Missouri's Travis Hodge Hauling Installs Large LPP System

When the bottom fell out of a wastewater lagoon under construction at a state park, a new, expansive LPP system solved a drainfield dilemma.
Missouri's Travis Hodge Hauling Installs Large LPP System
The new wastewater treatment plant at Stockton State Park in Missouri. At right is a stack of EZflow that became part of an LPP dispersal system. A sinkhole beneath the original system required a change of plans when work on the new system was partially complete.

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In the process of updating its wastewater system, Stockton State Park in Dadeville, Mo., discovered a sinkhole the hard way, and that is why Travis Hodge helped solve the park’s wastewater needs.

The park is on the edge of the Ozarks in southwestern Missouri, 254 miles southwest of St. Louis and 146 miles south of Kansas City. It had outgrown its 15-year-old system and the state began installing a new one. However the unusual geology in this part of the country put a kink in those plans. Geology provided an additional challenge for Hodge and the crew of his company, Travis Hodge Hauling, but it was a challenge they could easily meet.

The park

Stockton State Park sits on the end of a peninsula surrounded by two arms of the Y-shaped Stockton Lake. The wastewater system now serves 70 campsites and five cabins, plus restrooms and the concession stand at the park’s marina. It’s hard to find a spot in the park more than 1,000 feet from the shore, and people are drawn to the park, its 300-slip marina and the 24,900-acre lake.

The park was developed in about 1969 when the nearby Stockton Dam began impounding water. For many years, the park’s wastewater needs were met by a simple lagoon, and then by the addition of spray equipment to dispose of the effluent, according to Hodge. But park use continued to grow, and a few years ago the state began a project to expand the wastewater system. A different contractor was hired to build a new lagoon with a treatment plant and a large spray irrigation field to disperse water from the plant.

“And little did they know that particular area of land was susceptible to sinkholes,” Hodge says. Sinkholes appear in Missouri. They’re not common, but they’re not uncommon. “When the lagoon was near completion they had a huge rain one night. It turned out there was nothing holding up the soil beneath the lagoon, and they wound up with a hole about 16 feet wide and 16 feet deep.”

The contractor got a change order. The hole dug for the new lagoon – and the sinkhole – was filled in and leveled off. The treatment plant remained. It consists of a 10,000-gallon septic tank and a 5,000-gallon septic tank in series for denitrification, a recirculating pea gravel filter, and ultraviolet light disinfection. A new bid went out for the dispersal method. Instead of spray irrigation, the design now called for an LPP system with a large drainfield and a hydraulic load of 0.2 gallons per square foot per day. That’s where Hodge came in.

The system

The LPP solution installed by Hodge was large but simple. Water leaves the treatment plant through two force mains made of 2 1/2-inch Schedule 40 PVC. One main runs about 100 feet to one LPP field while the other main runs about 200 feet to the second field.

At the head of each field, each main enters a six-position indexing valve that mechanically doses the LPP zones. Valves are set higher than the field so they will not hold water in case of a sustained hard freeze. That is not common in this part of Missouri, and valves and the manifolds are buried above the frost line. This also kept them out of tough soil on the site.

The two dispersal fields are divided into six zones, each about 150 feet wide and 300 feet long, with six laterals per zone. The job required 10,386 feet of pipe. The mains in each field were also 2 1/2-inch pipe. Laterals were created with EZflow from Infiltrator Systems, meeting the engineer’s requirement that there be no compaction of the soil, Hodge says.

Laterals within each zone were laid 5 feet on center, and the spacing between zones varied from 5 to about 30 feet. Approximately 16 to 18 inches of native topsoil covered the laterals.

An LPP system like this one is an advantage in areas prone to sinkholes because it disperses water over such a large area, Hodge says. There is little chance of soil washing away. Yet the system design takes into account the possibility of another sinkhole. If one appears under one of the new LPP fields, the operator can shut off an entire zone. The system can run properly on 10 of its 12 zones even during a time of peak use in the park. Maintenance plans also contain a protocol for fixing sinkholes. Repair begins with large stone against bedrock, and then increasingly smaller grades of stone closer to grade. A layer of filter fabric is placed on the top layer of stone, some base rock is placed on top of that and then soil is used to meet the grade.

Challenges

The engineer’s concern about compaction of the soil extended to equipment. “He wouldn’t let me bring wheeled machines on the job site. Everything had to run on tracks,” Hodge says.

Fortunately that wasn’t a problem. Hodge switched to tracked equipment some time ago because it is much more stable on hillsides, and he says in his part of the country backhoes are unusual now because so many companies have changed to excavators. Hodge uses Kubota and Komatsu equipment. Most of this project was installed with a Kubota 161 tracked excavator.

The soil is unusual in this part of the country. It’s a deep red color with very fine particles, not sand but still with little structure. Even when damp it’s hard to compact a handful into a ball, Hodge says. “We haven’t seen anything quite like the dirt in this area. It drains so well that if it rains 2 inches on one day you can be hard at work two days later.”

One sinkhole appeared during the job, but it was only 6 or 7 feet deep and about the same in diameter, Hodge says. His guys filled it in and moved on.

They were also fortunate because they didn’t have to deal much with the hardpan. This is another feature of Missouri soils, Hodge says. It’s a fine gravel with a large fraction of red rock. You can dig through it, but there’s a great deal of flint in the rock. A broken piece of red rock can be sharp enough to cut skin, and it is not friendly to excavator teeth.

On the Stockton State Park job, the crew dug through hardpan for only 200 feet to bury the force mains. The laterals and indexing valves could be buried above the hardpan. As a result, Hodge’s crew wore out only a few teeth during the job. It can be worse. On one job a few years ago, a crew went through one set of teeth for about every 100 feet of digging, he says.

The other holdup was weather. Work started in March but did not end until June because of frequent rain. During some periods the crew of three to four could work only one day in every week, Hodge says.

Experience counts

What doubtless helped him win the bid was experience, Hodge says. His company does a large amount of government work, mostly for small and large cities that are extending or replacing municipal water and wastewater systems. Travis Hodge Hauling has installed LPP systems for subdivisions, but none as large as the Stockton State Park project.

Now, with help from Hodge and his crew, Stockton State Park is ready to provide many more years of recreation with a system that won’t disappear down a hole.



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