Economic, Innovative and Green

Civic Center Municipal Parking LotAPWA Project of the Year Award

Mayor - Brenda L. LawrenceDPW Director - Gary Mekjian DPW Deputy Director - Mike HabowskiCity Administrator - James Scharret

City of Southfield

Project DetailsProject:Civic Center Municipal Parking Lot

Client: City of Southfield 26000 Evergreen Road P.O. Box 2055 Southfield, MI 48037-2055

Project Cost:$1.1 Million

Design Cost: $90,000

Construction Cost:$1 Million

Design Completion:Summer 2007

Construction Completion:Spring 2008

Consulting Engineers:OHM (Orchard, Hiltz & McCliment, Inc.)

Contractor: Asphalt Specialists, Inc.

Geotechnical Analysis:Schleede Hampton Associates, Inc.

Project Site: 26000 Evergreen Rd., Southfield, MI, 48076

Project BackgroundCome to the City of Southfield, and according to its tag line, you are at The Center of it All™. So it was a problem for City officials to invite the public to the City’s municipal complex where the roads surrounding the complex had badly deteriorated. In addition, the original configuration of the parking lot posed safety issues for pedestrians and the path to the building was not truly ADA compliant. The overall condition of the parking lot was poor. Concrete thickness was substandard, base failure was evident in over 50% of the parking lot causing pavement settlement and drainage problems. The existing topography of the parking lot directed storm water run-off to sheet flow to the south and collect in a series of catch basins. Storm sewers conveyed run-off directly to the Evans Ditch, a tributary of the Rouge River. The deteriorated condition of the pavement caused debris to be carried to the catch basins and made it impossible for the lot to drain effectively after storm events; ponding water remained for several days until it evaporated. The City of Southfield contacted OHM to determine the best repair option. The project goals were to improve the parking lot condition, reduce its environmental impact and enhance safety and usability. Based on the existing conditions, OHM recommended the lot be reconstructed rather than rehabilitated to achieve a satisfactory service life and meet the City’s goals. This was also the most cost effective option.

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Reconstruction Improves Environmental ImpactThe City’s administration took the lead in environmental stewardship. An environmentally sensitive way to manage parking lot storm water run-off is to incorporate porous asphalt pavement into the design. Porous pavement is a permeable pavement surface and was used for one-third of the City’s parking lot. Under the pavement, a reservoir temporarily stores surface run-off before infiltrating it into the subsoil. This process provides some water quality treatment. It also reduces the amount of storm water run off into the drainage system and provides for groundwater recharge.

When the City decided to incorporate innovative design solutions to improve the site’s sustainability they didn’t stop at porous pavement. Another design element was reconfiguring the drainage to route storm water through a bioswale before it outlets to the Evans Ditch.

A bioswale is a shallow depression created in the earth to accept and convey storm water run-off. It uses natural means, including vegetation and soil, to treat storm water by filtering out contaminants in the water. This feature collects up to 80% of the run off from the parking lot, further reducing the direct discharge of contaminants to the drains.

A fuel station located in the middle of the parking lot added complexity to the design and construction planning, as it had to remain in service and in the current location.

While the City hoped to have the project completed in a single construction year, the schedule proved to be too aggressive. The project design finished in July 2007 and construction concluded in the spring of 2008.

Safety and Accessibility Benefit the CommunitySafety improvements were another major motivator for redesigning the parking lot’s traffic flow. In the existing lot, an access road separated the parking area from the municipal buildings, creating potential for conflicts between visitors to city hall and emergency personnel responding to calls. Traffic volume within the municipal complex has increased significantly since the complex opened in 1964. Today vehicles accessing the site are rerouted to the outside limits of the parking area, reducing potential conflicts between pedestrians and vehicles.

Meeting ADA requirements for accessibility was another important project goal. All pedestrian facilities were updated to meet ADA requirements. This required slight shifts in pedestrian traffic patterns to ensure that grades and walk alignments worked in relation to the accessible parking and the building.

New Technology can Create Adverse ConditionsInnovative design elements sometimes mean construction challenges. Since porous pavement is a relatively new process, success depended in part on the contractor’s determination, creativity and resourcefulness during installation. Key lessons learned included:

• Porous pavement design mix (which is manufactured without fine materials) is meant to be loose and moveable, at least until the surface hardens. This is contrary to traditional pavement designs.

• The design cross-section for the pavement included a base course or filter course of MDOT 6AA stone. This acts as a stable surface on which to place the porous pavement, and protects the filter fabric placed on top of the reservoir course. On this project, during construction, the contractor had a difficult time obtaining the specified 6AA stone, and substituted a 6A natural stone. Although the gradation is similar, the 6AA stone is a crushed limestone that would provide aggregate interlock for a stabilized base. The natural round shape of the substituted 6A material allowed the stones to slip and slide against one another and made paving a difficult task. One construction worker likened it to “driving on a bed of marbles.” While applying the asphalt, the paving equipment created deep ruts in the shifting base stones. To place the first lift of asphalt, the contractor turned to lighter equipment and manual raking.

• Foundations for the parking lot lights were difficult to secure in the looser base material during construction. The parking light foundations were changed to a foundation with a larger surface area after a pole was toppled by a construction vehicle.

• Porous pavement has received some criticism as not being effective in cold-weather climates. OHM’s design team researched applications in climates similar to Michigan’s and determined that evidence supported the use of porous pavements in cold climates, as long as the pavements were properly maintained. Porous pavements should be plowed, just like traditional pavements. However, if de-icing agents are used, “dirty” rock-salt with significant sediment should not be applied, as it will clog the pavement, filling the voids that allow water to filtrate. Many owners have found that snow melts much more quickly from the porous pavement and de-icing agents are needed less frequently. This project will contribute to a better understanding of porous asphalt’s long-term performance in cold weather climates.

Porous pavement requires more frequent maintenance than traditional impervious paved surfaces. Over time, the voids that encourage infiltration fill with dirt and debris, reducing its effectiveness. The Michigan Asphalt Paving Association recommends that porous pavement be cleaned with a vacuum sweeper at least twice a year to maintain proper function. Adding more routine maintenance projects to an already overtaxed maintenance crew is challenging for any municipality.

The site’s bioswale also requires periodic maintenance including weeding and replanting to keep the vegetation healthy and functional. The bioswale was populated with nearly 2,000 plants.

Social, Economic, and Sustainable Design Bolster Community RelationsParking lot improvements addressed the City’s desire to make the municipal complex accessible and safe for all citizens. One of the project’s primary goals was to allow disabled persons to traverse a barrier-free path from a vehicle or the bus stop to all of the municipal facilities within the complex. By rerouting the vehicle access road outside the parking areas, potential conflicts between people and vehicles were greatly reduced. After installing the porous pavement, municipal workers demonstrated the porous surface’s ability to absorb water by spraying 1,000 GPM from a fire-hose. The water quickly disappeared with no trace of ponding. Ecological improvements at the site are substantial. Since the parking area serves the Police Station, large amounts of salt are regularly deposited to keep the driving surface ice free at all times. Other types of vehicle run-off also affect the water quality in the immediate area. A typical bio-swale however, provides up to 80% pollutant removal, including decreases in petroleum products, excess nutrients, metals and sediments found in storm water.

ComplexityReconfiguring the lot’s traffic flow was complex because the area hosted a number of municipal functions: city hall, the police station, a golf course and a new library. Traffic volume had increased significantly since it was originally built. The area surrounding the Civic Center Municipal complex is distinctly urban, with high traffic counts and close proximity to heavily traveled freeways.

It was a significant challenge during both design and construction to meet the project’s aggressive schedule. The parking lot serves an entire municipal complex, so it was important to the City to minimize the disruption as much as possible.

A fuel station located in the middle of the parking lot had to remain in service and unmoved. This impediment added complexity to design and construction planning.

Meeting ADA requirements for accessibility was an important project goal. The site was bound by existing buildings. There were also new guidelines to interpret and meet through the design. During the project a retaining wall/ramp adjacent to one of the buildings was removed and regarded to meet slope requirements.

Pervious asphalt pavements are not yet commonly used in Michigan. The differing nature and function of the materials had a significant impact on the pavement design, the lighting system design and the construction of the project.

Engineering to Advance a Community

Throughout the planning, design and construction phases of this project, OHM worked with the community and its leaders to provide ideas and various methods to reach the city’s goals. OHM created several options for redesigning the parking lot, detailing the benefits and negative aspects of each approach.

OHM used its expertise in ADA compliant design to deliver a project that conformed both to FHWA’s standards and the City’s stricter building code. Most satisfyingly, a local citizen who is wheel-chair bound tested accessibility of the parking lot, its features and the building approaches with success.

City of Southfield employs an engineering staff. Although OHM designed the entire parking lot project, the City wanted to provide as much of the construction engineering services as possible. OHM assisted on an as-needed basis for construction engineering and inspection, but performed all of the construction staking. Interweaving these responsibilities with City staffers often meant responding to requests within short timeframes, and being flexible in the roles on the project.

World Class CityThe Southfield Civic Center Parking Lot reconstruction clearly improves the quality of life for residents and visitors. Thanks to the foresight of community leaders, the City was able to:

• Install porous pavement which reduces pollutants in storm water run-off

• Help alleviate flooding and contamination to streams• Increase groundwater recharge• Establish a bioswale to collect much of the remaining run-

off and further decontaminate the storm water• Remove much untreated storm water to the nearby Rouge

River. • Improve the aesthetics and functionality of the Civic Center

Complex.• Smooth vehicular and pedestrian traffic flow and create

safer access for all users.

The new parking lot and surrounding area now demonstrate the best of this world-class City and its administration: socially responsible, forward thinking and environmentally conscious. A

City at The Center of it All™.

OHM | 34000 Plymouth Road | Livonia, Michigan 48150 | www.ohm-advisors.com

City of Southfield | 26000 Evergreen Road | P.O. Box 2055 | Southfield, MI 48037-2055

Helping Build Better Communities for Tomorrow

Contact: Gary M. Mekjian, P.E. | Director of Public Works | 248.796.4804

Contact: Rhett Gronevelt, P.E. | Municipal Group Manager | 734.522.6711