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HomeMy WebLinkAboutWILLOW STREET LOFTS - PDP - 24-04 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTHYDRAULIC STRUCTURES DRAINAGE CRITERIA MANUAL (V. 2) i 1 1 1 1 I 11 I 1 1 Culvert outlet energy dissipator and flow spreading may require special structures downstream of the culvert outlet to limit local scour, general stream degradation, and troublesome head cutting. Local scour is typified by a scour hole produced at the culvert outlet. This is the result of high exit velocities, and the effects extend only a limited distance downstream. Coarse material scoured from the circular or elongated hole is deposited immediately downstream, often forming a low bar. Finer material is transported further downstream. The dimensions of the scour hole change due to sedimentation during low flows and the varying erosive effects of storm events. The scour hole is generally deepest during passage of the peak flow. Methods for predicting scour hole dimensions are found in HEC No. 14 (Corry, et al. 1975). Photograph HS-13 Culvert outlets are often left unprotected causing downstream degradation. The designer's job is not complete until the outlet hydraulic provisions are made. Burying of riprap and revegetation of ` the surface would have blended this structure better into the adjacent landscape. General storm degradation, or head cutting, can be a phenomenon independent of culvert performance. Natural causes produce a lowering of the streambed over time. The identification of a degrading stream is an essential part of the original site investigation. However, high-energy discharges from a culvert often cause stream degradation that is similar to the former, though limited in distance. Both types of scour can occur simultaneously at a culvert outlet. As described in HEC No. 14, various measures exist to control culvert outlet flow, as listed below. It is beyond the scope of this Manual to provide information about these controls, but the District encourages their proper application and design. 1. Colorado State University rigid boundary basin HS-70 O6/2001 Urban Drainage & Flood Control District C DRAINAGE CRITERIA MANUAL (V. 2) HYDRAULIC STRUCTURES 3.4.3.4 Basin Width. The minimum width, W, of the basin downstream of the pipe's flared end section is set as follows: for circular pipes, W = 4D (HS-20) for rectangular pipe, W = w+4H (HS-21) _ in which: W = basin width (Figure HS-18a) D = diameter of circular conduit w = width of rectangular conduit 3.4.3.5 Other Design Requirements. All slopes in the pre -shaped riprapped basin are.2H to 1V.- Provide pipe joint fasteners and a structural concrete cutoff wall at the end of the flared end section for a -. circular pipe or a headwall with wingwalls and a paved bottom between the walls, both with a cutoff wall that extends down to a depth of D H B=—+T or B=—+T 2 2 in which: B = cutoff wall depth D = diameter of circular conduit T= Equation HS-17 The riprap must be extended up the outlet embankment's slope to the mid -pipe level. 3.5 Culvert Outlets (HS-22) Culvert outlets in the Denver area represent a persistent problem because of concentrated discharges and turbulence that are not fully controlled prior to the flow reaching the standard downstream channel configuration. Too often the designer's efforts are focused on the culvert inlet and the culvert sizing with the outlet hydraulics receiving only passing attention. A culvert design is not complete until adequate attention is paid to the outlet hydraulics and proper stilling of the design flow. 06/2001 HS-69 Urban Drainage & Flood Control District HYDRAULIC STRUCTURES DRAINAGE CRITERIA MANUAL (V. 2) When the riprap sizing design parameter indicates conditions that place the design above the Type H riprap line in Figure HS-20, use B18, or larger, grouted boulders. An altemative to a grouted boulder or loose riprap basin is to use the standard USBR Basin Vl, as described in Section 3.2. After the riprap size has been selected, the minimum thickness of the riprap layer, T, in feet, in the basin is set at: T=1.75D50 in which: D50 = the median size of the riprap (see Table HS-9.) TABLE HS-9 Median (i.e., D50) Size of District's Riprap Riprap Type DS0—Median Rock Size inches L 9 M 12 H 18 B18 18 routed (HS-17) 3.4.3.3 Basin Length. The minimum length of the basin, L, in Figure HS-18a, is defined as being the greater of the following lengths: for circular pipe, L = 4D or LL= (D)'/z (V l ll2J) for rectangular pipe, L=4H or L=(H)ii2(V) 2 in which: L = basin length (Figure HS-18a) H = height of rectangular conduit V = design flow velocity at outlet D = diameter of circular conduit tea;. (HS-18) (HS-19) r HS-68 06/2001 Urban Drainage & Flood Control District DRAINAGE CRITERIA MANUAL (V. 2) HYDRAULIC STRUCTURES in which: Finally, A = area of the design flow in the end of the pipe (ftz) V = QIA in which: V = design flow velocity at the pipe outlet (ft/sec) 3.4.3.2 Riprap Size. For the design velocity, use Figure HS-20 to find the size and type of the riprap to use in the scour protection basin downstream of the pipe outlet (i.e., 1318, H, M or L). First, calculate the riprap sizing design parameter, Pd , namely, Pd _ (VZ +gd)u'- (HS-16) in which: V = design flow velocity at pipe outlet (ft/sec) g = acceleration due to gravity = 32.2 ft/seC2 d = design depth of flow at pipe outlet (ft) Photograph HS-12 Upstream and downstream views of a low tailwater basin in Douglas County protecting downstream wetland area. Burying and revegetation of the rock would blend the structure better with the adjacent terrain. 06/2001 HS-67 Urban Drainage & Flood Control District STRUCTURAL BEST MANAGEMENT PRACTICES DRAINAGE CRITERIA MANUAL (V.3) Side Slopes No Steeper than 4:1 Presedimentation Top Stage with Forebay 29%16 Slope Floor Drainage Pije JL JL J - .�H r �OwF/ow a- J JL bankment Side Slope Steeper than 3:1 Embankment Access to Outlet I,\ Outlet w(frash Rack -JL way PLAN NOT TO SCALE Frequent Runoff Pool 10% to 25% of WQCV Inflow presedementation Secondary Berm � Forebay Top of Low .Flow Flow Channel p T wo Dispersing L Size Outlet & . - - - Inlet n t` Drain Forebay / Volume in 45 Minutes Invert of Solid Driving Low Flow Surface Channel Could be Impact Basin, GSB Drop, Concrete Rundown, other Hardened Rundown Water Quality Capture Emergency Spillway Flood volume level (including Level 20% additional volume @ Spillway Crest for sediment storage) (e.g. 100-yr, SPF, PMF, etc.) Spillway Crest Cutoff Collar ? Embankment SECTION NOT TO SCALE S=0.0%± Outlet Works (see detail) DMa> Z Dwo(2' Min) FIGURE EDB-1 Plan and Section of an Extended Detention Basin Sedimentation Facility '9-1-99 Urban Urban Drainage and Flood Control District S-41 DRAINAGE CRITERIA MANUAL (V.3) STRUCTURAL BEST MANAGEMENT PRACTICES 10 A 3 2. 1.1 0.6( U fL7 a) UAC E aD cII 0.2( U a m C7 0.1 C M: 0.04 0.02 v EXAMPLE: DWQ = 4.5 ft WQCV = 2.1 acre-feet SOLUTION: Required Area per Row = 1.75 in? TEQUATION: WQCV a= K 40 . . 1 in which, K.40=0.013DWQ +0.22DWQ -0.10 I `pS� `ate � oeQra rL� Q�r O� J� c�F IF-T 0.01 0.02 �•�� �•VU U. iU U.zU UAU U.bU 1.0 2.0 4.0 6.0 Required Area per Row,a (in.2 ) FIGURE EDB-3 Water Quality Outlet Sizing: Dry Extended Detention Basin With a 40-Hour Drain Time of the Capture Volume ' Urban D Urban Drainage and Flood Control District S-43 DRAINAGE CRITERIA. MANUAL (V. 3) STRUCTURAL BEST MANAGEMENT PRACTICES. 0.50 0.45 0.40 70.35 01.30 d L 0.25 m 3 0.20 3 0.15 0.10 0.05 0.00 WOCV=a'10.91 i 3 -1.19i 2 +0. 6-hr drain time a = 0.7 12-hr drain time a = 0.8 24-hr_drain time a = 0.9 Extended Detention Basin & Sand Filter Basin 40-hour Drain Time Constructed Wetland Basin 24-hour Drain Time Retention Pond, Porous Pavement Detention and Porous Landscape Detention 12-hour Drain Time 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Total Imperviousness Ratio (i = I a1100) FIGURE SFB-2 Water Quality Capture Volume (WQCV), 80`h Percentile Runoff Event ' 9-1-99 S-51 Urban Drainage and Flood Control District STRUCTURAL BEST MANAGEMENT PRACTICES DRAINAGE CRITERIA MANUAL (V. 3) ' 7.3.3 Pollutant Removal. Although not fully tested to date in the Denver area, the tests on filter vaults in the Denver area and other parts of United States show that the amount of pollutant removed by this $,MP should be significant and should at least equal the removal rates by sand filters tested elsewhere. See Table SQ-6 for estimated ranges in pollutant removals. �J 7.3.4 Maintenance Needs. Before selecting this BMP, be sure that the maintenance specified in the Maintenance"chapter of the Manual will be provided by either a local government or by the owner. This BMP's performance is critical on having regular maintenance provided. 7.4 Design Procedure and Criteria The following steps outline the design procedure and criteria for an SFB. 1. Basin Storage Volume Provide a storage volume equal to 100 percent of the WQCV- based on a 40-hour drain time, above the sand bed of the basin. A. Determine the WQCV tributary catchment percent imperviousness. ' Account for the effects of DCIA, if any, on Effective Imperviousness. Using Figure ND-1, determine the reduction in impervious area to ' use with WQCV calculations. B. Find the required storage volume (watershed inches of runoff): Determine the Required WQCV (watershed inches of runoff) using ' Figure"SFB-2, based on the SFB§ 40-hour drain time. C. Calculate the Design Volume in acre-feet as follows: r Design Volume = (WQCV)* Area 12 In which: Area = The watershed area tributary to the extended detention pond (acres) 2. Basin Depth Maximum Design Volume depth shall be 3 feet. 3. Filte6 Surface Area Calculate the minimum sand filter area (A,) at the basin bottom with the following equation: A, = Design Volume /3 *43,560 (square feet) 4. Outlet Works An 18 inch layer of sand (ASTM C-33) over a 9 inch gravel layer (AASHTO No. 8; CDOT Section 703, #8) shall line the entire SFB for purpdses of draining the WQCV. If expansive soils are a concern or if the tributary catchment has chemical or petroleum products handled or stored, install an impermeable membrane below the gravel layer. In addition, an overflow shall be provided to convey Flows in excess of the WQCV out of the basin. �1 S-48 9-1-99 1 Urban Drainage and Flood Control District City of Fort Collins Rainfall Intensity -Duration -Frequency Table for using the Rational Method (31 minutes - 60 minutes) Figure 3-1b Duration (minutes) 2-year Intensity in/hr 10-year Intensity in/hr 100-year Intensity in/hr 31.00 1.27 2.16 4.42 32.00 1.24 2.12 4.33 33.00 1.22 2.08 4.24 34.00 1.19 2.04 4.16 35.00 1.17 2.00 -- 4.08 36.00 1.15 1.96 4.01 37.00 1.13 1.93 3.93 38.00 1.11 1.89 3.87 39.00 1.09 1.86 3.80 40.00 1.07 1.83 3.74 41.00 1.05 1.80 3.68 42.00 1.04 1.77 3.62 43.00 1.02 1.74 3.56 44.00 1.01 1.72 3.51 45.00 0.99 1.69 3.46 46.00 0.98 1.67 3.41 47.00 0.96 1.64 3.36 48.00 0.95 1.62 3.31 49.00 0.94 1.60 3.27 50.00 0.92 1.58 3.23 51.00 0.91 1.56 3.18 52.00 0.90 1.54 3.14 53.00 0.89 1.52 3.10 54.00 0.88 1.50 3.07 55.00 0.87 1.48 3.03 56.00 0.86 1.47 2.99 57.00 0.85 1.45 2-96 58.00 0.84 1.43 2.92 59.00 0.83 1.42 2.89 60.00 0.82 1.40 2.86 1 1� City of Fort Collins Rainfall Intensity -Duration -Frequency Table for using the Rational Method (5 minutes - 30 minutes) Figure 3-1a Duration (minutes) 2-year Intensity in/hr 10-year Intensity in/hr 100-year Intensity in/hr 5.00 2.85 4.87 9.95 6.00 2.67 4.56 9.31 7.00 2.52 4.31 8.80 8.00 2.40 4.10 8.38 9.00 2.30 3.93. -.8.03 10.00 2.21 3.78 7.72 11.00 2.13 3.63 7.42 12.00 2.05 3.50 7.16 13.00 1.98 3.39 6.92 14.00 1.92 3.29 6.71 15.00 1.87 3.19 6.52 16.00 1.81 3.08 6.30 17.00 1.75 2.99 6.10 18.00 1.70 2.90 5.92 19.00 1.65 2.82 5.75 20.00 1.61 2.74 5.60 21.00 1.56 2.67 5.46 22.00 1.53 2.61 5.32 23.00 1.49 2.55 5.20 24.00 1.46 2.49 5.09 25.00 1.43 2.44 4.98 26.00 1.40 2.39 4.87 27.00 1.37 2.34 4.78 28.00 1.34 2.29 4.69 29.00 1.32 2.25 4.60 30.00 1.30 2.21 4.52 M No Text APPENDIX E FIGURES AND TABLES E I WILLOW STREET LOFTS Emergency Overflow Spillway Sizing LOCATION: WILLOW STREET LOFTS PROTECT NO: 173-04 COMPUTATIONS BY: TDS SUBMITTED BY: NORTH STAR DESIGN, Inc. DATE: 6/29/04 Equation for flow over weir Q = CLH3 z where C = weir coefficient = H = overflow height L = length of the weir tolD of berm v b 3.1 4 + Spill elevation 0 100 yr WSEL Spillways will be designed with 0.50 ft flow depth, thus H = 0.55 ft Size the spillway assuming that the pond outlet is completely clogged. Water Quality Pond Q (100) = 25.00 cfs Spill elev = 4959.52 ft Min top of berm elev.= 4960.07 ft Weir length required: L = 19.77 ft Use L = 20.0 ft v = 1.92 ft/s 100 yr WSEL = 4959.52 ft Orifice Plate Perforation Sizing Circular Perforation Sizing Chart may be applied to orifice plate or vertical pipe outlet. Hole Dia (in) • Hole Dia (in) Min. Sc (in) Area per Row (sq in) n=1 n=2 n=3 1 4 0.250 1 0.05 0.10 0.15 5 16 0.313 2 0.05 0.15 0.23 3 8 0.375 2 0.11 0.22 0.33 0.438 2 0.15 0.30 0.45 2 0.39 0.59 0.25 0.50 0.75 3 0.31 M 0.37 0.74 1.11 E 3 0.44 0.88 1.33 3 0.52 .1.04 1.56 3 0.60 1.20 1.80 3 0.69 1.38 2.07 1 1.000 4 0.79 1.57 1 2.36 1 1 16 1.063 4 0.89 1.77 2.66 1 1 8 1.125 4 0.99 1.99 2.98 1 3 16 1.188 4 1.11 2.22 3.32 1 1 4 1.250 4 1.23 2.45 3.68 1 5 16 1.313 4 1.35 2.71 4.06 1 3 8 1.375 4 1.48 2.97 4.45 1 7 16 1.438 4 1.62 3.25 - 4.87 1 1 2 1.500 4 1.77 3.53 5.30 1 9 16 1.563 4 1.92 3.83 5.75 1 5 8 1.625 4 2.07 4.15 6.22 1 11 16 1.688 4 2.24 4.47 5.71 1 3 4 1.750 4 2.41 4.81 7.22 1 13 16 1.813 4 2.58 5.16 7.74 1 7 8 1.875 4 2.76 5.52 8.28 1 15 16 1.938 4 2.95 5.90 8.84 2 2000. 4 3.14 6.28 9.42 n = Number of columns of perforations Minimum steel plate thickness 1/4 ' 5/16 3/8 ' -• Designer may interpolate to the nearest 32nd inch to better match the required area, if desired. Rectangular Perforation Sizing Only one column of rectangular perforations allowed Rectangular Height = 2 inches Rectangular Width (inches) = Required Area per Row (sq in) 2" Urban Drainage and Flood Control District Drainage Criteria Manual (V.3) Fac DetaY&dwy (BSc. Rectangular Hole Width Min. Steel Thickness 5" 1 4 6" 1 4 7" 5/32 " 8" 5/16 „ 9" 11/32 " 10" 3/8 >1On 1/2 Figure 5 WQCV Outlet Orifice Perforation Sizing LOCATION: PROJECT NO: COMPUTATIONS BY SUBMITTED BY: DATE: Proposed Detention - Stage/Storage Willow Street Lofts 173-04 TDS North Star Design 5/26/04 V = 1/3 d ( A + B + sgrt(A'B)) where V = volume between contours, fts d = depth between contours, ft A = surface area of contour WATER QUALITY POND Required Water Quality = 0.064 acre-feet Stage (ft) Surface Area (ft`) Incremental Storage (ac-ft) Total Storage (ac-ft) 4958.18 0 0.00 0.00 4959.00 3180 0.02 0.020 4959.52 4151 0.04 0.064 4959.68 4450 0.02 0.079 NQ Elevation LOCATION: Willow Street Lofts ITEM: Water Quality Pond Outlet Sizing COMPUTATIONS BY: TDS SUBMITTED BY: North Star Design, Inc DATE: 6/l/04 From Urban Storm Drainage Criteria Manual, June 2001 (Referenced figures are attached in Appendix D) Use 40-hour brim -full volume drain time for extended detention basin Water Quality Capture Volume = WQCV = (required storage/12)'(tributary drainage area) MAJOR BASIN Trib. area (ac) % Imperv. Req. Storage (in. of runoff) from Fig. SQ-2(ac-ft) WQCV Dwo (ft) req. voi WQCV •1.2 (ac-ft) req. area/row (in'/row) from Fig. EDB-3 POND #1 1.60 90.0 0.40 0.054 1.34 0.064 0.29 Requlrea amrage = 1 - t u.`J I - rj - l .l `J - 1'2 + u. tts - I / WQ outlet sizing for pond 1 From Figure 5, for 5/8 in. hole diameter Area of hole = 0.29 in # of columns = 1 Area provided/row = 0.29 in Area Required/row = 0.29 in Use 1 column of 518" diam holes kQ4 ConlT��b�TiN� T a jFo"—' a-.c L.Jt l(�w S izee I Lo F"TS I 6/1/04 ' WQVOL.xls I APPENDIX D WATER QUALITY CALCULATIONS 1 1' 1 11 1" 1 6/2/04 Riprap Calculations for Circular Pipe Outlets LOCATION: Willow Street Lofts PROJECT NO: 173-04 COMPUTATIONS BY: TDS SUBMITTED BY: North Star Design DATE: 6/2/04 From Urban Strom Drainage Criteria Manual volume 2, June 2001 (Referenced figures are attached at the end of this section) Q = discharge, cfs D = diameter of circular conduit, ft d = tailwater depth, ft Pd= riprap sizing design parameter V = design flow velocity at pipe outlet, ft/s g = accelleration due to gravity 32.2 ft/secz Storm 1 15" RCP (x2) Q = 6.91 cfs D = 15 in = 1.25 ft d = 0.89 ft From StormCad Model V = 4.1 ft/s From StormCad Model Pd = (V 2 + g*d) 5 = 6.7 (From Figure HS-20, use Type L riprap) Riprap Depth: From Table HS-9, D50 = 9 in From Equation HS-17. Riprap depth = 1.75 * D50 = 16 in Basin Depth: From Equation HS-18a. Basin depth = 0.5 * D = 8 in Basin Length: From Equation HS-18, L = 4 * D = 5.0 ft From Equation HS-19, L = D 5 * V/2 = 2.3 ft Basin Width: From Equation HS-20, W = 4 * D = 5.0 ft Depth of Cutoff Wall: From Equation HS-22, B = D/2 + 1.75 * Dso = 1.9 ft USE: 10' W x 5' L x 16" Type L Riprap w/ 8" Basin Depth & 10'x 1.9' Cutoff wall Riprap.xls Page 1 Label: MH-3 Rim: 4,964.44 ft Sump: 4,960.10 ft Profile Scenario: Base O IZ Label: INLET 2 Rim: 4,963.50 ft . Sump: 4,961.00 ft Label: MH-5 Ri m: 4,964.21 ft Sump: 4,960.83 ft i i i i i I 3+50 3+60 3+70 +80 3+90 4+00 Station (ft) Label: P-6 Up. Invert 4,960.83 ft Dn. Invert 4,960.10 ft L: 50.60 ft Size: 15 inch S: 1.44 % 41964.50 4,964.00 4,963.50 4,963.00 4,962.50 Elevation (ft) 4,962.00 4,961.50 4,961.00 4,960.50 4,960.00 4+10 4+20 Label: P-7 Up. Invert 4,961.00 ft Dn. Invert 4,960.83 ft L: 11.50 ft Size: 15 inch S: 1.48 % I o e-.tV\ Z Title: Willow Street Lofts - Project Engineer: North Star Design n:\173-04 willow street\drainage\storm 1.stm North Star Design, Inc. StormCAD v4.1.1 [4.2014] 06/02/04 08:06:11 AM © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 1 Page 1 of 1 Label:0-1 Label: MH-1 Rim: 4,961.00 It Rim:4 961 35 It Sump: 4,958.76ft Su mp:4,9 Wil 8It Profile l�O Scenario: Base Label: MH-2 Rim: 4,965.28 It Sump: 4 959.58 It Label: MH-3 Label: MH-4 Label: IN LET-1 Rim: 4.964.44 It Rim: 4.964.00 it Rim: 4,963.25 ft ' Su mp: 4,960.10It Su mp: 4.960,221 Su mp: 4,960.5Oft -----------; 4.966.00 I � I , I I I , I 4,965.00 4,964,00 496300 0eva bon (it) 4,962.00 4,961 .00 4,96000 4,959.00 0+00 0+50 1+00 1+50 2+00 2+50 3+00 3+50 4,958.00 4+00 4+50 5+00 Stalion (ft) Label: Invert Up. Invert 4 958.76 It Label: Label: Label: P-4 Label: P-5 4,958.76 ft Up. Invert 4.958.88 ft Invert Invert Up. Invert 4,960.10 ft Up. Invert 4,960.22 ft Up. Invert 4.960.50 ft L 3Invert Invert 4,958.88 ft On. Invert 4,959.58 ft On. Invert 4,960.10 ft On. Invert 4 960.22 ft S: ze: S e -15 i inch L: Size: 15 i ft Size: 15 inch L: 18 i ft Sze: 18 inch - S e: 18 i Size: 18 inch S e: 18 ft Size: 18 inch 4 S: 0.34 % S: 0.38 % : S: 0.38 % S: 0.36 % S: 0.38 % 1 o RJA Title: Willow Street Lofts Project Engineer: North Star Design n:\173-04 willow street\drainage\storm 1.stnn North Star Design, Inc. StornnCAD v4.1.1 [4.2014] 06/02/04 08:05:20 AM I © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Page 1 of 1 Scenario: Base pp,j 2 Pipe\Node Report Label Number of Sections Section Size Length (ft) Slope (%) System Flow (cfs) I Full Capacity (cfs) Average Velocity (ft/s) Upstream Invert (ft) Upstream Crown (ft) Upstream HGL (ft) Downstream Invert (ft) Downstream Crown (ft) Downstream HGL (ft) P-1 2 15 inch 35.20 0.34 6.91 7.54 4.07 4,958.88 4,660.13 4,959.77 4,958.76 4,960.01 4,959.52 P-2 2 15 inch 184.60 0.38 6.91 7.96 3.47 4,959.58 4,960.83 4,960.48 4,958.88 4,960.13 4,959.87 P-3 1 18 inch 136.00 0.38 6.91 6.49 4.86 4,960.10 4.961.60 4.961.38 4,959.58 4,961.08 4.960.60 P-4 1 18 inch 33.80 0.36 6.04 6.26 3.51 4,960.22 4,961.72 4,961.61 4,960.10 4,961.60 4,961.52 P-5 1 18 inch 73.20 0.38 6.04 6.50 3.46 4,960.50 4,962.00 4,961.92 4,960.22 4,961.72 4,961.71 P-6 1 15 inch 50.60 1.44 0.87 7.76 0.98 4,960.83 4,962.08 4,961.52 4,960.10 4,961.35 4,961.52 P-7 1115 inch 1 11.501 1.481 0.871 7.851 1.541 4,961.001 4.962.251 4,961.511 4,960.831 4,962.081 4,961.53 Title: Willow Street Lofts - Project Engineer: North Star Design n:\173-04 willow street\drainage\storm 1.stm North Star Design, Inc. StormCAD v4.1.1 [4.20141 06/02/04 08:06:36 AM O Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Page 1 of 1 Title: Willow Street Lofts n:\173-04 willow street\drainage\storm 1.stm 06/02/04 08:04:10 AM Scenario: Base Project Engineer: North Star Design North Star Design, Inc. StormCAD v4.1.1 (4.2014] ©Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1.203-755-1666 Page 1 of 1 �fffe} Length of a Unit Inlet - L. 3 00•ft Local Depression, if any (not part of upstream Composite Gutter) aid = 2.00 inches Number of Unit Inlets No = 1' ' r' Grate Information Width of a Unit Grate W. 2.00 It Area Opening Ratio for a Grate (typical values 0.60-0.90) A - 6.36 Clogging Factor for a Single Grate (typical value 0.50) Co (G) = 0 50- . _ Grate Orifice Coefficient (typical value 0.67) Ca (G) = 0 67_ - Grate Weir Coefficient (typical value 3.00) C (G) ;3 00+ Curb Opening Information Height of Curb Opening in Inches H = 6.00=::inches '. ogle of Throat (see USDCM Figure ST-5) Side Width for Depression Pan Theta 64 3:degrees Wp 3.00,ft �N - OD Clogging Factor fora Single Curb Opening (typical value 0.10) - Co (C) 0.15 1 ` '. Curb Opening Orifice Coefficient (typical value 0.67) Curb Opening Weir Coefficient 2.30-3,00) Ce (C) ', 0.67 = �J,E (typical value C„. (C) 2.30. Grate Inlet Capacity in a Sum Calculated - - Design Discharge on the Street (from Street Hy) Q. - - 0.9'cts i Water Depth for Design Condition - Total Length of Combination Inlet Ya ' - 4.8_ inches L = 3 00.ft As a Weir Capacity as a Weir without Clogging ' Clogging Coefficient for Multiple Units - Clogging Factor for Multiple Units Coef '`" 4'00` Clog 0[ Capacity as a Weir with Clogging Q„„ " ;4:21 cfs - As an Orifice - - Capacity as an Orifice without Clogging Capacity as an Orifice with Clogging - - q <,7 4; cfs - C. i 3 7 cfs Grate Caoacitv for Design with Cloggingcfs Curb Opening Inlet Capacity in a Sum As a Weir Capacity as a Weir without Clogging QM -5.0'. cfs - Clogging Coefficient for Multiple Units Coef `.1'00, ' Clogging Factor for Multiple Units Capacity as a Weirwith Clogging _ Clog ' ° 0.1-5 Q _ _4.7 cfs ' As an Orifice " - Capacity as an Orifice without Clogging Qo ,. 3:4°;cfs - Capacity as an Orifice with Clogging Q, .` 2.9-. cfs Curb Opening Capacity for Design with Clogging Q a - Combination Inlet Capacity with Clogging Q }> 56:8 cfs pe) P � . Capture Percentage for the Combination Inlet /o ? 100.00'=.=.% 6D � (Q Note: Unless additional ponding depth or spilling over the curb is acceptable, a capture percentage of less than 100% in a sump may indicate the need for additional inlet units. ' Inlet 2 - 100yr.xls, Combo-S 4130/04, 2:21 PM '1 Curb rr✓"1 �r Flow Direction 4rlre} ngth of a Unit Inlet L, = 3.00.. It -al Depression, V any (not part of upstream Composite Gutter) a,,,i -.. _.. „2.00- inches mber of Unit Inlets No = ate Information dth of a Unit Grate W° = 2.00.. It a Opening Ratio for a Grate (typical values 0.60-0.90) A = -.- ..-_6.36 - gging Factor for a Single Grate (typical value 0.50) C° (G) _ ate Orifice Coefficient (typical value 0.67) Ca (G) = 0.67 ate Weir Coefficient (typical value 3.00) Cw (G) = 3 OOi. rb Opening Information ight of Curb Opening in Inches H = -. ._ 6.00E inches - gle of Throat (see USDCM Figure ST-5) Theta = 3; _.. 641 ''.. degrees e i or Depression an ft m Factor for a Single Curb Opening ical value 0.10 ) C. C ( ) 0 95'. _ fl A rb Opening Orifice Coefficient lue ) P 9 (typical value 0.67 C C = a - 0.67- `L no Opening Weir Coefficient (typical value 2.30-3.00) C (C) = 2.30- ^ p� ate Inlet Capacity in a Sumo fCalculatedl sign Discharge on the Street (from Street Hy) Q. - cfs iter Depth for Design Condition Ye = - .7.3 inches at Length of Combination Inlet - L 3 001 ft - a Weir pacity as a Weirwithout Clogging Qw-'10i0; cfs gging Coefficient for Multiple Units Coef = _..,...__-_. 1.001 gging Factor for Multiple Units - Clog 0.50`. pacity as a Weir with Clogging cfs an Orifice Dacity as an Orifice without Clogging Q = •; 9 1:'cfs Dacity as an Office with Clogging Q 4 6E cfs rte Capacity for Design with Cloggingcfs As As a Weir - CapacityasaWeirwithoutCloggingcfs Clogging Clogging Coefficient for Multiple Units Coef = 1.00 Clogging Factor for Multiple Units Clog = Capacity as a Weir with Clogging Q„, = - ., 8 F. cfs As an Orifice ' Capacity as an Orifice without Clogging Q° - 5.0'. cfs .Capacity as an Odfice with Clogging Q 4 3ti. cfs A , n Curb Opening Capacity for Design with Clogging Q,.cu,e _.,, ;,z `� 4:3 cfs No Combination Inlet Capacity with Clogging Q ` 1,„ .� g.'g, cfs Capture Percentage forthe Combination Inlet C%,n„t00.0U!%^-��Y/_ 0 T Note: Unless additional ponding depth or spilling over the curb is acceptable, a capture percentage of less than 100% in a sump may indicate the need for additional inlet units. Inlet 1 - 100yr.xls, Combo-S 4/20/04, 10:08 AM Inlet 1 - 100yr.xls, Combo-S 4/20/04, 10:08 AM APPENDIX C HYDRAULIC CALCULATIONS C r� �r rr rr rr r r� r �r rr r� r r� r� r� : �r r■ r �r North Star Design, Inc. 700 Automation Drive, Unit I. Windsor, CO 80550 LOCATION: PROJECT NO: COMPUTATIONS BY DATE: Willow Street Lofts 173-04 TDS 6/29/04 RATIONAL METHOD PEAK RUNOFF (100-YEAR) DIRECT RUNOFF CARRY OVER TOTAL Inlet Capacity REMARKS Desitm Point SUBBASIN DESIGNATION A (ac) Goo TOCioo (min) i (in/hr) Qioo (cfs) from Design Point Q1W (cfs) Quo Total (cfs) (cfs) PROPOSED 1 1 0.61 1.00 5.0 9.95 6.04 6.04 2 2 0.09 1.00 5.0 9.95 0.87 0.87 " 3 3 0.90 1.00 7.0 8.80 7.95 7.95 4 4 1.79 1.00 10.2 7.57 13.54 13.54 3 1-3 1.60 L00 7.0 8.80 14.07 14.07 Peak flow to size waterquality pond 4 1-4 3.39 1.00 12.1 7.14 24.19 24.19 Peak flow to size spillway Q=CiA Q = peak discharge (cfs) C = runoff coefficient i = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) flow.xls 0100 North Star Design, Inc. 700 Automation Drive, Unit I Windsor, CO 80550 RATIONAL METhIOD PEAK RUNOFF (10-YEAR) LOCATION: Willow Street Lofts PROJECT NO: 173-04 COMPUTATIONS BY: TDS DATE: 6/29/04 DIRECT RUNOFF CARRY OVER TOTAL Inlet Capacity REMARKS Design Point SUBBASIN DESIGNATION A (ac) CIO TOC, (min) t (in/hr) Qia (cfs) from Design Point Qia (cfs) Qip Total (cfs) (cfs) PROPOSED 1 1 0.61 0.90 5.0 4.87 2.65 2.65 2 2 0.09 0.95 5.0 4.87 0.41 0.41 3 3 0.90 '0.91 7.6 4.18 3.45 3.45 4 4 1 1.79 0.95 10.8 3.60 6.12 6.12 3 1-3 1.60 0.91 T6 4.18 6.07 6.07 4 1-4 3.39 0.93 12.9 3.40 10.72 10.72 Q = CiA Q = peak discharge (cfs) C = runoff coefficient i = rainfall intensity (in/hr) from IDF curve A = drainage area (acres) 8ow.xls Q10 r� �. � � �, �,_ .� ir. �. ram_ r . ar � � �_ rJ fir_ .�. a�■�_ LOCATION: PROJECT NO: COMPUTATIONS BY DATE: Willow Street Lofts 173-04 TDS 6/29/04 TIME OF CONCENTRATION 100-YEAR SUB -BASIN DATA INITIAL/ OVERLAND TIME W TRAVEL TIME / CIIANNEL FLOW 00 t, CHECK (URBANIZED BASIN) FINAL t, REMARKS DESIGN POINT SUBBASIN DESIGNATION (1) Area (ac) (2) C*Cf (Cf= 1.25) (3) Length (ft) (4) Slope (%) (5) t (min) (6) Length (ft) (7) Slope (%) (8) V (ft/s) (9) t, (min) (10) t, (min) (11) Total L (ft) (12) t� (L / 180)+10 (min) (13) (min) (14) PROPOSED 1 I 0.61 1.00 55 1.0 1.39 195 1.8 2.6 1.23 2.6 250 11.4 5.0 2 2 0.09 1.00 55 1.0 1.39 195 1.8 2.6 1.23 2.6 250 11.4 5.0 3 3 0.90 1.00 20 2.0 0.66 540 0.5 1.4 6.36 7.0 560 13.1 7.0 4 4 1.79 1.00 50 2.0 1.05 780 0.5 1.4 1 9.19 10.2 830 14.6 10.2 3 1-3 1.60 1.00 20 2.0 0.66 540 0.5 1.4 6.36 7.0 560 13.1 7.0 4 1-4 3.39 1.00 50 2.0 1.05 940 0.5 1.4 1 L08 12.1 990 15.5 12.1 EQUATIONS: t1=[1.87(1.1-C*Cf)L0.5)/S113 4=L/V where V=C *Sw' final t. = minimum of t; + t, and urbanized basin check (C from Table RO-2) LOCATION: PROJECT NO: COMPUTATIONS BY: DATE: Willow Street Lofts 173-04 TDS 6/29/04 TIME OF CONCENTRATION 10-YEAR SUB -BASIN DATA INITIAL / OVERLAND TIME (tJ TRAVEL TIME / CHANNEL FLOW (y) t. CHECK (URBANIZED BASIN) FINAL t� REMARKS DESIGN POINT SUBBASIN DESIGNATION (1) Area (ac) . (2) C*Cf (Cf= 1.0) (3) Length (ft) (4) Slope (%) (5) ti (min) (6) Length (tl) (7) Slope (%) (8) V (ft/s) (9) t, (min) (10) t° (min) (11) Total L (ft) (12) t� (L / 180)+10 (min) (13) (min) (14) PROPOSED 1 1 0.61 0.90 55 1.0 2.84 195 1.8 2.6 1.23 4.1 250 11.4 5.0 2 2 0.09 0.95 55 1.0 2.08 195 1.8 2.6 1.23 3.3. 250 11.4 5.0 3 3 0.90 0.91 20 2.0 1.24 540 0.5 1.4 6.36 7.6 560 13.1 7.6 4 4 1.79 0.95 50 2.0 1.57 780 0.5 1.4 9.19 10.8 830 14.6 10.8 3 1-3 1.60 0.91 20 2.0 1.27 540 0.5 1.4 6.36 7.6 560 13.1 7.6 4 1-4 3.39 0.93 50 2.0 1.78 940 0.5 1.4 11.08 IA 990 15.5 12.9 EQUATIONS: t° = ti + tt ti=(1.87(1.1-C*Cf)L05)/Sln i,=L/V where V=C *Sw5 final t, = minimum of t; + 4 and urbanized basin check (C,,from Table RO-2) M- NAM Des-.. M.. -_ M, M_ M M. W.: M M_ oft M 700 Automation Drive, Unit I - - Windsor, CO 80550 LOCATION: PROJECT NO: COMPUTATIONS BY: DATE: Willow Street Lofts 173-04 TDS 6/29/04 RUNOFF COEFFICIENTS & % IMPERVIOUS Recommended % Impervious from Urban Storm Drainage Criteria Manual Streets, parking lots (asphalt) Sidewalks (concrete) Roofs Lawns (Average 2-7%, heavy soil) Runoff % coefficient Impervious C 0.95 100 0.95 90 0.95 90 0.25 0 SUBBASIN DESIGNATION TOTAL AREA (ac.). TOTAL AREA (sq-ft) ROOF AREA (sq.ft) PAVED AREA (sq.ft) CONCRETE AREA (sq.11) LANDSCAPE AREA (sq.11) % Impervious RUNOFF COEFF. (CIO) RUNOFF COEFF. (CIM) PROPOSED 1 0.61 26,445 0 24,385 0 2,060 92 0.90 1.00 2 0.09 3,830 1 0 3,830 0 0 100 0.95 1.00 3 0.90 39,375 0 37,304 0 2,071 95 0.91 1.00 4 1.79 77,900 0 77,900 0 0 100 0.95 1.00 1-3 1.60 69650.00 0.00 65519.00 0.00 4131.00 94 0.91 1.00 1-4 3.39 147550.00 0.00 143419.00 0.00 4131.00 - 97 0.93 1.00 8ow.xls Cval I I APPENDIX B HYDROLOGIC COMPUTATIONS B ' m YOFY�E iC17' FOR T C- L.'OL NS i torn ater Bass 7 _LY.a . ry pack s asi CL Lr ry Old �(] u5J. 1-woo ikky Vine Sa�sCn 011 - 4�% �p a , IQ Lj BEL Foothiff; Basin. i1 �. 't'o 11 hFid {ra r 1 C McGT;d'Esnd$ Mail.. R . { i3 1 i k I YJ Tr1 4• F: d: I � i+ i I r I 1 J I I n i LJ 0 MUL ERRY R. O 0 SMT►1��7� J I �JJI 6^ L CR. BUCKINGHAM AVE. i F- LINCOLN A soG� 0 IVE ET� ED'L us WY. 1 LJ LAUPEL S _ VICINITY MAP PPROXIMATE SCALE: 1 = 500' SHEET 1 OF 1 DATE: 06/01 /04 %North Star SCALE: 1" = 500't WILLOW STREET LOFTS "��. design, inc. DRAWN BY: TDS VICINITY MAP 700 Automation Drive, Unit I Windsor, Colorado 80550 Phone: 970-68"939 JOB NO.: 173-04 Fax:970-686-1188 APPENDIX A VICINITY MAP A 1 7. REFERENC ES 1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March 1999. 2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria Manual", Volumes 1 and 2, dated June 2001, and Volume 3 dated September 2001. 1' i E It i r 1 5.2. Specific Details To limit the amount of silt leaving the site several erosion control measures shall be 1� implemented during construction. Inlets and the water quality structure shall be protected with gravel filters, straw bales will be used where appropriate, and the north and east ' boundaries of the site along with the north, east and south boundary of the proposed water quality pond shall have silt fence installed. Construction entrances shall be installed at the connection to Willow Street and Pine Street to control the mud being tracked onto the existing pavement. During overlot grading, disturbed areas are to be kept in a roughened condition and watered to reduce wind erosion. 6. CONCLUSIONS 6.1. Compliance with Standards All computations 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. No variances are required for the project. 6.2. Drainage Concept The proposed drainage concepts presented in this report, and on the construction plans, adequately provide for stormwater quality treatment of the proposed site. Conveyance elements have been designed to convey required flows to the proposed water quality pond to minimize future maintenance. i If, at the time of construction, groundwater is encountered, a Colorado Department of Health Construction Dewatering Permit will be required. i If at the time of construction, the clay cap on the old landfill is disturbed, the City of Fort Collins, the design engineer and all other applicable authorities shall be notified for a solution to correcting the damaged clay liner and maintaining acceptable drainage paths. i 1 5 t- r� 4.2. Specific Flow Routing 1 A summary of the drainage patterns within each basin is provided in the following paragraphs. L Basin 1 consists of portions of proposed and existing buildings, associated parking and landscaping. Stormwater runoff flows to Inlet 1 located at a low point situated in the curb ! & gutter near the center of the parking area. Runoff is conveyed to the water quality pond 1 by Storm 1. Basin 2 consists of portions of proposed & existing buildings, associated parking and landscaping. Stormwater runoff flows to Inlet 2 located at a low point situated in the curb & gutter at the corner of the parking area. Runoff is conveyed to the water quality pond by Storm 2. ly Basin 3 consists of portions of proposed & existing buildings, associated parking and landscaping. Stormwater runoff sheet flows in the existing United Way parking lot to the �i proposed water quality pond. 4.3. Drainage Summary 1 The water quality drainage facilities and all storm pipes which convey water to the water quality pond located outside of the right-of-way (north of the United Way building) will be maintained by the homeowners association (HOA) for Willow Street Lofts. 5. EROSION CONTROL �E 5.1. General Concept This site lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort Collins. A potential exists for tracking of mud onto existing streets that could then wash t into existing storm sewers. Erosion control (BMP's) has been used to mitigate this potential for sediment transport offsite. These measures include the use of silt fence, straw bales where applicable, inlet protection and construction entrances. Due to the { shallow clay barrier on the old landfill, over excavation of the water quality pond is not being proposed. i 9 3.3. Hydrologic Criteria Runoff computations are prepared for the 10-year minor and 100-year major storm frequency utilizing the Rational Method. All hydrologic calculations associated with the basins are included in Appendix B of this report. Water quality volume is calculated using the method recommended in the "Urban Storm Drainage Criteria Manual". Water quality calculations are included in Appendix D of this report. 3.4. Hydraulic Criteria All hydraulic calculations within this report have been prepared in accordance with the City of Fort Collins Drainage Criteria and are included in Appendix C of this report. No existing storm sewer exists on this site. The proposed storm sewers are designed to convey the 100yr storm event to the water quality pond with no ponding at the inlets. An overflow location has been provided in the entry drive in the event inlet 1 becomes clogged or a greater than a 100yr storm event occurs. DRAINAGE FACILITY DESIGN 4.1. General Concept During a 100yr storm event, runoff will flow to two inlets located at low points and will be conveyed by storm sewer to the proposed water quality pond. The proposed water quality pond is located to the north of the existing United Way building. In the event the inlet in basin 1 becomes clogged or a greater than a 100yr storm occurs, an overflow path is provided: This overflow path is located on the access. road from Pine Street to this development. The overflow runoff will flow south to Pine Street, then east to the existing low point in the existing United Way parking lot.. From here, the flow will enter the proposed water quality pond. Once the proposed water quality pond reaches capacity storm water will overtop the water quality structure and spill into the existing drainage swale. Runoff from this existing drainage swale will discharge into the Poudre River. The proposed water quality pond has been sized to treat stormwater for this development along with the adjacent portions of the existing Willow Street and the existing Pine Street. Historic flow paths have been maintained to the greatest extent possible. 3 2. 3 quality pond but id designed to flow over the spillway and not be treated in the water quality pond. DRAINAGE BASINS AND SUB -BASINS 2.1. Major Basin Description The proposed development lies within the Poudre River Drainage Basin. There is no City of Fort Collins master plan for the Poudre River Drainage Basin and detention is not required for this basin. However, releases from this site must not negatively impact downstream drainage facilities and adequate conveyance to a major drainage outfall must be maintained. 2.2. Sub -basin Description This site drains by storm sewer. pipes to a proposed water quality pond and then to the existing drainage swale. There are two drainage sub -basins for the proposed site. The sub -basins consist of buildings, associated parking and landscaping. Stormwater runoff flows to inlets located at low points situated in the curb & gutter. Runoff is conveyed to the water quality pond and then released into the existing drainage Swale which discharges flow into the Poudre River. DRAINAGE DESIGN CRITERIA 3.1. Regulations This report was prepared to meet or exceed the "City of Fort Collins Storm Drainage Design Criteria Manual' specifications. Where applicable, the criteria established in the "Urban Storm Drainage Criteria Manual" (UDFCD), 2001 has been used. 3.2. Development Criteria Reference and Constraints The runoff from this site has been routed to conform to the requirements of the City Stormwater Department. Detention is not required for this site. Water quality facilities are required for the site and will be provided off -site. 2 1. GENERAL LOCATION AND DESCRIPTION 1.1. Location Willow Street Lofts is located in northeast Fort Collins. This project is located in the Northwest Quarter of Section 12, Township 7 North, Range 69 West of the Sixth Principal Meridian, in the City of Fort Collins, County of Larimer, State of Colorado. See the location map in Appendix A. The project is bounded to the north by the Aztlan Community Center, to the east by the United Way building and parking lot, to the south by an existing building and Pine Street, and on the west by Willow Street. This site is located on an old landfill site. 1.2. Description of Property The project consists of approximately 1.0 acre of land. The proposed development will consist of 3 buildings which will contain 19 residential units and 2 commercial units along with associated drives, walks and landscape areas. Access to this development is gained from Willow Street and Pine Street. Storm water detention is not required, however water quality through an extended detention method is required. It is proposed to provide a water quality pond north east of this site on the United Way property. The location of the water quality pond is over the old landfill, which is capped by a clay liner. The water quality pond elevations are such as to prevent compromising the clay cap. In the event the clay cap is disturbed, the City of Fort Collins, the design engineer and all other applicable authorities shall be notified for a solution to correcting the damaged clay liner and maintaining the designed drainage path. Existing vegetation consists mainly of native grasses and small trees. The land currently slopes to the east at approximately 1%. There is an existing drainage swale located to the east of the site, which will be used to release storm water runoff. The drainage ditch eventually discharges storm water into the Cache La Poudre River (Poudre River). The proposed location of the water quality pond is on the north side of the existing United Way building. With this development, storm pipes will be installed to convey runoff from the development to the water quality pond. The proposed water quality pond will treat storm water for the proposed development, and the adjacent portions of Willow Street and Pine Street. Runoff from the United Way parking lot also drains into the water 1 I TABLE OF CONTENTS TABLEOF CONTENTS............................................................................................................... iii _ 1. GENERAL LOCATION AND DESCRIPTION_ 1.1 Location .................. I 1.2 Description of Property.............................................................................................I 2. DRAINAGE BASINS AND SUB -BASINS 2.1 Major Basin Description..........................................................................................2 i 2.2 Sub -Basin Description.............................................................................................2 3. DRAINAGE DESIGN CRITERIA 3.1 Regulations..............................................................................................................2 ? 3.2 Development Criteria Reference and Constraints....................................................2 3.3 Hydrologic Criteria...................................................................................................3 i 3.4 Hydraulic Criteria............................:.......................................................................3 4. DRAINAGE FACILITY DESIGN 4.1 General Concept.......................................................................................................3 4.2 Specific Flow Routing.......................:.....................................................................4 4.3 Drainage Summary ...................................................................................................4 5. EROSION CONTROL 5.1 General Concept......................................................................................................4 5.2 Specific Details ........................................................................................................5 6. CONCLUSIONS 6.1 Compliance with Standards....................................................................................5 6.2 Drainage Concept.....................................................................................................5 • 7. REFERENCES ...................................... .............................................................................. 6 APPENDICES A Vicinity Map B Hydrologic Computations C Hydraulic Calculations D Water Quality Calculations ' E Figures and Tables i iii I North Star design, inc. June 30, 2004 Basil Hamdan City of Fort Collins Stormwater 700 Wood Street Fort Collins, CO 80522-0580 RE: Final Drainage and Erosion Control Report for Willow Street Lofts Dear Basil, I am pleased to submit for your review and approval, this Final Drainage & Erosion Control Report for Willow Street Lofts. I certify that this report for the drainage design of Willow Street Lofts was prepared in accordance with the criteria in the City of Fort Collins Storm Drainage Manual. I appreciate your time and consideration in reviewing this submittal. Please call if you have any questions. Prepar d by: Troy Spraker, EIT Reviewed By: Patricia Kroetch, PE 700 Automation Drive, Unit I Windsor, Colorado 80550 ' 970-686-6939 Phone . 970-686-1 1 88 Fax FINAL DRAINAGE AND EROSION CONTROL REPORT WILLOW STREET LOFTS Prepared for: Lagunitas Company 3944 JFK Parkway Fort Collins, CO 80525 Prepared by: North Star Design 700 Automation Drive, Unit I Windsor, Colorado 80550 (970)686-6939 June 30, 2004 Job Number 173-04