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HomeMy WebLinkAbout14 - Design Report - Lot 7 Valley Commons Business Park - Water, Sewer, Storm ENGINEERING DESIGN REPOJ�ECEtV LOT 7 VALLEY COMMONS BUSINESS PARK BOZEMAN, MONTANA - - �-- City of Bozeman Montana VALLEY COMMONS —=d U' PARK LOT'] I '- VALLCY COMMONS RIVE U -CONCEPT MASTER PLAN- _ Prepared By:PC Associates,LLC Updated:6-7-2014 BDaDa:G 3 BDILam I_ .1 PAD A. y PAO B, I DESIGN NOTES: """"" I._1. ` SO%76'1•rl - - 1 �'%T4'(•.) BACKGAOUNU(E%1917NG) _-_.. l 46165E 1•rl _— — I st SF I•r1 I -1[1F 7-(.92AC.(a.2C AC.Oo),tii'ACFJ.I.6N AC_NFT d -A -DIIIIDIN(:H.Y51:11)XI AREA-26,Seo SQ.Fr. _ I__ _ __ I -MAS'rER1'IANPARIUNG-74(..)SPACFS — ..� ] 1 1 F I I .5�. CLV515RED BUDDING ENVELOPES j W/COMMON PARKING -RS PARKINGSPACPS(9 i26'1YP.) Vnu2x 1aw1 1 I *••- 1 A "-� f �'N�WrcP'� .gBUI1DING PAU AREAS(1F aa.xm SQ. ncAwn -PADA 6,om SQ.Pr. Bo'A7d(a:) I YS wniFr I. Ifi�55 -PADB 6.3w SQ.Fr. B3'X76'(•.-)lwi.�nlvumAxSl I Ii '- -i -PADC 4, SQ.FT. Bo7,5R'(i,-) 1 I�{ d $UIIDING f BUILDLNG -PAD D ! ,�i-• PAD C, Q ! PADD, I' I 21,7oo SQ.Fr.(.;) E N/X MI•rl �! B/'X SB 1•A PAAKINO RATIO/SOVAAF FOOTAGE P01F.DTRAI PS PER I.— {,(Ol SF l•rl 4.Ke SF(yl -x1,716 W. FT.BUILDING P(JrRNfNl U.S.HI 1^j •j(HUFFINE INE LANE) Scale In Feet North LAZY E BAR NINE CORPORATION SBL ENTERPRISES, LLP PREPARED BY: 2409 W, MAIN ST., STE. 2 BOZEMAN, MT 59718 P: 406.586,8407 F: 406.586.3745 • INFOQKEFIW1.i IDASSOCIATES.COM KERIU K ASSOCIATES, P.C. 1.0 INTRODUCTION This report addresses the engineering design criteria for the utilities and infrastructure that is scheduled to be installed to serve the four(4) business office buildings that will now be sited on Lot 7 of the Valley Commons Business Park(VCBP). Lot 7 is part of the Valley Commons Business Park Planned Unit Development(PUD)and was originally planned and designed to accommodate a 40-50 room motel within the development. Kerin and Associates, P.C., Consulting Engineers(KA)was retained by the owners of Lot 7 to design and administer the construction service contract for the site's infrastructure improvements. This particular lot,along with the adjacent and contiguous one immediately to the east of it, has sat vacant now for the past 20 years. Several attempts to build the motel for which it was designed were made, but none proved successful. In the past several years a number of new motels have been built in Bozeman, presumably saturating the market for a relatively small one on Bozeman's west end. The property owners now feel their Lot 7 property would be better suited if it build-out with office buildings. So,four(4)such buildings have been designed into this particular lot and are now scheduled to supersede the original planned motel. The major utilities, designed by KA,will be installed to accommodate the water,sanitary sewer and stormwater management needs of these newly configured 4-unit office building complex. The major site improvements discussed in this report are as follows: • Sanitary Sewer(8-inch diameter)Collector Main Extension from Fallon Street • A Looped 8-Inch Diameter Water Distribution Main • Storm Sewer Lateral Extension with Integral Catch Inlet Curb Drains and a small Stormwater Retention Basin • and Other Buried Utilities to Include Buried Natural Gas,Telephone, Electric, Fiber Optic Cable and Cable TV Service Additionally, KA provided with the firm's design services for major utilities a completed "Site Grading and Drainage Plan"that incorporates the integral curb and gutter(City of Bozeman Standard) and "hot mix" asphalt paved drive isles and parking pads,siting these improvements to their finished design grades. The Master Site Plan for the newly re-configured lot is shown on attached Exhibit 1 to this report. The water and sewer demand associated with these four new office structures when compared to the water and sewer demands of the originally planned motel are significantly less;so,the change from a motel to four(4) individual business offices presents a lower demand on the City's water and sewer service to the property. In particular the fire demand for Lot 7 will substantially be lowered because the water demand for individual office buildings that vary in size from 4,600 square feet(sf)to 6,300 sf is substantially less. Fire demand is computed based on the size of the individual buildings, not the cumulative size of all four. Whereas,the fire demand for the original motel would be based on the overall size of the structure. Of course the motel, if constructed,would have been sprinkled, which would lower its fire suppression demand by 50%over a non-sprinkled structure. The following sections of this report address each utility and the associated engineering design criteria for each improvement, including the surface improvements for the integral concrete curbs and paved surfaces. 2.0 SANITARY SEWER COLLECTOR MAIN EXTENSION The existing collector main in the Valley Commons Street right-of-way that fronts on Lot 7 is a standard 8-inch diameter pipeline that was originally installed in 1995 to accommodate Lot 7 (among other lots) when it was planned for a motel. The Valley Commons Street main services, quite adequately,the existing businesses that front along it. This pipe,while being a minimum-sized pipeline, was originally designed to accommodate the wastewater collection needs for all the existing Valley Common businesses, including the motel. The pipeline has successfully service the needs of the VCBP for the past 20 years. The land use change for Lot 7,from a motel to four office buildings, means less wastewater flow from Lot 7 into the Valley Unit sanitary sewerage collection system. The 8-inch diameter sanitary sewer lateral pipe that will be laid will connect directly to the existing Fallon Street collector main is shown on Exhibit 2—Lot 7 Utility Site Plan. Each office will at most accommodate up to 20 employees. Each employee in turn will generate approximately 15 gallons-per-day(gpd)on the average per person (gpdpp); so, approximately 300 gpd will be generated from each building over the course of the business day(say, 10-hour period from 7:30am to 5:30pm each day. For the four(4) buildings,the total flow that will be routed to the scheduled 8-inch diameter main extension installed in Lot 7,will be on the order of 1200 gpd or approximately 2-gpm ( 1200/(60min x 10 hrs))on the average throughout the day. The 8-inch main can accommodate a flow of slightly over 1000 gpm on a grade (slope)of 1.1% (Q=(1.49/.012)x85.9x0.1= 1066gpm) using the Manning equation to compute maximum pipe flow. A closed circular conduit,the 8-inch diameter pipe,carries its maximum rate of flow when the pipe is at 94%of its maximum (100%) cross sectional area (See Chow—Open Channel Hydraulics—1959). So, quite clearly the 8-inch diameter pipe extension from the Fallon Street collector sewer has more than adequate capacity to serve the four(4) planned buildings on Lot 7. For comparison purposes a 50 room motel (@ 2 people per room), with 10 employees,would generate on the order of S,OOOgpd. (100 guests max. @ 50 gpd+ 10 employees @ 15 gpd=5,150 gpd). So, clearly the four(4) scheduled office buildings will generate substantially less(computed @ 5x less) flow than the original planned motel(1,200 gpd vs 5,150 gpd). A minimum sized 8-inch diameter sanitary sewer collector is an adequately sized pipeline to accommodate the four(4)office buildings and a slope of 1.1%will assure a flow velocity in excess of the minimum 2-feet per second (fps)to keep wastewater solids in suspension. 3.0 WATER SYSTEM IMPROVEMENTS When the Valley Commons Business Park was originally platted in 1994 and developed in 1995,the minimum sized water main requirement from the City of Bozeman was 6-inch diameter mains. The City's minimum required main size is now 8-inch diameter. Because dead-ended mains(with the exception of large diameter transmission mains)are discouraged and loops are required for nearly all water main installations today, a looped 8-inch main is scheduled to be routed through Lot 7,as shown on attached Exhibit 2—Lot 7 Utility Site Plan. Certainly,the looped 8-inch main will adequately meet both the peak daily domestic demand plus the fire flow demands of the four(4)scheduled business office buildings. The average daily(domestic)flow demand will be on the order of 6 gpm (3 (peaking factor)x 20 employees x 4 office buildings x 15 gpd/person=3,600 gpd; 3,600 gpd/(10hrsx60 min/hr=6gpm). So, the domestic demand for water service is minimal when compared to the fire flow demand. The fire flow demand for the office buildings is at maximum 2,250 gallons per minute (gpm), according to the "Guide for Determination of Needed Fire Flow" (GDNFF), published by the Insurance Service Office (ISO) (See excerpt from GDNFF bound in the Appendix of this report). Of course with sprinkler systems in each building this fire flow requirement would be substantially reduced. There are no plans,though,to sprinkle the small footprint office buildings that KA is aware of. A flow of 2,250 gpm will easily be achieved from the looped system,while maintaining a minimum 20psi. By installing an 8-inch diameter main,the City of Bozeman has waived the requirement for a fire flow test(ISO rated test)within the VCBP. 4.0 STORM WATER IMPROVEMENTS Like the discussions,above,for sewer and water improvements,the storm water improvements scheduled for Lot 7 were originally planned to accommodate a moderate-sized motel. The stormwater runoff from the motel site was originally designed to flow directly into the existing stormwater detention basin just north of Kasey's Corner Gas Station and Convenience Store. This existing detention basin has operated trouble free now since its original installation 20-years ago. Kasey's Corner C-Store and gas station was one of the first buildings constructed within VC BP. With the completion of the site grading and drainage plan for Lot 7 by KA, it became clear that in order to accommodate storm water generated on the east side of re-configured Lot 7, a small retention basin was going to be needed in the green belt space along the eastern edge of Lot 7. So, one was designed and incorporated into the landscaping improvements along the pedestrian corridor that meanders through the linear open space corridor. To insure that the volume of stormwater runoff predicted from the original configuration of Lot 7 with the motel footprint was on parity with the runoff projected from a 10-year design storm for the business office buildings KA ran some computations comparing the two weighted runoff coefficients,C,from both sites. The weighted average runoff coefficient, C,for the newly configured business use versus the original configuration with the motel footprint are actually on parity with one another. The C-factor for the offices computes to be slightly less than the original motel (See Valley Commons—Lot 7 Storm Drainage Network Check, bound in Appendix A of this report. The original storm drainage plan for the motel did not include the construction of a separate on-site retention area to accommodate a portion of the stormwater flow. To accommodate stormwater from the western portion of the re-configured Lot 7,two additional inlet catch basins will be added to the extended storm water pipe (reinforced concrete)that extends south along the common line between Lots 7 and 8 (see attached Exhibit 2—Lot 7 Utility Site Plan). 5.0 SITE GRADING AND DRAINAGE PLAN As with all developed lots in a new or existing subdivision, KA prepared a Final Site Grading and Drainage Plan for Lot 7 (FSGDP)to accompany the design of the major site utilities. The grading plan is shown as Exhibit 1—Master Site Plan to this report. The FSGDP sets the finished floor elevations of each building pad and the final grade for the integral curb and gutter that outlines each office building pad site. The reviewer can seethe direction of flow that surface water will travel. Once the curbs are poured,then the construction contractor will set the finished pavement to its final grade. 5.1 —Integral City of Bozeman Curb and Gutter Curbs will be installed to conform to the City of Bozeman standard concrete curb and gutter template for integral curbs. 5.2 —Asphalt Pavement Mat The finished drive isles and parking stall areas,shown on the Master Site Plan, bound in the back of this report will be completed with hot-mix asphaltic concrete pavement. The finished lift of asphalt will be a 3-inch compacted mat. Once the perimeter curbs are in-place, the finished dirt subgrade will be compacted to a 97%of maximum dry density. Base course gravel will include a minimum of 12-inches of pit-run gravel-sub-base applied to the finished "dirt" subgrade,followed by a minimum lift of 3-inches of compacted crushed gravel top-surfacing material. This is the typical section that has been successfully used to construct drive isle and parking areas around existing buildings within the VCBP. 4 t Respectfully Submitted `r p v y 'x *� f i •.� r RichardT. Kerin, P.E. o- _ �co . ' • . .. . . . SHEET# T— x W N w _w f,Zm n Zm yl I L J¢ 1 az ¢ Z o }0 w z- CO wt` '' w Z `c ® Q 3 j oZS z,`- —Z. Woo z� 0 U U U O � � - ------------ Q F" — — - - - -- - - NIVIN NIM 8 I C W 1 z 4 o i to z m � � Q � =rcnM `W —) 10 iUO __J } Q oCO � ui m 2 U p m w > W , w 3 U w 2 F' - d � OU co ) �J� N a 0 o x U GUIDE FOR DETERMINATION OF NEEDED FIRE FLOW 545 Washington Boulevard Jersey City,New Jersey 07310-1686 (800)888-4ISO(4476) www.iso.com EDITION 06-2014 COPYRIGHT©Insurance Services Office,Inc.,2014 CHAPTER 2 Construction Factor (C) To determine the portion of the NFF attributed to the construction and area of the selected building, ISO uses the formula: C = 18F(,�A) Where A = effective area F = coefficient related to the class of construction: F = 1.5 for Construction Class 1 (Frame) = 1.0 for Construction Class 2(Joisted-masonry) = 0.8 for Construction Class 3 (Non-Combustible) = 0.8 for Construction Class 4(Masonry Non-Combustible) = 0.6 for Construction Class 5(Modified Fire Resistive) = 0.6 for Construction Class 6(Fire Resistive) Appendix A provides the values for the construction factor C, for a range of construction classes (F) and effective areas(A). 1. Construction Materials and Assemblies ISO uses the following definitions to determine the construction class for a building: a. Combustible: Wood or other materials that will ignite and burn when subjected to fire, including materials with a listed flame-spread raring greater than 25. Also included are assemblies or combinations of combustible materials with other materials,such as the following: (1) Metal walls or floors sheathed on either interior or exterior surfaces (with or without air space)with wood or other combustible materials(flame-spread rating over 25). (2)Metal floors or roofs with combustible insulation or other combustible ceiling material attached to the underside of the floor or interior surface of the roof deck,or within 18" of the horizontal supports. (3) Combustible wall materials with an exterior surface of brick, stone, or other masonry materials (commonly known as "masonry veneer"). (4) Noncombustible wall or roof construction on a skeleton wood frame (commonly known as "wood-iron clad"). (5) Combustible wall or roof construction on a noncombustible or slow-burning frame. (6) Composite assemblies of noncombustible materials with combustible materials, such as a combustible core between two noncombustible panels, or a noncombustible panel with a combustible insulation material(flame-spread rating over 25). EDITION 06-2014 -3- COPYRIGHT©Insurance Services Office,Inc.,2014 APPENDIX A Needed Fire Flow/Effective Area Table TYPE OF CONSTRUCTION FACTOR AS DETERMINED BY RANGE IN EFFECTIVE AREA s 1 2 ,4 Pass Factor(F) 1.5 1.0 .8 0.6 Effective Area(A) Effective Area(A) Effective Area(A) Effective Area(A) (C) t Least Not Over At Least Not Over t Least Not Over t Least Not Over 500 0 535 0 1,205 1,883 0 3,348 750 536 1,050 1,206 2,363 1,884 3,692 ,349 6,564 1,000 1,051 1,736 2,364 3,906 ,693 6,103 6,565 10,850 1,250 1,737 2,593 3,907 5,835 ,104 9,117 10,851 16,209 1,500 2,594 3,622 5,836 8,150 9,118 12,734 16,210 22,639 1,750 ,623 4,822 8,151 10,852 12,735 16,954 22,640 30,140 2,000 ,823 6,194 10,853 13,937 16,955 21,776 30,141 38,714 2,250 6,195 7,737 13,938 17,409 21,777 27,202 1�8,360 8,715 48,359 2,500 7,738 9,452 1�17,410 21,267 27,203 33,230 159,076 2,750 9,453 11,338 21,268 25,511 33,231 139,861170,865 59,077 70,864 3,000 11,339 13,395 1125,512 30,140 9,862 147,095 183,724 3,250 13,396 115,624 30,141 135,156 7,096 54,931 1183,725 197,656 3,500 15,625 18,025 35,157 40,557 54,932 63,374 97,657 1112,659 3,750 1�0,598 8,026 20,597 0,558 46,344 63,375 72,413 1112,660 128,734 4,000 123,341 1�6,345 152,517 72,414 82,058 128,735 1145,881 14,250 3,342 26,256 52,518 159,076 82,059 192,306 145,882 1164,100 4,500 6,257 129,342 59,077 66,020 2,307 103,156 11164,101 183,390 4,750 9,343 132,600 66,021 173,350 r126,667 3,157 1114,610 1183,391 203,751 5,000 1113,403 2,601 36,029 1173,351 81,066 4,611 126,666 03,752 225,185 5,250 6,030 39,630 81,067 89,168 139,325 225,186 247,690 5,500 ,631 43,402 1189,169 97,656 139,326 152,587 247,691 271,267 5,750 147,346 97,657 106,529 152,588 1166,452 271,268 1295,915 6,000 47,347 51,461 106,530 115,788 166,453 295,916 6,250 51,462 155,748 11115,789 1125,434 6,500 55,749 160,206 125,435 135,464 6,750 60,207 64,836 135,465 145,881 7,000 64,837 69,637 145,882 1156,684 7,250 9,638 174,6.09 156,685 1167,872 7,500 74,610 799753 167,873 179,446 7,750 1179,754 85,069 179,447 191,406 8,000 85,070 191,407 EDITION 06-2014 -30- COPYRIGHT©Insurance Services Office,Inc.,2014 51'°uh 22"Ave.Ste.4 ZEMAN.MT 59716 P:406 586 6407 ` F:406.586.3745 INFOOKERIN ASSOCIATES.COM KA KERIN s ASSOC'ATES,PC. Valley Commons Lot 7 Bozeman, Montana STORM DRAINAGE NETWORK CHECK Type of Analysis Storm Drain Network Adequacy Check Basin# Catchment#6 Basin Description Lot 7 Previous Plan Land Classification Commercial Neighborhood Area SF 63,683.32 sf As Built Record Area Acres 1.46 acres Calculated Max Allowable Runoff Coefficient CALLOWED- 0.71 jAs Built Record 2014 Development Plan Land Classification Commercial Neighborhood Area SF 63,683.32 sf Calculated Area Acres 1.46 acres Calculated Runoff Coefficient 2014 PUD C Area sf 11 0.951 43,796.73 Calculated 21 0.21 19,886.59 measured 63 683.32 sf CNEW= 0.716 Composite runoff coefficient Modification or Re-Evaluation of Storm Drain Network Required? (CALLOWED>CNEW) No,Capacity Ok Basin#Catchment#5 Basin Description Lot 7+Open Space Easement+South Side Valley Commons Drive Previous Plan Land Classification Commercial Neighborhood/Open Space/Road Area SF 45,423.00 sf As Built Record Area Acres 1.04 acres Calculated Max Allowable Runoff Coefficient CALLOWED- 0.63 As Built Record 2014 Development Plan Land Classification Commercial Neighborhood/Open Space/Road Area SF 45,423.00 sf Calculated Area Acres 1.04 acres Calculated Runoff Coefficient 2014 PUD C Area sf 11 0.951 26,039.05 21 0.21 19,383.96 45,423.00 sf CNEW= 0.630 Composite runoff coefficient Modification or Re-Evaluation of Storm Drain Network Required? (CALLOWED'CNEW) No,Capacity Ok 8/4/2014 1/2 5"'buth 2211 Ave,Ste.4 ZEIdAIJ,MT 59718 P:406 586 6407 F:406.586.3745 INFOOKERIN''!•ASSOCATES.CCM KA K=-RIN s ASSOCIATES.PC. Basin# Catchment#7 Basin Description Lot 7+Lot 8 Previous Plan Land Classification Commercial Neighborhood Area SF 32,421.55 sf As Built Record Area Acres 0.74 acres Calculated Max Allowable Runoff Coefficient CALLOWED' 0.71 As Built Record 2014 Development Plan Land Classification Commercial Neighborhood/Open Space/Road Area SF 32,421.55 sf Calculated Area Acres 0.74 acres Calculated Runoff Coefficient 2014 PUD C Area sf 1 0.95 21,493.65 21 0.21 10 927.90 32,421.55 sf CNEW= 0.697 Composite runoff coefficient Modification or Re-Evaluation of Storm Drain Network Required? (CALLOWED i CNEW) No,Capacity Ok 8/4/2014 2l2