Industry News

Dredging in the river valley

As with many operations across the extractive world, the Hanson Aggregates site was initially developed as a family operation. The Bunnell family started in the gravel business in the 1950s as the huge American highway development was evolving.

The family business grew in the following decades and expanded to the current plant. Subsequently, this operation was bought by Hanson Aggregates. {{image2-A:R-w:250}}

Ohio is located south of Lake Erie and is a large producer of a range of minerals, as well as aggregates. According to the  latest published figures2,5, Ohio has close to half the population that Australia does and produces about half the total construction aggregates (American figures separate sand and gravel from crushed stone).

The Ohio River forms at the confluence of the Allegheny and Monongahela rivers, at Pittsburgh, Pennsylvania. Its meandering path forms the southern borders of Ohio, Indiana and Illinois, flowing 1600km to the Mississippi River.

Dry Fork Creek traverses the western edge of Ohio, running into Whitewater River, which runs into the Great Miami River. The Great Miami River flows into the Ohio River at the southwest corner of Ohio. The Hanson Aggregates operations sits alongside Dry Fork Creek.

The Great Miami River Valley has been extensively studied for local water supply, plus aggregates and minerals. The bedrock of the valley consists of interbedded shale and limestone of the Ordovician Period (see Figure 4 on page 31). With the shale and limestone deposited and consolidated, the Early Palaeozoic seas retreated. {{image3-A:L-w:250}}

A pre-glacial river was prominent up to the Late Tertiary Period. With the beginning of the Quaternary Period, four major glacial events took place, advancing and retreating until the Holocene Epoch.

These glaciers brought both lodgement “till” (see glacial description) during advance, and large amounts of silt, sand and gravel with meltwater run-off during retreat. Valleys were formed, cutting through the shale and limestone bedrock.

The glacial deposits vary greatly in depth. Sand and gravel has been extracted in localised areas where there is generally significant depth.1,2,3

Figure 1 illustrates a cross-section of typical bedrock formations and glacial deposits in southwest Ohio.4

SAND PROCESSING EQUIPMENT{{image4-A:R-w:320}}In 1999 the Bunnell group built the current plant, based around the GreyStone washing equipment (now part of Superior Industries). This included a classifying tank, a 36” x 35’ log washer, a single 44” x 32’ sand screw and a twin 44” x 32’ sand screw.

The dredge was purchased and built five years earlier, with the heavy mobile equipment ranging in age from the early 1990s to 2006. {{image5-A:R-w:320}}

The mainstay of the extraction is a Rohr clam shell dredge (see page 30). Material extracted by the clam shell is placed on a 203mm grate type grizzly over a hopper, with any oversize returned to the pond. The throughs of the on-board screen are sent via three 30m floating conveyors and one 91m floating conveyor to shore, where a 38m radial stacker stockpiles the material.

It generally takes 24 hours of dewatering before they can load the material into a haul truck. There is also a Krebs 20” cyclone and dewatering screen on board the dredge. This has been used for the retention of fines but is not currently in use.

Separate to the wet mining, there is a dry mining process, with material conveyed from a pit on the other side of Dry Fork Road (shown in Figure 2). This operation, which supplements the wet feed, utilises a Caterpillar 988F rubber-tyred loader, loading a Cat 740 haul truck, which dumps the aggregate into a hopper. {{image6-A:L-w:200}}

This material is conveyed under the road to a 75 ton bin (US ton, equal to approximately 68 tonnes). Two Volvo A35C articulated trucks are used to haul material from this bin, as well as the stockpiled dredged material. Another Cat 988F loads the dewatered dredged material.

Figures 2 and 3 show the processing plant and the dredge with the floating conveyors and the conveyor under the road.

The trucks dump into the main plant hopper and the material is fed onto a 36” conveyor via an FMC electromagnetic feeder to a Tabor 8’ x 24’ (2.4m x 7.3m) primary screen.{{image7-A:R-w:250}}

All plus 1½” (40mm) material is scalped and sent to a Hazemag 1010Q horizontal shaft impactor for primary crushing. There is a bypass conveyor to stockpile the oversize when they are not crushing.

All crushed material is then conveyed to an ISC 66 vertical shaft impactor (VSI). The product of the VSI is sent to a 4’ x 12’ (1.2m x 3.7m) dry screen for final sizing. Any oversized material is recirculated to the VSI.

The throughs of the primary screen are conveyed across to the washing plant, feeding a 5’ x 16’ (1.5m x 4.9m) two-deck Tabor screen. The river rock or gravel is screened off and fed to the log washer. The log washer cleans the natural rock exceptionally well.

While 80 per cent of the product from the site is sand, a good clean river rock allows the opportunity to explore the landscape market, with some customers bagging their product for resale. {{image8-A:L-w:250}}

The clean rock is then screened on a Tabor 7’ x 20’ triple-deck wet screen. Four different sized products are produced: a #4 roofing gravel retained at 1½” (40mm), #57 gravel retained at 1” (25mm), #8 washed pea gravel retained at 3/8” (9.5mm) and a #9 grit that is a 5/16” (8mm) gravel. The #9 grit is sent to a 3’ x 6’ dewatering screen before stockpiling.

The classifying tank allows the operators to produce a range of fine aggregate or sand products, while removing silt or minus 200 mesh (75 micron). Typically they are producing Manson sand and concrete sand. With the classifying tank and sand screws, they have the flexibility to manage specialised products while still making their main product lines.

The concrete sand is directed to the twin sand screw as the main product. The single sand screw produces Mason sand or any specialty product they may consider.

Hanson took over the operation in 2003. The plant manager Bill Roell has worked at the site through the change of ownership.

Roell learned the operation under the Bunnell family and then moved up through the ranks under the Hanson stewardship. According to Roell, the operation’s main markets have been asphalt and concrete.

While the Hanson Group takes a sizeable portion of its production, it competes in the marketplace for other customers. Before the purchase Hanson drilled the deposit to 61m. Roell believes it will ultimately extract to the 61m level.

The primary feed to the plant is 600 tph (a combination of wet and dry mining). Roell advises it has processed 7.7 million tonnes in the 15 years of operation. Both owners have been extremely satisfied with the performance of the processing plant. With a location in the northern US, the Hanson operation has a defined production season due to inclement weather.

It typically produces from early April to late November, with sales and yard loading going all year round. With a stable, experienced workforce and a reliable and efficient processing plant, the Hanson Aggregates operation at Dry Fork Road continues to produce a high quality product, in spec and at an economical cost.

Jim Hankins, is the managing director of Rivergum Industries.

The author thanks Hanson Aggregates’ Bill Roell for making the site visit possible and for subsequent information (and patience). Thanks also to Superior Industries’ John Bennington and Frank Squires for their assistance.


1. Ground-water hydrology and geology of the Lower Great Miami River Valley, Ohio. Geological Survey Professional Paper 605-A. Prepared in co-operation with the Miami Conservancy District and the Ohio Department of Natural Resources, Division of Water, Columbus, Ohio. US Department of the Interior – United States Government Printing Office, Washington, 1968.
2. Wolfe ME. 2012 Report on Ohio mineral industries: An annual summary of the state’s economic geology. State of Ohio, Department of Natural Resources, Division of Geological Survey. Columbus 2013.
3. Barner M. A geologic overview – The Great Miami River Basin in Southwestern Ohio. The Miami Conservancy District, Groundwater 2000 Program, Aquifer Preservation Subdistrict, September 1998.
4. Modified illustration of selected domestic wells in hydrogeological study determining arsenic concentrations in southern Shelby County, Ohio. Courtesy of the United States Geological Survey, USGS Scientific Investigations Report 2005-5138.
5. Estimate courtesy of CCAA.
6. Illustration courtesy of Clive Maxfield High-Tech Consulting,
7. Brown DA, Campbell KSW, Crook KAW. The geological evolution of Australia & New Zealand. Pergamon Press Ltd, 1969.
8. Sawkins FJ, Chase CG, Darby DG, Rapp Jr G. The evolving earth – A text in physical geology. Macmillan Publishing Co, Inc, 1978.
9. Read HH, Watson J. Introduction to the Geology Volume 1 Principles. The Macmillan Press Ltd, 1979.
10. Bird’s eye view screenshots of Bing Maps © 2014 Microsoft Corporation. Pictometry Bird’s Eye © 2012 Pictometry International Corp.


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