Erosion Control Magazine,
July / August 2003 Issue:
Shoring Up Our Banks,
challenges of working in and around water.
By Linda Robinson
Wave action, whether a slow ripple over time or the dramatic impacts of severe wave pounding, can cause erosion and devalue property. The process can be mitigated by using best management practices for shorelines and proper constraints when performing construction around the shoreline. Many cities and towns now opt to make shorelines more natural and accessible by reconstructing previously limited shorelines with natural stone, sand, and vegetation.
This article looks at five case studies—where water and shorelines meet—to demonstrate how different cases call for different remedial measures.
Kissena Lake's Naturalization Project
In 1870, when horticulturist Samuel Brown Parsons began his tree nursery in New York, it's said that he also named the gentle flowing lake in the area Kissena Lake. The word Kissena is taken from the Native American Chippewa language and means "cool waters." Although cool water is a characteristic of Kissena Lake, Atlas Roll-Off construction workers got more than they bargained for when the lake froze during the second phase of the Kissena Lake rehabilitation project in December of 2002.
Kissena Lake is situated in the 282-ac. Kissena Park in Queens, NY. Glaciers formed the lake and the old Hudson River route that began before the last ice age. The lake is home to numerous fish, turtles, and other aquatic life. Surrounding the lake are many varieties of trees; some originally brought from Europe and Asia still grow in historic remains of the tree farm.
Gary Capparelli, project supervisor with Atlas Roll-Off Company, explains that a concrete wall had been built around the lake in the 1940s. Through the years, however, the wall began to appear unnatural and presented problems for the turtles that live in the lake. Between the City of New York and the New York Parks Department, the decision was made to take the wall down and create a more environmentally friendly, natural-looking shoreline for the lake.
"In order to do so, they had to cordon off the lake to divide it into two sections," Capparelli recalls. "One area was small and one large. The smaller area would be used for the work project. They used the AquaDams to dewater the construction area."
The concrete wall was taken down by sawing it horizontally and removing its top two-thirds. The remnants of the wall remain 2-4 ft. below the water line in the lake. The Department of Environmental Conservation (DEC) worked closely with the Atlas Roll-Off crew and mandated how far down the lake could be drawn to protect wildlife and the integrity of the lake. Additionally, the DEC supervised the fish removal during the lake dewatering process.
"The turtles and the fish had to be removed. The fish were corralled—approximately 5,000 fish in all. There were all different sizes, from fingerlings up to 36 inches. Plus, they had about 50 to 60 turtles that they corralled and removed."
Dewatering lakes can be a very problematic process and is done in phases to protect the lake and aquatic wildlife. It is often simpler to drain a body of water entirely, but that was not an option at Kissena Lake.
"They spent a lot of money on this project," states David Doolaege, owner of AquaDam and Water Structures Unlimited. "They could have drained the lake, but all the fish and turtles would have died. Isolating the work area and dewatering just the work area prevented this from happening. They chose to protect the aquatic life and restore the lake at the same time, mitigating the impacts of using the AquaDams. They did their work on one section and then moved the AquaDams to another corner of the lake."
Actually, Capparelli notes, there were two damming options considered in the beginning. One option was a more rigid dam that is lined. The second was the more flexible AquaDam. The decision to use the AquaDam was based on economy, ease of installation, and customer service.
"They didn't need to have any heavy equipment because basically it [AquaDam] unrolls itself," Capparelli explains. "They had contacted several people in the field before they found David Doolaege."
Once the decision was made to use AquaDams, the construction was ready to begin.
A 600-ft. line was first strung across the lake for a visual guide for workers. The first dam was floated in the water, and the pumps were set in place. Each one of the three main AquaDams measured 100 x 800 ft. The first dam was actually started up on the bank to ensure adequate filling. Using tie ropes, workers secured the first 25 ft. of the dam. After unrolling the proper distance, the dam was pulled into place to move toward the far shore.
After the first dam finished filling, a second dam was floated to the end to be hooked up to the first using a special coupling collar. The second dam was readied for filling and unrolled. Doolaege notes it is very important that the AquaDams abut well, because the first one must serve as a platform to start the second. This process continued until all three dams were in place.
To dewater the construction section that was dammed off, Capparelli's crew used two 800-gpm, 4-in. diesel pumps. Initially, he reports, they pumped some 2.5 million gal. of water out of Kissena Lake to prepare the site. Because the lake's depth is only about 4 ft., they were able to use a log pole to help push the AquaDams into position.
After small holes were cut in the collar to fit the fill tubes, the tubes were pulled through the holes, the pumps were put in place, and filling began. The dams provided a durable and stable platform for workers to carry equipment and walk to the end of the last dam, where a 5-ft.-high support dam was set in place to add support to the first dam. This backup dam held approximately 35,000 gal., as compared to the 60,000 gal. held by the main AquaDams. Once the entire dam system was ready, dewatering began.
It was well into December before the first side of the lake was finished. When it was time for the crew to move the AquaDams to the other side of the lake, they faced one of their worst challenges on the project: ice.
"When we moved into phase two—well, it hadn't frozen in 13 years in New York, but the year that we were involved in the Kissena Lake project, there was a lot of ice in December," Capparelli says, laughing.
The AquaDams were frozen solid in Kissena Lake. After trying rakes, crowbars, sledgehammers, and whatever else they thought might work to break up the ice, Capparelli and Doolaege consulted with Aqua Dam and Diversion Ltd. of Canada. That company, which has plenty of experience using AquaDams under icy conditions, told them that by using a chain saw they could cut large ice slabs that could then be moved or pushed away from the dams. Once the AquaDams were maneuvered across the lake to their new position and the backup dams put in place for support, this part of the project was finished.
The end result was a lake with a slow, 14% sloped shoreline, filled with turtles and fish. The lake is used for fishing and other sporting activities. In addition to the shoreline project, crews also installed three deep-water wells to resupply Kissena Lake with fresh aquifer water. Kissena Park is used for New York City bicycling races, baseball, bocce-ball and other recreational activities.
The Blue River Walkway
The city of Breckenridge, CO, has historical roots that run as deep as the gold veins that drew miners to the area in the 1800s. Located in the Swan River Valley about 80 mi. west of Denver, the city has become a popular spot for snow lovers and winter recreationists. During the summer months, Breckenridge residents cater to tourists who come to scout the old mining camps, pan along the rivers, and hike the picturesque mountains.
Unfortunately, visitors might find it difficult to actually locate some of the old camps. It seems that mining the ore that once was carried from Breckenridge to Swan City on Bronco Dave Braddock's stage line produced the rocky rubble that now buries many of the mining camps. The Blue River that runs through the heart of the city eventually began to sink into the landscape.
"The entire area had been mined, and the fines washed downstream," explains Bill Wenk, president and landscape architect with Wenk Associates in Denver. "It was mined so much, it was like a big sieve. It just wouldn't hold water."
The residents of Breckenridge have a long history of community pride, and their heritage is important to them. As the rumor goes, it was so important in 1862 that some of the townspeople actually broke into the Summit County office in Parkville and stole away with the records in the middle of the night. Breckenridge has since been known as the gold capital. With such a colorful history, the town couldn't sit and watch visitors pass it by because of the dredge mining ruins. The "Kingdom of Breckenridge"—as it is so fondly referred to by locals—decided to take action.
Fred A. Mueller of Siloam Stone was involved in the earliest stages of the plans the city developed for the Breckenridge downtown river walk. "When the town of Breckenridge approved its dynamic plans for revision and expansion, the priority item of their plan for the downtown area was the Blue River," he relates. "The river channel runs parallel to Highway 9 through Breckenridge, and the town business district runs parallel to the river and the highway. The Blue River was determined to be central to the downtown plan, [so] enhancing its attractiveness, as well as controlling its erosion capability, required serious consideration, technical engineering skill, and proper timing."
Bill Wenk agrees with this description of the project, but adds that it actually went well beyond that: "The Breckenridge project goes beyond erosion control, in that the river was a ditch that disappeared in the mined-out cobble through town."
Comparing the riverbed to a bathtub filled with marbles, former City Engineer Don Nilsson describes the river as only being visible after mountain snow runoff. It was only for that short time, Nilsson says, that you could actually see water in the stream.
"We knew that at the upper end, where the last dredge boat had stopped in 1942, we didn't have the problems of water infiltrating in the steam," he adds. "In the city it was basically draining on through."
After receiving the United States Army Corps of Engineers 404 permit for stream stabilization, Nilsson says, the city decided to line the portion of the river that ran thought the town to reclaim the area for a park, downtown river walk, and orchestra band shell. "We decided on a PVC liner that was installed under dry conditions. We had to literally reroute the stream around the work."
The PVC liner actually sits 5 ft. below the Blue River channel running through Breckenridge. To prevent silt from running downstream, and to adhere to Colorado Division of Wildlife and EPA regulations, the city temporarily moved the channel by pumping it and digging side channels while construction was going on. In a creative measure, Nilsson recalls, at one point they had to dig a hole through the rocks and let the water run into it, knowing it would seep on through.
Once the channel was lined, the project for Blue River Walkway was ready to get under way. The main area previously had been a parking lot. The lined channel is approximately a quarter mile long and includes a large, open town square where the stream widens to about 300 ft. In other areas, it narrows to 75-100 ft. to go between existing properties in the commercial district.
Ken Florey, superintendent of the Stan Miller Inc. excavation company that worked on the river walkway, describes what the quarter-mile project looked like and how it changed. The stretch of the Blue River that runs through Breckenridge had been eroding and sloughing off its banks for a very long time. In addition to the aesthetics of the project, retaining walls and rock slabs were used to shore up the banks and prevent erosion. This went well beyond the usual riprap techniques.
"They were trying to correct years of dredge mining," Florey states. "It was a reclamation project from mining activities of the early 1900s and is still an ongoing project."
The bulk of the Blue River Walkway was finished over one construction season—about six months. Because the river runs through the heart of the commercial district with shops, grocery stores, and the post office, residents wanted the park to be safe for visitors. With the previous 1:1 slope, it was perilous to get down to the river's edge.
The Town of Breckenridge decided to purchase all of the rock materials and multiton rock slabs from Siloam Stone of Canon City, CO. Florey notes that the benches and step areas that were widened out provide better access to the river and a more natural view of the stream. Rock slabs of various sizes were set in place using a hydroexcavator with a thumb attachment. With some of the stones weighing as much as 8 tons, it was "meticulous work," he remarks.
"It was determined that the Dakota formation sandstone found in south central Colorado was best suited for the project," says Siloam Stone's Mueller. "Large flat slabs approximately 8 feet by 6 feet by 8 inches were dry stacked to the predetermined height. This offered the desired natural decorative effect, solved the erosion problem, and furnished the retaining wall requirements for the future building construction plans along the now - extremely attractive waterway."
Mueller adds that the design of the dry-stacked sandstone slabs offered a further benefit of allowing runoff from melting snow and rain to filter through the stone slabs without disturbing the wall.
Posh Golf Course Property Gets a Face Lift
South Carolina is a state with many lakes, both manmade and naturally occurring. Lake Keowee is one of the manmade lakes constructed by Duke Power Company to help generate electricity. The Keowee area, named from the great Lower Cherokee Nation, means "place of the mulberries." It encompasses 18,500 ac. of water and borders more than 300 mi. of shoreline.
Lake Keowee is considered the area's most valuable economic resource. It is sought out for its mountain views, clean and clear water, and recreation. The deep blue waters of Lake Keowee are fed by the Jocassee Valley watershed and springs from the Sumter National Forest. Since the lake was formed by Duke Power in the 1970s, it has become increasingly important for drinking water, access to larger metropolitan areas such as Greenville and Atlanta, and the sports tourist trade. Properties at Lake Keowee have become popular for prestigious golf courses and sell for up to $1 million for 300-500 ft.2
Cliffs Keowee Vineyard purchased some of the Duke Power land for development and possible golf course development. The shoreline portion of the property, however, had suffered from 30 years or more of uncontrolled wave action and cutting erosion, according to Frank Brezeale, owner of Brezeale Shoreline Erosion Control.
"The owners hired us to go in and shore up the water line for cosmetic purposes," Brezeale says of the high-dollar project. "This is very expensive land, and they were fixing it up to be sold for golf courses."
After applying for and receiving the appropriate permits for lakeshore stabilization, the company proceeded with its plans. The 400-ft. shoreline had slopes ranging from a 2:1 gradual slope to a very steep 2:3 drop-off. The owners at Cliffs Keowee Vineyard decided on using Redi-Rock materials for the shoreline retaining walls. Brezeale's crew built the three-tiered retention walls over a week's time. "The most critical factor in the project was backfilling behind the walls," he concludes. "We had to bring in a lot of backfill material after the walls were up."
Lake Keowee is located in upstate South Carolina and is surrounded by breathtaking views and native deciduous trees, including white and red oak, Virginia pine, and the aromatic laurels of the South.
Detaining Stormwater at South Turnpike Bioswale
As part of implementing the Clean Water Act, the County of Santa Barbara, CA, developed Project Clean Water (PCW). The mission of PCW is to protect public health and enhance environmental quality in county watersheds and at the beaches, states Robert Almy, natural resources manager for the county.
The project's goals include:
To implement structural best management practices on South Turnpike Road, PCW built a "two stage" treatment system consisting of a CDS (Continuous Deflective Separation) Technologies separator underground and bioswale aboveground, explains Almy. PCW monitored the site between the southern terminus of Turnpike Road and north of Atascadero Creek for two years before the project began, finding high levels of fecal coliform, E. coli, and enterococcus bacteria in the creek.
The bioswale, or biological treatment system, treats the local stormwater for sediment, agricultural and lawn chemicals, bacteria, nutrients, and residual oils. After treatment, the stormwater is released back into the storm drain and discharged into Atascadero Creek. The bioswale, approximately 580 ft. long, was constructed by Soil Retention Systems.
"Verdura walls were used to increase surface area of the bottom [treatment surface] of swale and to break up 'slot' effect of the swale," Almy recalls, "and so that short walls could be climbed easily if people got into the swale in muddy conditions. Also, vegetation can establish itself, helping to soften the visual effects."
Sideslopes of the bioswale vary from 2:1 to 3:1 with a depth of 5-6 ft. The bottom treatment area ranges up to 16 ft. wide. Stormwater retention time is averaged to be 16-20 minutes, which is figured to be slow enough to treat the stormwater but not to "remobilize" the contaminants in the bioswale.
Pervious Concrete at Brushy Creek
Just as the old Texas cattle drivers searched for the "round rock" in the Brushy Creek to provide them safe crossing at the Chisholm Trail, hikers today in Round Rock, TX, look to Brushy Creek for a peaceful haven and for recreation.
The Williamson County Parks and Recreation Department is charged with providing safe trails for the visitors and residents at Round Rock. In 2002, as part of the master plan for a countryside trail system, the department used decomposed granite to provide 7.3 mi. of meandering trail along the historic Brushy Creek. Where cattle once were driven and wars fought between settlers and Native Americans, a city now thrives. Home of Dell Computers, Round Rock has prospered over the last decade and continues to be the jewel of central Texas.
A difficult situation exists in Round Rock, however. "Texas remains in a state of drought, occasionally interrupted by floods," says Jim Rogers, Williamson County Parks and Recreation director. He knows all too well the costs of constantly repairing and replacing the granite trails. "The washouts cost us dearly. In the course of a year we might replace a trail two or three times."
And with the challenge of keeping the granite trails in place, eliminating rutting and washouts is next to impossible. For help, Rogers turned to the park design team, Hall-Bargainer Inc. (HBI), the landscape architectural firm that originally designed the park.
Together, Rogers and Brian Binkowski, registered landscape architect and senior project manager from HBI, looked for a solution that would allow the water to pass through, but not erode, the banks of the creek. Ideally they wanted to slow the stream flow as much as possible. After researching other options, the two decided on using a pervious concrete material from Stoney Creek Materials LLC. When installed, the material would slow the cross-drainage and eliminate the downstream erosion. With 4 in. of permeability per minute, the material allows the water to pass and eliminates undermining of the base. Because of its strength (5,000 psi), the pervious concrete eliminated the need for a lot of base work, with no rebar or steel reinforcements necessary.
"It allowed us to match the color of the granite and transition the material under the stone, so we get no erosion around or underneath," notes Binkowski.
Linda Robinson is a journalist specializing in agriculture and land-use planning.