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HomeMy WebLinkAboutDrainage Reports - 10/07/1982DRAINAGE MASTER PLAN FOR THE SOUTH SIDE SERVIC CENTER AND FINAL DRAINAGE PLAN FOR THE CITY OF FORT COLLINS TRANSFORT FACILITY Sin SIMONS, [I & ASSOCIATES, INC. 1� - 1 1 DRAINAGE MASTER PLAN FOR THE SOUTH SIDE SERVICE CENTER AND FINAL DRAINAGE PLAN FOR THE CITY OF FORT COLLINS TRANSFORT FACILITY 1 1 Prepared for 1 ZVFK Architects/Planners 218 West Mountain Avenue 1 Fort Collins, CO 80521 1 1 By Simons, Li & Associates, Inc. 1 P.O. Box 1816 1 Fort Collins, CO 80522 ' Our Project Number: CO-ZVFK-01 ' October 4, 1982 TABLE OF CONTENTS Page I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 II. DRAINAGE AREA DESCRIPTION . . . . . . . . . . . . . . . . . . 2.1 III. SCOPE OF WORK . . . . . . . . . . . . . . . . . . . . . . 3.1 IV. DATA SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 V. DESIGN CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . 5.1 VI. ANALYSIS AND MASTER DRAINAGE PLAN FOR SOUTHSIDE SERVICE CENTER . . . . .. . . . . . . . . . . . . . . . . . . . . . . . 6.1 6.1 Existing Conditions . . . . . . . . . . . . . . . . . . . 6.1 6.2 Developed Conditions . . . . . . . . . . . . . . . . . . 6.4 6.3 Site Development Master Plan . . . . . . . . . . . . . . 6.4 6.3.1 Detention Pond . . . . . . . . . . . . . . . . . . 6.5 6.3.2 Channels . . . . . . . . . . . . . . . . . . . . . 6.5 VII. ANALYSIS AND DESIGN OF DRAINAGE IMPROVEMENTS FOR TRANSFORT FACILITY . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 APPENDIX BACKGROUND CALCULATIONS I. INTRODUCTION This report has been prepared for ZVFK Architects/Planners as a final ' plan of the storm drainage system for the proposed development of the City of Fort Collins South Side Service Center. Included in this drainage report are ' all pertinent data, methods, assumptions, and calculations used in the analy- sis, and design details for the storm drainage system of the proposed new ' TransFort facility. The proposed location for the new TransFort facility is on a 60 acre site on Trilby Road west of U.S. 287 in southeast Fort Collins. Proposed develop- ment on the 60 acre site includes a 35,000 square foot TransFort administra- tion, maintenance and storage facility, a southside service center for all ' city departments, and an electrical substation for the City of Fort Collins Light and Power Utility. 2.1 II. DRAINAGE AREA DESCRIPTION The project site is located in the Fossil Creek drainage basin. The total tributary area to the site is 629 acres. The tributary area is charac- terized by rolling topography sloping toward the east. Natural drainage enters at the southern boundary of the site through an existing 2 foot diameter corrugated metal pipe with a projecting entrance beneath Trilby Road and flows north along a natural channel through the center of the site. The drainage then flows into a west to east unnamed tributary of Fossil Creek at the northern boundary of the site. A marshy area in the north -central region of the site is vegetated with tall grass and a few cottonwood trees. The rest of the site is sparsely vegetated with grass and weeds. Contour slopes vary from 3 to 5 percent in the southern region to nearly flat in the marshy north central region. Figure 2.1 shows the drainage basin divided into 14 subareas for the pur- pose of runoff computations. The proposed 60 acre development site is designated as subbasin 70. Drainage areas to the west of U.S. 287 (subbasins 1 through 5) were delineated in order to model the storage capacities behind each culvert of the existing roadway. Likewise, the available storage capa- city behind the culvert of Trilby Road was included for subbasin 69. 2.2 38.0 13.0 12.0 ca POrtner 72.0 70 15.0 Ir County Road 32 SUB -BASIN NUMBER \mo/ SUB -BASIN (ACRES) ` ' BASIN BOUNDARY EXISTING DRAINAGES -------- ELEVATIONS ~~~~~~~~~ APPROX. SITE LOCATION ^� SWAMP AREA Figure 2.1. Tributary areas of the proposed development site. 3.1 III. SCOPE OF WORK The purpose of this report is to analyze drainage conditions in the area affected by the proposed TransFort facility development and design appropriate drainage control measures to accommodate City of Fort Collins Drainage Criteria. The scope of work consists of the following: 1. Conduct a field visit to familiarize ourselves with the physical environ- ment, define the exact drainage basin boundaries based on recent develop- ment for both initial storm and major storm, and collect all pertinent data. 2. Collect, collate, and review available hydrologic, hydraulic, and topographic data pertinent to the study including drainage plans of the existing developments in the vicinity, master drainageway planning stu- dies, and the drainage plans of the proposed development in the surrounding area. A master drainageway planning study for the Fossil Creek basin includes the proposed site and tributary area as one sub - catchment. For this area hydrologic parameters are available. 3. Interact with ZVFK and City staff to establish building layout alter- natives for determining drainage courses and possible detention and pre- paring site grading plan. A possible location of a detention facility is at the north end of the property in the existing boggy area. 4. Determine the storm runoff peaks and volumes for both the ten-year (initial) and 100-year (major) storm with developed basin conditions. Hydrologic methods used were Rational and SWMM. Rational Method was not applicable when the entire area was larger than 200 acres. 5. Prepare a preliminary drainage plan including analysis of on -site and off -site tributary drainage areas and sizing drainage facilities required. Drainage facilities may include storm sewer, channels, multiple use detention facility, and culverts. All will be sized in accordance with the City's Storm Drainage Design Criteria. 6. Prepare a preliminary drainage report including detailed analysis of on - site drainage areas, off -site drainage areas, capacities of receiving structures, and proposed on -site drainage facilities; drawings presenting the entire development and all off -site drainage areas; drawings showing building location on a two -foot contour interval map; drawings showing location and size of all drainage facilities; and a grading plan showing drainage patterns within the proposed development. 7. Prepare cost estimates for proposed improvements. 8. Assist ZVFK in presenting the preliminary drainage report to the City. 9. Interact with ZVFK staff to determine revisions required on the prelimi- nary drainage report after the review by the City. 3.2 10. Perform additional detailed analysis based on the review comments from the City and revisions made by ZVFK. 11. Prepare a final drainage report including detailed study and analysis of the proposed development; detailed calculations for runoff and the design of all drainage facilities within the development; construction plans for all drainage facilities and grading plans for site preparation (including existing and proposed contours); and engineering drawings required to meet the requirements of the City. 12. Assist ZVFK in presenting the final drainage report to the City. 4.1 IV. DATA SUMMARY ' The following is a list of data, reports, maps and other pertinent infor- mation used in the analysis, design and general preparation of this prelimi- nary drainage report: ' - City of Fort Collins Topographic Mapping, scale 1" = 1001, CI = 2', NE 12-6-69, NW 12-6-69, SE 12-6-69, SW 12-6-69, NE 13-6-69, NW 13-6-69, ' April 1981. - USGS 7.5 minute topographic maps for Loveland and Fort Collins quadrangles. ' - Preliminary Geotechnical Investigation for Fuqua Site, South of Fort Collins, CO, Empire Laboratories, Inc., Fort Collins, CO, April 1982. - Master Drainageway Planning Study, Fossil Creek Basin, Fort Collins, CO, Simons, Li & Associates, Inc., Fort Collins, CO, May 1982 (Draft). ' - User's Manual of the Storm Water Management Model (SWMM), Environmental Protection Agency, September 1971. ' - City of Fort Collin's Storm Drainage Design Criteria, Department of Public Works and Water Utilities, Engineering Division, January 1980. - Larimer County Storm Water Management Manual, Resource Consultants, Inc., Fort Collins, CO, May 1979. - Topographic Mapping for TransFort Site by M&I Consultants, Fort Collins, CO. Scale 1" = 50', CI = 11, 1982. Site Grading Plan by M&I Consultants, Fort Collins, CO. 5.1 V. DESIGN CONSIDERATIONS Design considerations in the analysis, design and general preparation of this report are in compliance with standards set forth by the City of Fort Collins Storm Drainage Design Criteria and results of the Fossil Creek master ' drainageway planning study. A summary of the preliminary site specific design considerations follows: ' 1. Initial storm provisions are for the 10-year storm. (Frequency Factor- 1.0.) ' 2. Major storm provisions are for the 100-year storm. (Frequency Factor 1.25.) ' 3. Minimum allowable storm sewer pipe diameter - 15". 4. Minimum velocity in storm sewer - 2 fps. ' S. Site land use classified as a Public Building Area. 6. Rational Method Runoff Coefficient for developed area - 0.95. ' 7. Percentage of impervious area for developed site - 0.90. t8. Roughness coefficients utilized in analysis and design: n value ' Concrete pipe 0.013 Corrugated metal pipe 0.024 Riprap channel 0.035 Grass channel (d > 2.0 feet) 0.035 ' 9. Maximum allowable side slope for unlined channel - 4:1, maximum flow depth - 4.0 feet, minimum channel velocity - 2.0 fps, maximum - 7.5 fps. ' 10. The preliminary soils investigation indicates that construction should not occur in the marshy northern area of the site. This area is more suitable for a detention facility and should be considered for such use. 11. Analysis of runoff includes available storage upstream of culverts along U.S. 287 and at Trilby Road. ' 12. Detention facilities should be designed to reduce the runoff peak/volume from the developed conditions to that of the natural site conditions. t 1 6.1 ' VI. ANALYSIS AND MASTER DRAINAGE PLAN FOR SOUTHSIDE SERVICE CENTER 6.1 Existing Conditions ' The existing runoff conditions of the study area were computed in two parts, on -site and off -site tributary areas. Due to the large size of off - site tributary areas a hydrologic computer model was used to analyze runoff conditions. The on -site tributary areas were analyzed by use of the Rational ' Method. The computer model chosen for computation of runoff from off -site tribu- tary areas was the Environmental Protection Agency's Storm Water Management ' Model (SWMM). The delineation of tributary areas was shown in Figure 2.1. The physical parameters of the watershed used were taken from the Draft Master Drainageway Study for Fossil Creek (May 1982). The rainfall input to the SWMM model were taken from the Larimer County Stormwater Management Manual ' (May 1979). Values used are presented in Table 6.1. The flows calculated for off -site tributary areas are presented in Table 6.2. ' The computation of discharges from on -site tributary areas was done in accordance to the guidelines for use of the Rational Method found in the City of Fort Collins Storm Drainage Design Criteria. The actual calculations for ' the 100-year event under existing conditions are as follows: ' 1. Estimate runoff coefficient for existing (historical) condition. For unimproved areas: C = 0.20. 2. Calculate time of concentration: For 2-year storm, C = 1.00 , for ' 100-year storm, Cpp = 1.25 Drainage Area: A = 60.3 acres. Overland Flow Slope = 0.040, length = 400 feet. Channel Slope = 0.0193, length = 1,800 feet. ' T= Ti + T c £ where T= total time of concentration c 1 ' Ti = time of concentration for.overland flow, 1.87(1.1 - CCf)D ' Tf = time of concentration for channel flow, L 51�3 V L = channel length ' V = average velocity For 2-year storm T. = 21.2 minutes For 100-year storm 1Ti = 20.0 minutes. From Manning's equation and assuming a trapezoidal channel with a 10 foot base width, 4:1 side slopes, n = 0.035, slope = 0.0193. For an estimated 6.2 Table 6.1. Rainfall Input to SWMM. 10-year, 1-hour Rainfall Depth = 1.62" ' End of Period Depth Rainfall Rate (minutes) Percent of 1-hour Rainfall Depth (in) (in/hr) ' 5 4 0.07 0.84 10 4 0.07 0.84 15 5 0.08 0.96 ' 20 6 0.10 1.20 25 9 0.15 1.80 30 26 0.41 4.92 ' 35 15 0.24 2.88 40 11 0.18 2.16 45 6 0.10 1.20 50 5 0.08 0.96 ' 55 5 0.08 0.96 60 1 4 0.07 0.84 100-year, 1-hour Rainfall Depth = 2.60" End of Period Depth Rainfall Rate ' (minutes) Percent of 1-hour Rainfall Depth (in) (in/hr) 5 4 0.11 1.32 ' 10 4 0.11 1.32 15 5 0.13 1.56 20 6 0.16 1.92 25 9 0.24 2.88 30 26 0.68 8.16 35 15 0.39 4.68 40 11 0.29 3.48 ' 45 6 0.16 1.92 50 5 0.13 1.56 55 5 0.13 1.56 ' 60 1 1 4 0.11 1.32 6.3 Table 6.2. Design Flows. Location Storm Frequency Conditions Peak Discharge (cfs) Volume (ac-ft) Time to Peak (minutes) At Trilby Road 100-year U/S Undeveloped 276 22.9 50 Area = 160.0 Acres 10-year Lot Undeveloped 108 60 At North End of Site 100-year 388 32.3 55 Area = 448.0 Acres 10-year 151 60 Tributary Area West 100-year 264 50 of Site 10-year 87 55 Area = 394.0 Acres Downstream of Site 100-year 664 57.3 55 10-year 241 65 6.4 2-year depth of 0.8 feet, Q = 43 cfs and V = 4.7 fps. For a 100-year flow of 112 cfs d = 1.4 feet and V = 6.3 fps. For 2-year storm Tf = 6.4 minutes. For 100-year storm Tf = 4.8 minutes. For 2-year storm T = 27.6 minutes. For 100-year storm cT c = 24.8 minutes. 3. Calculate discharge from 60 acre site for Existing Conditions. For 2-year storm i = 1.75 in/hr. Q = 21 cfs For 100-year storm i = 4.6 in/hr, Q = 70 cfs. 6.2 Developed Conditions The developed runoff conditions were calculated for on -site tributary areas. It was assumed that runoff from off -site tributary areas will not increase. The calculations for the determination of runoff for developed con- ditions of the project site for the 100-year event are as follows: ' 1. Estimate runoff coefficients for developed condition. ' For Public Building Areas: C = 0.95 . 2. Calculate Time of Concentration. (See previous example for explanation of procedure, Section 6.1.) For the 100-year event: ' C= 1.25. Drainage Area: A = 60.3 acres. Overland Flow Slope: 6.400, length = 400 feet. Channel Slope: 0.0193, length = 1,800 feet. ' The product of C and Cf must be less than or equal to 1. Use CC = 1. For 100-year storm T. = 2.4 minutes , Tf = 4.8 minutes , the value for Tf calculated in Section 6.1 will be used: Tc = 7.2 minutes. ' 3. Calculate Discharge. From Intensity -Duration Curve for a Duration of 8 minutes: i = 8.0 in/hr. ' Using the Rational Method the peak discharge from the 60 acre site for developed conditions is 480 cfs. ' 6.3 Site Development Master Plan As a result of the determination of on -site and off -site runoff, a Master ' Plan for the development of the entire project site was made. This plan is general in nature and is therefore subject to the refinement gained from each ' development phase. 6.5 Basically, the Master Plan calls for the control of runoff by the use of open channels and a minimum of closed conduit storm drains. A stormwater detention pond is also planned to prevent an increase in the peak runoff discharge downstream of the development site. Plate 17 of the Engineering drawings is a schematic of the proposed master plan for the entire evelopment site. 6.3.1 Detention Pond The calculations used to determine the preliminary necessary volume of the proposed stormwater detention pond are presented in Table 6.3. Detention storage was provided so that the peak flow from the 60 acre site will not exceed the existing 2-year storm peak as calculated from the rational method. The design volume is based on the 100-year storm volume for developed con- ditions at the 60 acre site as determined from the rational method. The existing peak flow upstream of the site at Trilby Road for a 100-year storm (276 cfs) will not be detained. It is passed downstream. A comparison of time to peaks shows that releasing a maximum of 297 cfs will effectively detain the on -site 100 year peak. Table 6.4 shows the time to peak and peaks for the site. This information is compared to a time to peak of 55 minutes and a peak of 388 cfs at the north end of the site for the site undeveloped and the area upstream of Trilby as existing. Table 6.3 shows a required detention volume of 11.4 ac-ft. The maximum release rate is 297 cfs based on a 21 cfs peak from the site and 276 cfs upstream of the site at Trilby Road. 6.3.2 Channels Two channel sizes were required on the site. The flow rates used to size the channels were from a SWMM analysis. The peak flows at design points are listed in Table 6.5. A trapezoidal channel was assumed to carry the drainage from upstream of Trilby Road and the property to the north end of the pro- perty. The design flow is 400 cfs. A drainage swale is provided parallel to the north end of the 60 acre site. Here the design flow is 680 cfs. The channel design data are summarized in Table 6.6. Table 6.3. For Developed Condition, Maximum Allowable Release Rate attributable to the 60.3 Acre Site from the Detention Facility is 21 cfs. Thus, the Calculations for Required Storage are as Follows: Release Duration Intensity Time Volge Volge Required Storage (min) Cf.C.A* (in/hr) (sec) (ft ) (ft ) (ac-ft) 5 60.3 9.00 300 164,170 6,300 3.62 10 60.3 ( 7.02 600 256,100 12,600 5.59 15 60.3 5.92 900 323,960 18,900 7.00 20 60.3 5.18 1,200 377,950 25,200 8.10 25 60.3 4.58 1,500 417,710 31,500 8.87 30 60.3 4.10 1,800 448,720 37,800 9.43 35 60.3 3.74 2,100 477,540 44,100 9.95 40 60.3 3.45 2,400 503,440 50,400 10.40 45 60.3 3.20 2,700 525,330 56,700 10.76 50 60.3 2.98 3,000 543,570 63,000 11.03 55 60.3 2.78 3,300 557,800 69,300 11.21 60 60.3 2.60 3,600 569,110 75,600 11.33 65 60.3 2.44 3,900 578,600 81,900 11.40** 70 60.3 2.29 4,200 584,600 88,200 11.40 75 60.3 2.16 4,500 591,000 94,500 11.39 *C .0 = 1.0 **Maximum Storage Required 6.7 Table 6.4. Summary of Time to Peaks. Peak Time to Peak Method Used to (cfs) (mins) Calculate Results Catchpoint 480 8 Rational 60.3 acre South Side Service Center Site, fully developed 276 50 SWMM Upstream of Trilby Road, existing conditions 297 50 Table 6.3 North end of Site and SWMM 6.8 Table 6.5. Design Flows, Site Developed - U/S Undeveloped. Storm Peak Discharge Volume Location Frequency Conditions (cfs) (ac-ft) At Trilby Road 100-year U/S Undeveloped 276 22.9 10-year Lot Undeveloped 108 At North End of Site 100-year 400 34.8 10-year 194 Downstream of Site 100-year 682 59.9 10-year 277 6.9 Table 6.6. Channel Design Data. Depth Design Bottom of Discharge Manning's Width Side Flow Velocity ROW1 Channel (cfs) Slope n (ft) Slopes (ft) (fps) (ft) Channel 1 400 0.0153 0.035 8 4:1 2.6 7:5 50 Channel 2 680 0.0105 0.035 1 20:1 2.6 5.0 120 1 Includes an additional 1/3 of the design capacity as freeboard in accordance with Fort Collins specifications. 7.1 VII. ANALYSIS AND DESIGN OF DRAINAGE IMPROVEMENTS FOR TRANSFORT FACILITY Presented in this section are the necessary improvements for managing stormwater at the new TransFort facility. Included is a list of improvements for major drainage of and site drainage through the new TransFort facility. The new TransFort facility is the first phase of development scheduled at the project site. The proposed facility is to be located in the southeast corner of the project site on 5.8 acres. The area involved is generally flat and presently has a natural channel running south to north through the west side of the site. The site is bounded to the south by Trilby Road and to the east by the property boundary. Plate 17 of the Engineering Drawings show the general topography and location. Major drainage improvements are based on a design inflow of 276 cfs. The channel slope was chosen to conform with the proposed site grading plan of M&I and the storm drainage design criteria for the City of Fort Collins. Based on this selected channel slope, two drop structures were required in the design. Riprap drop structures were chosen for economic and aesthetic reasons. The Site Drainage Improvements are based on the Rational Method used to determine the discharge at a given location. Fort Collins Storm Drainage Criteria Nomographs were used to determine inlet capacities and Manning's equation was used to determine pipe capacities. A summary of the storm sewer design calculations is given in Table 7.1. A summary of the hydraulic analysis for the box culverts are presented in Table 7.2. All calculations are summarized in the Appendix. The proposed improvements are presented under two headings. The first covers drainage for off -site runoff that must be carried through the property, the second covers on -site drainage that crosses the site. Major Drainage Improvements 1. A 94 foot, 4' x 8' reinforced concrete box culvert with wing walls and riprap aprons at Trilby Road. 2. A 55 foot, 4' x 8' reinforced concrete box culvert with wing walls and riprap aprons at the south entrance to the facility. 3. A 40 foot, 4' x 8' reinforced concrete box culvert with wing walls and riprap aprons at the north entrance to the facility. 7.2 u v. 4J 0 w ro �i U .H '-I ro u W O 0) r-� ro H ro �81 �11181 IU�111 1 0111101111HIIIIIII UNION —27— i - iaAn s `I z o _r_ i, In 4j }-I U x O M w 0 In ..H W r-1 N fi U r-I a x 0 O 4-I r� H it r0 m N to J �C W G C-1 •,,l F3c- I JI00 �� � a J • � v W � X AlI0Ol3A �> _ � G I—� 13iino v1 �-- V NIllON1NOJ Z U W W U W Q C O O N `� W W `1 F- 3 0 > > n u Q S o ri J Q� S O W W U z �l 4 I w� U b y 3 J I Q x W � W Q ti .•. � 0O (L�t� = J W — f.. + 2 " 1 _ h O I U JrN-- O n 1 n 11 Q z v a U o W M = 0� o = j i �1- S v W w ¢ O J J In 0 0, o 3 z Z� W W N O OX 1, J� it It 0 w W h Q ~ ~ N tJ F= O 3 oC1 (�i Z Q Q FI cc 0 0 Qa �= z N U W a . "� Wy w 1� Z O Ll �O N p Q w W = dL d U Lu o o �� W O 11 11 lV �' O cfj z i O - c! S — O N O o C1 O �� F. > x a i. v a }_ W— y r 3p N it a kn U W \' I .� From EPR FIGURE 13 DESIGN COMPUTATION FORM FOR CULVERTS -40- 1-I�R(� ATTACHMENT 1 C TABLE IV: Entrance Loss Coefficients Coefficient ke to apply to velocity head V2/2g for determination of head loss at entrance to a structure, such as a culvert or conduit, operating full or partly full with control at the outlet. Entrance head loss He = ke V2/2g Type of Structure and Design of Coefficient ke Type of Structure and Design of Coefficient ke Entrance Box, Reinforced Concrete Entrance Box, Reinforced Concrete Headwall parallel to embankment (no wing walls) Wing walls at 100 to 250 to barrel Square -edged on 3 edges . . . . . . 0.5 Square -edged at crown . . . . . . . . 0.5 Rounded on 3 edges to radius of 1/12 Wing walls parallel (extension of sides) barrel dimension . . . . . . . 0.2 Square -edged at crown . . . . . . . . 0.7 Wing walls at 30e to 750 to barrel Square -edged at crown . . . . . . 0.4 Crown edge rounded to radius of 1/12 barrel dimension . . . . . . . . 0.2 BUREAU OF PUBLIC ROADS -JAN. 1963 FIGURE 4: Head for Concrete Box Culverts Flowing Full, n = 0.012 5000 4000 --;iw, ' N 3000 1 NW _''- ^, 2000 12 x 12 1000 800 10 x 10 100 9 x 9 80 600 500 8 x 8 60 — 400—_ 7 x 7 50 .. 40`_ 00 6 x 6 CA U. U0.225 30 5 [21100-�- 20Lu 4x4 6x3 ¢ Box 3.5 x 3.5 00 y 80 3x3 10 0 8 60 LU 50 2.5x2.5 6 z 40 J 5 t7 2 x 2 4 Z 30 Cr X X m ~ m 20 cc ¢ Q J W W Q LL in LU Z W U. UU Q ¢ LL 10 Z Z W CI 8 0 ¢ to fO LL Z Z 0- -6 w 5 p LU ¢ Q $I,DF Sor SUBMERGED OUTLET CULVERT FLOWING FULL ' N W • H • ^,-LSD For outlet crown not submerged, compute HW by methods described in the design procedure. 4 5 6 .8 1.0 Ka� ry {�2 W L e 2� y n�CT FLCT LL = ke=0.2 �� 3 z CP p GJCA 4 0 p� w a 6� H' 5 22 6 x 8 10 20 BUREAU OF PUBLIC ROADS • JAN 1963 5 7.5 4. Two 55' x 29' riprap drop structures located between the two entrances. 5. 295 linear feet of grass lined, trapezoidal open channel with 4:1 side slopes and a 4' trickle channel. Site Drainage Improvements 1. Three Type 13 Stormwater Inlets. 2. One Type R Stormwater Inlet 3. One Storm Sewer Manhole 4. 205 linear feet of 18" RCP. 5. 390 linear feet of 21" RCP. 6. 24 linear feet of 24" RCP. Developers at Mobily Heights are aware of and are able to match the invert elevation of 4953.6 at the Trilby Road box culvert. The box culvert under Trilby Road is designed for 276 cfs. The capacity is adequate to handle the existing 100-year flow as directed by the City staff. APPENDIX BACKGROUND CALCULATIONS M%] 00,000 m -Oc .9t.10 8 -47 ab log i. go 00 SE 1— 3 00 SE 1— 3 SIMONS. LI b ASSOCIATES CLIENT Zy rK Joe No.�-�yf� a'� PACE ENGINEERING CONSULTANTS PROJECT DATE CHECKED DATE %13o/,V? FORT COLLINS. COLORADO DETAIL CHECKED BY COMPUTED BY Ldl `- Desig„ 4 = z76 e- fs — !ov—W� Peverl . SIMONS LI & ASSOCIATES ENGINEERING CONSULTANTS FORT COLLINS. COLORADO CLIENT_ PROJECT DETAIL— 21 l7�aP STL'dGTURi= Qtoo =z76 G�-- JosNO. PAGE DATE CHECKED DATE CHECKED BY COMPUTED BY %iSSUnrg 8 " W,'d'1'/1 C S / 2-76 d f = � 7%Dp ti;6.8 1f �•.eti-fie W��(•1y � ?���',8t2,�=i8.�•' G i q2 P i / = 9' Z��'�5•GS = f7.64.cfs� U S z r dam= 9 = �•r, LcSe G�'e = Z �O i, h y = -271v/4, = 1745 q 2 J D= o,iz.4 by' t YL SIMON& LI 3 ASSOCIATES CLIENT JOB NO. PAGE ENGINEERING CONSULTANTS PROJECT DATE. CHECKED DATE FORT COLLIN& COLORADO DETAIL CHECKED BY COMPUTED BY T��G 6 //:.q beasin rleodr 44,e d'& us- ek , r � L Z �d r � _ . use s l a-p-P_ d, -� :54 -c4 -e , Fet.,,--- s 2 3. 64- , u se z4-'-o , L, 4 �' = t�.�¢t� Ute 20=o„ n:p�L.� P,,{;A ��� z�K�-rflpi+,� - 2 CA-5 •e `� -- — ---- �.vJ aCCt 5' 12 : -i p. 1 i.z D n w�_ vi - i�-�1 Gam. -.gyp �4L i_ _ � �o.i— 'r--� ro•; /o i3 _ _ _ _ .__... __. ___ . &o-,.ed eri c)v bn R A. U-Se Aso = r2^, �. tn„ rt'per F,� z�It. _- -- j2' �,..,-� f/ �r•f �cv - /t,C a_•r-<, , - f _ s,� e .'.-f �'c,.-� S f,�,,.e x�r_. �,',ie.� ; N d.-.....r:'•.'S , ._. SIMONS, LI 6 ASSOCIATES CLIENT JOB NO. PAGE ENGINEERING CONSULTANTS PROJECT DATE CHECKED DATE FORT COLLINS. COLORAOO DETAIL CHECKED BY COMPUTED BY 3 - �STo,�.y sGc✓z2 12a.1 euee,1A)1ET 4= Z.B�fs ee,F rAjve-vf �(e�,ffzA -R! e, t3. Vl C� 45•so' - f--to✓J d-epi-h -f-CL2 8'x4` e� lvt>'% @ ham . C, 4,.n„ ItQ A 4e.5':f nJer1 �} O-n PSI P�YdI1i 9o'i'-i.l_ t- 4-L� c..�� d�c 1>e '24" 2¢"� 42,s - 3Cz� _. 4/•l�', _Sam( 4/.ao' - 24 t ISM t 112 tlLl r 2d�= lord l - 4a z¢`'�j o�..{ l�.t'= e 5 5- 4 f 2 4,3 - F26 2. / Ca= Z.ec�S - v_Se Mi ;wu, 54F-1 cl .n;.. S: Ig" In c11.10/3 ' "w N(i ni... �. V@i0 ti ±-r.� oZ 2.J .��S .� S= O.OD/l C/Y=ZUS ra.ov//=D•2j/ SIMONS. LI A ASSOCIATES CLIENT JOB NO. PAGE ENGINEERING CONSULTANTS PROJECT DATE CHECKED DATE FORT COLLINS, COLORADO DETAIL CHECKED BY COMPUTED BY - - . s%tea ul-�rrc� = d•o 084 � vf•/ = n•oo�4.� ///- a•93 � _ 5/afx Le .;<«C = o•o /l ar/ o-0/1x /22 ,u. /•-/-'// -�o C.S, G� n //.ate•% _ - ...__ _-- --`- . 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