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HomeMy WebLinkAboutDrainage Reports - 08/17/2000oM� o Final e1 Rem d G 0 PROP We OF We �� / FORT COBS 9 2000 -1� 0 �I� o Addendum No. 2 to g the Drains e 1 � o O O and Erosion Control Report O O Southmoor Village Fifth Filing 0 Fort Collins/ Colorado 00 June/7, 2000 10 0 O 0 11 11 1 THE SEAR -BROWN _ GROUP Standards in Excellence 1 i ' ARCHITECTURE 2095outh Meldtum ENGINEERING Fort Collins, CO 80521-2603 SEAR BROWN PLANN' 970.482.6368 phone Corvsrnucnory 970.4ffi.6368 fax CONSTRUCTION www.se,Rbown.conn 1 June 7, 2000 Mr. Basil Hamdan City of Fort Collins Water Utilities --Storm Water 700 Wood Street ' Fort Collins, Colorado 80521 RE: Addendum No. 2 to the Drainage and Erosion Control Report for The Southmoor Village Fifth Filing Subdivision Mr. Hamdan: We are pleased to submit to you, for your review and approval, this addendum to the Drainage and Erosion Control Report for the Southmoor Village Fifth Filing Subdivision. All computations within this report have been completed in compliance with the City of Fort Collins Storm Drainage Design Criteria. We appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. ' Respectfully, ' The Sear -Brown Group Prepared by: Revie ed by: QPoc REC/s 4336 r- John Gooch, EIT ?Jimllen-Mo E. Drainage Engineer Project Manag `• , �r�`'� bNAL cc: File 035-180 1 1 1 1 1 TABLE OF CONTENTS DESCRIPTION PAGE I. GENERAL LOCATION AND DESCRIPTION A. Location 4 B. Description of Property 4 II. DRAINAGE BASINS A. Major Basin Description 4 III. DRAINAGE DESIGN CRITERIA 5 A. Regulations 5 B. Development Criteria Reference and Constraints 5 C. Hydrologic Criteria 5 D. Hydraulic Criteria 5 E. Variances from Criteria 5 W. DRAINAGE FACILITY DESIGN 6 A. General Concept 6 V. STORM WATER QUALITY 7 A. General Concept 7 VI. CONCLUSIONS 7 A. Compliance with Standards 7 B. Drainage Concepts 7 C. Storm Water Quality Concept 7 D. Erosion Control Concept 7 REFERENCE g APPENDIX 9 A: VICINITY MAP 10 B: RATIONAL METHOD HYDROLOGY 11 C: FLOWMASTER ANALYSIS 12 ADDENDUM NO. 2 TO THE DRAINAGE AND EROSION CONTROL REPORT FOR THE ' SOUTHMOOR VILLAGE FIFTH FILING SUBDIVISION FORT COLLINS, COLORADO I. GENERAL LOCATION AND DESCRIPTION A. Location The Southmoor Fifth Filing Subdivision is a commercial development located on the Southwest corner of the Mathews Street and Swallow Road intersection in Fort Collins, Colorado. It lies immediately to the West of the Colorado State Building (DMV) and directly South of The Thunderbird Estates Ninth Subdivision, Block 5. The site location can also be described as being situated in the Southwestern Quarter of Section 25, Township 7 North, Range 69 West of the 6th Principal ' Meridian, City of Fort Collins, Larimer County, Colorado. The project site can be seen on the Vicinity Map in the Appendix. B. Description of Property The Southmoor Fifth Filing Subdivision contains approximately 9.52 acres, of ' which the Goodyear Site comprises 1.09 acres. Presently, the site contains a commercial building with the remaining majority of the site covered by asphalt. The topography of the site provides for three drainage basins, each sloping between ' 1 and 3 percent to the Southeast and converging in the Southeast comer of the site. H. DRAINAGE BASINS A. Major Basin Description The site is located within the City of Collins' "Foothills Drainage Basin". The ' Foothills basin is approximately 1.5 miles wide (North to South) and 3 miles long (East to West). Its East and West boundaries include East County Road 9 and West County Road 19 respectively. Its North and South boundaries include Kirkwood ' Drive and Breakwater Drive respectively. All storm water from the Foothills Drainage Basin flows predominately to the East and feeds into the Foothills Reservoir Inlet Ditch. 1 4 1 Cl III. DRAINAGE DESIGN CRITERIA A. Regulations The City of Fort Collins Storm Drainage Design Criteria is being used for the subject site. B. Development Criteria Reference and Constraints The addendum to the Drainage and Erosion Control Report for The Southmoor Village Fifth Filing covers additions to 1.09 acres of the 9.52 acre Subdivision. The most recent utility plans for The Southmoor Village Fifth Filing date back to 1972. Upon reviewing the utility plans, no Drainage or Erosion Control Plans were ' found. Likewise, no Drainage and Erosion Control Reports were found for The Southmoor Village Fifth Filing. Therefore, we have chosen to use the Drainage Criteria associated with the LDGS System. C. Hydrological Criteria The Rational Method for determining surface runoff was used for this commercial site. Runoff values were calculated using the 2-year and 100-year storm event ' intensities, provided by the City of Fort Collins. These calculations and criteria are included in the Appendix. D. Hydraulic Criteria All hydraulic calculations within this report have been prepared in accordance with ' the City of Fort Collins Drainage Criteria and are also included in the Appendix. E. Variances from Criteria A variance to exclude an extended detention water quality pond is being requested for the proposed project site. This request is being made, as the nearest storm water inlet is approximately 190' from the proposed detention pond site (East of Building). Furthermore, the addition of a 6-inch layer of small gravel (below the swale invert) below the 6-inch cobble stone layer will mitigate extended water ' quality detention. I 1 5 FI u IV F I I DRAINAGE FACILITY DESIGN A. General Concept The Southmoor Village Fifth Filing Subdivision has been divided into three basins with no off -site basins contributing any flow. The primary revision to the drainage design for the site is the reduction of impervious area, thereby minimizing storm water runoff. The addendum to the drainage plan for Southmoor Village Fifth Filing accomplishes this by the implementation of 9,979 square feet (0.23 acres) of pervious grass area along with a stone-lined/grass berm swale, which handles 60% of the site runoff and provides for on -site remediation. With these two revisions, storm water detention is not required for the site. Therefore, the general concept for the passage of storm water through the site is to remediate as much storm water as possible while allowing any remaining overland flow to collect in and be conveyed by cross -pan trenches and curb and ' gutter to the Southeast corner the site. After reaching the Southeast corner of the site, the combined runoff from the three basins will flow South to a storm water ' inlet on Mathews Street (see sheet 7 of Utility Plans). Basin 1 will collect storm water runoff from the West and South areas of the site and transport runoff, via a cross -pan trench, to the storm water inlet on Mathews Street. ' Basin 2 will collect storm water from the West and North areas of the site as well as the roof of the building. This combined flow will be directed Easterly via a cross -pan trench system and conveyed through a curb cut at the Northeast corner ' of the building and into the swale at the East end of the site. After filtration and remediation in the swale, any remaining runoff will be directed through the curb cut on the Southeast corner of the building and allowed to flow South toward the storm water inlet on Mathews Street. It is important to note that 60% of the runoff from the site will pass through the stone -lined (6-inch base layer of gravel with 6- inch cobble stone layer above) /grass -berm swale. This will not only reduce runoff from the site, but also provide for filtration/leaching and on -site storm water remediation. In addition, grass areas surrounding the swale will provide increased permeability for the storm water, thus far exceeding the existing permeabilty of the site. Basin 3 will collect storm water from the far East side of the site. This region slopes to the Southeast , thus allowing the storm water to gather in the guttering on Mathews Street and flow South to the same storm water inlet as Basins 1 and 2. I 7 u IV. STORM WATER QUALITY ' A. General Concept ' Storm water quality shall be achieved by 60% of the storm water flow being routed through the stone-lined/grass-berm swale. The swale shall be constructed so that 6 inches of gravel lines the bottom of the swale, with a 6-inch layer of cobble stone ' on top of the gravel. This will allow for filtration/ leaching of minimum storm flows and allow pollutants to settle out of the storm water before entering the storm water inlet at Mathews Street. VI. CONCLUSIONS A. Compliance with Standards All computations that have been completed within this report are in compliance with the City of Fort Collins Erosion Control Reference Manual for Construction ' Sites and the Storm Drainage Design Criteria Manual. B. Drainage Concept The proposed drainage concepts presented in this report and on the construction plans provide for 60% on -site remediation of site runoff by means of the stone- lined/grass-berm swale, with transmission of the remaining 40% of site runoff to the existing and proposed drainage inlet at the Southeast corner of the project site. ' C. Storm Water Quality Concept The proposed design has addressed the water quality aspect of storm water runoff. ' The stone-lined/grass-berm swale will provide an opportunity for storm water pollutants to filter out of the storm water runoff before the runoff enters the storm water inlet at Mathews Street. D. Erosion Control Concept ' The existing ground cover surrounding this commercial building is approximately 95 % asphalt, with trees bordering the site to the North. Furthermore, the proposed ' addendum to the drainage for The Southmoor Village Fifth Filing will decrease runoff for the site, thus further diminishing water erosion. With these things in mind, wind and water erosion should be very minimal. However, standard erosion ' and control methods will be implemented as described on the Drainage Plan sheet (sheet 7). I i 1 1 i 1 i 1 1 1 1 1 1 1 1 1 1 1 i 1 1. Storm Drainage Design Criteria and Construction Standards, by the City of Fort Collins, Colorado, May 1984, interim revision January 1997. 2. Erosion Control Reference Manual for Construction Sites by the City of Fort Collins, Colorado, January 1991. 0 I APPENDIX 1J I 1 P 1 I 1 1 '�J C� 1 I I I 1 11 I I 11 I I Ll I t I F r r I I I I J •''30I1 . VICINITY MAP 10 I � ~ ------ U � -- � -- - ZE ' � W.wDNRD[ DR. 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I [l I I I I I I I I I I I I I APPENDIX C FLOWMASTER ANALYSIS 12 0 Cross -Pan Trench: North Side Building Worksheet for Triangular Channel Project Description Project File c:\haestad\fmw\goodyear.fm2 Worksheet Cross -Pan Trench: North Side Building ' Flow Element Triangular Channel Method Manning's Formula Solve For Channel Depth LJ 1 Input Data Mannings Coefficient 0.013 Channel Slope 0.020000 ft/ft Left Side Slope 2.000000 H : V Right Side Slope 2.000000 H : V Discharge 2.40 cfs Results Depth 0.46 It Flow Area 0.43 ft' Wetted Perimeter 2.06 ft Top Width 1.84 ft Critical Depth 0.62 ft Critical Slope 0.004229 Wit Velocity 5.64 ft/s Velocity Head 0.49 ft Specific Energy 0.96 ft Froude Number 2.07 Flow is supercritical. Notes: Cross -Pan design is based on Q1oc '04/03/00 FlowMaster v5.13 . 09:13:31 AM Hassled Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203) 755-1666 Page 1 of 1 11 1 I I Swale: North Side Building (Roof) Worksheet for Triangular Channel Project Description Project File c:\haestad\fmMgoodyear.fm2 Worksheet Swale: North Side of Building (Roof) Flow Element Triangular Channel Method Manning's Formula _Solve For Channel Depth Input Data Mannings Coefficient 0.030 Channel Slope 0.020000 ft/ft Left Side Slope 3.000000 H : V Right Side Slope 3.000000 H : V Discharge 2.07 cfs Results Depth 0.51 ft Flow Area 0.77 ft' Wetted Perimeter 3.20 ft Top Width 3.03 ft Critical Depth 0.49 ft Critical Slope 0.022414 ft/ft Velocity 2.70 ft/s Velocity Head 0.11 ft Specific Energy 0.62 ft Froude Number 0.95 Flow is subcritical. Notes: 'Swale design is based on Qloc a 04/03/00 FlowMaster v5.13 09:39:40 AM Haestad Methods, Inc, 37 Brookside Road Waterbury, CT 08708 (203) 755-1666 Page 1 of 1 Curb Cut: Northeast Corner of Building ' Worksheet for Rectangular Channel ' Project Description Project File c:\haestad\fmw\goodyear.fm2 Worksheet Curb Cut: Northeast Comer of Building Flow Element Rectangular Channel Method Manning's Formula Solve For Channel Depth Input Data Mannings Coefficient 0.013 Channel Slope 0.020000 ft/ft Bottom Width 2.00 ft ' Discharge 2.07 ds Results ' Depth 0.21 It Flow Area 0.41 ft' Wetted Perimeter 2.41 ft ' Top Width 2.00 ft Critical Depth 0.32 ft Critical Slope 0.005213 ft/ft ' Velocity 4.99 ft/s Velocity Head 0.39 ft Specific Energy 0.59 ft ' Froude Number 1.93 Flow is supercritical. ' Notes: Curb Cut design is based on Qri, '04/03/00 FlowMaster v5.13 09:47:40 AM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 08708 (203) 755-1888 Page 1 of 1 1' Curb Cut: North Edge of Swale ' Worksheet for Rectangular Channel Project Description Project File c:\haestad\fmw\goodyear.fm2 Worksheet Curb Cut: North Edge of Swale Flow Element Rectangular Channel ' Method Manning's Formula Solve For Channel Depth Input Data Mannings Coefficient 0.013 Channel Slope 0.020000 ft/ft Bottom Width 2.00 ft ' Discharge 4.47 cfs Results Depth 0.34 ft Flow Area 0.69 ft' Wetted Perimeter 2.69 ft Top Width 2.00 ft Critical Depth 0.54 ft Critical Slope 0.005375 ft/ft Velocity 6.51 ft/s Velocity Head 0.66 It Specific Energy 1.00 ft Froude Number 1.96 Flow is supercritical. ' Notes: Curb Cut design is based on Ql,t 1 11 04/03/00 FlowMaster v5.13 09:49:10 AM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06706 (203) 755-1666 Page 1 of 1 Swale: East Side of Building Worksheet for Trapezoidal Channel El ' Project Description Project File c:\haestad\fmw\southmoo.fm2 Worksheet Swale: East side of building ' Flow Element Trapezoidal Channel Method Manning's Formula Solve For Channel Depth Input Data Mannings Coefficient 0.060 Channel Slope 0.005000 ft/ft Left Side Slope 4.000000 H : V Right Side Slope 4.000000 H : V Bottom Width 6.00 ft Discharge 4.47 cfs Results Depth 0.55 ft Flow Area 4.50 ft' Wetted Perimeter 10.53 ft Top Width 10.39 ft Critical Depth 0.24 ft Critical Slope 0.088567 ft/ft Velocity 0.99 ft/s Velocity Head 0.02 ft Specific Energy 0.56 ft Froude Number 0.27 Flow is subcritical. Notes: `Swale design is based on Q/oc 06/06/00 FlowMaster v5.13 05:00:42 PM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203) 755-1666 Page 1 of 1 Swale: East Side of Building Cross Section for Trapezoidal Channel Project Description Project File c:\haestad\fmw\southmoo.fm2 Worksheet Swale: East side of building Flow Element Trapezoidal Channel Method Manning's Formula Solve For Channel Depth Section Data Mannings Coefficient 0.060 Channel Slope 0.005000 ft/ft Depth 0.55 ft Left Side Slope 4.000000 H : V Right Side Slope 4.000000 H : V Bottom Width 6.00 ft Discharge 4.47 cfs 11 r— L_ e �0.55 ft °1 1 6.00 ft V H 1 NTS I 06/06/00 FlowMaster v5.13 '04:59:24 PM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203) 755-1666 Page 1 of 1 Curb Cut: South end of Swale Worksheet for Rectangular Channel ' Project Description Project File c:\haestad\fmw\goodyear.fm2 Worksheet Curb Cut: South end of Swale ' Flow Element Rectangular Channel Method Manning's Formula Solve For Channel Depth Input Data Mannings Coefficient 0.035 ' Channel Slope 0.020000 ft/ft Bottom Width 2.00 ft Discharge 4.47 cfs Results Depth 0.68 ft Flow Area 1.36 ft' Wetted Perimeter 3.36 ft ' Top Width 2.00 ft Critical Depth 0.54 ft Critical Slope 0.038959 ft/ft Velocity 3.29 ft/s Velocity Head 0.17 ft Specific Energy 0.85 ft ' Froude Number 0.70 Flow is subcritical. ' Notes: 1 I IJ L, 1 ' Curb Cut design is based on Qi,c 04/03/00 FlowMaster v5.13 09:54:34 AM Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 (203) 755-1666 Page 1 of 1 -=T!� EMSIING CONTOURS PROPOSED CONTOUR DIRECTION OF FLOW DESIGN POINT MEFMEEM DRAINAGE BASIN BOUNDARY NUMBER eBASIN LAaD BASIN AREA IF PROPOSED OUTFAIL CURB k GU lEF9 PROPOSED INFLOW CURB AN CUTLER B SWAIE/DITCH ON/ FLOW ARROW NOTE: TME IY LAYERS OF WWBB��EES5 AND GRAVEL ALLOWS F01! FlL1RA1ItM/IMM OF MINIMUM SiMM WATER FLOWS. •6.O wl vIW�NN� Y.:•:J:f:'l. GRASS S� 1— UU OC Go i LU SCALE t'=20'AS I III�d � � n a � STANDARD EROSION CONTROL CONSTRUCTION PLAN NOTES R The city of Fort costae Sbrm.ater Utility erosion lomFVMtQr most Ge noulW a at least noun prim to m mr ewm construction this ale. AN Sol In an fe " May be FsmIM gjg to my two aeumi9 activity (Na4prbg. stripping. 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