GEOWEB® Load Support System

Project Name: Manitowoc Harbor Access Road

Project Location: Manitowoc, WI

The Manitowoc Containment Facility is an engineered structure designed to hold materials excavated during dredging activities in the Manitowoc Harbor. The facility is also part of the Manitowoc Lakeshore Birding Area, along with Lake Michigan, the harbor, and the surrounding bluff areas. The Lakeshore Birding Area is one of Wisconsin’s most popular birdwatching destinations, with more than 300 recorded species of birds—some nesting, others feeding or resting during migration. The area is managed by the City of Manitowoc and the Woodland Dunes Nature Center, with additional project support from the U.S. Dept. of Interior Fish & Wildlife Services, the U.S. Army Corps of Engineers, and the Lakeshore Natural Resource Partnership.

Confined Disposal Facilities (CDFs) like the Manitowoc Containment Facility are one of the most widely used strategies for managing and containing dredge materials. Also known in some states as Dredge Material Management Areas (DMMAs), these facilities require long-term maintenance to ensure the confinement dikes and drainage structures function as designed. If the facility approaches its design capacity, it will either need to be expanded or permanently closed. Closed CDFs often present communities with an opportunity to evaluate options for beneficial reuse. Alternatives can include new developments, additional green space, boat launches, recreational areas, and even new habitats for wildlife. The Manitowoc Containment Facility, which is essentially an island situated along the Lake Michigan shoreline, has become an integral part of the physical landscape for both wildlife habitats and recreational activities.

Inherently Soft Soils Present Challenges for Equipment Access

The materials contained within CDFs typically comprise a mix of unconsolidated soft sediments, organic silts, and compressible materials generated from years of dredging operations. For heavy equipment, these soft ground conditions translate to site access challenges for facility maintenance, dredge material handling/management, closure activities, and site redevelopment. The weak soils surrounding the Manitowoc Harbor were no different. Exhibiting a strength of less than 1% CBR, the ground conditions were unable to support the repeated heavy loads required to keep up with dredging operations.

Extremely wet, soft soil surrounding the harbor.

Presto Geosystems worked closely with the US Army Corps to develop a sustainable solution to provide equipment access to the CDF and overcome the facility’s soft ground issues. The GEOWEB® 3D Soil Stabilization System was chosen for its superior load distribution, low maintenance, and cost-saving benefits.

The GEOWEB System Provides Sustainable, Low-Impact Solution for Haul Road

Engineers designed a 36,000-square-foot haul road over weak soil using the GEOWEB system. Due to the low subgrade strength and anticipated heavy traffic patterns, a dual-layer of GEOWEB GW30V6 (6-inch-deep) reinforcement was required. An enhanced woven geotextile was installed on the prepared subgrade to provide separation and filtration. The GEOWEB system was infilled with low-maintenance crushed aggregate.

As part of the complete GEOWEB system, ATRA® Keys were used to connect adjacent GEOWEB panels. The ATRA key connection device significantly reduces contractor installation time and provides three times the connection strength versus metal staples. It is also a corrosion-free connection appropriate for marine environments and applications where the system will remain submerged below the groundwater table or subjected to cyclic wetting and drying due to seasonal variations.

Quick deployment of the GEOWEB system over soft soil.

Additionally, given the site’s location in an environmentally sensitive area, a low-impact solution was necessary. The GEOWEB system performs as a load support structure, and with aggregate infill material, provides an additional benefit in terms of on-site stormwater detention/retention. The latter benefit can help reduce, or even eliminate, requirements and costs for on-site stormwater containment systems.

Project Results

Since the installation, the GEOWEB haul road has withstood repeated heavy traffic and heavy rain events. Crews have operated 70-ton haul trucks and heavy tracked equipment over the GEOWEB system with no issues.

Project lead, Mark Olsen from Roen Salvage Company says, “We’ve been running 120-ton haul trucks and excavators over it with absolutely no problems at all. We’ve had heavy rainstorms—2 to 3-inch rainstorms—and it doesn’t affect it at all. It’s been a really good product. Putting it down and prepping for the road is very easy.”