More than a century of engineering effort has made the Chicago River — a 251-km long system of rivers and canals that snakes through urban Chicago, IL, US — into what the American Society of Civil Engineers (ASCE, Reston, VA, US) today considers a “civil engineering monument of the millennium.” One result? Water quality has improved dramatically in the past 30 years, according to Margaret Frisbie, executive director of the Chicago-based conservation group Friends of the Chicago River (Friends).
A downside, however, is that in many areas of the system, the downed trees and natural riverbanks that created good fish habitat and would ordinarily be present have been replaced with concrete seawalls, thus preventing the return of healthy fish populations to the now improved river environment. To address the loss of fish habitat and encourage healthy repopulation, Friends worked with the Illinois Department of Natural Resources (IDNR) to design nesting cavities for channel catfish, a native species that surveys had shown should be more abundant in the system.
The simple cavity design mimicked an underwater hollow log. It was designed using 31-cm-diameter PVC pipe cut to 81-cm lengths and attached by steel cables to concrete blocks to weigh the pipes down and keep them on the bottom of the river. The plan was to install 400 fish habitat and spawning units (FHSUs), introduce 100,000 baby channel catfish, donated by IDNR, that would mature in the river and, ultimately, see them use the FHSUs as nesting cavities.
Before FHSU production began, Friends had an opportunity to consult with Brian Lutey, VP – sustainability at Ozinga Green Building, a division of Ozinga Bros. Inc., a Chicago-based builder and concrete supplier. He examined the initial FHSU design and suggested that there was a better way to make them.
Lutey is active on the board of another non-profit called Urban Habitat Chicago (UHC, Chicago). The group’s mission is to demonstrate the viability of green infrastructure, urban agriculture and materials reuse/recycling, and to work with disadvantaged and at-risk youth. He knew a microbiologist and fish expert from that board, so they met to discuss the needs of catfish and the possibility of using Ozinga’s Filtercrete “pervious” concrete in FHSUs.
Pervious concrete is fairly porous. Thanks to use of the chunky aggregate that creates pores in its finished structure, it’s often used in parking lots of green buildings to encourage rainwater to infiltrate soils rather than run off to overloaded storm drains. The biologist already knew that pervious concrete’s pores help to clean water by trapping large particles (mechanical filtration) and by providing habitat for microbes and invertebrate colonies, which eat organic matter (chemical filtration) and, in turn, are eaten by fish fry (baby fish) and larger vertebrates. The pores also would help reduce the structure’s mass.
“We’ve been working with Dr. Issa for about 10 years on different types of basalt rebar,” explains RockWerks partner, Jack Rigsby. “I brought the first composite rebar over from Russia 12 years ago when I was head of R&D at Dukane Precast [Naperville, IL, US]. Dukane built the first building in the US I’m aware of that was reinforced in key sections with basalt rebar for Argonne National Laboratory [Lemont, IL, US]. They needed a building free of steel because their equipment created magnetic fields around anything ferrous, which affected their readings. When we tested basalt rebar, we found it was three times stronger than steel, easy to install and didn’t rust, so we asked ourselves ‘why aren’t we using it here?’”
Tony Celucci, another RockWerk partner adds,
We’ve had Dr. Issa test basalt rebar from many manufacturers to check product consistency, quality and fiber content across various sizes of rebar. We found they varied dramatically — from 60% to 83% fiber in some cases. Since there didn’t seem to be any established standard for quality control, we decided to partner and establish a strategic supply chain where we could control everything from rock to finished product.
In addition to ACT, RockWerk currently is partnered with basalt rovings producer Mafic SA (Kells, Ireland), resin supplier Ashland Inc. (Columbus, OH, US) and an unnamed pultruder. RockWerk arranged to supply #3 (10-mm diameter) basalt-reinforced unsaturated polyester rebar to Lutey for the project.