Dervin Witmer Seeks a Better Small-Lot Treatment Solution

Dig-It Excavating used Infiltrator Advanced Treatment Leachfield technology to cope with a small-lot replacement system

Dervin Witmer Seeks a Better Small-Lot Treatment Solution

With the trenches dug, the Dig-It crew begins laying lines of Infiltrator’s Advanced Treatment Leachfield on a bed of sand. Jim Sanders, left, sets the lines while Dervin Witmer runs the excavator. (Photos courtesy Dervin Witmer)

The system in the Indiana subdivision failed due to nothing more than old age and heavy soil. A couple of the old trenches were plugged, the result of root intrusions from the extensive landscaping around the house.

Dervin Witmer, owner of Dig-It Excavating of Cassopolis, Michigan, started looking for solutions. The job was located north of South Bend, Indiana, and only 1,000 feet from the state line, but this gave Dig-It the opportunity to use the Infiltrator Water Technologies Advanced Treatment Leachfield, a technology recently approved by St. Joseph County, Indiana.

The lot was 118 feet by 155 feet. A 15-foot drainage and utility easement along the rear, and a 7 1/2-foot easement along one side reduced the available space for a drainfield, as did a well setback on a neighbor’s property and the setback for another well next to the street. The home used most of the space on this lot. “He had mature landscaping all around there, one little strip of grass in the backyard,” Witmer says.

The customers were a man and woman, longtime real estate brokers planning to downsize to a smaller home. The couple had been conservative with their water use — which saved them from running into immediate trouble with the old onsite system — but they wanted a new system so a family of four or five could buy their house. Under county rules, they would have needed a 3- or 4-foot-tall mound system with long tapers, and that was not possible in the space available, Witmer says. The owners also did some research of their own and wanted to use an alternative technology.

Synthetic aggregate

The existing tank under the patio was in good condition and of suitable size, so that was reused. (The property was so tight, Witmer says, that a replacement tank could only have been a plastic model maneuvered into position by hand.) Only the bad drainfield was replaced.

About 6 feet separates the old tank from the edge of the new drainfield. The ATL field consists of 280 linear feet divided into four sections set about 2 feet on center. Each piece of ATL consists of a 4-inch perforated pipe surrounded by a layer of coarse synthetic aggregate and a layer of fine synthetic aggregate, with geotextile fabric wrapping each layer.

ATL pipes sit on top of 1 foot of No. 23 sand. Another foot of sand surrounds the pipes. Cover is about a foot of fill soil. Water flows through the system by gravity.

Technicians from Dig-It depended on two pieces of equipment: a new Cat 310 excavator and a Cat 299 track loader. One of the company’s Kenworth T880s was used to bring in the 60 to 80 yards of sand and backfill.

The excavator is less than two years old and has an engcon EC209 Tiltrotator, an attachment that rotates buckets and other tools 360 degrees and to a 45-degree angle. “That makes it really nice for digging in tight areas, and improves efficiency when installing systems” Witmer says.

A laser catcher on the excavator integrates with Trimble Earthworks software to provide precise digging and cutting.

The excavator did most of the cutting, including ripping out the old drainfield of stone and pipe. There were roots all through it, Witmer says.

Witmer — along with technicians Joshua Sanders and Jim Sanders — dug the new drainfield trenches slightly larger than needed in order to add extra washed sand around the edges. The larger area allows for a wider dispersal area and the coarse washed sand should help discourage roots from invading the new drainfield, Witmer says.

Protecting the earth

The small working space and need to protect landscaping and a brick-paved driveway created the biggest challenges.

Getting the excavator and track loader up from the street was done with a SlatTrax system. The modular slabs of recycled plastic spread the weight of equipment, Witmer says. In the backyard was a small strip of irrigated sod that equipment had to cross to reach the job site. “It was a little soft, and we did very little compaction on it when we had the mats down,” he says. Even the T880 did minimal damage when it moved loads across the SlatTrax.

The other challenge was staging material. Technicians covered a patio with tarps and on them piled as much material from the excavation as possible. To minimize the need for holding excavated soil on the site where there was minimal room, the crew started installing at the end of the drainfield farthest from the driveway. The Kenworth dump truck would bring in a load of sand for bedding the ATL, and the crew would load the empty truck with extra spoils to be hauled away.

When the job was done, Dig-It did a final grade, and the owners’ landscaper handled the restoration, seeding, trimming and resetting patio pavers.

Also, the crew worked in stages. The excavator did the digging and used its long reach for the first part of sand filling. Once the sand depth was great enough to allow the loader to move around, the crew parked the excavator and used the loader to move material.

“We liked that job,” Witmer says. “We like a job with creativity and that makes you think.”


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