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HomeMy WebLinkAboutSW PROSPECT AND I 25 ROADWAY PROJECT - RP180001 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE RELATED DOCUMENTDecember 24, 2018 DRAINAGE LETTER SW Prospect & I-25 Fort Collins, Colorado Prepared for: Colorado State University Research Foundation (CSURF) Michael “Bo” Brown P.O. Box 483 Fort Collins, Colorado 80522 Prepared by: 301 North Mason Street, Suite 100 Fort Collins, Colorado 80524 Phone: 970.221.4158 www.northernengineering.com Project Number: 232-043 Drainage Letter – SW Prospect & I-25 Date: December 24, 2018 Project: SW Prospect & I-25 Project No. 232-043 Public Improvement Construction Plans (PICP) Fort Collins, Colorado Attn: City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80521 To whom it may concern: This letter serves to address the stormwater impacts of the proposed project known as “SW Prospect & I-25”. The site is located in northeast Fort Collins and is bounded to the north by East Prospect Road, to the east by the existing Interstate 25 access ramp and frontage road, to the south by a gravel road and to the west by Boxelder Creek (Figure 1). The proposed development consists of the removal of a portion of the existing Interstate 25 Frontage Road, and the construction of a new asphalt Frontage Road with a revised alignment. This project will also involve the construction of two culverts under the new road that will be utilized in the later development of the site. This letter is intended to show that the proposed construction of the new road will reduce the amount of imperviousness of the site, and that the swales and culverts constructed will be sufficient in the interim at maintaining existing drainage patterns, and for use at the time of full build out on the north side of the road as part of a larger storm drain system. Site Imperviousness Construction of the new Interstate 25 Frontage Road will begin with the removal of the existing road. Approximately 2,750 liner feet of 30-foot wide asphalt road will be removed accounting for 82,441 square feet. The new road will then be constructed along an updated alignment, consisting of approximately 2,295 linear feet of 28-foot wide asphalt pavement. The new roadway will have a total impervious area of 66,053 square feet; a reduction in impervious area of 16,388 square feet. The resulting reduction in impervious area negates the need for quantity detention for the roadway project. Please see the Impervious exhibit provided in the attachments. Drainage Patterns With the construction of the Frontage Road, existing drainage patterns will be maintained, generally traveling from northeast to southwest. The north side of the road will contain a drainage swale that will channel sheet flow from the north side of the existing site to one of two culverts. These culverts are sized to remain in place and become part of a larger storm drain system when build out on the north side of the Frontage Road. An imperviousness of 90% for the future site was used to calculate the ultimate flows for these culverts. The culverts will be sufficient in conveying the minor events (2-yr and 10-yr), with the major events (100-yr) overtopping the roadway. Stormwater will then travel through swales to the existing pond, maintaining existing drainage patterns. Please see calculations in the attachments. Page | 3 FIGURE 1 Vicinity Map I-25 E. Prospect Rd. Frontage Rd. Page | 4 Floodplains The FEMA designated Boxelder Creek Flood Zone exists to the west of the project site, as shown in Figure 2, below. The proposed project will not involve the placement of any offsite project improvements within the Boxelder Creek Flood Zone. FIGURE 2 City Floodplain Map (Floodplain shown is a FEMA-Designated Flood Zone) Page | 5 Conclusions The proposed grading concept closely matches the original drainage patterns and decreases overall site imperviousness and additional detention is proven to be unnecessary. The drainage system is sufficiently designed to handle existing drainage and to be utilized in the storm drain system when ultimate build out occurs. Therefore, it is my professional opinion that SW Prospect & I-25 satisfies all applicable stormwater criteria and will effectively limit potential damage associated with its stormwater runoff. Please do not hesitate to contact me if you have questions or require additional information. Sincerely, Benjamin Ruch, P.E. Project Engineer ATTACHMENT 1 HYDROLOGIC CALCULATIONS CHARACTER OF SURFACE: Runoff Coefficient Percentage Impervious Project: CSURF- I25/Prospect Road Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: B. Ruch Asphalt ……....……………...……….....…...……………….………………………………….0.95 . 100% Date: Concrete …….......……………….….……….………………..….………………………………… 0.95 90% Gravel ……….…………………….….…………………………..……………………………….0.50 . 40% Roofs …….…….………………..……………….…………………………………………….0.95 . 90% Pavers…………………………...………………..…………………………………………….0.40 . 40% Lawns and Landscaping Sandy Soil ……..……………..……………….…………………………………………….0.15 . 0% Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year Cf = 1.00 100-year Cf = 1.25 Basin ID Basin Area (ac) Area of Asphalt (ac) Area of Concrete (ac) Area of Roofs (ac) Area of Gravel (ac) Area of Pavers (ac) Area of Lawns and Landscaping (ac) 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient 100-year Composite Runoff Coefficient Composite % Imperv. A 14.39 0.00 0.00 0.00 0.00 0.00 0.00 0.90 0.90 1.00 90% B 22.57 0.00 0.00 0.00 0.00 0.00 0.00 0.90 0.90 1.00 90% Total Onsite 36.96 0.00 0.00 0.00 0.00 0.00 0.00 0.90 0.90 1.00 90% DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I. 10-year Cf = 1.00 December 4, 2018 Overland Flow, Time of Concentration: Project: CSURF- I25/Prospect Road Calculations By: Date: Gutter/Swale Flow, Time of Concentration: Tt = L / 60V Tc = Ti + Tt (Equation RO-2) Velocity (Gutter Flow), V = 20·S ½ Velocity (Swale Flow), V = 15·S ½ NOTE: C-value for overland flows over grassy surfaces; C = 0.25 Is Length >500' ? C*Cf (2-yr Cf=1.00) C*Cf (10-yr Cf=1.00) C*Cf (100-yr Cf=1.25) Length, L (ft) Slope, S (%) Ti 2-yr (min) Ti 10-yr (min) Ti 100-yr (min) Length, L (ft) Slope, S (%) Velocity, V (ft/s) Tt (min) Length, L (ft) Slope, S (%) Velocity, Rational Method Equation: Project: CSURF- I25/Prospect Road Calculations By: Date: From Section 3.2.1 of the CFCSDDC Rainfall Intensity: Design Point Basin(s) Area, A (acres) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) C2 C10 C100 Intensity, i2 (in/hr) Intensity, i10 (in/hr) Intensity, i100 (in/hr) Flow, Q2 (cfs) Flow, Q10 (cfs) Flow, Q100 (cfs) Flow, WQ (cfs) A A 14.39 21 21 21 0.90 0.90 1.00 1.59 2.71 5.53 20.5 35.0 79.6 10.27 B B 22.57 26 26 26 0.90 0.90 1.00 1.40 2.39 4.87 28.4 48.5 109.9 14.22 DEVELOPED RUNOFF COMPUTATIONS B. Ruch December 4, 2018 Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1 Q = C f ( C )( i )( A ) Basin ID Basin Area (s.f.) Basin Area (ac) Composite % Imperv. Flow, WQ (cfs) Flow, Q2 (cfs) Flow, Q100 (cfs) A 627028 14.39 90% 10.27 20.53 79.60 B 983024 22.57 90% 14.22 28.43 109.90 Rational Summary (Proposed) / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / V AULT ELEC / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / ATTACHMENT 2 CULVERT AND SWALE SIZING Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Friday, Dec 7 2018 West Swale - Culvert 2 - 2yr Trapezoidal Bottom Width (ft) = 2.00 Side Slopes (z:1) = 4.00, 4.00 Total Depth (ft) = 3.25 Invert Elev (ft) = 100.00 Slope (%) = 0.50 N-Value = 0.200 Calculations Compute by: Known Q Known Q (cfs) = 20.50 Highlighted Depth (ft) = 2.58 Q (cfs) = 20.50 Area (sqft) = 31.79 Velocity (ft/s) = 0.64 Wetted Perim (ft) = 23.28 Crit Depth, Yc (ft) = 0.89 Top Width (ft) = 22.64 EGL (ft) = 2.59 0 5 10 15 20 25 30 35 40 Elev (ft) Depth (ft) Section 99.00 -1.00 100.00 0.00 101.00 1.00 102.00 2.00 103.00 3.00 104.00 4.00 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Friday, Dec 7 2018 West Swale - Culvert 2 - 10yr Trapezoidal Bottom Width (ft) = 2.00 Side Slopes (z:1) = 4.00, 4.00 Total Depth (ft) = 3.25 Invert Elev (ft) = 100.00 Slope (%) = 0.50 N-Value = 0.200 Calculations Compute by: Known Q Known Q (cfs) = 35.00 Highlighted Depth (ft) = 3.20 Q (cfs) = 35.00 Area (sqft) = 47.36 Velocity (ft/s) = 0.74 Wetted Perim (ft) = 28.39 Crit Depth, Yc (ft) = 1.15 Top Width (ft) = 27.60 EGL (ft) = 3.21 0 5 10 15 20 25 30 35 40 Elev (ft) Depth (ft) Section 99.00 -1.00 100.00 0.00 101.00 1.00 102.00 2.00 103.00 3.00 104.00 4.00 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Friday, Dec 7 2018 East Swale - Culvert 3 - 2yr Trapezoidal Bottom Width (ft) = 2.00 Side Slopes (z:1) = 4.00, 4.00 Total Depth (ft) = 4.00 Invert Elev (ft) = 100.00 Slope (%) = 0.50 N-Value = 0.200 Calculations Compute by: Known Q Known Q (cfs) = 28.40 Highlighted Depth (ft) = 2.95 Q (cfs) = 28.40 Area (sqft) = 40.71 Velocity (ft/s) = 0.70 Wetted Perim (ft) = 26.33 Crit Depth, Yc (ft) = 1.04 Top Width (ft) = 25.60 EGL (ft) = 2.96 0 5 10 15 20 25 30 35 40 45 Elev (ft) Depth (ft) Section 99.00 -1.00 100.00 0.00 101.00 1.00 102.00 2.00 103.00 3.00 104.00 4.00 105.00 5.00 Reach (ft) Channel Report Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Friday, Dec 7 2018 East Swale - Culvert 3 - 10yr Trapezoidal Bottom Width (ft) = 2.00 Side Slopes (z:1) = 4.00, 4.00 Total Depth (ft) = 4.00 Invert Elev (ft) = 100.00 Slope (%) = 0.50 N-Value = 0.200 Calculations Compute by: Known Q Known Q (cfs) = 48.50 Highlighted Depth (ft) = 3.65 Q (cfs) = 48.50 Area (sqft) = 60.59 Velocity (ft/s) = 0.80 Wetted Perim (ft) = 32.10 Crit Depth, Yc (ft) = 1.34 Top Width (ft) = 31.20 EGL (ft) = 3.66 0 5 10 15 20 25 30 35 40 45 Elev (ft) Depth (ft) Section 99.00 -1.00 100.00 0.00 101.00 1.00 102.00 2.00 103.00 3.00 104.00 4.00 105.00 5.00 Reach (ft) ATTACHMENT 3 DRAINAGE EXHIBIT ST / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / F E S LID LID LID M SS SS SS SS SS SS SS S S VAULT ELEC / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / PROPOSED CULVERT PROPOSED 36" RCP CULVERT A 14.40 AC B 22.57 AC A B E PROSPECT RD INTERSTATE 25 REST AREA ACCESS RD SW FRONTAGE ROAD SW FRONTAGE ROAD SW FRONTAGE ROAD INTERSTATE 25 PROPOSED 2 - 36" RCP CULVERTS CULVERT 2 CULVERT 3 EAST SWALE WEST SWALE NORTH KEYMAP F E S M VAULT ELEC INTERSTATE 25 PROSPECT ROAD MCLAUGHLIN LN ( IN FEET ) 1 inch = ft. 100 0 100 Feet 100 200 300 LEGEND: PROPOSED CONTOUR PROPOSED STORM SEWER EXISTING CONTOUR PROPOSED CURB & GUTTER PROPERTY BOUNDARY PROPOSED INLET A DESIGN POINT FLOW ARROW DRAINAGE BASIN LABEL DRAINAGE BASIN BOUNDARY BENCHMARK FOR DRAINAGE REVIEW ONLY NOT FOR CONSTRUCTION C PROJECT DATUM: NAVD88 CITY OF FORT COLLINS BENCHMARK 2-01 LOCATED ON THE NORTH SIDE OF HORSETOOTH ROAD ON THE CONCRETE BASE OF THE WEST GATE POST TO THE LARGE GRAVEL PIT APPROX. 1/2 MILE EAST OF ZIEGLER ROAD. ELEVATION=4861.39 CITY OF FORT COLLINS BENCHMARK 29-01 LOCATED ON THE SOUTH SIDE OF PROSPECT ROAD, EAST OF THE INTERSECTION OF THE WEST FRONTAGE ROAD OF I-25 AND PROSPECT ROAD, EAST OF THE COLORADO WELCOME CENTER, ON A CONCRETE HEADWALL TO AN IRRIGATION PIPE. ELEVATION=4904.41 BASIS OF BEARINGS ASSUMING THE NORTH LINE OF THE NORTHEAST QUARTER OF SECTION 21, T.7N., R.69W., AS BEARING NORTH 88°38'29" WEST BEING A GRID BEARING OF THE COLORADO STATE PLANE COORDINATE SYSTEM, NORTH ZONE, NORTH AMERICAN DATUM 1983/92, A DISTANCE OF 2642.40 FEET WITH ALL OTHER BEARINGS CONTAINED HEREIN RELATIVE THERETO. CONCEPTUAL DRAINAGE EXHIBIT ULTIMATE SITE FORT COLLINS, CO CSURF PROPERTY E NGINEER ING N O R T H E RN DECEMBER 7, 2018 D:\PROJECTS\232-043\DWG\EXHIBITS\232-043_FUTURE DRAINAGE.DWG Rational Summary (Proposed) Basin ID Basin Area (s.f.) Basin Area (ac) Composite % Imperv. Flow, WQ (cfs) Flow, Q2 (cfs) Flow, Q100 (cfs) A 627028 14.39 90% 10.27 20.53 79.60 B 983024 22.57 90% 14.22 28.43 109.90 CONCEPTUAL ULTIMATE SITE PLAN INTERSTATE 25 CSURF EXISTING ASPHALT ROAD TO BE REMOVED / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / VAULT ELEC / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / INTERSTATE 25 CSURF PROPOSED ASPHALT ROAD ASPHALT SURFACE AREA (SF) % IMPERV. IMPERV. AREA (SF) 82,441 100% ASPHALT SURFACE AREA (SF) % IMPERV. IMPERV. AREA (SF) 66,053 100% EXISTING PROPOSED 82,441 66,053 D:\PROJECTS\232-043\DWG\DRNG\232-043_IMPERVIOUS.DWG CSURF PROPERTY INTERSTATE 25 / PROSPECT ROAD FORT COLLINS 301 N. Howes Street, Suite 100 COLORADO Fort Collins, Colorado 80521 E NGINEER ING N O R T H E RN PHONE: 970.221.4158 www.northernengineering.com DESCRIPTION EXISTING VS. PROPOSED IMPERVIOUS AREA DRAWN BY B. RUCH DATE DECEMBER 7, 2018 PROJECT 232-043 SK-C1 SCALE DRAWING 1"=300' V (ft/s) Tt (min) 2-yr Tc (min) 10-yr Tc (min) 100-yr Tc (min) A A NO 0.25 0.25 0.31 0 N/A N/A N/A N/A 1775 0.50% 1.41 20.9 0 NA N/A N/A 21 21 21 B B No 0.25 0.25 0.31 0 N/A N/A N/A N/A 2225 0.50% 1.41 26.2 0 NA N/A N/A 26 26 26 DEVELOPED TIME OF CONCENTRATION COMPUTATIONS Gutter Flow Swale Flow Design Point Basin Overland Flow B. Ruch December 4, 2018 Time of Concentration (Equation RO-4) ( ) 3 1 1 . 87 1 . 1 * S C Cf L Ti = −