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HomeMy WebLinkAboutFIRST STOP PLAZA - BDR180031 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE RELATED DOCUMENTFORT COLLINS: 301 North Howes Street, Suite 100, 80521 | 970.221.4158 GREELEY: 820 8 th Street, 80631 | 970.395.9880 | WEB: www.northernengineering.com February 26, 2018 Mr. Wes Lamarque City of Fort Collins 700 Wood Street Fort Collins, Colorado 80522 RE: Final Drainage Memorandum for 1st Stop Plaza Second Filing Fort Collins, Colorado Dear Wes: Northern Engineering Services is pleased to submit this Final Drainage Memorandum for 1st Stop Plaza Second Filing. As a result of the recent design improvements to the intersection of Suniga Drive and College Avenue, the driveway access for Lots 1 and 2 of 1st Stop Plaza will be relocated. The existing driveway is a full-service access from College Avenue. In conjunction with the improvements to Suniga Drive, the access on College Avenue will become right turn in and out only and relocated 60 feet north of the current location. A three-quarter access will be provided from Suniga Drive 390 feet east of College Avenue. A shared driveway will be constructed to allow vehicular movement between the two new access locations. As part of the improvements for Suniga Drive and College Avenue intersection, Interwest Consulting Group prepared a drainage memorandum to North East College Corridor Outfall (NECCO) Design Report dated August 13, 2018. Lots 1 and 2 of 1st Stop Plaza Second Filing coincide with Basin B of the Interwest Drainage Memorandum. Interwest assumed an impervious area of 44.4% and a runoff coefficient of 0.53 for Lots 1 and 2 of 1st Stop Plaza. The impervious area with the proposed driveway improvements is 33% and the runoff coefficient is 0.57. The proposed driveway improvements comply with assumptions used in the Interwest Drainage Memorandum for Suniga Drive. Detention for the site is part of the North East College Corridor Outfall (NECCO), but the project does not meet the City’s water quality and LID requirements. Upon redevelopment of Lots 1 and 2 for 1st Stop Minor Subdivision, the developer will need to provide the necessary water quality and LID improvements for that portion of the driveway, asphalt, parking lot, and concrete of this project that falls within their property. Table 1 below summarizes the required volumes necessary to satisfy the City’s water quality requirements for this project. Table 1: Required Water Quality Volume Description Water Quality Volume (ft3) Water Quality Volume (Acres) Lot 1 669 0.015 Lot 2 285 0.007 FORT COLLINS: 301 North Howes Street, Suite 100, 80521 | 970.221.4158 GREELEY: 820 8 th Street, 80631 | 970.395.9880 | WEB: www.northernengineering.com Interwest Consulting Group assumed the entire flow from this site will flow towards a CDOT Type-D inlet at the southeast corner of the project. Due to the necessary grading improvements to connect the proposed driveway into the Suniga Road Improvements, the site was divided into four basins: Basin B1, B2, OS1, and OS2. Basin B1 sheet flows from the northwest corner of the project site towards the southeast corner of the site per Interwest Consulting Group’s assumptions. The CDOT Type-D inlet will collect stormwater from Basin B1 and discharge into the NECCO storm sewer system. Basin B2 flows from the northwest corner of Lot 2 to Inlet B2 along the south side of the project. Inlet B2 will discharge into a 30” storm sewer provided as part of the Suniga Road Improvements, and as an extension of the NECCO storm sewer system. Basin OS1 will sheet flow into the curb and gutter provided by the Suniga Road Improvements. The curb and gutter discharges into a storm inlet located on Suniga Road, provided by the Suniga Road Improvements, at the upstream location of the same storm sewer collecting drainage from Basin B2. Basin OS2 follows historic patterns and discharges into the curb and gutter along North College Avenue. Drainage from North College Road ultimately discharges into the same storm sewer inlet collecting drainage from Suniga Road and Basin OS1. We feel the current proposed drainage plan for 1st Stop Plaza Second Filing is in compliance with the concepts shown in the NECCO Design Report and the Interwest Drainage Memorandum for Suniga Drive and College Avenue. Upon redevelopment of Lots 1 and 2 of 1st Stop Minor Amendment, the developer will need to provide water quality and LID improvements for that portion of the driveway improvements that fall within their property. If you have any questions, please feel free to contact me at your earliest convenience. NORTHERN ENGINEERING SERVICES, INC. Frederick S. Wegert, PE Project Engineer 1st Stop Plaza CHARACTER OF SURFACE: Runoff Coefficient 1 Percentage Impervious 2 Project: Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: Asphalt ………………… ................... .......................................................... 0.95 100% Date: Concrete ………………. ................... .......................................................... 0.95 96% Gravel (packed) ………. ................... .......................................................... 0.50 40% Roofs………………….. ................... .......................................................... 0.95 90% Pavers…………………. ................... .......................................................... 0.40 40% Lawns and Landscaping Sandy Soil Flat <2% ………….. ................... .......................................................... 0.10 0% Average 2% to 7% ................... .......................................................... 0.15 0% Steep >7% ………… ................... .......................................................... 0.20 0% Clayey Soil Flat <2% ………….. ................... .......................................................... 0.20 0% Average 2% to 7% ................... .......................................................... 0.25 0% Steep >7% ………… ................... .......................................................... 0.35 0% 2-year C f = 1.00 10-year C f = 1.00 USDA SOIL TYPE: C Sub-Basin ID Sub-Basin Area (sq. ft.) Sub-Basin Area (ac.) Area of Asphalt & Concrete (ac.) Area of Roofs (ac.) Area of Gravel (ac.) Area of Landscaping 2% to 7% (ac) 2-year Composite Runoff Coefficient 10-year Composite Runoff Coefficient 100-year Composite Runoff Hansen Development Project: 1st Stop Plaza Calculations By: Date: Is Length >500' ? C*C f (2-yr C f =1.00) C*C f (10-yr C f =1.00) C*C f (100-yr C f =1.25) T i 2-yr (min) T i 10-yr (min) T i 100-yr (min) Velocity, V (ft/s) T t (min) Velocity, V (ft/s) T t (min) 2-yr T c (min) 10-yr T c (min) 100-yr T c (min) Hansen Development Project: Calculations By: Date: b1 B1 2.53 23 20 20 0.39 0.39 0.48 1.51 2.74 5.60 1.48 2.69 6.86 b2 B2 0.52 6 6 5 0.84 0.84 1.00 2.76 4.72 9.95 1.21 2.06 5.16 os1 OS1 0.11 10 10 10 0.20 0.20 0.25 2.26 3.86 7.88 0.05 0.08 0.21 os2 OS2 0.05 10 10 8 0.46 0.46 0.58 2.21 3.78 8.38 0.05 0.09 0.25 site Site 3.21 21 18 18 0.46 0.46 0.57 1.56 2.90 6.01 2.28 4.24 10.99 F. Wegert 1st Stop Plaza PROPOSED RUNOFF COMPUTATIONS C 100 Design Point Flow, Q 100 (cfs) Flow, Q 2 (cfs) 10-yr T c (min) 2-yr T c (min) C 2 Flow, Q 10 (cfs) Intensity, i 100 (in/hr) Sub-Basin(s) Rational Method Equation: Rainfall Intensity: Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8 February 22, 2019 Intensity, i 10 (in/hr) C 10 Area, A (acres) Intensity, i 2 (in/hr) New Impervious Area 0.187 Ac. Paver Area 0.048 Ac. Traditional Pavement Area 0.139 Ac. Other Impervious Surfaces (Roofs, Concrete Walks, etc.) 0.000 Ac. Required Minimum Impervious Area to be Treated 0.094 Ac. Paver LID Treatment Paver area 0.048 Ac. Run-on area for Pavers (parking area) 0.125 Ac. Run-on area for Pavers (other - concrete walks, etc.) 0.000 Ac. Impervious Area Treated by LID Pavers 0.173 Ac. Rain Garden Treatment Rain Garden Area 0.000 Ac. Run-on area for Rain Garden 0.000 Ac. Impervious Area Treated by Rain Gardens 0.000 Ac. Total Impervious Area Treated 0.173 Ac. Percent of Impervious Area Treated 92.38 % New Pavement Area 8,165 Sq. Ft. Required Minimum Area of Permeable Pavement 2,041 Sq. Ft. Total Permeable Pavement Area 2,099 Sq. Ft. Actual % of Permeable Pavement Provided 25.7 % 50% On-Site Treatment by LID Requirement 25% Permeable Pavement Requirement Interwest Consulting Group RUNOFF COEFFICIENTS & % IMPERVIOUS LOCATION: SUNIGA PROJECT NO: 1326-069-00 COMPUTATIONS BY: ES DATE: 7/18/2018 Recommended Runoff Coefficients from Table RO-11 of City of Fort Collins Stormwater Code, Volume I Recommended % Impervious from Table RO-3 Urban Storm Drainage Criteria Manual, Volume I Runoff % coefficient Impervious C Streets, parking lots (asphalt): 0.95 100 Sidewalks (concrete): 0.95 96 Roofs: 0.95 90 Gravel or Pavers: 0.50 40 Landscape Areas (Flat, heavy) : 0.20 0 Landscape Areas (Steep, heavy) : 0.35 0 SUBBASIN TOTAL TOTAL ROOF PAVED PAVERS SIDEWALK LANDSCAPE RUNOFF % DESIGNATION AREA AREA AREA AREA AREA AREA AREA COEFF. Impervious REMARKS (ac.) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (sq.ft) (C) A 0.98 42,631 0 42,631 0 0 0 0.95 100 NORTH HALF SUNIGA B 3.22 140,134 0 62,219 0 0 77,914 0.53 44.4 C 0.98 42,720 0 42,720 0 0 0 0.95 100 SOUTH HALF SUNIGA Equations - Calculated C coefficients & % Impervious are area weighted C = Σ (Ci Ai) / At Ci = runoff coefficient for specific area, Ai Ai = areas of surface with runoff coefficient of Ci n = number of different surfaces to consider At = total area over which C is applicable; the sum of all Ai's 7-18-18 FC Flow Suniga.xls From Suniga Road Design College Avenue to Blondel Street Drainage Memorandum prepared by Interwest Consulting Group and dated August 13, 2018. Basin B coincides with Lots 1 and 2 of 1st Stop Plaza Area Inlet Performance Curve: Existing Inlet at Basin B1 Governing Equations: At low flow depths, the inlet will act like a weir governed by the following equation: * where P = 3.1416*Dia.of grate * where H corresponds to the depth of water above the flowline At higher flow depths, the inlet will act like an orifice governed by the following equation: * where A equals the open area of the inlet grate * where H corresponds to the depth of water above the centroid of the cross-sectional area (A) The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown. However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation will cross at a certain flow depth. The two curves can be found below: If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir. Input Parameters: Type of Grate: CDOT Type D Diameter of Grate (ft): 3.8 Open Area of Grate (ft2): 24.70 Rim Elevation (ft): 4966.430 Reduction Factor: 50% Depth vs. Flow: Depth Above Inlet (ft) Elevation (ft) Shallow Weir Flow (cfs) Orifice Flow (cfs) Actual Flow (cfs) 0.00 4966.43 0.00 0.00 0.00 0.20 4966.63 1.60 29.68 1.60 0.40 4966.83 4.53 41.98 4.53 0.53 4966.96 6.83 48.14 6.83 0.60 4967.03 8.32 51.41 8.32 0.80 4967.23 12.81 59.36 12.81 1.00 4967.43 17.91 66.37 17.91 1.20 4967.63 23.54 72.71 23.54 1.40 4967.83 29.66 78.53 29.66 1.60 4968.03 36.24 83.95 36.24 1.80 4968.23 43.24 89.05 43.24 100-Year Design Flow = 6.86 cfs 10-Year Design Flow = 2.69 cfs Q = 3 . 0 P H 1 . 5 Q = 0 . 67 A ( 2 gH ) 0 . 5 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 Discharge (cfs) Stage (ft) Stage - Discharge Curves 3130 Verona Avenue • Buford, GA 30518 (866) 888-8479 / (770) 932-2443 • Fax: (770) 932-2490 © Nyloplast Inlet Capacity Charts June 2012 0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Capacity (cfs) Head (ft) Nyloplast 2' x 3' Curb Inlet Diagonal Grate Inlet Capacity Chart High Hood Setting (8.47" Curb Setting) Low Hood Setting (4.47" Curb Setting) Mid Hood Setting (6.47" Curb Setting) Q100 = 5.16 cfs D100 = 0.275 ft Capacity of Inlet B2 D VAULT F.O. F.O. FO FO FO FO FO FO E E E E EE G G G G D ST ST ST ST S T ST ST ST T 2.53 ac. B1 EX. COLUMN (TYP.) UTILITY & DRAINAGE EASEMENT (SEE PLAT) 5' DRAINAGE EASEMENT PER 1ST STOP PLAZA 15' UTILITY EASEMENT PER 1ST STOP PLAZA UTILITY & DRAINAGE EASEMENT (SEE PLAT) 31' UTILITY EASEMENT 5' DRAINAGE EASEMENT PER 1ST STOP PLAZA PROPOSED SIDEWALK BY INTERWEST CONSULTING GROUP B1 PROPOSED 15' UTILITY EASEMENT 15' DRAINAGE EASEMENT (RECEPTION NO. 199400063870) EXISTING SIDEWALK PROPOSED SIDEWALK BY INTERWEST CONSULTING GROUP (SEE SUNIGA DRIVE IMPROVEMENTS PREPARED BY INTERWEST CONSULTING GROUP). SF SF SF SF SF SF SF SF SF SF SF SF SF SF RS RS RS RS IP IP RS SF SF SF CW IP RS EXISTING BUILDING 1006 N. COLLEGE AVENUE LOT 2 1ST STOP MINOR SUBDIVISION LOT 1 1ST STOP MINOR SUBDIVISION NORTH COLLEGE AVENUE 1008 N. COLLEGE AVENUE 1010 N. COLLEGE AVENUE 1180 N. COLLEGE AVENUE CROWNE AT OLD TOWN NORTH SUBDIVISION 1108 N. COLLEGE AVENUE EX. SIDEWALK PROPOSED 20' EMERGENCY ACCESS EASEMENT PROPOSED 20' EMERGENCY ACCESS EASEMENT 22' UTILITY EASEMENT PER 1ST STOP PLAZA UTILITY & DRAINAGE EASEMENT (SEE PLAT) PROPOSED BICYCLE RACK (RE: LANDSCAPE ARCHITECT) PROPOSED 2' WIDE SIDEWALK CULVERT MATCH INTO EXISTING LIP OF GUTTER EX. TRASH ENCLOSURE MATCH INTO EXISTING CONCRETE PAD FOR TRASH ENCLOSURE EX. CONCRETE BLOCK RETAINING WALL EX. CONCRETE VALLEY PAN EX. CONCRETE VALLEY PAN PROPOSED STORM INLET PROPOSED STORM SEWER PROPOSED 30" STORM SEWER BY INTERWEST CONSULTING GROUP (SEE SUNIGA DRIVE IMPROVEMENTS PREPARED BY INTERWEST CONSULTING GROUP),. PROPOSED STORM INLET BY INTERWEST CONSULTING GROUP (SEE SUNIGA DRIVE IMPROVEMENTS PREPARED BY INTERWEST CONSULTING GROUP). PROPOSED STORM MANHOLE BY INTERWEST CONSULTING GROUP (SEE OF SUNIGA DRIVE PROPOSED TRAFFIC LIGHT BY INTERWEST CONSULTING GROUP (TYP.) PROPOSED MIN. 6" DEEP (ACTUAL DEPTH VARIES) SWALE WITH 4:1 SIDE SLOPES 2' WIDE VALLEY PAN 2' WIDE VALLEY PAN IP TRM TRM TRM 0.52 ac. B2 B2 0.05 ac. OS2 0.11 ac. OS1 OS1 OS2 Sheet 1ST STOP PLAZA SECOND FILING These drawings are instruments of service provided by Northern Engineering Services, Inc. and are not to be used for any type of construction unless signed and sealed by a Professional Engineer in the employ of Northern Engineering Services, Inc. NOT FOR CONSTRUCTION REVIEW SET E NGINEER ING N O R T H E RN FORT COLLINS: 301 North Howes Street, Suite 100, 80521 GREELEY: 820 8th Street, 80631 970.221.4158 northernengineering.com of 10 PROPOSED CURB & GUTTER C5.0 DRAINAGE & EROSION CONTROL PLAN 7 CALL UTILITY NOTIFICATION CENTER OF COLORADO Know what'sbelow. Call before you dig. R LEGEND: ( IN FEET ) 0 1 INCH = 20 FEET 20 20 40 60 PROPERTY BOUNDARY EXISTING RIGHT-OF-WAY EXISTING EASEMENTS NOTES: 1. EXISTING UNDERGROUND AND OVERHEAD PUBLIC AND PRIVATE UTILITIES AS SHOWN ARE INDICATED ACCORDING TO THE BEST INFORMATION AVAILABLE TO THE ENGINEER. THE ENGINEER DOES NOT GUARANTEE THE ACCURACY OF SUCH INFORMATION. EXISTING UTILITY MAINS AND SERVICES MAY NOT BE STRAIGHT LINES OR AS INDICATED ON THESE DRAWINGS. THE CONTRACTOR SHALL BE RESPONSIBLE TO CALL ALL UTILITY COMPANIES (PUBLIC AND PRIVATE) PRIOR TO ANY CONSTRUCTION TO VERIFY EXACT UTILITY LOCATIONS. 2. REFER TO THE "FINAL DRAINAGE MEMORANDUM FOR 1ST STOP PLAZA" BY NORTHERN ENGINEERING, DATED FEBRUARY 22, 2019 FOR ADDITIONAL INFORMATION. 3. EASEMENTS SHOWN FOR REFERENCE. SEE 1ST STOP PLAZA SECOND FILING PLAT FOR DIMENSIONS AND LOCATIONS OF EXISTING, PROPOSED, AND VACATED EASEMENTS. PROPOSED INFRASTRUCTURE BY OTHERS EXISTING MAJOR CONTOUR EXISTING MINOR CONTOUR PROPOSED STORM SEWER PROPOSED STORM INLET PROPOSED MAJOR CONTOUR PROPOSED MINOR CONTOUR A DRAINAGE BASIN LABEL BASIN DESIGNATION BASIN AREA (AC) DRAINAGE BASIN BOUNDARY B2 1.45 ac DESIGN POINT FLOW ARROWS PROPOSED STORM SEWER THIS PROJECT DOES NOT MEET THE CITY'S LID REQUIREMENTS. UPON REDEVELOPMENT OF LOTS 1 & 2 FOR 1ST STOP MINOR SUBDIVISION, THE DEVELOPER SHALL PROVIDE LID IMPROVEMENTS FOR THAT PORTION OF THE DRIVEWAY, ASPHALT, PARKING LOT, AND CONCRETE THAT FALLS WITHIN THEIR PROPERTY. OFFSITE DRAINAGE FROM THE NORTH MUST BE MAINTAINED, CONVEYED, OR RE-ROUTED TO FLOW INTO THE NORTH EAST COLLEGE CORRIDOR OUTFALL STORM SEWER SYSTEM WITHIN SUNIGA DRIVE. REQUIRED WATER QUALITY VOLUME DESCRIPTION WATER QUALITY VOL. (FT3 ) WATER QUALITY VOL. (ACRES) LOT 1 669 0.015 LOT 2 285 0.0070 TEMPORARY BMP'S INLET PROTECTION ROCK SOCK SILT FENCE SF CONCRETE WASHOUT CW SF RS IP PERMANENT BMP'S TURF REINFORCEMENT MAT TRM Weir Flow Orifice Flow 100-yr T c (min) Q = C f ( C )( i )( A ) 2/22/2019 2:57 PM D:\Projects\1564-001\Drainage\Hydrology\1564-001_Rational Fort Collins.xlsx\Runoff b1 B1 No 0.39 0.39 0.48 20.2 20.2 17.4 N/A N/A 1.54 2.8 22.9 20.2 20.2 b2 B2 No 0.84 0.84 1.00 4.3 4.3 1.7 1.74 1.6 N/A N/A 5.9 5.9 5.0 os1 OS1 No 0.20 0.20 0.25 8.1 8.1 7.7 1.47 1.8 N/A N/A 10.0 10.0 9.5 os2 OS2 No 0.46 0.46 0.58 8.8 8.8 7.2 1.31 1.3 N/A N/A 10.1 10.1 8.5 site Site No 0.46 0.46 0.57 18.2 18.2 15.0 N/A N/A 1.54 2.8 21.0 18.2 17.8 PROPOSED TIME OF CONCENTRATION COMPUTATIONS F. Wegert February 22, 2019 Design Point Sub-Basin Overland Flow Gutter Flow Time of Concentration Velocity (Gutter Flow), V = 20·S ½ T t = L / 60V T c = T i + T t (Equation RO-2) Velocity (Swale Flow), V = 15·S ½ NOTE: C-value for overland flows over grassy surfaces; C = 0.25 Overland Flow, Time of Concentration: Gutter/Swale Flow, Time of Concentration: Swale Flow (Equation RO-4) ( ) 3 1 1 . 87 1 . 1 * S C Cf L Ti − = 2/22/2019 2:57 PM D:\Projects\1564-001\Drainage\Hydrology\1564-001_Rational Fort Collins.xlsx\Tc Coefficient Composite % Imperv. B1 110,388 2.53 0.51 0.12 0.00 1.90 0.39 0.39 0.48 24% B2 22,599 0.52 0.36 0.09 0.00 0.07 0.84 0.84 1.00 84% OS1 4,703 0.11 0.00 0.00 0.00 0.11 0.20 0.20 0.25 0% OS2 2,199 0.05 0.02 0.00 0.00 0.03 0.46 0.46 0.58 35% Total Site 139,891 3.21 0.89 0.21 0.00 2.12 0.46 0.46 0.57 33% 2) Percent impervious are taken from Suniga Road Design, College Avenue to Blondel Street Drainage Memorandum prepare by Interwest Consulting Group. 100-year C f = 1.25 1) Runoff coefficients are taken from the Fort Collins Stormwater Criteria Manaual, Table 3.2.1 and Table 3.2.2. Composite Runoff Coefficient with Adjustment PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS 1st Stop Plaza F. Wegert February 22, 2019 2/22/2019 2:57 PM D:\Projects\1564-001\Drainage\Hydrology\1564-001_Rational Fort Collins.xlsx\Composite C