Location: Fargo, ND
Client: City of Fargo
In 2009, the Red River overran its banks when the flood of record crested at nearly 41 feet. One year later, the Red River crested with the seventh largest flood on record; the year after that, it peaked with the fourth largest.
For three years, the residents of Fargo faced grueling fights against the floods, fights which involved sandbags, clay levees, and construction equipment throughout their backyards. The City sought the means to protect its residents and spare them from exhaustive (and expensive) emergency fights in the future.
The 4th Street South neighborhood stood out immediately as one of the areas warranting better permanent protection, not only because of its dense residential population but also the presence of Fargo’s water treatment plant (WTP). The loss of clean drinking water—something most take for granted—would elevate a flood emergency to an outright disaster.
The project began in anticipation of updated Flood Insurance Rate Maps (FIRMs), which became effective January 2015. The City was required to verify that the Provisionally Accredited Levee (PAL) would be certifiable again with the new flood maps. Certification would continue to eliminate the flood insurance requirements in this area; however, an analysis revealed the levee was too low, unstable, and penetrated by several old water plant pipes at its core. In order for the levee to retain its certification, the City of Fargo worked with Houston Engineering, Inc. (HEI) to identify and design improvements.
A goal of any civil works project is to avoid disruptions such as shutting down businesses for any period of time; however, the nature of the WTP’s work made it imperative that operations continued without disruption. This meant, among other things, maintaining access to the WTP for approximately two dozen semi deliveries each week.
The WTP has two entrances that trucks can utilize. HEI helped plan and coordinate construction staging so that at least one entrance remained open at all times. HEI additionally worked with the contractor to minimize downtime to the water supply processes.
Other impacts and disruptions to daily life were avoided in the residential area. For example, a pipe boring process was used to prevent the need to tear up South River Road when installing new pipes.
When one thinks of construction safety, it’s often in the context of on-site safety—hardhats, fall protection, safety vests. But this project had the additional potential to harm people miles from the site who lived nowhere near the construction. Construction had the potential to inadvertently impact the WTP by cutting off access to potable water for tens of thousands of nearby residents.
The WTP as well as residents faced an additional threat during construction—another flood. A flood during construction could have brought serious consequences since the levee was completely removed where the gatewell and lift station were while the floodwall was being constructed. To protect the residents and properties in the area—including the WTP—a contingency plan was developed, which included constructing a temporary levee/ coffer dam in the event of a rising Red River. Construction was also timed so that it occurred after high spring river stages, when a rainfall event had little chance of raising the river to flood stages.
The construction itself brought on its own potential dangers. The project required deep excavations, which meant careful planning to avoid impacting the underground utilities; unfortunately, older technology from the time of the pipes’ installations struggled to adequately mark underground pipe locations, which meant that HEI and the WTP had to take extra precautions as pipes were uncovered.
A shared use path also runs between the levee and the Red River. Construction fencing was installed to keep pedestrians from entering the construction site and to protect them by keeping them a safe distance from all construction activities. It also provided a clear barrier for construction crews, keeping them from crossing onto the path.
Residents in the area had endured flooding, construction, and more flooding over the previous years, and this project asked them to endure even more hardships before they would ultimately receive reliable flood protection. This meant early and open communication with residents in the impacted area.
HEI met with the public, especially residents in the condo building, which is within 20 feet of the floodwall construction, and kept residents informed on the project. A formal public informational meeting ensured that residents understood why the project had to happen as well as what the project actually entailed, including possible alternatives. Perhaps most valuable, the frequent conversations with residents forewarning the potential impacts they might experience during construction granted time to prepare for those impacts.
During the construction process, it was discovered that the extreme vibrations generated from driving sheet pile was heavily felt throughout the condo building. To resolve the disturbances, HEI changed the floodwall construction approach on the fly and chose to proceed without sheetpile shoring. The new approach not only fixed the immediate vibration problem but also resulted in an overall cost savings to the City.
HEI also strove to make it feel as though the floodwall belonged. The floodwall along 4th Street has an aesthetic touch with stamped and stained concrete to match both the WTP and the condo building, creating the sense that the area is part of one single community and that every structure has a shared purpose and a sense of belonging.
The construction also had the potential of impacting a popular shared use path that runs between the levee and the Red River and enjoys significant use by residents during the summer months. With the exception of very short and unavoidable periods of time during certain phases, HEI and the contractor managed to keep the path open throughout construction.
Protecting the Environment
Construction took place near the river and had the potential to impact several trees in the area. HEI reached out to and worked with the Fargo Park District to identify a clear zone away from trees, many of which were more than 100 years old. This kept construction equipment out of the root zones and protected these old trees. The project also resulted in the planting of nearly 100 new trees, helping mitigate impacts the project had as well as add new nature elements to the area.
A silt fence was also installed to control erosion from the site, which directly borders the Red River.
The proximity of the WTP to the levee project meant that the flood protection had to not only protect residents and infrastructure from high waters but also accommodate the WTP’s needs. Several pipes run through the levee; some were abandoned and closed off, and the remaining pipes were incorporated into the levee design.
Two 48-inch overflow lines from the WTP were incorporated into the storm sewer lift station and gatewell, and a separate valve box was created in the levee to allow a 10-inch reverse osmosis discharge line to be closed if problems with the pipe occurred during flooding. The reverse osmosis process is vital to the WTP; if it goes down, the plant goes down. So working this process into the levee design was paramount. The project included additional work with the underground pipes. The two 48-inch pipes combined into a single 48-inch pipe which itself combined with the local storm sewer outfall in one gatewell and lift station structure. The lift station accommodated the overflows from the WTP as well as local storm sewer runoff. The reverse osmosis line was valved off at the line of protection in a separate structure.
Because of the importance of the WTP, the WTP was on call during critical construction portions, and meetings were held as issues arose. The nature of the project meant many decisions had to be made as construction moved forward, which required fast and efficient communication between HEI, the contractor, the City, the WTP, and others. The lack of information about what would be found under the ground in terms of old and existing pipes meant that all parties had to adapt quickly as information became available.
Field conditions during construction also required that a portion of the floodwall be redesigned on the fly.
As a result of the project, residents and the WTP will continue to rely on the certified flood protection, reducing the likelihood for future emergency flood fighting efforts. This project also continues to keep properties out of the floodplain preventing them from being subjected to paying flood insurance, continuing to save residents hundreds of dollars per year.
North Dakota Chapter of the American Public Works Association (APWA) recognized this project with the 2016 Project of the Year Award based on its strong contruction techniques, safety, community relations, unusual accomplishments, and protection of the environment.
American Council of Engineering Companies of North Dakota (ACEC/ND) recognized this project with the 2017 Engineering Excellence Award for its exceptional degree of innovation, complexity, achievement, and value.
Chapter 4 of the North Dakota Society of Professional Engineers (NDSPE) recognized this project with the 2016 Outstanding Engineering Design Award for its exceptional engineering design and success.