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Legacy of Rochester Hills

Rochester Hills, Michigan


Goldberg Companies, Inc.  


Professional Engineering Associates, Inc. 


Stante Excavating 


January 2020

Technical Description:

  • 719' LF of 144" Aluminized Steel Type 2
  • Vortechs® Hydrodynamic Separator

A 22-acre property used for illegal dumping starting in the 1950s is being transformed into the Legacy of Rochester Hills, a 359-unit upscale apartment complex with four two-story buildings. Amenities will include a dog park, pet spa, fitness studio, outdoor entertainment areas and package delivery lockers.

According to city documents, the property housed Christensen Dump from the mid-1950s to the mid-1960s and was used for “illegal dumping activities.” The land has sat vacant and contaminated since. The developer is cleaning up the site’s hazardous contaminants under a brownfield redevelopment plan.

The site had numerous physical constraints, with stormwater being an important consideration. A large volume of water was required to be stored (81,500 cubic feet of volume) in a small green-belt area behind a proposed building footprint.  The area had an invert to grade of between 17 and 25 feet. High groundwater was also a concern. The engineer worked with Contech’s stormwater design team to find the most cost-effective system layout that could fit within the proposed footprint and allow the system to be constructed using typical construction methods.

Based on these factors, the design team specified a detention system made from 144 inch (12-foot diameter) corrugated metal pipe. Using large diameter pipe maximized the storage volume in a minimal footprint. Contech fabricated the system with unique bulkheads designed for excessive soil heights and groundwater considerations.  Special risers were designed to accept the 10 foot of soil cover over the system to allow for future access and maintenance activities.  The pipe runs were connected using a header pipe system on one end. This design allowed each piece to be installed separately using an excavator. The backfill operation was conducted using standard construction methods. 

The detention system is pretreated with a Vortechs hydrodynamic separator. By capturing the majority of sediment, trash and debris upstream of the storage system, maintenance becomes much easier as the material is collected into a smaller device with clear access for cleanout.  

In addition to designing and fabricating the system, Contech provided the necessary buoyancy and structural calculations for the 15 feet of soil cover as required by the municipal engineer review process.

The underground detention system design provided by Contech was the only way 81,000 cubic feet of water volume could fit in such a small footprint and be installed within the financial constraints of the project. The alternate design included removing a separate building to provide the necessary volume of detention which was not the preferred option.

"We like working with Contech as they know what they are doing and take the time to thoroughly explain the process of installing really large diameter pipe.  We were pleased with the final outcome of the project,” said Bobby Morgan, Project Superintendent for Stante Excavating.  “This was a major portion of the stormwater system that was required to be installed prior to any buildings being constructed, so it was important we got it done quickly and done right."

Technical Description:

  • 719' LF of 144" Aluminized Steel Type 2
  • Vortechs® Hydrodynamic Separator

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