Pump station sited on private property eliminates sanitary sewer overflow
Rick Lang, Director of Public Services, City of Allen Park, Michigan; Mark Schobert, P.E., Project Manager, Wade Trim, Detroit, Michigan; and Kelly McRobb-Ackland, P.E., Project Manager, Wade Trim, Taylor, Michigan
Viable locations for infrastructure improvements are not always flexible. When the City of Allen Park, Michigan, began a wet weather pump station project to improve system hydraulics and eliminate a sanitary sewer overflow, existing infrastructure required that it be located within a private parking lot just upstream of an outlet. While eminent domain was a legitimate option for advancing this project, the City chose to work cooperatively with a private property owner for the benefit of all. The new pump station represents the first step toward a long-term solution to provide capacity for wet sanitary flow.
Allen Park's long-term sanitary sewer flow reduction program is being mandated to address insufficient capacity in receiving systems and the elimination of existing sanitary sewer overflows to watershed areas within the city. The sanitary system of concern is known as District 1 and impacts both the Rouge River and Ecorse Creek watersheds. Footing drain connections to the sanitary sewer combined with the close proximity of the sewer to the watercourses has created this wet system.
|The large scale of underground pump station elements, like the wetwell, is not visible from the surface minimizing impact to the private property.|
When significant rain events occur, the sanitary system becomes inundated with rainwater causing surcharging conditions in areas with insufficient upstream pipe capacity. Surcharging is further amplified when the increased flow reaches the city limits and tries to outlet into a receiving system that is already full. This causes backwater surcharging that has led to basement flooding, grade flooding and dislocated manhole covers. For nearly 40 years, the relief point was an old sanitary sewer overflow that discharged untreated sewage to the Rouge River.
With historic issues clearly documented, the City began implementing its first significant short-term improvement consisting of a wet weather pump station at the end of the City system, just upstream of the outlet. Allen Park worked with Wade Trim to design and construct a pump station that would "lift" the flow to an elevation higher than the receiving surcharged flow whenever they could not discharge by gravity. Allen Park simultaneously applied for and obtained a Rouge River National Wet Weather Demonstration grant that partially covered the cost of constructing the pump station. This grant was made available since the project included eliminating the existing sanitary sewer overflow to the Rouge River.
Site layout and pump station location challenges were numerous. The pump station had to be located at the end of the City system in an area highly congested with underground utilities and limited available right-of-way. Constructing the facility on private property was determined to be the most viable solution. Initial discussions with the property owner to secure the necessary permanent easement revealed that the property was vacant and for sale. At this point, the City could have used eminent domain to secure the property; however, they did not want to encumber the property and potentially prevent a sale. The City decided to wait until the property was sold and negotiate with the new owner.
Once the property changed hands, discussions began with the new owner and the City gained approval to begin constructing the pump station within the private parking lot. However, even though the "green light" had been given for construction to begin, the agreement between the City and the property owner had not been finalized. The owner continued to add conditions to the agreement and further required granting approval to field changes that arose during construction. The owner was concerned about the seemingly large layout of the pump station and necessary appurtenances, restoration, impact within their parking lot, layout and beautification through landscaping and decorative fencing. The sale price of the permanent easement was also debated.
As negotiations continued, construction was put on hold. The schedule had little room for extensions as delays could potentially jeopardize grant funding and result in claims from the contractor.
|The packaged pump station's layout was modified to reduce the easement area required on private property.|
Property owner concerns were addressed through changes in design and responsibility. A prefabricated, packaged pump station was specified in the plans to minimize the needed property. After meeting with the owner, the layout was reviewed and modified to reconfigure the above-ground site in an attempt to further reduce the area of the permanent easement. In addition, the property owner assumed responsibility for landscaping and fencing activities. Estimates were prepared for the beautification work and rolled into the sale price of the permanent easement. This flexible plan gave the property owner discretion over the type of plantings and fencing to be installed and provided them with the necessary compensation to accomplish the work. It also gave the City oversight in approving the types of materials to be used and the timeframe in which the work was to be completed.
Completed in 2006, Allen Park's wet weather pump station is currently being monitored by various flow meters and levels. The pump station has already functioned during several wet weather events and improved the system hydraulics by allowing the flow to outlet to the receiving system at the necessary, higher elevation. Combined with the closure of the bypass outlet to the Rouge River, the improvements have reduced the manpower required to bypass pump stormwater within flooded streets adjacent to the watercourses in an effort to prevent basement flooding. The new pump station lifts the sewage to where it needs to go, allowing gravity to do the rest.
|Pump station performance is being monitored to verify the effectiveness of hydraulic system improvements during wet weather events.|
While working within private property can increase available design options, it can also result in unforeseen challenges. Allen Park's approach to work cooperatively with the property owner resulted in an agreement that benefited all parties. It gave the property owner the flexibility they desired with restoration and beautification, allowed the project to proceed with a relatively minor delay and permitted the City to retain the desired oversight in regards to site security and budget. The contractor further assisted in overcoming challenges by delaying the onset of construction and working to negotiate a fair delay claim.
Allen Park remains committed to reducing its overall flow through additional projects such as a potential voluntary footing drain disconnection program, and the addition of storage with potential upgrades to their conveyance system. Financing and completing these projects within the limited timeframe necessary to meet agreements established with permitting agencies will be a challenge. Collaborative efforts with contractors and property owners to implement the corrective measures will be essential to the City's long-term sanitary sewer flow reduction program.
Rick Lang has 37 years of experience working on municipal public works projects and can be reached at (313) 928-4134 or firstname.lastname@example.org. Mark Schobert has 15 years of experience working on sanitary sewer projects and can be reached at (313) 961-3650 or email@example.com. Kelly McRobb-Ackland works with a variety of communities on civil engineering projects and can be reached at (734) 947-9700 or firstname.lastname@example.org.