[ Copyright ©2015 American SocietyofCivil Engineers. All rightsreserved. 68 ]

Civil Engineering A and economic development opportunities. Designed with the environment in mind, and economicdevelopmentopportunities.Designedwiththeenvironmentinmind, Minnesota Twins, thestationoffers anamphitheater, publicgatheringspaces, N it also features innovative measures for collecting and reusing stormwater it alsofeaturesinnovativemeasuresforcollectingandreusingstormwater In addition to facilitating the flow of large crowds to the home of the In additiontofacilitatingtheflowoflargecrowdshome

runoff andsnowmelt. e w Target FieldStationismorethan simplyalight-railhub.

Light Garden, whichfeatures nineprogrammable light-emitting r e b m e v o n along withtheGreat Lawn, agreen expansecomplete witha diode fixtures interspersedamongtheplaza’s tree trenches, 15 by 30ftvideoscreen located ontopoftheelevator bank. C The station’s upper-level plazaincludesanarea calledthe i Located in downtown Minneapolis, Located indowntownMinneapolis, v i

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b m e v o n © MORGAN SHEFF/COURTESY OF PERKINS EASTMAN creating distinctiveurbanspaces. Target Field ed an “open transit” station plan that focuses on sit andforothers.Theproject team incorporat- a varietyof activities both forusersofmasstran- common areaswerespeciallylaid outtosupport its residents’loveoftheoutdoors. Theproject’s spiration fromMinnesota’s distinctseasonsand complishing muchmore. station achievedalltheseobjectiveswhileac- easily, andsafely. Foritspart,thedesignof orient themselvesandfindtheirtrainsquickly, layout andadequatesignstohelppassengers offer therightamountofspacewithasuitable of passengersrapidlyandefficiently. Ithadto station hadtobeablehandlelarge numbers after aTwins game.Againstthisbackdrop,the rail trainoraNorthstarCommuterRail upon the station’s platforms to board a light- For example,morethan8,000peopledescend music concerts,andotherevents atTarget Field. Minneapolis toattendTwins games,outdoor number ofriderswhousetherailnetworkin was designedtoaccommodatethesignificant light environmentalfootprint. and construction techniques employed give it a and the various other context-sensitive design the stationfeaturessustainablelandscaping, adjacent energy facilityandreused. Moreover, novative snowmeltsystemareconveyedtoan tured on-siteandwaterobtainedthroughanin- and placesforpeopletoshop.Stormwatercap- new development opportunities for businesses etation, anda1,000-seatamphitheater. Itoffers complete withexpansivegreenlawns,lushveg- provides a year-round public meeting space tiuse stationisacommunitydestinationthat transit stationandmoverofpeople.Thismul- attractions intheTwin Citiesarea. concerts whileenablingtravelerstovisitother tral Station” for Minneapolis, providing links Target FieldStationisthenew“GrandCen- more than500trainspassingthrougheachday, Field, thehomeofMinnesotaTwins. With disadvantage thatitisalsoconnectedtoTarget opment andyear-round publicspace.Itisno corporating complementarymixed-useddevel- of-the-art, multimodalmasstransitstationin- The designofTarget FieldStationtookin- On afundamentallevelTarget FieldStation However, thefacilityismorethanjustamass destinations, major sporting events, and destinations, majorsportingevents,and to residential areas, workplaces, shopping r e

2015 arget downtown Minneapolis, is a state-

Civil Engineering F ield

Station, located in located in

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THE CHALLENGES associated with the site led to the use of a unique trilevel design. construction of various temporary access lanes to maintain herc operations. Because of poor soils at the site, all of the project structures had to be built on steel pipe piles and H-piles. Posttensioned concrete was used because of its strength and constructability. The design, however, also called for concrete curves, cascades, and stairs, complicating the construction process. The challenges associated with the site led to the use of a unique trilevel design. The third, or uppermost, level in- cludes the light-rail station, which is located under a light- ed canopy and serves the metro Blue and Green lines. The massive 300 ft long canopy stands 25 ft above the platforms, and its fins comprise a total of 2,400 pieces of aluminum. The canopy features programmable light-emitting diodes that can change to any color, creating a must-see attraction. The plaza on this level includes an area called the Light Garden, which features nine fixtures with programmable light-emitting diodes interspersed among its tree trenches. The plaza also invites people to enjoy the Great Lawn, a large green expanse complete with a 15 by 30 ft video screen lo- cated on top of the elevator bank. The screen is used for game day broadcasts as well as for other events hosted by Henne- pin County, Target Corporation, or the Minnesota Twins. Yet another feature of the plaza is the light-rail bridge, which comprises 13 precast-concrete spans ranging in length

Station embodies the five primary design principles of open North. To create additional parcels for development, the The train platform is covered by a 300 ft long, 25 ft tall transit in that it incorporates all modes of transit; promotes project realigned and added a signalized intersection at both canopy whose fins comprise 2,400 pieces of aluminum, development; creates iconic indoor and outdoor spaces; ap- 6th Avenue North and 6th Street North. opposite. Two large cisterns, right, can store 40,000 gal peals to passengers, residents, office workers, and visitors alike; Meeting all of the project design needs required using ev- of rainwater and snowmelt from the upper-level plaza and integrates culture with mass transit by placing the latter ery square inch of the compact 8-acre site, which is owned by and the bridge. Stored temporarily in the cisterns, the in the heart of the public square. Incorporating these design Hennepin County and includes the herc. When completed, water is pumped to the nearby Hennepin Energy Recovery principles resulted in a project that offers significant benefits the Target Field Station project site encompassed approxi- Center, which reuses it in various industrial processes. to those attending games, as well as to the surrounding com- mately 58 percent of the total parcel. The herc occupies the munity, visitors, mass transit users, and the environment. remaining 42 percent. completed in April 2014, and the station opened to The 104,000 sq ft station is situated in a highly urban- Scheduling pressures prompted the project owner, Hen- the public the following month. ized site that once included government administration nepin County, to realize the project through the design/build In addition to dealing with a pronounced lack of buildings and still contains the Hennepin Energy Recov- approach. In fact, the eventual design/build team would have space, the project team, as part of its construction ery Center (herc), a waste-to-energy facility that burns only 24 months to complete the project after winning the planning and logistics efforts, had to remove con- 365,000 tons of waste a year to generate electricity. Besides contract in June 2012. This accelerated schedule was dictat- taminated soil from areas in which excavation per- the station itself, the site had to offer pedestrian plazas, ele- ed by the need for the station to be constructed by the time taining to foundation construction and piling instal- vated light-rail tracks and a supporting bridge, a 286-space the light-rail route known as the metro Green Line became lation was planned and to demarcate utilities that parking structure, room for retail businesses, and a system operational, in May 2014. Another important consideration would be either abandoned or relocated. Construc- for managing stormwater. was that Major League Baseball’s 2014 All-Star Game would tion phasing also was essential given the critical op- The project team also factored into the site design the be played at Target Field on July 15. erations of the herc. That facility generates enough need to facilitate future economic development. To this end The Minneapolis office of Knutson Construction led the steam energy to provide electricity to 25,000 homes, the site design involved the realignment of nearby roadways design/build team, which included the Minnetonka, Minne- as well as to power heating and cooling systems in to offer the flexibility that would attract and be conducive to sota, office of Short Elliott Hendrickson, Inc. (seh). The lat- nearby buildings. Therefore, the project team had to development. In fact, the project’s preliminary design was ter provided design services pertaining to civil engineering, ensure that the 200 garbage trucks that visit herc modified to improve the development potential of two road- landscape architecture, geotechnical engineering, and storm- each day would continue to have access during con- SEH ways adjacent to the site: 6th Avenue North and 5th Street water management. Begun in July 2012, construction was OF PERKINS EASTMAN © MORGAN SHEFF/COURTESY struction. This required a detailed phasing plan and

[70] Civil Engineering n o v e m b e r 2015 0885-7024/15-0011-0068/$30.00 PER ARTICLE n o v e m b e r 2015 Civil Engineering [71] THE PROJECT TEAM opted to use large geofoam blocks as a lightweight alternative, in some areas stacking them to a height of 15 to 20 ft. from 40 ft to 90 ft. Approximately 1,050 ft long, the bridge here takes Northstar Commuter Rail passengers to the north- supports the rail lines, the station terminal, and the platforms ern suburb of Big Lake, nearly 45 mi outside of Minneapolis. for the metro Blue and Green lines. Its design will facilitate The station on the third level serves two light-rail lines. connections to two other light-rail lines planned for the future. One platform there is for the metro Blue Line, which con- This level also includes tail, or storage, tracks having suf- nects passengers to Minneapolis–St. Paul International Air- ficient capacity to store six light-rail trains. The tail tracks port and the Mall of America, south of downtown Minne- were constructed to stage as many cars as necessary to handle apolis. A second platform serves the metro Green Line, the rush of spectators leaving Target Field at the conclusion which takes passengers east to downtown St. Paul, Minne- of a large event. Beginning at the west end of the bridge, the sota’s capital. tail tracks wrap around the south side of the herc. Built on As light-rail lines are added to the system, Target Field grade, the tails required the construction of large retaining Station can be expanded to offer additional platforms. In fact, walls, and because of poor soil conditions, these walls were the station is designed to accommodate several planned lines, built on pilings. These same poor soils ruled out the use of including the 16 mi long Southwest line and the 13 mi long traditional fill in many locations within the retaining walls Bottineau line. Scheduled for completion in 2019, the South- because the sheer weight of the fill and the waiting trains west line will stop at Target Field Station and serve the south- would have caused settling. As a result, the project team opt- west Minneapolis suburbs of St. Louis Park, Hopkins, Min- ed to use large geofoam blocks as a lightweight alternative, in netonka, and Eden Prairie. Scheduled for completion in 2021, some areas stacking them to a height of 15 to 20 ft. the Bottineau line will serve Target Field Station and feature Located at street level, the second level is home to Station stops in the northwest Minneapolis suburbs of Golden Val- Square and to a coffee shop and other planned businesses. The ley, Robbinsdale, Crystal, and Brooklyn Park. By accounting square gives pedestrians and cyclists access to the sidewalks for these upcoming needs, the design of Target Field Station and trails in the surrounding community. It is also home to a is expected to reduce the construction costs associated with massive outdoor amphitheater featuring a curved design and the new lines by tens of millions of dollars and ensure that the a built-in cascading stairway that leads to the third level. Vis- station will continue to serve as a major mass transit hub and itors entering Station Square from the street proceed past the community gathering space well into the future. coffee shop and beneath the light-rail platforms and bridge Certain site considerations led the design team to develop City of Minneapolis, Hennepin County, and Situated in a highly urbanized project team took advantage of the waste before entering the amphitheater and the cascading staircase. an innovative system for collecting and reusing stormwater. the Mississippi Watershed Management Or- site, the 104,000 sq ft Target heat from the nearby herc and created a The underside of the bridge also has programmable light- For example, the presence of petroleum-based contamina- ganization, which is based in Minneapolis. Field Station was carefully laid system for melting snow. All of the station’s emitting diodes that illuminate the part of the square at the tion in various places precluded the possibility of allowing Rising to these challenges, the project team out to accommodate elevated concrete surfaces and the herc parking ar- foot of the amphitheater. The second level also includes the stormwater to infiltrate into the ground. With the Missis- developed an innovative stormwater collec- light-rail train tracks and a sup- eas form part of an integrated snowmelt sys- upper portion of the two-level parking garage. sippi River only about 1 mi downstream of the project site, tion and reuse system, a circulatory snowmelt porting bridge, as well as such tem designed by the Minneapolis-based firm The first level, the bottommost, is belowground and in- the design team sought to prevent any movement of existing system, and a low-impact landscape design. features as pedestrian plazas Michaud Cooley Erickson. cludes the Northstar Commuter Rail station and the lower contamination plumes in the area that drains to the water- Although largely invisible to the thousands and a 1,000-seat amphitheater. After a snowfall, accumulated snow is melt- portion of the parking garage. The garage offers the flexibili- way. This and other challenges complicated efforts to meet of people who pass through the station each ed by approximately 50 mi of glycol-filled tub- ty to add spaces to support future development. The platform the stormwater management requirements specified by the OF PERKINS EASTMAN COURTESY day, these novel approaches to stormwater management are ing that runs beneath a significant part of the station’s pave- among the station’s most notable features. ments and plazas. Once the snow has melted, the glycol is The first of its kind in Minnesota, the stormwater col- returned to the herc, reheated, and then routed back through lection system captures rainfall and snowmelt runoff year- the tubing in a continuous process. This system will eliminate round from the plaza on the third level, from two large the maintenance and labor costs associated with shoveling and green roofs, and from the light-rail bridge and station plat- plowing snow and distributing sand and salt, which is normal- forms. Rainwater and snowmelt enter surface drains on the ly used in the winter to help melt residual snow and ice. The plaza and the bridge and flow through pipes to two cisterns snowmelt system will also extend the life of all of the project’s located below the bridge on the station’s second (ground) concrete since it will reduce the amount of expansion and con- level. The two 15 by 15 ft cisterns have a combined storage traction that the concrete undergoes in response to the melting capacity of 40,000 gal. Stored temporarily in the cisterns, and refreezing that are typical of a Minnesota winter. All told, the stormwater is pumped at a rate of 9 gpm to the herc, including runoff from melted snow, the water system will cap- which passes the water through a sand filter and reuses it in ture approximately 3 million gal of runoff per year and convey various industrial processes. it to the herc, reducing the center’s overall demand on the mu- Because every square inch of the site was needed for com- nicipal water supply. muters and other users of the station, the area around the In addition to the system for collecting and reusing run- With its unique trilevel design, Target Field Station station afforded little room for snowplows, and there was off, Target Field Station implements several low-impact SEH includes a cascading staircase linking the top two levels PERKINS EASTMAN even less room for shoveled snow. In devising a solution, the landscape and stormwater collection (Continued on Page 77) and a parking garage that is split between the lower two levels.

[72] Civil Engineering n o v e m b e r 2015 n o v e m b e r 2015 Civil Engineering [73] A New Civic Identity Is Born The project design also included a of the curve when it comes to caring for plan to reduce the effects of construc- the environment. (Continued from Page 73) design prac- tion on the nearby 10-story Ford Cen- In August 2014, the U.S. Green tices, including tree trenches, landscaped ter, which was constructed in 1914 and Building Council, of Washington, D.C., bioretention planters, and the two green used as a manufacturing facility for the and Green Business Certification, Inc., roofs. Although the cisterns capture rain- Model T. Because the building is list- announced that the station had met fall from the plaza and surfaces on the top ed in the National Register of Historic the requirements for certification in the level, the stormwater that falls elsewhere Places, the station design was subject Leadership in Energy and Environmen- at the site is captured by storm sewer in- to review and approval by Minnesota’s tal Design (leed) program. The project lets, permeable pavers, and bioswales, the State Historic Preservation Office. earned a total of 44 points, 4 more than pavers and swales dispensing the water to To help inform the public about required for certification. It was also built the 150 trees, 1,300 shrubs, and 5,400 the sustainable aspects of Target Field in accordance with the Minnesota energy native plants on-site. To address concerns Station, Short Elliott Hendrick- conservation program known as Build- about the contamination within the site, son installed permanent signs in and ing, Benchmarks, and Beyond (B3). a liner was included at the base of the in- around the project site. These informa- The term “sustainability” has been filtration features, and clean soil was add- tion boards highlight the system used defined in many ways. However, the ed to help filter runoff. to capture and reuse stormwater and most fundamental definitions are the Any runoff that is not routed to the snowmelt and illustrate how the system “ability to sustain” and the “capacity to cisterns is captured by the storm sew- operates. They also explain how the sys- endure.” The Target Field Station proj- er inlets and conveyed directly to a tem reduces the amount of runoff from ect offers the community and mass tran- 7,000 cu ft underground storage sys- Target Field Station, enables water to be sit users an insight into what is possible tem consisting of three rows of 300 ft reused on-site at the herc, and signifi- through sustainable engineering and long, 60 in. diameter pipes. This sys- cantly improves the overall quality of construction. The community and vis- tem is used to control the rate at which water that leaves the site and enters the itors alike are deriving benefits from a stormwater is discharged into the city’s Mississippi. The informational signs project realized by a team that refused to collection system. Any rainwater that help visitors understand how these sus- disregard the natural environment. The falls on Station Square is captured on tainable features directly benefit the en- station will meet the mass transit needs the parking deck. From there it drains vironment and the community. of people today and tomorrow, and its to the bioswales, where it is filtered and Target Field Station is the center of a design gives full scope to opportunities routed to the same underground stor- well-planned network with connections for future economic development. Ulti- age system. Furthermore, any overflow to residential areas, an employment cen- mately, the $79.3-million project cre- from the cisterns is routed to the bio- ter, shopping and retail destinations, ed- ated more than 300 construction jobs. swales and the station’s permeable pav- ucation and training institutions, and a With its mix of uses, its central loca- ers, which feed water to the street trees. medical clinic. By offering access to so tion, and its purposeful design, Target In combination with the stormwater many amenities, the station has reduced Field Station has helped to create a new and snowmelt collection system, these the need for city residents to rely on au- civic identity and instill pride within features reduce the amount of runoff tomobiles, thereby lowering Minneapolis and Hennepin from the Target Field Station site by 27 transportation costs. Because County. CE percent, lower the total suspended sol- the station can easily be ac- ids in the runoff by 97 percent, and de- cessed by bike and on foot, the Justin Gese, p.e., m.asce, is a crease total phosphorus in the runoff by project may enable some resi- project manager in the Minneton- 62 percent. Ultimately, inclusion of the dents to do away with a vehi- ka, Minnesota, office of Short El- stormwater management system is in cle altogether, further helping liott Hendrickson, Inc. keeping with an environmentally re- to lower transportation costs. sponsible design that will benefit Hen- The Target Field Station Gese PROJECT CREDITS nepin County and Minneapolis and en- project reflects a passion to Owner: Hennepin County, dure for decades. devise innovative, sustainable solutions Minnesota Architecture and station As with most projects, the design that directly benefit the environment, design: ee&k, a Perkins Eastman com- adhered to local, state, and federal stan- community residents, and businesses. In pany, New York City Civil engineer- dards, criteria, and regulations. In com- approaching this project, the team in- ing, landscape architecture, geotech- pliance with the Americans with Dis- corporated many elements and features nical engineering, and stormwater abilities Act, the station includes an embodied in the sustainability goals of management design services: Short elevator bank and has ramps that can Hennepin County and Minneapolis. Elliott Hendrickson, Inc., Minneton- be used by those in wheelchairs. More- With ecofriendly mass transit, a focus ka, Minnesota, office Snowmelt sys- over, the station’s waiting areas are cov- on bicycling instead of driving, and the tem design: Michaud Cooley Erickson, ered and have on-demand heating for construction of rain gardens and green Minneapolis Design/build team lead- increased passenger comfort during roofs, the project helps place Henne- er: Knutson Construction, Minneapo-

Minnesota’s cold winters. pin County and Minneapolis far ahead lis, office

n o v e m b e r 2015 Civil Engineering [77]