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HomeMy WebLinkAboutDrainage Reports - 10/05/1998Fin d Report safe �v S 9� Final Drainage and Erosion Control Report for INNERWILEA I •ti• The Howes Street Hideaways II [_�_ Amendment to The Howes Street Hideaways (approved 05/27/97) Fort Collins, Colorado Previously known as Lot 1 I, Block 105, Harrison's Addition Prepared for: RAYLINE DEVELOPMENT CORPORATIO 3555 Stanford Road Suite 12 Ft. Collins, Colorado 80525 Phone: (970) 204-0306 Prepared by: SHEAR ENGINEERING CORPORATION ti Project No: 1536-08-97 DATE: September, 1998 PRINT DATE SEP 17 1998 SHEAR ENGINEERING CORP 4836 S. College, Suite 12 Ft. Collins, Co 80525 (970) 226-5334 FAX (970) 282-0311 No Text December 15, 1997 Project No: 1536-08-97 Basil Harridan City of Ft. Collins Stormwater Utility P.O. Box 580 Ft. Collins, Colorado 80524 Re: Howes Street Hideaways H Previously Known as Lot 11, Block 105, Harrison's Addition; Fort Collins, Colorado Dear Basil, Enclosed, please find the Final Drainage and Erosion Control Report for Lot 11, Block 105, Harrison's Addition. The hydrology data and the hydraulic analysis presented in this report complies with the requirements of the City of Fort Collins Storm Drainage Criteria Manual; dated March, 1984, the City of Fort Collins Erosion Control Reference Manual and the Old Town Master Drainage Basin Plan for the City of Fort Collins. Please note that this project consists of the construction of 1 single family home and parking adjacent to the existing alley which was improved with Howes Street Hideaways (Lots 12-14, Block 105, Harrison's Addition). This report has been prepared as an amendment to the approved Final Drainage and Erosion Control Report for Howes Street Hideaways (Lots 12-14, Block 105, Harrison's Addition) since the product is exactly the same as that constructed with the original Howes Street Hideaways. If you have questions, or require further information on any item, please call at (970) 226-5334. Shear Engineering Corporation BWS/mb cc: Rayline Development Corporation 4836 S. College, Suite 12 Ft. Collins, CO 80525 (970) 226-5334 FAX (970) 282-0311 Final Drainage and Erosion Control Report for Howes Street Hideaways Il Project No. 1536-08-97 Page 2 of 10 I. GENERAL LOCATION AND DESCRIPTION: A. Location The project site is located in the Northeast One Quarter (1/4) of Section 14, T7N, Range 69 West of the 6th P.M., Ft. "Collins, Colorado. The site is Lot 11, Block 105, Harrison's Addition. 2. More specifically, the project site is located between West Mulberry Street and Myrtle street nearest the north end of the westernmost lots of Block 105 (See Vicinity Map). 3. The site is a part of Old Town Fort Collins and is developed. The proposed duplex will be constructed along the existing alley at the rear of the existing lot. B. Description of Property There is currently a single family residence on this lot. The existing house fronts on South Howes Street. 2. The site area is approximately 0.20 acres. 3. Development of the site will consist of the construction of 1 single family residence at the rear of the existing lot along the alley. 4. An existing paved alley borders the site on the east side. 5. The alley was paved with the Mulberry Green and the Howes Street Hideaways projects. 6. The alley has an inverted crown section to assist in the conveyance of stormwater to West Mulberry Street. 7. There are no major drainageways located on or within 150' feet the project site. See Drainage and Erosion Control Plan in stuffer envelope. II. DRAINAGE BASINS AND SUB -BASINS: A. Major Basin Description The site is situated within the Old Town Drainage Basin as designated on the City of Fort Collins Stormwater Basin Map. Final Drainage and Erosion Control Report for Howes Street Hideaways II Project No. 1536-08-97 Page 3 of 10 II. DRAINAGE BASINS AND SUB -BASINS (Continued): A. Major Basin Description (continued). 2. According to the conceptual review summary letter dated October 27, 1997, the drainage basin fee associated with grid #71 in the Old Town Basin, is $4,150.00 per acre. 3. The approximate limits of ponding in the area of Mason and Mulberry are shown on fig 5.1 of the Old Town Report in appendix IV and the ponding exhibit on the Drainage and Erosion Control plan. 4. Stormwater from the site drains to conveyance element 205 as delineated on figure 4.1 of the Old Town Master Drainage Basin Plan. 5. According to the Old Town Master Drainage Basin Plan, stormwater flows in conveyance element 205 are split at the intersection of Mason Street and Mulberry Street. 6. Some of the flows are conveyed east in the existing storm sewer while others are conveyed north on Mason when the storm sewer capacity is reached. B. Sub -Basin Description 2. The site is extremely flat. The site was surveyed to determine if there was a defined flow path. Slopes across the entire Howes Street Hideaways site ranges from 0.5% to 0.70% from east to west and from south to north. There is very little fall from the rear of the existing houses to the walk at Howes Street. At the rear of the existing houses the site begins to slope to the north towards lot 10. Runoff then flows in a northeasterly direction across lots 11 and 10 to the alley. The site is divided into 3 sub -basins defined as Ae, Aw and Am. 3. Sub -basin Ae contributes runoff to the alley. 4. Sub -basin Aw contributes runoff to the Howes Street. 5. Sub -basin Am contributes runoff to Lot 10 located north of the site. 6. Existing spot elevations are shown on the grading plan. 7. Development of the site will increase the area in basin Ae because this area will be developed and therefore it is deemed better to convey as much of the runoff from sub -basin Ae to the alley. Final Drainage and Erosion Control Report for Hones Street Hideaways 11 Project No. 1536-08-97 Page 4 of 10 III. DRAINAGE AND EROSION CONTROL DESIGN CRITERIA: A. Regulations 1. All storm drainage design criteria from the City of Fort Collins Drainage Criteria Manual was considered. 2. Recommendations made in the Old Town Master Drainage Basin Plan prepared by Resource Consultants & Engineers, Inc. were also considered. 3. Flood elevations noted in the Old Town Master Drainage Basin Plan were utilized to establish the minimum allowable Finished Floor Elevations of the proposed single family residence. 4. All erosion control design criteria from the City of Fort Collins Erosion Control Reference Manual was considered. B. Development Criteria Reference and Constraints 1. All grading design must match the existing elevations at the property line due to fully developed properties adjacent to the site. 2. The nearby intersection of Mason Street and West Mulberry Street is subject to flooding due to insufficient capacity of the existing storm sewer. 3. According to the Old Town Master Drainage Basin Plan, the 100-year flood elevation on Mulberry Street in the area of Howes Street Hideaways is approximately 4993.5 feet. Refer to figure 5.6 in the Old Town Master Drainage Basin Plan attached in Appendix IV. 4. The lowest existing elevation on the site based on survey information is 4993.93 feet. 5. Minimum Allowable finished floor elevations shall be 4995.0 feet in order to provided the minimum 1.5 feet separation above the defined 100-year water surface elevation. A note stating this is provided on the Master Grading, and the Drainage and Erosion Control Plan. 6. Detention is required if the imperviousness of the site exceeds seventy percent (70.0%). This is in accordance with the assumptions of the Stormwater Management Model (SWMM) for subcatchment 205 in the Old Town Basin. Final Drainage and Erosion Control Report for Howes Street Hideaways Il Project No. 1536-08-97 Page 5 of 10 III. DRAINAGE AND EROSION CONTROL DESIGN CRITERIA: C. Hydrological Criteria The Rational Method (Q = CIA) was used to determine the pre -developed and/or post development peak flows for the 2, 10 and 100-year storm events at critical points. D. Hydraulic Criteria Storm sewer and drainage channel capacities were based on the Mannings Equation. The Mannings coefficients are as suggested by the City of Fort Collins Storm Drainage Criteria Manual. IV. DRAINAGE FACILITY DESIGN: A. General Concept 1. Stormwater is conveyed to West Mulberry Street by a combination of overland and gutter flow. 2. The alley has been graded with an inverted crown to facilitate conveyance of Stormwater into Mulberry West Street. 3. Detention is not required because the imperviousness of the developed site does not exceed 70%. Final Drainage and Erosion Control Report for Ho%N es Street Hideaways Il Project No. 1536-08-97 Page 6 of 10 IV. DRAINAGE AND EROSION CONTROL DESIGN CRITERIA (Continued): B. Specific Details 1. The following table summarizes the land cover and the appropriate percent imperviousness on the existing site. Existing Site Area acres C C*A Percent Impervious I*A Asphalt 0.06 0.95 0.0570 100% 6.0% Concrete 0.03 0.95 0.0285 100% 3.0% Gravel 0.03 0.50 0.0150 50% 1.5% Roof 0.26 0.95 0.2470 100% 26.0% Lawn 0.45 0.20 0.0900 0% " 0.0% Total 0.83 0.4375 36.5% Year C 2 & 10 6.53 100 0.66 Existing Site is I 43.98% Impervious 2. The imperviousness of the existing site is 43.98%. This does not include the alley or the 1/2 right-of-way which fronts on the property. The imperviousness percentages are taken from Table 3-1 in the Urban Storm Drainage Criteria Manual - Volume 1. The Runoff Coefficient is taken from the City of Fort Collins Drainage Criteria Manual. Final Drainage and Erosion Control Report for Howes Street Hideaways 11 Project No. 1536-08-97 Page 7 of 10 IV. DRAINAGE FACILITY DESIGN (Continued): B. Specific Details (continued) 3. The following table summarizes the land cover and the appropriate imperviousness on the developed site: Daeloped Site Arta sacs C C-A Pa t Intpavious 1'A ,Vrkdt 0.09 0.95 0.0855 100% 9.0% Conaete 0.04 0.95 0.0380 100% 4.0°/ Gael 0.03 0.50 0.0150 50% I.5% Roof 0.29 0.95 0.2755 100'/0 29.0°/ un 0.38 0.20 0. a / ot. / yea C 2 & 10 0.59 100 0.74 JLL�eo rtea o 4. The resultant imperviousness of the developed site is 52.41%. This does not include the alley or the 1/2 right-of-way which fronts on the property. The imperviousness percentages are taken from Table 3-1 in the Urban Storm Drainage Criteria Manual - Volume 1. The Runoff Coefficient is taken from the City of Fort Collins Drainage Criteria Manual. 5. The proposed development results in an increase from 43.98% impervious to 52.41% impervious. Detention is not required because the site is less than 70% impervious. 6. The overall imperviousness of the developed site, the alley and.the 1/2 right-of-way of Howes Street is 60.96 percent. 7. Retaining walls will be constructed along the north property line because the grading around the new building will be higher than existing grade at the property line. Final Drainage and Erosion Control Report for Hones Street Hideaways II Project No. 1536-08-97 Page 8 of 10 IV. DRAINAGE FACILITY DESIGN (Continued): B. Specific Details (continued) 8. The alley has a minimum slope of 0.50%. Concrete will be used in the alley and parking lot. The alley will act as a channel for the runoff from the site. 9. The capacity of the alley at the minimum slope is 2.83 cfs. 10. Grading constraints do not allow an increase in the minimum slope of the alley without adversely affecting the adjoining properties. 11. The peak flows from the site onto Lot 10 to the north have been compared using the historic conditions and developed conditions. Historic condition is defined as being the site prior to construction of Howes Street Hideaways. The grading of Howes Street Hideaways has been done so as to reduce the amount of area which contributes runoff onto Lot 10. The table below summarizes the peak flows for the 2, 10 and 100-year storms onto Lot 10. Refer to pages 10 and I I in Appendix I for the calculations. Final Drainage and Erosion Control Report for Howes Street Hideaways 11 Project No. 1536-08-97 Page 9 of 10 V. EROSION CONTROL: B. General Concept 1. Erosion control measures will be as identified on the Final Grading, Drainage and Erosion Control Plan. 2. An erosion control security deposit is required in accordance with City of Fort Collins policy (Chapter 7, Section C: SECURITY; page 7.23 of the City of Fort Collins Development Manual). In no instance shall the amount of the security be less than $1,000.00. 3. Refer to the Erosion Control Security Document located in Appendix II for the amount of the deposit. VI. VARIANCE REQUEST: B. Variance from City of Fort Collins Requirements There will be no requests for any variances from the City of Fort Collins Storm Drainage Criteria for The Howes Street Hideaways. VII. CONCLUSIONS: B.. Compliance with Standards 1. All drainage analysis has been performed according to the requirements of the City of Fort Collins Storm Drainage Criteria Manual, the City of Fort Collins policy, and the Old Town Master Drainage Basin Plan. 2. All Erosion Control design complies with the City of Fort Collins Erosion Control Reference Manual and generally accepted practices. C. Drainage Concept 1. The drainage design for The Howes Street Hideaways and Howes Street Hideaways II is in accordance with the City of Fort Collins requirements and the recommendations of the Master Drainage Basin Plan for Old Town Basin. 2. There will be no adverse downstream effects due to the development of the site. Final Drainage and Erosion Control Report for Howes Street Hideaways II Project No. 1536-08-97 Page 10 of 10 VIII. REFERENCES: A. Fort Collins Storm Drainage Criteria Manual B. , Urban Drainage and Flood Control District Drainage Criteria Manual C. Fort Collins Storm Erosion Control Reference Manual D. Old Town Master Drainage Basin Plan; Prepared by Resource Consultants & Engineers, Inc.; Dated January 7, 1993 E. Final Drainage and Erosion Control Report for Mulberry Green; prepared by Shear Engineering Corporation ; Project No: 1151-24-95; Dated: June, 1996 F. Final Drainage and Erosion Control Report for Howes Street Hideaways; prepared by Shear Engineering Corporation ; Project No: 1536-08-97, Dated: April, 1997 APPENDIX I Storm Drainage Calculations Project No. 1536-08-97 Shear Engineering Corporation 9/16/98 By: MEO - Howes 2 Run RUNOFF Page 1 of 11 Project No. 1536-08-97 Shear Engineering Corporation 9/17/98 By: MEO Howes2Run FLOW SUMMARY FOR HOWES STREET HIDEAWAY II DESIGN CONTRIBUTING AREA C2 C100 Tc To I2 I100 Q2 Q100 POINT SUB 2,10 100 BASIN(S) ac. - min. min iph iph cfs cfs 3 Aw 1 A. & ALLEY 3 ROW 2 Am 2 Ae,Am,ALLEY HISTORIC LOT 10 Am DEVELOPED LOT 10 Am 0.31 0.49 0.61 11.5 11.5 2.42 6.82 0.37 1.30 0.47 0.81 1.00 11.5 11.5 2.42 6.82 0.92 3.20 0.22 0.78 0.97 8.0 8.0 2.84 8.00 0.49 1.72 0.14 0.31 0.38 12.0 12.0 2.28 6.71 0.10 0.36 0.61 0.69 0.87 12.0 12.0 2.38 6.71 1.01 3.55 0.32 0.20 0.25 11.00 11.00 2.46 6.92 0.16 0.55 0.14 0.31 0.38 1 10.50 10.00 2.50 7.14 1 0.11 0.38 SUMMARY OF SUBBASIN BREAKDOWN PLATTED AREA HOWES STREET HIDEAWAY II 0.830 ACRES ROW 0.22 ACRES ALLEY 0.09 ACRES TOTAL 1.14 ACRES DEVELOPED CONDITIONS IMPERVIOUS PERVIOUS SUB- GRAVEL ASPHALT ROOF/ LAWN C2 C100 BASIN CONCRETE DRIVES Cfactor 0.50 0.95 0.95 0.20 1 IMPERVIOUS 50.001 100.001 100.001 0.001 ACRES ACRES ACRES ACRES ACRES SITE 0.83 0.03 0.13 0.29 0.38 0.59 0.74 1/2 ROW 0.22 0.00 0.17 0.00 0.05 0.78 0.97 ALLEY 0.09 0.00 0.09 0.00 0.00 '0.95 1.00 TOTAL 1.14 0.03 0.39 0.29 0.43 0.66 0.82 Aw 0.31 0.00 0.02 0.10 0.19 0.49 0.61 A. Ae&ALLEY 0.38 0.03 0.10 0.18 0.07 0.78 0.97 0.47 0.03 0.19 0.18 0.07 0.81 1.00 Am Ae, AmAlley 0.14 0.00 0.01 0.01 0.12 0.31 0.38 0.61 0.03 0.20 0.19 0.19 0.69 0.87 0.31 0.38 0.47 0.14 0.61 TOTAL 1 0.83 0.03 0.13 0.29 0.28 0.59 0.74 1 IMPERVIOUS = 60.96% - INCLUDES 1/2 ROW AND ALLEY AND DEVELOPED SITE 1 IMPERVIOUS = 52.41i - SITE ONLY- DEVELOPED CONDITIONS i IMPERVIOUS = 43.98' - SITE ONLY- EXISTING CONDITIONS Page 2 of 11 Project No. 1536-08-97 Shear Engineering Corporation By: MEO 9/16/98 Howes 2 Run SUB -BASIN BREAKDOWN FOR HOWES-STREET HIDEAWAYS II EXISTING CONDITIONS PROJECT HOWES STREET HIDEAWAYS II NOTES SITE ONLY RUNOFF SURFACE COEF. CHARACTERISTICS AREA C C*A (acres) IMPERVIOUS STREETS ASPHALT 0.060 0.950 0.057 100.00% 0.0600 CONCRETE 0.030 0.950 0.029 100.00% 0.0300 GRAVEL 0.030 0.500 0.015 50.00% 0.0150 ROOFS 0.260 0.950 0.247 100.00% 0.2600 LAWNS SANDY SOIL FLAT < 2% 0.000 0.100 0.000 0.00% 0.0000 AVERAGE 2 - 7% 0.000 0.150 0.000 0.00% 0.0000 STEEP > 7% 0.000 0.200 0.000 0.00% 0.0000 LAWNS HEAVY SOIL FLAT < 2% 0.450 0.200 0.090 0.00% 0.0000 AVERAGE 2 - 7%s 0.000 0.250 0.000 0.00% 0.0000 STEEP > 7% 0.000 0.350 0.000 0.00% 0.0000 TOTAL AREA 0.830 0.438 0.3650 C2 C10 C100 COMPOSITE C VALUE 0.527 0.527 0.659 % IMPERVIOUS 43.98% SITE ONLY Page 3 of 11 Project No. 1536-08-97 Shear Engineering Corporation By: MEO SUB -BASIN BREAKDOWN FOR HOWES STREET HIDEAWAYS DEVELOPED CONDITIONS PROJECT HOWES STREET HIDEAWAYS II NOTES SITE ONLY SURFACE CHARACTERISTICS STREETS ASPHALT CONCRETE GRAVEL ZKo77&* LAWNS SANDY SOIL FLAT < 2% AVERAGE 2 - 7% STEEP > 7% LAWNS HEAVY SOIL FLAT < 2% AVERAGE 2 - 7% STEEP > 7% TOTAL AREA COMPOSITE C VALUE IMPERVIOUS RUNOFF COEF. AREA C (acres) C*A 96 IMPERVIOUS 9/16/98 Howes 2 Run 0.090 0.950 0.086 100.00% 0.0900 0.040 0.950 0.038 100.00%s 0.0400 0.030 0.506 0.015 50.00°; 0.0150 0.290 0.950 0.276 100.00% 0.2900 0.000 0.100 0.000 0.000 0.150 0.000 0.000 0.200 0.000 0.380 0.200 0.076 0.000 0.250 0.000 0.000 0.350 0.000 0.830 0.490 C2 C10 C100 0.590 0'.590 0.738 52.41% SITE ONLY 0.00% 0.0000 0.00% 0.0000 0.00% 0.0000 0.00% 0.0000 0.00% 0.0000 0.00% 0.0000 0.4350 Page 4 of 11 Project No. 1536-08-97 Shear Engineering Corporation By: MEO FLOW TO CONCENTRATION POINT 3 FROM SUBBASIN Aw PROJECT: HOWES STREET HIDEAWAY II NOTE: CP 3 IS AT THE NORTHWEST CORNER OF THE SITE IN THE STREET AREA (A)= 0.310 ACRES RUNOFF COEF. (C) SEE SPREAD SHEET ATTACHED ON PAGE 2 2 YEAR _ 10 YEAR 100 YEAR C = 0.49 0.49 0.61 9/16/98 Howes 2 Run TIME OF CONCENTRATION (TC) OVERLAND TRAVEL TIME (Ti) LENGTH = 95 FEET SLOPE = 1.00 a 2 YEAR 10 YEAR 100 YEAR C = 0.20 0.20 0.25 Ti (min)= 16.40 16.40 15.49 TRAVEL TIME (Tt)=L/(60*V) NOTE: ALL VELOCITIES TAKEN FROM FIGURE 3-2 Length Slope Flow Type Velocity Tt ft o fps min 190 1 GUTTER 1.50 2.11 ? ? ? ? 0.00 ? ? ? ? 0.00 TOTAL TRAVEL TIME (min) = 2.11 TOTAL LENGTH = 285 L/180+10= 11.58 < 18.51 =Ti+Tt TC =Ti+TOTAL TRAVEL TIME Choose lesser of L/180+10 or Ti+Tc 2 YEAR 10 YEAR 100 YEAR TC (min)= 11.58 11.58 11.58 USE Tc = 11.5 11.5 11.5 INTENSITY (I) (iph) NOTE: INTENSITIES TAKEN FROM FIGURE 3-1 2 YEAR 10 YEAR 100 YEAR I = 2.42 4.24 6.82 RUNOFF (Q= CIA) (cfs) 2 YEAR 10 YEAR 100 YEAR IQ = 0.37 0.64 1.30 CONCLUDE: PEAK FLOW FROM WESTERN PORTION OF SITE AFTER DEVELOPMENT Page 5 of 11 Project No. 1536-08-97 Shear Engineering Corporation By: MEO Developed Flow FLOW TO CONCENTRATION POINT 1 FROM SUBBASIN Ae & ALLEY PROJECT: HOWES STREET HIDEAWAY II NOTE: CP 2 IS @ NE CORNER OF SITE IN ALLEY AREA (A)= 0.470 ACRES RUNOFF COEF. (C) SEE SPREAD SHEET ATTACHED ON PAGE 2 2 YEAR 10 YEAR 100 YEAR C = 0.81 0.81 1.00 OVERLAND TRAVEL TIME (Ti) 9/17/98 Howes 2 Run LENGTH = 100 FEET SLOPE = 0.50 e 2 YEAR 10 YEAR 100 YEAR C = 0.20 0.20 0.25 Ti (min)= 21.16 21.16 19.98 TRAVEL TIME (Tt)=L/(60*V) NOTE: ALL VELOCITIES TAKEN FROM FIGURE 3-2 Length Slope Flow Type Velocity Tt ft fps min 190 1 GUTTER 1.50 2.11 ? ? ? ? 0.00 ? ? ? ? 0.00 TOTAL TRAVEL TIME (min) = 2.11 TOTAL LENGTH = 290 L/180+10= 11.61 < 23.27 =Ti+Tt Tc =Ti+TOTAL TRAVEL TIME Choose lesser of L/180+10 or Ti+Tc 2 YEAR 10 YEAR 100 YEAR Tc (min)= 11.61 11.61 11.61 USE Tc = 11.5 11.5 11.5 INTENSITY (I) (iph) NOTE: INTENSITIES TAKEN FROM FIGURE 3-1 2 YEAR 10 YEAR 100 YEAR 1 = 2.42 4.24 6.82 RUNOFF (Q= CIA) (Cf S) 2 YEAR 10 YEAR 100 YEAR IQ = 0.92 1.61 3.20 CONCLUDE: PEAK FLOW FROM SITE TO ALLEY MINIMUM SLOPE OF ALLEY = 0.005 FT/FT CAPACITY OF ALLEY = 2.83 CPS Page 6 of 11 Project No. 1536-08-97 Shear Engineering Corporation By: MEO FLOW TO CONCENTRATION POINT 3 FROM SUBBASIN ROW PROJECT: HOWES STREET HIDEAWAY II NOTE: CP 3 IS AT THE NORTHWEST CORNER OF THE SITE IN THE STREET AREA (A)= 0.220 ACRES RUNOFF COEF. (C) SEE SPREAD SHEET ATTACHED ON PAGE 2 2 YEAR 10 YEAR 100 YEAR C = 0.78 0.78 0.97 9/16/98 Howes 2 Run ♦1vin Ur \Iuj OVERLAND TRAVEL TIME (Ti) _ LENGTH = 20 FEET SLOPE = 2.00 2 YEAR 10 YEAR 100 YEAR C = 0.20 0.20 0.25 Ti (min)= 5.99 5.99 5.66 TRAVEL TIME (Tt)=L/(60*V) NOTE: ALL VELOCITIES TAKEN FROM FIGURE 3-2 Length Slope Flow Type Velocity Tt ft % fps min 190 1 GUTTER 1.50 2.11 ? ? ? ? 0.00 ? ? ? ? 0.00 TOTAL TRAVEL TIME (min) = 2.11 TOTAL LENGTH = 210 L/180+10= 11.17 > 8.10 =Ti+Tt Tc =Ti+TOTAL TRAVEL TIME Choose lesser of L/180+10 or Ti+Tc 2 YEAR 10 YEAR 100 YEAR Tc (min)= 8.10 8.10 7.77 USE Tc = 8 8 8 INTENSITY (I) (iph) NOTE: INTENSITIES TAKEN FROM FIGURE 3-1 2 YEAR 10 YEAR 100 YEAR I = 2.84 4.93 8.00 RUNOFF (Q= CIA) (cfs) 2 YEAR 10 YEAR 100 YEAR IQ = 0.49 0.84 1.72 CONCLUDE: PEAK FLOW TO NORTHWEST CORNER OF PROPERTY IN STREET FROM 1/2 ROW Page 7 of 11 Project No. 1536-08-97 Shear Engineering Corporation By: MEO FLOW TO CONCENTRATION POINT 2 FROM SUBBASIN Am PROJECT: HOWES STREET HIDEAWAY II NOTE: CP 2 IS NE OF SITE IN ALLEY AREA (A)= 0.140 ACRES RUNOFF COEF. (C) SEE SPREAD SHEET ATTACHED ON PAGE 2 2 YEAR 10 YEAR 100 YEAR C = 0.31 0.31 0.38 OVERLAND TRAVEL TIME (Ti) 9/17/98 Howes 2 Run LENGTH = 20 FEET SLOPE - 1.00 2 YEAR 10 YEAR 100 YEAR C = 0.20 0.20 0.25 Ti (min)= 7.53 7.53 7.11 TRAVEL TIME (Tt)=L/(60*V) NOTE: ALL VELOCITIES TAKEN FROM FIGURE 3-2 Length Slope Flow Type Velocity Tt ft % fps min 300 0.5 Swale 1.00 5.00 ? ? ? ? 0.00 ? ? ? ? 0.00 TOTAL TRAVEL TIME (min) = 5.00 TOTAL LENGTH = 320 L/180+10= 11.78 < 12.53 =Ti+Tt Tc =Ti+TOTAL TRAVEL TIME Choose lesser Of L/180+10 or Ti+Tc 2 YEAR 10 YEAR 100 YEAR Tc (min)= 11.78 11.78 11.78 USE Tc = 12 12 12 INTENSITY (I) (iph) NOTE: INTENSITIES TAKEN FROM FIGURE 3-1 2 YEAR 10 YEAR 100 YEAR I = 2.38 4.17 6.71 RUNOFF (Q= CIA) (cfs) 2 YEAR 10 YEAR 100 YEAR IQ = 0.10 0.18 0.36 CONCLUDE: PEAK FLOW FROM SUB -BASIN Am TO ALLEY MINIMUM SLOPE OF ALLEY = 0.005 FT/FT CAPACITY OF ALLEY = 2.83 CPS B Page 8 of 11 Project No. 1536-08-97 Shear Engineering Corporation By: MEO FLOW TO CONCENTRATION POINT 2 FROM SUBBASIN Am PROJECT: HOWES STREET HIDEAWAY II NOTE: CP 2 IS NE OF SITE IN ALLEY AREA (A)= 0.130 ACRES RUNOFF COEF. (C) SEE SPREAD SHEET ATTACHED ON PAGE 2 2 YEAR 10 YEAR 100 YEAR C = 0.26 0.26 0.32 9/16/98 Howes 2 Run TIME OF CONCENTRATION (Tc) OVERLAND TRAVEL TIME (Ti) LENGTH = 20 FEET SLOPE = 1.00 e 2 YEAR 10 YEAR 100 YEAR C = 0.20 0.20 0.25 Ti (min)= 7.53 7.53 7.11 TRAVEL TIME (Tt)=L/(60*V) NOTE: ALL VELOCITIES TAKEN FROM FIGURE 3-2 Length Slope Flow Type Velocity Tt ft °s fps min 300 0.5 Swale 1.00 5.00 ? ? ? ? 0.00 ? ? ? ? 0.00 TOTAL TRAVEL TIME (min) = 5.00 TOTAL LENGTH = 320 L/180+10= 11.78 < 12.53 =Ti+Tt Tc =Ti+TOTAL TRAVEL TIME Choose lesser of L/180+10 or Ti+Tc 2 YEAR 10 YEAR 100 YEAR Tc (min)= 11.78 11.78 11.78 USE Tc = 12 112 12 INTENSITY (I) (iph) NOTE: INTENSITIES TAKEN FROM FIGURE 3-1 2 YEAR 10 YEAR 100 YEAR I = 2.38 4.17 6.71 RUNOFF (Q= CIA) (cfs) 2 YEAR 10 YEAR 100 YEAR IQ = 0.08 0.14 0.28 CONCLUDE: PEAK FLOW FROM SUB -BASIN Am TO ALLEY MINIMUM SLOPE OF ALLEY = 0.005 FT/FT CAPACITY OF ALLEY = 2.83 CFS Page 8 of 11 Project No. 1536-08-97 Shear Engineering Corporation By: MEO FLOW TO CONCENTRATION POINT 2 FROM SUBBASIN Ae,Am,ALLEY PROJECT: HOWES STREET HIDEAWAY II NOTE: CP 2 IS NE OF SITE IN ALLEY AREA (A)= 0.610 ACRES RUNOFF COEF. (C) SEE SPREAD SHEET ATTACHED ON PAGE 2 2 YEAR 10 YEAR 100 YEAR C = 0.69 , 0.69 0.87 9/17/98 Howes2Run -limb ur �uv�nNi�IIUIN kic) OVERLAND TRAVEL TIME (Ti) LENGTH = 20 FEET SLOPE = 1.00 0 2 YEAR 10 YEAR 100 YEAR C = 0.20 0.20 0.25 Ti (min)= 7.53 7.53 7.11 TRAVEL TIME (Tt) =L/(60*V) NOTE: ALL VELOCITIES TAKEN FROM FIGURE 3-2 Length Slope Flow Type Velocity Tt ft o fps min 300 0.5 Swale 1.00 5.00 ? ? ? ? 0.00 ? ? ? ? 0.00 TOTAL TRAVEL TIME (min) = 5.00 TOTAL LENGTH = 320 L/180+10= 11.78 < 12.53 =Ti+Tt Tc =Ti+TOTAL TRAVEL TIME Choose lesser of L/180+10 or Ti+Tc 2 YEAR 10 YEAR 100 YEAR Tc (min)= 11.78 11.78 11.78 USE Tc = 12 12 12 INTENSITY (I) (iph) NOTE: INTENSITIES TAKEN FROM FIGURE 3-1 2 YEAR 10 YEAR 100 YEAR I = 2.38 4.17 6.71 RUNOFF (Q= CIA) (cfs) 2 YEAR 10 YEAR 100 YEAR IQ = 1.01 1.77 3.55 CONCLUDE: PEAK FLOW FROM SITE TO ALLEY @ DP 2 MINIMUM SLOPE OF ALLEY = 0.005 FT/FT CAPACITY OF ALLEY = 2.83 CFS Page 9 of 11 B Project No. 1536-08-97 Shear Engineering Corporation 9/16/98 By: MEO Howes 2 Run HISTORIC FLOW TO NORTH PROPERTY LINE FROM SUBBASIN Am PROJECT: HOWES STREET HIDEAWAY II NOTE: AREA (A)= 0.320 ACRES REFER TO EXISTING CONDITIONS PLAN IN REPORT RUNOFF COEF. (C) GRASS, CLAYEY _SOIL 2 YEAR 10 YEAR 100 YEAR C = 0.20 0.20 0.25 TIME OF CONCENTRATION (TC) OVERLAND TRAVEL TIME (Ti) LENGTH = 20 FEET SLOPE = 1.00 e 2 YEAR 10 YEAR 100 YEAR C = 0.20 0.20 0.25 Ti (min)= 7.53 7.53 7.11 TRAVEL TIME (Tt)=L/(60'V) NOTE: ALL VELOCITIES TAKEN FROM FIGURE 3-2 'Length Slope Flow Type Velocity Tt ft fps min 185 0.5 Lawn 0.50 6.17 ? ? ? ? 0.00 ? ? ? ? 0.00 TOTAL TRAVEL TIME (min) = 6.17 TOTAL LENGTH = 205 L/180+10= 11.14 < 13.69 =Ti+Tt Tc =Ti+TOTAL TRAVEL TIME Choose lesser of L/180+10 or Ti+Tc 2 YEAR 10 YEAR 100 YEAR TC (min)= 11.14 11.14 11.14 USE TC = 11 11 11 INTENSITY (I) (iph) NOTE: INTENSITIES TAKEN FROM FIGURE 3-1 2 YEAR 10 YEAR 100 YEAR I = 2.46 4.31 6.92 RUNOFF (Q= CIA) (Cfs) 2 YEAR 10 YEAR 100 YEAR IQ = 0.16 0.28 0.55 CONCLUDE: COMPARE WTIH DEVELOPED Page 10 of 11 Project No. 1536-08-97 Shear Engineering Corporation By: MEO DEVELOPED FLOW TO NORTH PROPERTY LINE FROM SUBBASIN Am PROJECT: HORS STREET HIDEAWAY II AREA (A)= 0.140 ACRES ZUNOFF COEF. (C) 2 YEAR 10 YEAR 100YEAR = 0.31 0.31 0.38 >EE SPREAD SHEET ATTACHED ON PAGE 2 TIME OF CONCENTRATION (Tc OVERLAND TRAVEL TIME (Ti) LENGTH = 20 FEET 2 YEAR C = 0.20 Ti (min)= 7.53 SLOPE = 1.00 °s 10 YEAR 100 YEAR 0.20 0.25 7.53 7.11 9/17/98 Howes 2 Run VEL TIME (Tt)=L/(60*V) NOTE: ALL VELOCITIES TAKEN FROM FIGURE 3-2 gth Slope Flow Type Velocity Tt fps min 185 0.5 Swale 1.11 2.78 ? ? ? ? 0.00 ? ? ? ? 0.00 TOTAL TRAVEL TIME (min) = 2.78 AL LENGTH = 205 L/180+10= 11.14 > 9.89 =Ti+Tt =Ti+TOTAL TRAVEL TIME Choose lesser of L/180+10 or Ti+Tc 2 YEAR 10 YEAR 100 YEAR (min)= 10.30 10.30 9.89 Tc = 10.5 10.5 10 :NTENSITY (I) (iph) NOTE: INTENSITIES TAKEN FROM FIGURE 3-1 2 YEAR 10 YEAR 100 YEAR = 2.50 4.38 7.14 ZUNOFF (Q= CIA) (cfs) 2 YEAR 10 YEAR 100 YEAR = 0.11 0.19 0.38 /ERSUS )HIST = 0.16 0.28 0.55 ;ONCLUDE: PEAK FLOW ONTO LOT 10 TO THE NORTH DEVELOPED PEAK FLOW IS LESS THAN HISTORIC Page 11 of 11 CHANNEL Proj. No. 1536-08-97 Shear Engineering Corporation 9/16/98 By: MEO Howes 2 Chan CHANNEL CAPACITY SWALE DESCRIPTION: PAVED ALLEY WITH INVERTED CROWN CAPACITY OF TRIANGULAR OR TRAPEZOIDAL CHANNEL CHANNEL CONFIGURATION: TRIANGULAR Q100 (cis) = 3.27 CHANNEL LINING: CONCRETE REFER TO PAGES 6-9 Da Db Dc Sc n W I (ft) (ft) (ft) (1) (ft) (ft) 10.00 1 10.00 1 0.20 1 0.500 1 0.016 0.00 1 0.05 0.02 = LEFT BANK SLOPE 0.02 = RIGHT BANK SLOPE DEPTH WIDTH AREA PERIM R 2/3 Sc 1/2 Q V (ft) (ft) (s.f.) (ft) (A/P) (cfs) (ft/sec) 0.20 20.00 2.00 20.00 0.22 0.07 2.83 1.41 0.15 15.00 1.13 15.00 0.18 0.07 1.31 1.17 0.10 10.00 0.50 10.00 0.14 0.07 0.45 0.89 0.05 5.00 0.13 5.00 0.09 0.07 0.07 0.56 0.00 0.00 0.00 0.00 0.00 0.07 0.00 0.00 DEPTH WIDTH AREA PERIM R 2/3 Sc 1/2 Q V (ft) (ft) (s.f.) (ft) (A/P) (cfs) (ft/sec) CONCLUDE: ALLEY CAPACITY IS ADEQUATE BECAUSE SLOPE OF ALLEY INCREASES TO NORTH Page 2 of 2 APPENDIX II Erosion Control Calculations Erosion Control Sequencing schedule Erosion Control security deposit estimate December 15, 1997 Project No: 1536-08-97 Basil Hamdan City of Fort Collins Storinwater Utility, P.O. Box 580 Ft. Collins, Colorado 80522 Re: Erosion Control Cost Estimate Howes Street Hideways H Lot 11, Block 105, Harrison's Addition; Fort Collins, Colorado Dear Basil, SHEAR ENGINEERING CGRPGRATIGN Attached is the erosion control security deposit estimate for Howes Street Hideaways II ESTIMATE 1: 145 LF of Silt Fence Q $ 3.00 per LF $ 435.00 TOTAL ESTIMATED COST: $ 435.00 x 1.50 $ 652.50 ESTIMATE 2: re -vegetate the disturbed area of 0.19 acres at $636.00 per acre 120.84 TOTAL ESTIMATED COST: $ 120.84 x 1.50 $ 181.26 In no instance shall the amount of the security be less than $1,000.00. Therefore, the total required erosion control security deposit for Lot 11, Block 5, Harrison's Addition will be $ 1,000. If you have any questions, please call at 226-5334. Sincerely, Mark Oberschmidt Shear Engineering Corporation MEO/ meo cc: Rayfine Development Corporation Jean Pakech; City of Fort Collins Storinwater Utility 4836 S. College, Suite 12 Ft. Collins, CO 80525 (970) 226-5334 FAX (970) 282-031 1 December 15, 1997 Project No: 1536-08-97 Re: EROSION CONTROL SECURITY DEPOSIT REQUIREMENTS: Lot 11, Block 105, Harrison's Addition; Fort Collins, Colorado A. An erosion control security deposit is required in accordance with City of Fort Collins policy (Chapter 7, Section C: SECURITY; page 7.23 of the City of Fort Collins Development Manual). In no instance shall the amount of the security be less than $ 1000.00. a. The cost to install the proposed erosion control measures is approximately $ 435.00 Refer to the cost estimate attached in Appendix I. 1.5 times the cost to install the erosion control measures is $ 652.50 b. Based on current data provided by the City of Fort Collins Stormwater Utility, and based on an actual anticipated net affected area which will be disturbed by construction activity (approximately 0.19 acres), we estimate that the cost to re - vegetate the disturbed area will be $ 120.84 ($ 636.00 per acre x 0.19 acres). 1.5 times the cost to re -vegetate the disturbed area is $ 181.26 The $ 636.00 per acre for re -seeding sites of less than 5 acres was quoted to us by the City of Fort Collins Stormwater Utility personnel. CONCLUSION: The erosion control security deposit amount required for Lots 11, Block 5, Harrison's Addition will be S 1,000.00. 4836 S. College, Suite 12 Ft. Collins, CO 80525 (970) 226-5334 FAX (970) 282-0311 CONSTRUCTION SEQUENCE PROJECT: Howes Street Hideaways H STANDARD FORM C SEQUENCE FOR 1998-99 ONLY COMPLETED BY:MEO/Shear Engineering Corp. Indicate by use of a bar line or symbols when erosion control measures will be installed. Major modifications to an approved schedule may require submitting a new schedule for approval by the City Engineer. Year 98 99 Month O N D J F M A M J )VERLOT GRADING *** WIND EROSION CONTROL Soil Roughening *** Perimeter Barrier Additional Barriers Vegetative Methods Soil Sealant Other RAINFALL EROSION CONTROL STRUCTURAL: Sediment Trap/Basin Inlet Filters Straw Barriers Silt Fence Barriers *** *** *** *** *** Sand Bags Bare Soil Preparation Contour Furrows Terracing Asphalt/Concrete Paving *** *** *** Other VEGETATIVE Permanent Seed Planting Mutching/Scalant Temporary Seed Planting Sod Installation *** *** *** *** Nctti ngs/MatsBlankets Other STRUCTURES: INSTALLED BY: OWNER MAINTAINED BY: OWNER VEGETATION/MULCHING CONTRACTOR: OWNER DATE PREPARED: 9/16/98 DATE SUBMITTED: 9/17/98 APPROVED BY TILE CITY OF FORT COLLINS ON: APPENDIX III Backup Diagrams and Exhibits Table 3-3; Rational Method Runoff Coefficients for Composite Analysis Table 3-4; Rational Method Frequency Adjustment Factors Figure 3-2; Estimate of Average Flow Velocity for Use with the Rational Formula Figure 3-1; City of Ft. Collins Rainfall Intensity Duration Curve R-M-P Medium Density Planned Residential District — designation for medium density areas planned as a unit (PUD) to provide a variation in use and building placements with a minimum lot area of 6,000 square feet. R-L-M Low Density Multiple Family District— areas containing low density multiple family units or any other use in the R-L District with a minimum lot area of 6,000 square feel for one -family or two-family dwellings and 9,000 square feet for multiple -family dwellings. M-L Low Density Mobile Home District — designation for areas for mobile home parks containing independent mobile homes not exceeding 6 units per acre. M-M Medium Density Mobile Home District — designation for areas of mobile home parks containing independent mobile homes not exceeding 12 units per acre. B-G General Business. District — district designation for downtown business areas, including a variety of permitted uses, with minimum lot areas equal to 1/2 of the total floor area of the building. B-P Planned Business District — designates areas planned as unit developments to provide business services while protecting the surrounding residential areas with minumum lot areas the same as R-M. H-B Highway Business District — designates an area of automobile -orientated busi- nesses with a minimum lot area equal to 112 of the total floor area of the building. B-L Limited. Business District — designates areas for neighborhood convenience centers, including a variety of community uses with minimum lot areas equal to two times the total floor area of the building. C Commercial District —designates areas of commercial, service and storage areas. I-L Limited Industrial District —designates areas of light industrial uses with a minimum area of lot equal to two times the total floor area of the building not to be less than 20.000 square feet. I-P Industrial Park District —designates light industrial park areas containing controlled industrial uses with minimum lot areas equal to two times the total floor area of the building not to be less than 20,000 square feet. I-G General Industrial District — designates areas of major industrial development. T Transition District — designates areas which are in a transitional stage with regard to ultimate development. For current and more explicit definitions of land uses and zoning classifications, refer to the Code of the City of Fort Collins, Chapters 99 and 118. Table 3-3 RATIONAL METHOD RUNOFF COEFFICIENTS FOR COMPOSITE ANALYSIS Character of surface Runoff Coefficient Streets, Parkii Asphalt . Concrete Gravel .. Roofs ........... Lots, Drives: Lawns, Sandy Soil: Flat <2% ................ Average 2 to 7% .... Steep >7% ............ Lawns, Heavy Soil: Flat <2% ............... Average 2 to 7% .... Sleep >7% .........%. 0.95 0.95 0.50 0.95 0.10 0.15 0.20 0.20 0.25 0.35 MAY 1984 3-4 DESIGN CRITERIA 3.1.7 Time of Concentration In order to use the Rainfall Intensity Duration Curve, the time of concentration must be known. This can be determined either by the following equation or the "Overland Time of Flow Curves" from the Urban Storm Drainage Criteria Manual, included in this report (See Figure 3-2). Tc=1.87 (1.1 -CC,) D"Z S� Where Tc =Time of Concentration, minutes S = Slope of Basin, C = Rational Method Runoff Coefficient D = Length of Basin, feel C, = Frequency Adjustment Factor Time of concentration calculations should reflect channel and storm sewer velocities as well as overland flow times. 3.1.8 Adjustment for Infrequent Storms The preceding variables are based on the initial storm, that is, the two to ten year storms. For storms with higher intensities an adjustment of the runoff coefficient is required because of the lessening amount of infiltration, depression retention, and other losses that have a proportionally smaller effect on storm runoff. These frequency adjustment factors are found in Table 3-4. Table 3-4 RATIONAL METHOD FREQUENCY ADJUSTMENT FACTORS Storm Return Period Frequency Factor 2 to 10 1.00 11 to25 1.10 26 to 50 1.20 51 to 100 1.25 Note: The product of C times C, shalt not exceed 1.00 3.2 Analysis Methodology The methods presented in this section will be instituted for use in the determination and/or verification of runoff at specific design points in the drainage system. These methods are (1), the Rational Method and (2) the Colorado Urban Hydrograph Procedure' (CUHP). Other computer methods. such as SWMM, STORM, and HEC-1 are allowable if results are not radically different than these two. Where applicable, drainage systems proposed for construction should provide the minimum protection as determined by the methodology so mentioned above. 3.2.1 Rational Method For drainage basins of 200 acres or less, the runoff may be calculated by the Rational Method, which is essentially the following equation: Q = C,CIA Where Q = Flow Quantity, cfs A =Total Area of Basin, acres C, = Storm Frequency Adjustment Factor (See Section 3.1.8) C = Runoff Coefficient (See Section 3.1.6) 1 = Rainfall Intensity, inches per hour (See Section 3.1.4) 3.2.2 Colorado Urban Hydrograph Procedure For basins larger than 200 acres, the design storm runoff should be analvzed by deriving synthetic unit hydrographs. It is recommended that the Colorado Urban Hydrograph Procedure be used for such ana!ysis. This procedure is detailed in the Urban Storm Drainao- Criteria Manual, Volume 1, Section 4. MAY 1984 3-5 DESIGN CRITERIA w O rr, o � Q U � � z 0 Z �7N O U °°� LL QN N ' iil �y rr W K 0 Z Q) H r Q J 0 �aZo J 0a w. O d w tt V m 1— Co crw LL f C/) 0 (L - w � Z w c� 3w O w ,> Q n L LL I— O a N a:Z Z Q� 0 LL — =1 L> O Oa0 C Q Q <0Z 03 U Z Q I O N I N (O N 11 to N unOH aid S3HON1—NOUVild1038d z MAY 1984 3-2 DESIGN CRITERIA DRAINAGE CRITERIA MANUAL RUNOFF 50 kra, l- 20 Z w U cc a 10 Z w a t. O w cc 3 O U 2 W F— Q 1 2 .s .5 1 2 3 5 10 20 VELOCITY IN FEET PER SECOND FIGURE 3-2. ESTIMATE OF AVERAGE FLOW VELOCITY FOR USE WITH THE RATIONAL FORMULA. *MOST FREQUENTLY OCCURRING"UNDEVELOPED" LAND SURFACES IN THE DENVER REGION. REFERENCE: "Urban Hydrology For Small Watersheds" Technical Release No. 55. USDA, SCS Jan. 1975. 5 -1-84 URBAN DRAINAGE & FLOOD CONTROL DISTRICT APPENDIX IV Portions of the Old Town Master Drainage Basin Plan Colo. Hwy. 267 Long Pond Co,,' c Claymore Lake N c- La Willox Ln. Lindenmeier Lake \j Lee co 1\7 Lake o� -Vine Dr. c A .2 Ili > 0 0 V-0 ake 16e g a L Lake ProsPect Rd. cr cree o 11 Williams Lake Drake Rd. < > < cr !Nelson �- Dixon U V '01 Res. U a E c Res. HOrsetooth Rd Scale: MI. Figure 1.1: GENERAL LOCATION MAP OLD TOWN MASTER DRAINAGE BASIN PLAN for the CITY of FORT COLLINS RESOLnCE CONSULTANTS L ENGINEERS, NC. &;hefkV CoaViny 1.2 LU J j ¢ oo :1 Crl C �.p ZOInk," Y �Il OfIL 1 f L q� ��//: .. L. 'r` !f i�'1- ,"•r�� i. � If r �� �Cii ..1�It_ Il ;; - 1I- -- I -- i- FD v IL c - Ej FI'--f - I 1 i it 10, Table 4.1. Design Storms for Old Town Basin. ear at hand, recognizing that it is always possible to make additional refinements or revisions tuany model. 4.1.2Basin Subdivision As can be seen from Figure 4.1, the Old Town Basin below Larimer County Canal No. ? was subdivided into three smaller sUhhnCinsnumbered 1, 2, and 3. SuhhasiA 1 encompassed the area in the northern part 0fthe drainage; SUhhaoin 2 encompassed the central part, including the downtown area; and Sobhasio 3covered the southern part. Each ofthe subbasinswas drained by u major storm sewer. 4.3 Table 4.3. Differences in Impervious Area Percentages for Existing and Future Conditions. Subcatchmenf Percent`Imini.pervious Number Existing Future, . 6 40 70 102 50 70 108 40 60 109 40 60 201 40 60 203 50 70 204 60 70 205 50 70 206 40 60 211 40 60 304 40 60 305 40 60 312 .40 50 360 20 40 361 60 100 10 No Text `I N Storage functions were used at elements 203, 204, 205, and 206 in Subbasin 2 to simulate the ponding of floodwaters behind the various north -south streets with high crowns. During the 100-year flood, these ponds filled before the peak runoff. Once filled, the ponds did little to attenuate flood peaks; the inflow rate essentially equaled the outflow rate. However, this was not the case with the less severe storms. ' .Splitterh=ioms were userl at elements 227-228- as vv4 225 226tp .-dist ib ut spills from the ponding areas behind College and Mason to either the downtown �ace a My171 Street Splitter functions were used at elements 21 5-216-217 and 218- 21 9-220to direct a portion of the runoff near the intersection of Myrtle and Peterson : Streets into Subbasin 3. Splitter functions were also used at elements 324-325-326 and 327-328-329to determine the amount of water that would be carried under Riverside through the storm drains and the amount that would be left flowing down Riverside parallel to the railroad tracts. A splitter function was used at elements 357-358-359to account for surface returns back to Mulberry along Smith Street.' Runoff in Upper Part of Subbasin 3. In the upper part of Subbasin 3, most of the flood runoff, which included spills from the Larimer County.Canal No. 2, collected along Elizabeth -Street. The runoff moved across Shields and onto CSU property. Storm drains diverted some of the runoff to the south and into the Spring Creek drainage, although most of the runoff flowed across CSU through the intramural field and eventually discharged into an open reach of the Arthur Ditch. The Arthur Ditch diverted much of the intercepted.. flood runoff into a box culvert that extended under the CSU campus. The culvert, in turn, carried water out of the Old Town drainage and into the Spring Creek drainage.' The '•.'.i .. capacity of the open reach of the ditch was exceeded during the course of the 100-year flood, resulting in excess waters spilling into the CSU lagoon located immediately: .downstream of the ditch near the CSU Student center: - Routing and storage of floodwaters in the Arthur Ditch and CSU lagoon were simulated through the use of splitter functions at elements 353-354-355 and 336-337-338 and through the use of the storage'function.for element 315.• It was assumed that the Arthur Ditch was carrying 60 cfs of irrigation water for the duration of the flood. It was estimated that the ditch could carry an additional 35 cfs before water would overtop the ditch banks and spill into the CSU lagoon. Inflows exceeding 35 cfs were routed into the lagoon using the splitter function for elements 353-354-355. It was further estimated that releases through the Arthur Ditch box culvert under the CSU campus would increase once the water elevation in the lagoon reached the top of the open ditch. The dam creating the CSU lagoon is higher in elevation than the Arthur Ditch.: Estimates for the additional . surcharged capacity of the box culvert were incorporated into the release rates for the . storage pond function at element 315. Surface spills,which would result from a complete filling of the lagoon, were simulated to occur first at the low spot near the intersection of Pitkin and Center Streets and then over the top of the dam itself near the Student Center. The splitter function for elements 336-337-338was used to distribute any surface spills. Surface spillage did not occur from the lagoon for the future condition runs. The. regional detention pond near Skyline and Elizabeth Streets coupled with improvements to the Larimer #2 Canal, reduces the current spilling into the Old Town Basin. The future condition runs assumed those proposed improvements, The simulated spillage from the lagoon for existing conditions was all to the south, near the intersection of Pitkin and Center; no spillage occurred over the top of the dam into the lower part of Subbasin 3. UM s. N O n N m N m m m m m m m v a v O m m O m O m m O m m O N m O m m O m 0 m m m m m m m o a C m m v vi m m v m m m v h m m v r m m v of m m a o m m v N m m r 0 O 0 O 0 O 0 O 0 M 0 M O m O a m M Cl m n m m M m m a m m v m m a m m v m m v m m v m m v m m v 0 0 o o N 0 N 0 N N N m O W M m m V m m v vi m m v L'I m a � W a h m O1 a m m °1 a ai m m v ry m m v O o 0 0 0 O o 0 n m o n r m n m m v m m a m m v m m v m m a m v m v m m v 0 v 0 v 0 v 0 v 0 v 0 c 0 v m m M N M M n M m m r m m N m m m m m m m m m m m m 0 m m m 0 m m m O W O m 0 n m o n m 0 m O n m O o n a N r M a c o c a m v A ©meow. N M M l7 m m m m m n m v v m m m m m V V V C r ml al 010l of Onl m I I N D I N 0 N imm ©m©ir. a l v v l v l v l c l m v rvl01-101-1010 am ©mm vl vl a v vl rl a I®UMMME n v v v a v c a Ml �l O^l MI ol O^I O vl vl vl vl al roI c m o 0 0 0 0 v cr n m m m m ci m t U m Z vi in m i � 5.17 w M m b v m OJ m N m OI m O O 0 a 0 0 0 0 0 m m ro m ai m o 0 uoi c r0000 =o� I[1 0 0 m ziz��©tom mI ml ml ml o m m m m O v v v v m O I 01 01 01 O W W W W W N N N N N b m v b m v m m v n m v n m v n m v n m v n m v m m v m m v O b M O M m m .- o_ o 0 M v m m O W N b M n b m v b m v b m v n m v n m v n m v C6 n m v m n m v m m v m m v 0 m 0 m 0 m 0 M 0 m 0 m 0 N 0 N 0 b 0 O e m n n ui m aJ o 0 n n n m m V � � Nl of Nl al 01 m1 01 01 p1 b t` m ai O rri v n v m v v v v v v O v O v W W w m m m On m T O 0 0 0 N m m r-4 m m ma; m m m m o p o rri b m ri m m v vi m m v ai m 10 n m n �: n m m 0 n m m of n m m o m m IMEMEMOOMMMMMMMM a W m m v n m m v m m m v W m m v m m m a m m m v m b b m v O m b m v O n m v m N n m v m M n m v W b n m v O n n m v m n m v p O m m v v c 0 o n tpp m m 0 O 0 0 O o m m m 0 O 0 M b 0 m ON m Om O b C L U U cc b m n 1fI m m m b O b m m m m m m IJ m m n 5.18 a I I C I 211�u. 51 ---�— �• 5i Fi �J- .. Figure S.T;: .� i may:•; PROFILE of REACH 3 t I !Si 1 V OLD TOWN MASTER "' DRAINAGE BASIN PLAN CITY of FORT COLLINS �i.� O U• 11 I I I I I I I I Legend: .�ru<a.:..Y�ti.�.•.K.r RCE III I I 1 I V Figure Y PROFILE of REACH 4 I OLD TOWN MASTER DRAINAGE BASIN PLAN CITY of FORT. COLLINS Legend: ro:u ..a I ...,, RCE.-".x:r�tir.•..s. PONDING EXHIBIT NTS ,�1 i1 Ftaf '� lye ��:. ?\ii c� � ;�.Cj+:fR&4.�•f♦'Sf�6 4 -4k�� •F: • ii! L` tia'• �~ 1 .. '`rJ. i _t cA. 'Wcc L 1 t MULBERRY STREET 6jF '` AVP X. LI LLJ .ctl vF r t t I �. • �1 LU Y ♦w�:, r I�'9 '� 1 J19 "I } §' .•'.. �,,- F�., i'% C� • �`i. ice;,. ` �Tl' r .. � s :. + - ya;�;';Y ,, • 1 ♦ �, ; �,'.�f'•�, - f %" { 'r• y. r tom, .. A. 1 ,j! f7a . l _ _ i t'`'� . y4} �� r1 �IS.'.i�'1.,� .. •i �i- wcJ�r -r- {�;'K- =v. X4995.0 MYRTLE STRf?ET X4994.9 t, X4993.4 tT +\ A ` � ,�� ]v r,� c• w�kr� y55, I _ !4 VV ,II\ i ,'�,I 1 k . Lk r p �- v r •` T f /1 ' I t;�4:� 1�t� :Y '7•".1 Appendix V Stuffer Envelope Drainage and Erosion Control Plan «roaoa ova rso.w. oa _.-..,_, __. __ — .a.. ._�___ d 5 _ter _. •� ______ _�"_ �yy__ )_ _. �>` " Tom• � �• ."____ w ..._ d(id�T -� m[e _ _ _C��V �— _ �' _ '" II--�,�y _• � � v[MSr4yl mil[ O .rw � ~��rz�o. Fxasw r — a•_ � •— — _.— — � � � — — — _ —;Yam I — — — - — — — 1 — EXIST VJG DISnev WKING GARAGE 1 41 I /I �a 9+.iaEx. =9394 -94.4-7 _� Ah1 . i1 I it .4_A'" i y N 0.32 0.25 ' �•� w 1 BLOCK 105 ga.g.., �94.02 �g4.59 a —j 10 ' w3 _; a yam---------------- � "I � � +94.75 459 Fo EXISTING I� .� 0 L, F J 2 STORY 1 EXISTING l EXISTING I BRICK & FRAME ---� I STORY 1 I STORY li EXISTING BRICK & FRAME BRICK & FRAME ICI 2 HOUSE I ,; rJ EXISTING � 65 ail sa..]eEx- I e 1 STORY 4 194.Io8 $ s BRICK & FRAME F Lr-----T-Al J } al --T_�i I ------------------------------------------ . . i i EXISTING CONDITIONS EXI-IIBIrI' 1 f r, I. i i lIj I G r'I I I I rx— -- — 3w. KDON, x - — — — — — — — � --- _ -- r 1 `_ all 5 r _ _4 1 Re _AAlip I 2 TI — t TV a — — — — OR rh�a•, I BLOCK 105FAA; .... /T , I It, AAVA-RAA.`FVVTI.AA., L T Lm fr B __, _� _—�o.mT,.m_ s +1' = _--j _ A Az'v Y I \ _ _ . — I A .-n ma. w,-.. a a Ee ... II FAVARAVAR minimal HOWES STREET HIDEAWAYS PHASE II BLOCK 105 y EXISTING MOBILE 116ME Art AFT, — —T — "und f QFINAL to, . 16D0 Bh VATTAT 1 �e 1 fiTOW A AT AT AAAA MTWV Frown" VAN,,: $ �94 Ito �I t fill�p{ 4 1 1 1 dEdlH� ]Vot A, AT zE� EVA Iq J mL J piD DeN __ TA ! II — _ — — f0 00 M g o SSfaf DTE'EUI a°in". ,- . wI _---,I whoox xK `t P jF I L Exm.;wux jpj 4 1 EP •seS F•SS.So AA, SEE X—SECTIONS ON SHEET 4 9411 It II I a o jII `rz______ asSes o I 4 rJ BLOCK 105 0 SAW "HOW I. 1 I 10 11 F I L -- J x 1�. 1 — = SILT FENCE Fn a' . a � se.� .V AVA7 -- _—, I fJ� ` �' ISIDDEi Kcwsd� III 'L _ 1 J I` EXISTCRY ING INI I'i� L, BRICK SEE FRAME 1 �_F 1 W BASEMENT ] J EXISTING � I r I To REMUN) /I 9 1 STORY I I f p BRICK k FRAME I J I I L PAT A L rJ �. LECEN 11i F i I I I—L _J —iL __J — MITIMANUTAXI ON A __ _ — nXT� STOP It ._____�____. EROSION CONTROL LE END m xA.mLES SCAUE: FEW 7?—=� —APPL—OrJDai E[,n—sEwCa — — a OE Ee i°H'i -- - Wool �� DIEIkM1lL T- -� aA, A, AAAAAAAAAAAAAAAAAAAAFARI T__� y rm .. oEHCi � 1 1 11 1 �o m w MAL It It y3 glsr."dam It ' I�almxs s7m .�,..... alu. I�ra'r .+VOA. Or s 1 70]E. 1 L17 is I I \ �mm2iril EXISTING e 5 2 STORY EXISTING BRICK IT FRAME_ IBRICK k FRAME I ri I ? I I I I I I L rA ti r I I rJ j I I At A A .._ 11, W rIF at IF Al I A j m Eyni. OF yr [.y�y Cry M21g �.gg SOUTH HOWES STREET ICA RIGHT-OF-WAY no FA ALVIVEALVA"FrAVALARTA ANN' "A" 'It 11 d,...- 01 I 1 AAAAAAL J T "_< __- I AN...__ VIA____�____1�___ A. - _ _ -------`. E•A W W > a: F In o Wp F o a— i IF Olt n. ao Tx., A VAN L ,....... _ .: :P.., .. nOAV Al VI ILAAAA,, 14 A. NA NATO A OF FAFAT "A AW or I FIN PMNT DATE SEP 17 IM SHERENCINFFRINCCORP City of Fort Collins, Colorado OTWTY PLAN APPROVAL APPROVEDDRETOR OF �N�INO am CHECKED BT CHECKED SAY� nun um CHECKED ED CHECKED BV CHECKED BY' "Ho"A"T NO. SMf[i W. NO. O. Ts 153E—OB-87 3 4 Al �, axs I DaE Drown cAOSFaX I MMXI SHEAR ENGINEERING CORPORATION D�rvna, FIND BaoRT GncDK.D M.E.O. RAYL[NE DEVELOPMENT CORPORATION 436 SO. COLLEGE AVE. SUITE 12, FORT COLUNS. COLORADO 60525 TITM MASTER GRADING, DRAINAGE AND EROSION CONTROL PLAN LOT 11, BLOCK 105, HARRISON'S ADDITION FORT COLLINS. COLORADO