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Home My WebLink About7-ELEVEN @ COLLEGE & MAGNOLIA - PDP/APU - PDP120026 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTDRAINAGE REPORT FOR 7-ELEVEN – COLLEGE AND MAGNOLIA Fort Collins, Colorado October 10, 2012 OWNER/DEVELOPER: Verdad Real Estate 1121 Grant St. Denver, CO 80203 ENGINEER 7853 E. Arapahoe Ct., Suite 2500 Centennial, CO 80112 303-841-9365 f: 303-548-6212 Prepared by: Kevin S. Roth, P.E. REG PROJECT NO. 120805 TABLE OF CONTENTS I. GENERAL LOCATION AND DESCRIPTION ...................................................................... 2 A. Location ........................................................................................................................... 2 B. Description of Property..................................................................................................... 2 C. Floodplain Submittal Requirements.................................................................................. 3 II. DRAINAGE BASINS AND SUB-BASINS ............................................................................ 3 A. Major Basin Desciption .................................................................................................... 3 B. Sub-Basin Description ..................................................................................................... 3 III. DRAINAGE DESIGN CRITERIA ......................................................................................... 4 A. Regulations ...................................................................................................................... 4 B. Development Criteria Reference and Constraints ............................................................ 4 C. Hydrological Criteria ......................................................................................................... 4 D. Hydraulic Criteria ............................................................................................................. 5 E. Floodplain Regulation Compliance ................................................................................... 5 F. Modifications of Criteria.................................................................................................... 5 IV. DRAINAGE FACILITY DESIGN .......................................................................................... 5 A. General Concept .............................................................................................................. 5 B. Specific Details ................................................................................................................ 2 V. CONCLUSIONS .................................................................................................................. 3 A. Compliance with Standards ............................................................................................. 3 B. Drainage Concept ............................................................................................................ 3 VI. REFERENCES .................................................................................................................... 2 APPENDIX A –FIRM, floodplain, and Soils Maps.................................................... A APPENDIX B – Hydrologic Calculations .................................................................. B APPENDIX C ........................................................................................................... C MAP POCKETS....................................................................................................... C 1) DRAINAGE PLAN AND DETAILS ................................................................... C W. MULBERRY ST. S. COLLEGE AVE. W. MAGNOLIA ST. S. MASON ST. W. OLIVE ST. SITE CANYON AVE. W. MOUNTAIN AVE. October 10, 2012 7-Eleven – College and Magnolia Drainage Report Page 2 I. GENERAL LOCATION AND DESCRIPTION A. Location The proposed site is located in the northwest quadrant of the intersection of South College Avenue and West Magnolia Street. Refer to the previous page for the location shown on the Vicinity Map. More specifically this project is comprised of Lots 1 and 2 of Block 113 in Fort Collins, located in the southeast 1/4 of Section 11, Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. The site is bounded by South College Avenue (140’ right-of way) to the east, West Magnolia Street (100’ right-of-way) to the south, a public alley (20’ right-of-way) to the west, and the existing Clocktower Square Condos building to the north. This area is part of the high density Downtown District for zoning and planning purposes. The site is located within a City of Fort Collins regulatory 100-year floodway and flood fringe area in the Old Town Basin. The area is not considered a floodway according to FEMA. The flood maps are included in Appendix A. B. Description of Property The 7-Eleven College and Magnolia (Project) consists of an area of 0.436 acres. The site is currently covered with a packed gravel parking lot with several trees on the site. The site is located within a City of Fort Collins regulatory flood fringe area in the Old Town Basin. The surrounding right-of-ways for College and Magnolia are considered to be within the 100-year floodway. The area is not considered a floodway according to the FEMA Flood Insurance Rate Map for the area. The flood maps are included in Appendix A. The proposed development will consist of a convenience store and associated access roads and parking. Accessible sidewalks will be connected to the existing sidewalks in the surrounding right-of-way. Revisions to the public right-of-way will include expanding the existing southern and eastern drive entrances and removing the second drive entrance along West Magnolia Street. No existing major irrigation facilities are located within the site nor impact the site directly. The proposed land use will be a convenience store with associated parking lot. October 10, 2012 7-Eleven – College and Magnolia Drainage Report Page 3 C. Floodplain Submittal Requirements Revisions to the Floodplain will be addressed via separate document according to the requirements of the “City of Fort Collins Floodplain Review Checklist”. The design will comply with the City of Fort Collins floodplain regulations. II. DRAINAGE BASINS AND SUB-BASINS A. Major Basin Desciption The site is located within the Old Town Drainage Basin and is included in the Old Town Master Drainage Plan. The development is located within the City of Fort Collins regulatory flood fringe area. Design of the site has been prepared to set the building a minimum of eighteen inches above the Base Flood Elevation (BFE). The surrounding right-of-ways for College and Magnolia are within the 100-year floodway. The area is not considered a floodway according to the FEMA Flood Insurance Rate Map for the area. The flood maps are included in Appendix A. The Old Town Drainage Basin is a high-density, urban drainage basin located in north- central Fort Collins. The majority of the runoff from the Basin drains east to the Poudre River. The basin is entirely urbanized. Future planning for the basin will utilize improvements to the storm infrastructure to reduce the regular flooding that occurs in the area. No known irrigation facilities are located within 150’ of the property boundary. B. Sub-Basin Description Historically, the site flows from the northeast corner to the College and Magnolia intersection, across the gravel parking lot. A small portion of the site along the west property line drains to the alley right-of-way. Slopes on the site range from 0.6% to 3%. The College Avenue right- of-way adjacent to the site drains to the north. The Magnolia Street right-of-way adjacent to the site drains to the west. The alley drains to the south. The proposed development will match the existing drainage patterns as closely as possible. The overall site will drain to the south and east, with one small portion draining to the alley along the west property line. October 10, 2012 7-Eleven – College and Magnolia Drainage Report Page 4 The site is not impacted by any offsite flows during minor storm events. During small events, the runoff will be contained within the surrounding curb and gutter in Magnolia and College. The building to the north drains to College and to the alley without impacting the 7-Eleven site. During major storm events, the site is included in the flood fringe for the Old Town drainage basin and may experience flooding on the site from the off-site basin. The building finished floor has been set above the anticipated base flood elevation for the area to prevent flooding of the building. III. DRAINAGE DESIGN CRITERIA A. Regulations Deviations from the criteria are not requested for development of the proposed site. B. Development Criteria Reference and Constraints The site is included in the Old Town Master Drainage Plan and has been designed to conform to the master plan. Since the area experiences regular flooding, the building elevation has been raised above the Base Flood Elevation (BFE) for the property. Adjacent drainage studies do not impact this site. The site is constrained on three sides by City right-of-way. The drainage patterns within the right-of way have not been impacted by the proposed development. The proposed on-site sidewalks will tie into the existing sidewalks within the right-of-way. The proposed vehicular access from College and Magnolia will tie back into the existing roadway without affecting the existing slopes in the curb and gutter. C. Hydrological Criteria Hydrologic calculations have been prepared for the 100-year storm events. All calculations have been prepared using the Rational Method Formula. Proposed Time of Concentration and Rational Method calculations and references have been included in Appendix B. October 10, 2012 7-Eleven – College and Magnolia Drainage Report Page 5 Detention and water quality have not been determined for the site. Water quality treatment for the site and surrounding area is provided by the Udall Natural Area water treatment facility. The hydrology of the site has been designed according to the City of Fort Collins criteria. D. Hydraulic Criteria The capacity of the proposed on-site curb and gutter and concrete pan will be designed to convey the major storm. Although Fort Collins design criteria requires designing curb and gutter for the minor storm, the final design intends to demonstrate that the major storm can be conveyed through the site via curb and gutter. Revisions to the Floodplain will be addressed via separate document according to the requirements of the “City of Fort Collins Floodplain Review Checklist”. The design will comply with the City of Fort Collins floodplain regulations. E. Floodplain Regulation Compliance Revisions to the Floodplain will be addressed via separate document according to the requirements of the “City of Fort Collins Floodplain Review Checklist”. The design will comply with the City of Fort Collins floodplain regulations. F. Modifications of Criteria Modifications to criteria are not requested for this project. IV. DRAINAGE FACILITY DESIGN A. General Concept The proposed site will generally follow the existing patterns. Runoff will drain via overland flow and roof drains to the proposed parking lot and drive isle. The access then drains from a high point in the northwest corner, south to Magnolia Street, and east to College Avenue. A small portion of the site will continue to drain to the alley on the west. The drainage patterns for the surrounding right-of-way will not be modified with the development of the site. The site is not impacted by any offsite flows during minor storm events. During small events, the off-site runoff will be contained within the surrounding curb and gutter in Magnolia and College. During major storm events, the site is included in the flood fringe for the Old Town October 10, 2012 7-Eleven – College and Magnolia Drainage Report Page 2 drainage basin. The building finished floor has been set above the anticipated base flood elevation for the area to prevent flooding of the building. All proposed design calculations for the proposed site improvements have been included in Appendix B. B. Specific Details All runoff coefficients are based on the City Runoff Coefficients for Zoning Classifications. The site is a commercial business, so the Coefficient is 0.95 for all three basins, per Table RO-10. Basin A - Design Point 1 Basin A consists 0.192 acres I located on the western half of the proposed site. A portion of the building drains to the parking area and drive isle and is conveyed via curb and gutter and a 2’ concrete pan to Design Point 1 located at the southern property line. This basin drains to the West Magnolia Street right-of-way and is conveyed off-site via the existing Magnolia curb and gutter. Basin B - Design Point 2 Basin B consists of 0.029 acres along the west property line. The entire basin drains west into the alley right-of-way and south to Design Point 2 at the southern property line. The alley drains south to West Magnolia Street. Basin C - Design Point 3 Basin C consists of 0.215 acres located in the eastern half of the site. Half of the building drains via roof drains to the parking area and drive isle north of the building. The drive isle then drains east via curb and gutter to Design Point 3 at the property boundary. Runoff is conveyed off-site via the existing South College Avenue curb and gutter. Detention and water quality are not proposed for the site. Water quality for the area is provided by the Udall Natural Area water treatment facility. Maintenance access will be via the drive isle through the site. The slopes for the site are flat and will not prevent access for maintenance vehicles. October 10, 2012 7-Eleven – College and Magnolia Drainage Report Page 3 The site does not have any easements or tracts proposed for drainage purposes. No additional off-site facilities are needed to convey the minor or major flows from the site. V. CONCLUSIONS A. Compliance with Standards The design has been prepared to meet the City of Fort Collins Stormwater Criteria Manual. The site has been designed to meet the City of Fort Collins Master Drainage Plan. The site has been designed in compliance with the City of Fort Collins Floodplain regulations. Revisions to the Floodplain will be addressed via separate document according to the requirements of the “City of Fort Collins Floodplain Review Checklist”. The design will comply with the City of Fort Collins floodplain regulations. The site has been designed in compliance with State of Colorado and Federal regulations. B. Drainage Concept The proposed site will not create a negative impact on the storm runoff in the area. The proposed convenience store is being developed on a site that is zoned for commercial development. Therefore the project meets the requirements for the master plan for the downtown area. October 10, 2012 7-Eleven – College and Magnolia Drainage Report Page 2 VI. REFERENCES 1. City of Fort Collins, Storm Drainage Design Criteria and Construction Standards. Utilities Department, Stormwater Division. 2. Urban Drainage and Flood Control District, Urban Storm Drainage Criteria Manual. Regional County of Governments, Denver, CO, June 2001 (with current revisions) 3. FIRM Flood Insurance Rate Map, Larimer County, Colorado and Incorporated Areas. Panel 979 of 1420. Map Number 09069C0979H. Revised May 2, 2012. APPENDIX A –FIRM, floodplain, and Soils Maps # 4990 4989 4988 499 5 4994 4996 4987 4997 4992 4991 4993 4998 4999 5000 4990 4990 4993 4994 4999 4994 # 3957 682 1929 2446 0 1087 804 1205 1364 74 948 2510 2890 1699 1529 280 198 1882 2690 2037 547 3402 3505 3012 3883 2068 2896 3218 2234 3724 346 3376 3225 2358 403 3164 3795 95 2703 2143 3016 3490 3325 3697 1987 3059 2372 2386 2214 3182 2304 3205 3062 3022 2510 2890 0 2690 S MASON ST Mason St Olive St College Ave Magnolia St College Ave ¤£287 35 493320 493320 493350 493350 493380 493380 493410 493410 493440 493440 493470 493470 493500 493500 4492380 4492380 4492410 4492410 4492440 4492440 4492470 4492470 4492500 4492500 4492530 4492530 4492560 4492560 4492590 4492590 4492620 4492620 4492650 4492650 0 50 100 200 300 Feet 0 10 20 40 60 ± Meters 40° 35' 5'' 105° 4' 35'' 40° 34' 55'' 105° 4' 35'' 40° 34' 55'' 40° 35' 5'' 105° 4' 45'' 105° 4' 45'' Map Scale: 1:1,460 if printed on A size (8.5" x 11") sheet. Soil Map—Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 1 of 3 MAP LEGEND MAP INFORMATION Area of Interest (AOI) Area of Interest (AOI) Soils Soil Map Units 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 Gully Short Steep Slope Other Political Features Cities Water Features Streams and Canals Transportation Rails Interstate Highways US Routes Major Roads Local Roads Map Scale: 1:1,460 if printed on A size (8.5" × 11") sheet. 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 accurate map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov Coordinate System: UTM Zone 13N NAD83 This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 7, May 1, 2009 Map Unit Legend Larimer County Area, Colorado (CO644) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 35 Fort Collins loam, 1 to 3 percent slopes 9.5 100.0% Totals for Area of Interest 9.5 100.0% Soil Map–Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 3 of 3 Engineering Properties This table gives the engineering classifications and the range of engineering properties for the layers of each soil in the survey area. Depth to the upper and lower boundaries of each layer is indicated. Texture is given in the standard terms used by the U.S. Department of Agriculture. These terms are defined according to percentages of sand, silt, and clay in the fraction of the soil that is less than 2 millimeters in diameter. "Loam," for example, is soil that is 7 to 27 percent clay, 28 to 50 percent silt, and less than 52 percent sand. If the content of particles coarser than sand is 15 percent or more, an appropriate modifier is added, for example, "gravelly." Classification of the soils is determined according to the Unified soil classification system (ASTM, 2005) and the system adopted by the American Association of State Highway and Transportation Officials (AASHTO, 2004). The Unified system classifies soils according to properties that affect their use as construction material. Soils are classified according to particle-size distribution of the fraction less than 3 inches in diameter and according to plasticity index, liquid limit, and organic matter content. Sandy and gravelly soils are identified as GW, GP, GM, GC, SW, SP, SM, and SC; silty and clayey soils as ML, CL, OL, MH, CH, and OH; and highly organic soils as PT. Soils exhibiting engineering properties of two groups can have a dual classification, for example, CL-ML. The AASHTO system classifies soils according to those properties that affect roadway construction and maintenance. In this system, the fraction of a mineral soil that is less than 3 inches in diameter is classified in one of seven groups from A-1 through A-7 on the basis of particle-size distribution, liquid limit, and plasticity index. Soils in group A-1 are coarse grained and low in content of fines (silt and clay). At the other extreme, soils in group A-7 are fine grained. Highly organic soils are classified in group A-8 on the basis of visual inspection. If laboratory data are available, the A-1, A-2, and A-7 groups are further classified as A-1-a, A-1-b, A-2-4, A-2-5, A-2-6, A-2-7, A-7-5, or A-7-6. As an additional refinement, the suitability of a soil as subgrade material can be indicated by a group index number. Group index numbers range from 0 for the best subgrade material to 20 or higher for the poorest. Rock fragments larger than 10 inches in diameter and 3 to 10 inches in diameter are indicated as a percentage of the total soil on a dry-weight basis. The percentages are estimates determined mainly by converting volume percentage in the field to weight percentage. Percentage (of soil particles) passing designated sieves is the percentage of the soil fraction less than 3 inches in diameter based on an ovendry weight. The sieves, numbers 4, 10, 40, and 200 (USA Standard Series), have openings of 4.76, 2.00, 0.420, and 0.074 millimeters, respectively. Estimates are based on laboratory tests of soils sampled in the survey area and in nearby areas and on estimates made in the field. Liquid limit and plasticity index (Atterberg limits) indicate the plasticity characteristics of a soil. The estimates are based on test data from the survey area or from nearby areas and on field examination. Engineering Properties–Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 1 of 3 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. Engineering Properties–Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 2 of 3 Report—Engineering Properties Absence of an entry indicates that the data were not estimated. The asterisk '*' denotes the representative texture; other possible textures follow the dash. Engineering Properties– Larimer County Area, Colorado Map unit symbol and soil name Depth USDA texture Classification Fragments Percentage passing sieve number— Liquid limit Plasticity index Unified AASHTO >10 inches 3-10 inches 4 10 40 200 In Pct Pct Pct 35—Fort Collins loam, 1 to 3 percent slopes Fort collins 0-7 *Loam CL-ML, CL A-4 0 0 100 100 85-95 60-75 25-30 5-10 7-22 *Loam *Clay loam CL A-6 0 0 95-100 90-100 85-95 60-75 25-40 10-20 22-60 *Loam *Silt loam *Fine sandy loam CL, CL- ML, ML A-4 0 0 95-100 90-100 80-95 50-75 20-30 NP-10 Data Source Information Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 7, May 1, 2009 Engineering Properties–Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 3 of 3 Physical Soil Properties This table shows estimates of some physical characteristics and features that affect soil behavior. These estimates are given for the layers of each soil in the survey area. The estimates are based on field observations and on test data for these and similar soils. Depth to the upper and lower boundaries of each layer is indicated. Particle size is the effective diameter of a soil particle as measured by sedimentation, sieving, or micrometric methods. Particle sizes are expressed as classes with specific effective diameter class limits. The broad classes are sand, silt, and clay, ranging from the larger to the smaller. Sand as a soil separate consists of mineral soil particles that are 0.05 millimeter to 2 millimeters in diameter. In this table, the estimated sand content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 millimeters in diameter. Silt as a soil separate consists of mineral soil particles that are 0.002 to 0.05 millimeter in diameter. In this table, the estimated silt content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 millimeters in diameter. Clay as a soil separate consists of mineral soil particles that are less than 0.002 millimeter in diameter. In this table, the estimated clay content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 millimeters in diameter. The content of sand, silt, and clay affects the physical behavior of a soil. Particle size is important for engineering and agronomic interpretations, for determination of soil hydrologic qualities, and for soil classification. The amount and kind of clay affect the fertility and physical condition of the soil and the ability of the soil to adsorb cations and to retain moisture. They influence shrink- swell potential, saturated hydraulic conductivity (Ksat), plasticity, the ease of soil dispersion, and other soil properties. The amount and kind of clay in a soil also affect tillage and earthmoving operations. Moist bulk density is the weight of soil (ovendry) per unit volume. Volume is measured when the soil is at field moisture capacity, that is, the moisture content at 1/3- or 1/10-bar (33kPa or 10kPa) moisture tension. Weight is determined after the soil is dried at 105 degrees C. In the table, the estimated moist bulk density of each soil horizon is expressed in grams per cubic centimeter of soil material that is less than 2 millimeters in diameter. Bulk density data are used to compute linear extensibility, shrink-swell potential, available water capacity, total pore space, and other soil properties. The moist bulk density of a soil indicates the pore space available for water and roots. Depending on soil texture, a bulk density of more than 1.4 can restrict water storage and root penetration. Moist bulk density is influenced by texture, kind of clay, content of organic matter, and soil structure. Saturated hydraulic conductivity (Ksat) refers to the ease with which pores in a saturated soil transmit water. The estimates in the table are expressed in terms of micrometers per second. They are based on soil characteristics observed in the field, particularly structure, porosity, and texture. Saturated hydraulic conductivity (Ksat) is considered in the design of soil drainage systems and septic tank absorption fields. Physical Soil Properties–Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 1 of 4 Available water capacity refers to the quantity of water that the soil is capable of storing for use by plants. The capacity for water storage is given in inches of water per inch of soil for each soil layer. The capacity varies, depending on soil properties that affect retention of water. The most important properties are the content of organic matter, soil texture, bulk density, and soil structure. Available water capacity is an important factor in the choice of plants or crops to be grown and in the design and management of irrigation systems. Available water capacity is not an estimate of the quantity of water actually available to plants at any given time. Linear extensibility refers to the change in length of an unconfined clod as moisture content is decreased from a moist to a dry state. It is an expression of the volume change between the water content of the clod at 1/3- or 1/10-bar tension (33kPa or 10kPa tension) and oven dryness. The volume change is reported in the table as percent change for the whole soil. The amount and type of clay minerals in the soil influence volume change. Linear extensibility is used to determine the shrink-swell potential of soils. The shrink-swell potential is low if the soil has a linear extensibility of less than 3 percent; moderate if 3 to 6 percent; high if 6 to 9 percent; and very high if more than 9 percent. If the linear extensibility is more than 3, shrinking and swelling can cause damage to buildings, roads, and other structures and to plant roots. Special design commonly is needed. Organic matter is the plant and animal residue in the soil at various stages of decomposition. In this table, the estimated content of organic matter is expressed as a percentage, by weight, of the soil material that is less than 2 millimeters in diameter. The content of organic matter in a soil can be maintained by returning crop residue to the soil. Organic matter has a positive effect on available water capacity, water infiltration, soil organism activity, and tilth. It is a source of nitrogen and other nutrients for crops and soil organisms. Erosion factors are shown in the table as the K factor (Kw and Kf) and the T factor. Erosion factor K indicates the susceptibility of a soil to sheet and rill erosion by water. Factor K is one of six factors used in the Universal Soil Loss Equation (USLE) and the Revised Universal Soil Loss Equation (RUSLE) to predict the average annual rate of soil loss by sheet and rill erosion in tons per acre per year. The estimates are based primarily on percentage of silt, sand, and organic matter and on soil structure and Ksat. Values of K range from 0.02 to 0.69. Other factors being equal, the higher the value, the more susceptible the soil is to sheet and rill erosion by water. Erosion factor Kw indicates the erodibility of the whole soil. The estimates are modified by the presence of rock fragments. Erosion factor Kf indicates the erodibility of the fine-earth fraction, or the material less than 2 millimeters in size. Erosion factor T is an estimate of the maximum average annual rate of soil erosion by wind and/or water that can occur without affecting crop productivity over a sustained period. The rate is in tons per acre per year. Wind erodibility groups are made up of soils that have similar properties affecting their susceptibility to wind erosion in cultivated areas. The soils assigned to group 1 are the most susceptible to wind erosion, and those assigned to group 8 are the least susceptible. The groups are described in the "National Soil Survey Handbook." Physical Soil Properties–Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 2 of 4 Wind erodibility index is a numerical value indicating the susceptibility of soil to wind erosion, or the tons per acre per year that can be expected to be lost to wind erosion. There is a close correlation between wind erosion and the texture of the surface layer, the size and durability of surface clods, rock fragments, organic matter, and a calcareous reaction. Soil moisture and frozen soil layers also influence wind erosion. Reference: United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. (http://soils.usda.gov) Physical Soil Properties–Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 3 of 4 Report—Physical Soil Properties Physical Soil Properties– Larimer County Area, Colorado Map symbol and soil name Depth Sand Silt Clay Moist bulk density Saturated hydraulic conductivity Available water capacity Linear extensibility Organic matter Erosion factors Wind erodibility group Wind erodibility index Kw Kf T In Pct Pct Pct g/cc micro m/sec In/In Pct Pct 35—Fort Collins loam, 1 to 3 percent slopes Fort collins 0-7 -44- -41- 10-15- 20 1.25-1.40 4.23-42.34 0.14-0.18 0.0-2.9 1.0-2.0 .28 .28 5 5 56 7-22 -38- -36- 18-27- 35 1.45-1.55 4.23-14.11 0.16-0.18 3.0-5.9 0.0-0.5 .24 .24 22-60 -42- -38- 12-20- 27 1.45-1.55 4.23-14.11 0.16-0.18 0.0-2.9 0.0-0.5 .24 .24 Data Source Information Soil Survey Area: Larimer County Area, Colorado Survey Area Data: Version 7, May 1, 2009 Physical Soil Properties–Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 4 of 4 APPENDIX B – Hydrologic Calculations SOUTH COLLEGE AVENUE (140' ROW) WEST MAGNOLIA STREET (100' ROW) ALLEY (20' ROW) COMPOSITE RUNOFF COEFICIENT & PERCENT IMPERVIOUS CALC'D BY: KSR PROJECT: DATE: 10/05/12 PROJ. NO: SCS Soil Type: B REVISED : Per City of Ft. Collins Table 3-3 Land coverage C %I* Roof 0.95 90 Gravel Packed 0.50 40 Drives and Walks 0.95 100 Soil 0.25 0 * Values taken from the Urban Drainage and Flood Control District's Strom Drainage Criteria Manual, Vol. 1 Basin Basin Area (ac) Roof (ac) Gravel Packed (ac) Drives / Walks (ac) Pervious Ground (ac) C100 %I ONSITE BASINS A 0.436 0.001 0.436 0.50 50.05 Basin Basin Area (ac) Roof (ac) Gravel Packed (ac) Drives / Walks (ac) Pervious Ground (ac) C100 %I ONSITE BASINS A 0.436 0.096 0.256 0.085 0.81 81.37 Proposed Land Use Existing Land Use 7-Eleven College and Magnolia 120805 CALCULATED BY: KSR JOB NO: 120805 DATE: 10/2/2012 PROJECT: 7- Eleven College and Magnolia CHECKED BY: REVISED: FINAL REMARKS Tc AREA C100 LENGTH SLOPE Ti LENGTH SLOPE VELOCITY Tt COMPOS. TOTAL Tc = (L/180)+10 BASIN (AC) (FT) % (MIN) (FT) % Cv (FPS) (MIN) Tc (MIN) LENGTH (MIN) (MIN) A 0.192 0.95 20 2.00 -2.7 120 0.75 20.00 1.7 1.2 5.0 140 10.8 5.0 B 0.029 0.95 16 2.00 -2.4 93 0.70 20.00 1.7 0.9 5.0 109 10.6 5.0 C 0.215 0.95 20 2.00 -2.7 150 1.00 20.00 2.0 1.3 5.0 170 10.9 5.0 Cv = Conveyance Coefficient TOV =(1.87(1.1-CCf )D^1/2)/s^1/3 Land Surface Cv Heavy Meadow 2.5 Cf= 1.25 for 100 year storm Tillage/field 5 PAGE: 1/1 Short pasture and lawns 7 Nearly bare ground 10 Grassed waterway 15 Paved areas and shallow paved swales 20 DATA TIME (Ti) (Tt) (URBANIZED BASINS) STANDARD FORM SF-2 TIME OF CONCENTRATION SUB-BASIN INITIAL/OVERLAND TRAVEL TIME Tc CHECK DEVELOPED BASINS CALCULATED BY: KSR STANDARD FORM SF-3 JOB NO: DATE: PROJECT: 7-Eleven College and Magnolia CHECKED BY: STORM DRAINAGE SYSTEM DESIGN DESIGN STORM: 100 YR (RATIONAL METHOD PROCEDURE) TRAVEL TIME BASIN (s) DESIGN POINT AREA (AC) RUNOFF COEFF Tc (min) C x A (AC) I (IN/HR) Q (CFS) Tc (MIN) S(C x A) (AC) I (IN/HR) Q (CFS) SLOPE (%) STREET FLOW (CFS) DESIGN FLOW (CFS) SLOPE (%) PIPE SIZE (IN) LENGTH (FT) VELOCITY (FPS) Tt (min) REMARKS A 1 0.192 0.95 5 0.18 9.95 1.81 B 2 0.029 0.95 5 0.03 9.95 0.27 C 3 0.215 0.95 5 0.2 9.95 2.03 Page: DIRECT RUNOFF TOTAL RUNOFF STREET PIPE 120805 10/2/2012 APPENDIX C MAP POCKETS 1) DRAINAGE PLAN AND DETAILS Date(s) aerial images were photographed: 8/6/2005 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. Soil Map–Larimer County Area, Colorado Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 10/8/2012 Page 2 of 3 S HOWES ST MATHEWS ST S MELDRUM ST REMINGTON ST W OAK ST S COLLEGE AVE W OLIVE ST W MYRTLE ST CANYON AVE E OAK ST E OLIVE ST S SHERWOOD ST E MAGNOLIA ST E MULBERRY ST MONTEZUMA FULLER ALLEY S SHERWOOD ST # 3957 682 1929 2446 0 1087 804 1205 1364 74 948 2510 2890 1699 1529 280 198 1882 2690 2037 547 3402 3505 3012 3883 2068 2896 3218 2234 3724 346 3376 3225 2358 403 3164 3795 95 2703 2143 3016 3490 3325 3697 1987 3059 2372 2386 2214 3182 2304 3205 3062 3022 2510 2890 0 2690 S MASON ST S HOWES ST MATHEWS ST S MELDRUM ST REMINGTON ST W OAK ST S COLLEGE AVE W OLIVE ST W MYRTLE ST CANYON AVE E OAK ST E OLIVE ST S SHERWOOD ST E MAGNOLIA ST E MULBERRY ST MONTEZUMA FULLER ALLEY S SHERWOOD ST Areas outside of FEMA and City mapped 100-year and 500-year floodplains. Local drainage problems may still exist. Low Risk . 0 200 400 800 Feet All floodplain boundaries are approximate. This information is based on the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) and the City of Fort Collins Master Drainageway Plans. This letter does not imply that the referenced property will or will not be free from flooding or damage. A property not in the Special Flood Hazard Area or in a City Designated Floodplain may be damaged by a flood greater than that predicted on the map or from a local drainage problem not shown on the map. This map does not create liability on the part of the City, or any officer or employee thereof, for any damage that results from reliance on this information. High Risk City Floodway - Area of 100-year floodplain with greatest depths and fastest velocities. City Flood Fringe - May Include: - Areas of FEMA 100-year floodplain (FEMA Zones A, AE, AO, and AH) - Areas of City 100-year floodplain including ponding areas and sheet flow areas with average depths of 1-3 feet. There is a 1% annual chance that these areas will be flooded. Moderate Risk May include: - Areas of FEMA 500-year floodplain (FEMA Zone X-shaded). - Areas of FEMA or City 100-year floodplain (sheet flow) with average depths of less than 1 foot. - Areas protected by levees from the 100-year flood. City Flood Risk Map Printed: 6/21/2010 4992 4997 4994 4990 4995 4998 4994 4995 4992 4996 4996 4991 4995 4993 4998 S MASON ST S HOWES ST MATHEWS ST S MELDRUM ST REMINGTON ST W OAK ST S COLLEGE AVE W OLIVE ST W MYRTLE ST W MAGNOLIA ST W MULBERRY ST CANYON AVE E OAK ST E OLIVE ST S SHERWOOD ST E MYRTLE ST E MULBERRY ST MONTEZUMA FULLER ALLEY S SHERWOOD ST # 4990 4989 4988 4995 4994 4996 4987 4997 4992 4991 4993 4998 4999 5000 4990 4990 4993 4994 4999 4994 4992 4997 4994 4990 4995 4998 4994 4995 4992 4996 4996 4991 4995 4993 4998 S MASON ST S HOWES ST MATHEWS ST S MELDRUM ST REMINGTON ST W OAK ST S COLLEGE AVE W OLIVE ST W MYRTLE ST W MAGNOLIA ST W MULBERRY ST CANYON AVE E OAK ST E OLIVE ST S SHERWOOD ST E MYRTLE ST E MULBERRY ST MONTEZUMA FULLER ALLEY S SHERWOOD ST Areas outside of FEMA and City mapped 100-year and 500-year floodplains. Local drainage problems may still exist. Low Risk . 0 200 400 800 Feet All floodplain boundaries are approximate. This information is based on the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) and the City of Fort Collins Master Drainageway Plans. This letter does not imply that the referenced property will or will not be free from flooding or damage. A property not in the Special Flood Hazard Area or in a City Designated Floodplain may be damaged by a flood greater than that predicted on the map or from a local drainage problem not shown on the map. This map does not create liability on the part of the City, or any officer or employee thereof, for any damage that results from reliance on this information. High Risk City Floodway - Area of 100-year floodplain with greatest depths and fastest velocities. City Flood Fringe - May Include: - Areas of FEMA 100-year floodplain (FEMA Zones A, AE, AO, and AH) - Areas of City 100-year floodplain including ponding areas and sheet flow areas with average depths of 1-3 feet. There is a 1% annual chance that these areas will be flooded. Moderate Risk May include: - Areas of FEMA 500-year floodplain (FEMA Zone X-shaded). - Areas of FEMA or City 100-year floodplain (sheet flow) with average depths of less than 1 foot. - Areas protected by levees from the 100-year flood. City Flood Risk Map Printed: 6/21/2010