Working the Channels

Dec. 16, 2016

For erosion control specialists, channel stabilization can bring a host of challenges. Working around water means choosing solutions that will be durable and environmentally friendly at the same time. Approaches may include the combination of hard and soft armor or vegetative techniques.

Yet for those companies with the right crews, equipment, and mitigation approaches, there’s plenty of work to be done. Recent severe weather events that have eroded slopes and coastlines have opened the floodgates for such projects.

New Stapleton Waterfront
Case in point: The Homeport, a 35-acre decommissioned US naval base on the north shore of Staten Island, had been slated for a mixed-use residential community project, the New Stapleton Waterfront.

The New Stapleton Waterfront had actually been designed 10 years ago, but budgeting issues prevented it from going forward, says Peter Lauro Jr., vice president of J.R. Cruz Corp. The Aberdeen, NJ, company provides services in micro tunneling, wastewater, water supply, transportation, and general construction.

In 2011, the Ironstate Development Company entered into an agreement with the city to acquire parcels and develop the first phase of a new, sustainable, mixed-use waterfront community at the former Homeport, located within walking distance of the Stapleton Staten Island Railroad station. But in 2012, damage from Hurricane Sandy required coastline mitigation, further delaying the project.

“Hurricane Sandy decimated that area,” says Lauro. The damage required some changes to the originally planned project. “Once we got into the job and started to uncover what was underneath all of the rubble and debris, we got a bunch of change orders, which led to the design you see today.”

The developer broke ground on the first phase of the project in 2013, ­turning 7 acres into a sustainable ­development of retail and residential space—including affordable housing—for Staten Island residents.

“The New Stapleton Waterfront area is in the process of getting a complete makeover,” says Lauro. “The city is pumping a ton of money into that area to rehabilitate it and make it like a little downtown Brooklyn.”

The $130 million project is financed by New York City and by a state Environmental Protection Fund grant. It was designed by the New York City Department of Design and Construction and is expected to draw more traffic to the waterfront with affordable housing, restaurants, bicycle lanes, a Ferris wheel and other entertainment, retail stores, and newly created tidal wetlands, according to information from New York City Economic Development Corporation (NYCEDC).

The marine work was designed by the McLaren Engineering Group. HDR provided oversight consultation.

J.R. Cruz Corp. was tasked with phase II of the project, which entailed reconstructing the park along the waterfront and intersecting two streets. The company also had to reconstruct the cove area adjacent to the park and rehabilitate five connector streets connecting Bay Street to Front Street with new utilities, new roadway reconstruction, curbs, and sidewalks.

“A lot of the work we did was all a result of what Sandy did,” points out Lauro. “The tides became high again. The designers were trying to mitigate the damage.” Some of that work was done with Reno mattresses.

Richard Prejs, Maccaferri’s northeast area manager, says J.R. Cruz installed 27 Reno mattresses measuring 12 by 6 feet by 9 inches thick with stainless steel Spenax fastening rings.

Maccaferri developed the gabion and Reno mattresses nearly 140 years ago, developing a double-twist wire mesh for hydraulic applications including erosion protection and channel lining, notes spokesperson Craig Foster.

The mattresses are cages engineered from double-twisted, hexagonal, woven steel wire mesh. They are assembled onsite and filled with stones to form flexible and permeable monolithic structures for riverbank protection and channel lining.

Photo: CMI
Sheet pilin gwas used to create a stilling basin to slow water relocity.

Plantings were placed along the waterfront near the Verrazano Narrows upper bay to be the first line of defense against regular scour in an area where cruise ships enter and exit. Reno mattresses were installed behind the plantings.

The mattresses will serve as a slope protection measure to help prevent scouring along the waterline as a second line of higher and stronger defense to help deflect and prevent erosion, says Prejs.

“It also provides a nice buffer between the planting area and above the Reno installation to help deflect and absorb some of the wave action from potential storm surge from a Superstorm Sandy-type event or the more common nor’easter,” he says.

Photo: CMI

Other mitigation measures were taken, as well, to augment the Reno mattresses, notes Lauro. Underneath the Reno mattresses are Maccaferri Polymeric Marine Mattresses. These mattresses are constructed from HDPE punched and extruded geogrids and fabricated into a mattress container.

“It’s about 18 inches thick, filled with a No. 5 stone, like a riprap stone, and if we do get high tides, that’s to prevent it from washing everything out as the tide recedes” says Lauro. “Those mats are supposed to lock everything we did into place.”

On top of those mattresses, J.R. Cruz constructed a new bulkhead wall of precast concrete along half the area and piles of timber lagging for the other half.

“That wall was built to help absorb some of the energy as the waves and the high tides come in, so they will not destroy some of the planting work that we did there,” notes Lauro, adding that salt-tolerant Spartina plants were used in the area.

“They are low marsh plantings, special plantings in one-gallon plugs. We put thousands and thousands of them in to help prevent some of the erosion,” he says. “Beneath all of that sand is a big jute mesh layer. We put sand on top to allow natural habitats to grow and flourish.”

A third phase of the project will continue a similar coastal mitigation approach to connect with the Verrazano Narrows bridge area.

Lauro says the project highlights the need for an experienced crew and the right equipment to work in such conditions.

“We had to build a temporary bulkhead with steel sheeting. We had to do some extreme pumping. We had to really spend a lot of time and money preparing to keep the area dry so we could perform our work,” he says.

Lauro credits J.R. Cruz’s Mike Russo, the superintendent who spearheaded all of the work and ensured the crew consisted of people with the skills to execute the plan.

The project necessitated a range of equipment, including special vibratory hammers with excavators on pontoons.

“We had all types of heavy-duty pumps, discharge tanks, and large generators,” notes Lauro. “A lot of this stuff we had to invent as we went along, because we really couldn’t work from the marina—the mud lines were so high and we couldn’t get a barge in there. Everything had to be done from the land. With everything being done from the upstream position, we had to have long-stick excavators reach out there and do the job, and, at the same time, control the water.”

Lauro says the job has been a big success. “The NYEDC and the designers are very happy with how the job came out. The community is also very happy. They had a ribbon cutting ceremony. The borough president was pleased with what was happening there and how that whole area is being revamped. Once they are done with those phases, there’s going to be a total transformation of that area.”

Crestview, FL
In the predominantly flat state of Florida, Crestview—located in the state’s Panhandle region—stands out as one of the few hilly areas.

A violent storm system during the spring of 2014 brought more than 24 inches of rain and massive flooding to northwest Florida, with disaster assistance topping $66 million. For Crestview, the storm caused significant erosion in one of the residential areas. Water blew out a slope in a ravine near some houses.

“All of that rain was funneled down through this gulley, and it tore out structures and essentially found a new path,” explains Joe Klaus, project manager for CH2M Hill in Pensacola, FL. “We were tasked with analyzing where the water was going and then stabilizing the slopes and somehow harnessing the power of the waters that went through this channel.”

Photo: CMI
The NRCS helped fund the Crestview project.

In 2015, CH2M Hill designed a stilling basin, which was installed in early 2016 on Gil Ava Street,
to slow the water down and release it at a lower velocity to prevent it from doing any further damage.

The sides of the stilling basin are composed of 273 linear feet of Crane Materials International (CMI) ShoreGuard SG-950 sheet piling. CMI also supplied ArmorWare rods and wale for the deadman anchors on the project. RBM Contracting Services served as the subcontractor on the project.

Photo: CMI

In considering the options, CH2M Hill chose vinyl sheet pile, which was more cost efficient and provided the potential for a greater return on the investment in terms of meeting the project’s goals, notes Klaus. CMI’s ShoreGuard vinyl sheet piling is designed as an alternative to other sheet piling materials such as steel, concrete, and treated wood, which may present environmental and maintenance challenges.

“It’s pretty stout,” says Klaus of the installation in Crestview, adding that it has been designed for the 100-year-storm.

CH2M Hill considered some vegetative alternatives for the bank stabilization, choosing sod in order to obtain the correct slope, says Klaus.

Photo: CMI

“The challenge in stabilizing these gullies or drainage ways is to do it so that you’re not creating a channel that’s going to maximize the energy coming through, but somehow tying it into the natural flow,” he says. “Sometimes you can’t, especially in an urban setting where the objective is multipurpose. You want to stabilize that stream, but you also want it to be aesthetically pleasing.”

One advantage for the project was that it was funded in part by the Natural Resources Conservation Service (NRCS). “They had several other projects in the area where they had to address the same type of issues of water eroding out a channel, but not of this magnitude,” says Klaus. “This project had a quick fuse to it so it would get stabilized before the next storm. The NRCS was instrumental in moving this project along, both financially and schedule-wise.”

CH2M Hill is now working on the project’s second phase. During the 2014 storm, the turbulent waters picked up a significant amount of soil and moved it farther downstream. “Now that we’ve got this stabilized, the next phase is to reestablish the channel downstream and remove most of the sediment,” he says, adding that the company is currently brainstorming ideas for solutions. 

About the Author

Carol Brzozowski

Carol Brzozowski specializes in topics related to resource management and technology.