Missouri development benefits from creative civil engineering

Branson Landing, Branson, Mo.
Civil engineer:
Walter P Moore, Kansas City, Mo.
Product application:
A custom-designed filtration system keeps a new development dry and treats stormwater discharging into an adjacent, pristine lake.

Storm sewer improvements protect important water resources.

Since its first theatre was built in 1935, Branson has been Southern Missouri’s top tourist destination. More than 8 million tourists visit Branson each year for its entertainment, shopping, and family venues, as well as scenic Ozark Mountain beauty. One of the attractions is Lake Taneycomo, which has more than 2,800 surface acres of clear, cold waters that provide some of the world’s finest trout fishing and a variety of recreational activities. Consequently, redevelopment of the downtown and waterfront area to create Branson Landing required consideration of water quality as a top priority.

Branson Landing, a $420 million, 95-acre development adjacent to historic downtown Branson, was delivered by a public/private partnership between the city of Branson and HCW Development Company, LLC. The Landing includes approximately 450,000 square feet of retail shops and waterfront restaurants, condominiums, entertainment venues, marinas, a boutique hotel, structured and surface parking, and a boardwalk along the lake. Key elements of the project are the Branson Convention Center, offering 220,000 square feet of meeting space and a ballroom; the 12-story Hilton Branson Convention Center Hotel; and a one-mile stretch of a new, five-lane thoroughfare known as Branson Landing Boulevard.

Branson Landing, a $420 million, 95-acre development adjacent to historic downtown Branson, Mo., and Lake Taneycomo, includes a convention center and 12-story hotel, as well as five-lane Branson Landing Boulevard (foreground).
CREDIT: Ken Geise

Water quality mission
Walter P Moore, which specializes in design of large-scale site development projects, was hired to design the development’s civil engineering components. And of the many design facets considered for the development, stormwater quality management was among the most important. The city engineer charged Walter P Moore with designing a stormwater management system that not only keeps the development’s establishments dry, but also improves the quality of stormwater runoff to prevent degradation of Lake Taneycomo, the downstream receiving body of water. Protecting the integrity and water quality of the lake, which is a flood-control reservoir regulated by the U.S. Army Corps of Engineers, was crucial to public support and U.S. Environmental Protection Agency approval.

One option was to install pre-manufactured, pre-engineered water treatment systems in each storm sewer system inlet. With the national emphasis on improving the quality of stormwater runoff, many products are now available to intercept stormwater runoff at the point where it enters a system, filter it of debris, and settle solids and particulates. This option was quickly judged to create an undue maintenance burden on the city, given the scale of the development and its location downstream of an approximately 80-acre watershed consisting of historic downtown Branson.

Instead, Walter P Moore devised a system to collect stormwater runoff from the upstream watershed as well as the development, route it safely through the development, and provide treatment at the downstream end just before discharge to Lake Taneycomo.

Branson Landing is an extremely linear development. Stretching nearly one mile along the lake shoreline, the development is only about 400 feet wide. Retail shops and restaurants front Branson Landing Boulevard on the west and Lake Taneycomo on the east; a central promenade runs the length of the project. With all of the retail establishments at the same floor elevation, developing a drainage system through the long central promenade presented some interesting challenges.

Quickly visualizing a concept, the engineers divided the project site into three segments. A primary storm sewer system through the center of each segment extends from the lake upstream through the width of the development to connect historic downtown Branson’s storm sewers. Secondary storm sewer systems draining the new complex through the center of the long promenade feed the development’s runoff to primary systems. The drainage areas are served by what became commonly known as the 99-acre South System, the 35-acre Central System, and the 30-acre North System.

The established design criteria required treatment of runoff from a 50-percent storm removing no less than 80 percent of the total suspended solids, while also providing adequate hydraulic capacity to convey runoff from a 1-percent storm safely through the development. Hydrologic analyses established the runoff from the 50-percent storm to be 268 cubic feet per second (cfs), 103 cfs, and 90 cfs for the South, Central, and North Systems, respectively.

Two key goals were accomplished by selecting a primary storm sewer system comprised of multiple-barrel, reinforced concrete pipes: The system height was minimized, and a means was provided to separate the runoff to be treated from the runoff that would have to bypass treatment during less frequent (more severe) storms. A special structure in the downstream reaches of each system was used. By selecting varying discharge pipe sizes, varying invert elevations, and carefully analyzing the hydraulic characteristics, a network was created so that, at maximum head in these special structures during the less frequent storms, just the correct amount of runoff was diverted through a parallel system that included the stormwater treatment element. Flow rates in excess of the runoff generated by a 50-percent storm bypass the water treatment element and are discharged directly to Lake Taneycomo. The system operates solely on the hydraulic characteristics of the network during a variety of storms.

With no pre-engineered system available with the capacity to treat the expected runoff rates and volumes, the city of Branson, with technical assistance from Walter P Moore, solicited proposals for custom-designed treatment systems. BaySaver Technologies, Inc., was selected and assisted in designing and furnishing custom components for installation in field-cast water treatment structures designed by Walter P Moore.

Three, 72-inch-diameter pipes comprise the outfall of the south portion of storm sewer system along the west bank of Lake Taneycomo.
CREDIT: Walter P Moore

Water quality + tourism = Environmental success
The Branson Landing storm sewer system, currently in operation, consolidates the city of Branson’s maintenance requirements to three central locations, and is highly effective. The improvements prove that striking a delicate balance of environmental quality and economic advancement is mutually beneficial. Branson Landing has already impacted the community’s economy—generating significant increases in revenue to local businesses—all while helping Lake Taneycomo remain a beautiful natural playground, teaming with life.

"If any project is innovative and demonstrates engineering excellence, the Branson Landing Storm Sewer improvement is certainly that project," said David Miller, city engineer. "The engineers developed the best solution to handle large stormwater flows and yet keep the intimate atmosphere of the entertainment area. The system provides state-of-the art treatment of the stormwater from the entire downtown Branson area and protects the quality of Lake Taneycomo—which is the most critical component of the Branson economy."

Jerry Nachtrab, P.E., is a principal and managing director of civil engineering in Walter P Moore’s Kansas City, Mo., office. He can be reached at jnacbtrab@walterpmoore.com or 816-701-2100.

Posted in Uncategorized | January 29th, 2014 by

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