A A/D B B/D C C/D D Not rated or not available Soil Rating Lines A A/D B B/D C C/D D Not rated or not available Soil Rating Points A A/D B B/D C C/D D Not rated or not available 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: http://websoilsurvey.nrcs.usda.gov 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 Table—Hydrologic Soil Group (Ziegler Townhomes) Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 34 Fort Collins loam, 0 to 1 percent slopes B 3.4 0.9% 35 Fort Collins loam, 0 to 3 percent slopes C 24.0 6.6% 36 Fort Collins loam, 3 to 5 percent slopes B 42.9 11.9% 41 Garrett loam, 1 to 3 percent slopes B 1.0 0.3% 73 Nunn clay loam, 0 to 1 percent slopes C 51.4 14.2% 74 Nunn clay loam, 1 to 3 percent slopes C 185.8 51.5% 76 Nunn clay loam, wet, 1 to 3 percent slopes C 44.4 12.3% 103 Stoneham loam, 5 to 9 percent slopes B 8.1 2.2% Totals for Area of Interest 361.0 100.0% Rating Options—Hydrologic Soil Group (Ziegler Townhomes) Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher Custom Soil Resource Report 27 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 28 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 29 MAP POCKET DR1 –DRAINAGE EXHIBIT Survey Area Data: Version 10, Sep 22, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Apr 22, 2011—Apr 28, 2011 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 26 the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 10, Sep 22, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Apr 22, 2011—Apr 28, 2011 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 9 Design Storm Required Detention Volume Developed "C" = D:\Projects\1124-002\Drainage\LID\1124-002_FAA_Vault 1.xlsm\ è = æ 12 hr D:\Projects\1124-002\Drainage\WatQual\1124-002_WQ Volume_Vault 1.xls Stage (ft) Stage - Discharge Curves Weir Flow Orifice Flow Q = 3 . 0 P H 1 . 5 Q = 0 . 67 A ( 2 gH ) 0 . 5 D:\Projects\1124-002\Drainage\Inlets\1124-002_Area Inlets.xls 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 Discharge (cfs) Stage (ft) Stage - Discharge Curves Weir Flow Orifice Flow Q = 3 . 0 P H 1 . 5 Q = 0 . 67 A ( 2 gH ) 0 . 5 D:\Projects\1124-002\Drainage\Inlets\1124-002_Area Inlets.xls COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS A. Reese January 11, 2017 Design Point Basins Tc Calculated at Upstream Design Point Additional Gutter Flow Additional Swale Flow Time of Concentration (Equation RO-4) ( ) 3 1 1 . 87 1 . 1 * S Ti C Cf L - = D:\Projects\1124-002\Drainage\Hydrology\1124-002_Rational-Calcs_Proposed.xlsx\Combined-Tc Q = C f ( C )( i )( A ) (min) 10-yr Tc (min) 100-yr Tc (min) A1 A1 No 0.25 0.25 0.31 26 6.82% 4.3 4.3 3.9 0 - - - 207 1.59% 1.89 1.8 6 6 6 A2 A2 No 0.95 0.95 1.00 46 2.64% 1.4 1.4 0.9 162 1.80% 2.68 1.0 0 - - - 5 5 5 A3 A3 No 0.25 0.25 0.31 10 16.77% 1.9 1.9 1.8 164 2.53% 3.18 0.9 - - - 5 5 5 B1 B1 No 0.25 0.25 0.31 24 2.85% 5.4 5.4 5.0 235 1.96% 2.80 1.4 - - - 7 7 6 B2 B2 No 0.25 0.25 0.31 14 1.72% 5.0 5.0 4.6 52 0.52% 1.44 0.6 - - - 6 6 5 B3 B3 No 0.25 0.25 0.31 11 1.76% 4.4 4.4 4.1 21 0.47% 1.36 0.3 - - - 5 5 5 C1 C1 No 0.25 0.25 0.31 16 3.36% 4.2 4.2 3.9 369 0.50% 1.41 4.4 46 1.55% 1.87 0.4 9 9 9 C2a C2a No 0.95 0.95 1.00 31 2.77% 1.1 1.1 0.7 184 1.00% 2.00 1.5 - - - 5 5 5 C2b C2b No 0.95 0.95 1.00 39 3.50% 1.2 1.2 0.8 82 1.00% 2.00 0.7 - - - 5 5 5 C3 C3 No 0.25 0.25 0.31 40 3.07% 6.9 6.9 6.4 - - - - - - 7 7 6 C4 C4 No 0.25 0.25 0.31 17 6.93% 3.5 3.5 3.2 - - - 51 1.63% 1.91 0.4 5 5 5 D1 D1 No 0.25 0.25 0.31 6 2.47% 2.9 2.9 2.7 - - - - - - 5 5 5 D2 D2 No 0.95 0.95 1.00 40 3.39% 1.2 1.2 0.8 237 1.49% 2.44 1.6 - - - 5 5 5 OS1 OS1 No 0.95 0.95 1.00 32 1.56% 1.4 1.4 0.9 326 0.31% 1.11 4.9 - - - 6 6 6 OS2 OS2 No 0.95 0.95 1.00 26 1.97% 1.1 1.1 0.8 505 0.87% 1.86 4.5 - - - 6 6 5 DEVELOPED TIME OF CONCENTRATION COMPUTATIONS Gutter Flow Swale Flow Design Point Basin Overland Flow A. Reese January 11, 2017 Time of Concentration (Equation RO-4) ( ) 3 1 1 . 87 1 . 1 * S Ti C Cf L - = C4 0.13 0.00 0.00 0.03 0.00 0.00 0.09 0.44 0.44 0.55 24% D1 0.40 0.00 0.00 0.00 0.00 0.00 0.40 0.25 0.25 0.31 0% D2 0.46 0.27 0.03 0.00 0.00 0.00 0.16 0.71 0.71 0.88 65% Onsite Total 3.96 0.84 0.66 1.02 0.00 0.00 1.44 0.70 0.70 0.87 59% OS1 2.06 0.27 0.03 0.12 0.00 0.00 1.63 0.39 0.39 0.49 20% OS2 0.41 0.21 0.06 0.00 0.00 0.00 0.14 0.71 0.71 0.89 65% 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 January 11, 2017