DIGZ Combats Soil Problems for Industrial Park Grading

Mon July 12, 2004 - Northeast Edition
James Van Horn

From off site, DIGZ’s job in Bordentown, NJ, looks like a fairly simple, standard site grading project.

Once on site, however, the complexion changes. It’s actually the largest and probably most complex, earthmoving project currently under way in New Jersey. DIGZ LLC, of Wall, NJ, is moving more than 2 million cu. yds. (1.52 million cu m) for a build-to-suit industrial park, Central Crossings Business Park, located on 174 acres (70 ha).

The park is slated to have 1.65 million sq. ft. (153,000 sq m) under roof, including a single “big box” structure with just over a million square feet. There will be three other warehouse-type buildings: 257,000 sq. ft. (23,800 sq m) , 213,000 sq. ft. (19,170 sq m) , and 150,000 sq. ft.. (13,900 sq m), plus a separate building for the fire control system. The buildings are planned with walls up to 43 ft. (13 m) high, with plenty of room for trucks, designed for the super distribution centers envisioned by today’s logistics planners.

In addition to site grading, DIGZ is in charge of the utilities and drainage, some of which is subbed out. (Other contractors likely will do the paving and slabs.) Owners and developers are the Kor Companies, Wall, NJ. Exclusive leasing agent is Cushman & Wakefield of New Jersey Inc., a branch of the New York City-based Cushman & Wakefield, a global real estate services firm with more than $700 million in revenues in 2002. Designer is CSR Group, Nutley, NJ.

The geographical location of Central Crossings is ideal. It’s within an hour’s drive of the ports and airports of Newark/Elizabeth and Philadelphia and just over an hour from New York City. It’s next to I-295, within a mile of the New Jersey Turnpike and Route 130, and close to I-195. Not far away are two stations on the new Southern New Jersey Light Rail Transit System connecting Trenton and Camden.

The physical location likewise appears to be way above average. It’s an almost level site with more than 90-percent clay soils. Farms, other commercial developments and a residential subdivision surround the area, a designated growth corridor.

But the soil conditions on the site are far from optimum. Kor’s plans call for siting concrete pads atop approximately 38 acres (15.4 ha), or over one-fifth of the site. These pads require a solid underpinning of structural earth material, which is not easy to find on the site. This area, geologically speaking, lies in the transition between the Piedmont — rock overlain with clay — just to the north and the Atlantic Coastal Plain, which is mostly sand with some clay, to the south and east. In these transition areas, there are usually at least six or seven different soil types in proximity. And this job site, according to Andrew Braverman, managing partner of DIGZ, has a lot of glauconitic silty clay, which he said has little, if any, structural qualities for fill. Consequently, DIGZ can’t just strip topsoil and bring the underlying surface to grade before concrete is poured.

Plus, some of the clay formations found in the New Jersey transition area are not only unsuitable for structural fill, they can contain pyrites, which when exposed to air and water form acid. (Pyrites also cause acid drainage problems in coal mines.) As a result, DIGZ has to contain, separate and impound potential acid-producing clays to keep them from contaminating natural and man-made drainage systems.

Furthermore, to be cost-effective, DIGZ is aiming to make this a zero net export-import job — that is, keep all material on site and use it in some way, and import as little as necessary. Clean structural-grade fill is not readily available in this part of New Jersey. (DIGZ does have to import quarried crushed stone and riprap for drainage — they use lots of it, Braverman noted.) That’s why Braverman is relying extensively on mining techniques to uncover and utilize good structural material, while simultaneously excavating and stockpiling acid-producing soils away from the main building areas. Working in DIGZ’s favor is the site plan, which calls for three large retention ponds going up to 25 ft. (7.5 m) below grade.

This enabled excavating crews to uncover several pockets of good material.

Obviously, equipment figures heavily in DIGZ’s plan of attack. DIGZ is using the excavator-haul truck-dozer method of grading, with the following hydraulic units set up as mass excavators: a Kobelco 330 with a 54-in. (137 cm) bucket: a Samsung 350, also with a 54-in. (137 cm) bucket, and a John Deere 270 with a 48-in. (122 cm) bucket. The off-highway haulers are all Volvo articulated end dumps: two A30C 19.6 cu. yd. (15 cu m) capacity units and between four and 10, depending on the workload, A25D units, with 22.9 cu. yd. (17.5 cu m) capacities. Dozers are all Komatsu except for a Deere unit used for finish-grading.

Supplying dealers are: Kobelco and Deere, Harter Equipment Inc., Englishtown, NJ; Volvo and Samsung, LB Smith, which has New Jersey offices in Deptford and Somerville; Komatsu, Binder Machinery Co., South Plainfield, NJ.

DIGZ has had as many as 24 units on site, depending on project schedules and weather, which has been something of an unforeseen factor in this job. Braverman said, “We’ve been hampered by over 60 inches of rain in the past year, in addition to the presence of unstable soils.” Far from draining easily, the clay ponds hold water like a sponge, maintaining a gumbo-like consistency. When it dries, it almost instantly turns to dust or an almost rock-hard material.

DIGZ started demolition and land-clearing in late April 2003 and expects to finish site grading by this November.

“Obviously we weren’t expecting the amount of rainfall we got. We have to be very careful when laying down material,” Braverman said, referring to meeting exacting specs for the finished grading in terms of soil density and moisture, as well as load-bearing capability.

Braverman said they have been moving an average of 5,000 cu. yds. (3,800 cu m) a day, working a single long shift (nine to 10 hours), six days a week. Hauls run 1.2 mi. (1.9 km) round trip on the average; most are fairly level, except on the detention basins, which are up to 25 ft. (7.5 m) below grade and require at least 100,000 cu. yds. (76,000 cu m) of excavation. DIGZ uses maintained haul roads where possible, but sometimes short haul lengths and soil conditions don’t justify them — machines have to “slug it out” with water and waterlogged clay.

Although his crews are moving more than 500 cu. yds. (380 cu m) an hour, they have to watch almost every yard — both to conserve good material for structural fill and to separate the potentially acid-producing clays. Pointing to a high mound of material where trucks dump excavated earth as a dozer shapes the pile, Braverman explained, “That material’s no good, so we’ll use it for landscaping around the buildings, or we’ll build berms with it, or we’ll stockpile it.” He turned to a stretch of ungraded land just beyond recently installed curbing. “Now, that’s good material, so we’ll dig it up and use it for structural fill.”

But Braverman’s selective mining techniques do not mean he’s stuck with hundreds of thousands of yards of “waste;” he actually has the opportunity for some value engineering.

“We promised to put up a sound barrier between us and the residential development being built next door. I suggested we build a berm with the ’waste’ clay, protect it from causing acid drainage with an overlay of impermeable material — which we also find on site here — and top off with landscaping dirt and plantings. We then save ourselves the $300,000 it would cost to build a separate structure.”

For the sound barrier DIGZ is building 25 ft.-high (7.5 m) rolling berms, each more than a quarter-mile (.4 km) in length.

“The severe soil conditions also forced us to think outside the box on erosion control measures,” said Braverman. So, for example, his crews took standard black erosion control fabric used on many construction projects throughout the area, “then we beefed it up with turkey wire [a strong welded-wire fencing material] and stretched it between 4 by 4s,” he said. “We installed over 15,000 linear feet of this hand-made erosion control fencing on the site.”

Braverman thinks his excavator-hauler method is paying off and singles out the end dumps for praise. “The Volvos are superior trucks, in terms of their ability to move materials. In fact, they go like armored tanks. We’ve pushed them to the limit, and they don’t stop, whether in rain, snow, scorching heat or dust. They are better than any other truck I’ve ever had.

“I looked at what this would be as a pan job,” said Braverman. “I figured it for two scrapers hauling 60 yards at a time, with a Cat D-8 class dozer to pull them, another D-8 to push, and third D-8 on standby to pull the units out when one of them got stuck. With the soil conditions, and the fact that we are moving dirt all over the site, I just didn’t see how that would work out.”

The job’s challenges — except for the unprecedented rainfall — weren’t surprises for either DIGZ or the Kor Companies.

“We tried to anticipate as many problems as possible by using extensive soil investigation reports,” said Braverman. “We pride ourselves in providing a superior product at a cost-effective price for the end user. We are continually evolving, trying to adapt to a changing marketplace.

“And we work very closely with the client — on a project of this magnitude you have to. We are in constant contact — we walk the site at least two times a day with a client representative. We have to be able to react quickly to the changing needs of both the site and the client.

“Kor has been very receptive to our ideas — we couldn’t ask for a better client.” (Kor Companies is a leading, diversified real estate investment and development company with over 26 years’ experience; to date, Kor has built in excess of $450 million in real estate.)

DIGZ is a full-service excavation and site work company with more than 25 years’ experience, not only in standard areas of grading, trenching and utilities but newer requirements such as erosion control, building retaining walls and site remediation.

Braverman said, “We’re built on three integral concepts — teamwork, cost-effectiveness, and scheduling. I feel our success is due to both organization and our great people — everyone takes great pride in their work. We also try to keep the best interests of client in mind in terms of getting job done.”

That’s not to say the job isn’t fun.

“Sometimes I think we’re a little like kids, playing with big toys in a sandbox, although there’s no sand. But it isn’t just play — at the end of the day I can look out and see that we’ve accomplished something,” Braverman said.

And next fall, when DIGZ’s part of the project is winding down, Braverman can look forward to another “sandbox” next door — Phase II of the Crossings project, Old York Road, calling for approximately 645,120 sq. ft. (59,932 sq m) under roof. “We’ll be well prepared,” he said.