Onsite techniques for erosion and sediment control

By Bill Tice

According to the Environmental Protection Agency, “the most environmentally dangerous period of development is the initial construction phase when land is cleared of vegetation and graded to create a proper surface for construction.”

The source of this information is the EPA’s Web site, which dedicates a large section to erosion and sediment control. The site goes on to explain that “the removal of natural vegetation and topsoil makes the exposed area particularly susceptible to erosion, causing transformation of existing drainage areas and the disturbance of sensitive areas.”

Photo: Filtrexx

In general terms, erosion control is widely defined by erosion specialists as preventing the soil from becoming displaced, while sediment control is stopping that process once movement has started to take place. The importance of containing sediment has been amplified over the past few years with the implementation of more stringent National Pollutant Discharge Elimination System (NPDES) regulations. This attention to sediment control has spurred a number of companies to produce products to satisfy this market, and today there are a number of options available to erosion control companies, from filters and silt fence products to continuous sandbags and additives that contain flocculants.

At H&G Erosion Control Inc. in Norcross, GA, owner Henry Hughes knows how important it is to prevent sediment from moving. His company specializes in “keeping the soil from leaving the property.” The company, which was formed on the fateful day of September 11, 2001, operates six days a week, rain or shine. “We only handle the erosion aspect of property development,” says Hughes. “Our market is mainly the residential home and subdivision business, and we generally work on jobs that range between 50 and 150 lots.”

In Norcross, business is good, as the community that is located in Gwinnett County 10 miles north of Atlanta is seeing rapid growth in residential construction. That growth is creating a lot of what Hughes calls “clear-cut jobs” where all of the trees and vegetation are removed to make the construction process easier. “With clear-cut jobs we have to act fast,” he notes. “We are working on a project right now that is a 175-lot subdivision where everything has been cleared. On a job like this, we go in as soon as the clearing is completed and install two rows of wire-back silt fence around the entire perimeter of the property. We then revegetate, and within seven to 10 days we will have the vegetation growing so that the soil is not as likely to leave the property.”

In most cases, Hughes says the silt fence, which the company sources from Robert Hood & Son Inc. in nearby Cumming, GA, is just the beginning. On many jobs, crews also use hay bales and 2 to 4 inches of straw that is applied over the graded and disturbed site. On steeper slopes, a mat product may be used. “The fence is the starting point on most jobs, and then we use another product or practice in conjunction with that fence. Proper maintenance is also key, because if you don’t do this, the products you use, including the fence, are not going to do the job for you. We put best management practices [BMPs] in place and inspect the job site at least two or three times a week, and if we are experiencing a rainy period, we inspect the site and the fence at night and in the morning. We also measure the rainfall and keep very accurate records of the rainfall and the maintenance work that has been done. It is very important to document, or you will end up in trouble.”

Photo: H&G Erosion Control

H&G Erosion Control crews often supplement silt fence with straw and mat products to prevent sediment from moving.

That trouble can come in the form of a government inspector. However, Hughes says the inspectors the company works with at the city, county, and state levels are reasonable, and he finds they are easy to get along with. “The developers of the property have to work under an NPDES permit, and they will have an engineer that tells us what we need to do in terms of erosion and sediment control. If we get 5 inches of rain, there is not much we can do, but most of the time, if the inspectors know you are doing your job right, they will work with you. If you are not doing your job right, you are going to have a problem. It’s a pretty simple business. You just have to do it right.”

The father and son team of Richard and Eddie Willis is also finding the rapid growth in the Metro Atlanta region is creating a lot of work for their company, Willis Contracting. “Our office is located 35 miles east of Atlanta in Oxford, Georgia, and from there, we work in three of the 10 fastest growing counties in the nation,” explains Richard. “This includes Newton County, which is where Oxford is located, and Rockdale and Henry counties.”

Willis Contracting, which has been in business for 33 years and has 13 employees, specializes in site grading and installing sewer and stormwater drains in new subdivisions. In most cases, they work on projects that range from a minimum of 60 lots to a maximum of 200 lots. “We work through the entire development stage until the plat is recorded with the county,” adds Richard. “We use subcontractors for some tasks, but we manage the entire job when it comes to site development. That includes making sure the NPDES requirements are met, including accounting for erosion and sediment control.”

Richard notes that the developer has an engineer that specifies what has to be done on each site for erosion and sediment control, and when the plans are submitted to the governing authority, a review will be conducted to ensure the BMPs and erosion control plans are going to be adequate. “If the governing body is not satisfied with the plans and we need to make alterations, then we have to go back to the engineer and have them make the necessary modifications.”

Photo: H&G Erosion Control

Removing all trees and shrubs from a site streamlines the construction process, but it is important to revegetate ASAP.

Once the job is started, Willis Contracting uses a number of techniques to make sure the erosion control plans are adhered to and that sediment stays within the boundaries of the site. “We use a combination of things,” explains Richard. “We use mulch berms, silt fence, riprap, check dams, and other filtration devices. We really use the whole gamut of what is out there.”

One of Richard’s favorite product lines is the Silt-Saver line from Conyers, GA–based Silt-Saver, a designer and manufacturer of temporary drain inlet safety filtration devices. “We helped the owner of Silt-Saver by testing some of his products when he was still in the design stage, so we are very familiar with what they have available and how they work,” notes Richard. “We use the Silt-Saver covers and frames for storm drains and catch basin structures, and with all of their products we have found they offer labor savings, they are easy to use, they satisfy the requirements of the inspectors, and they work well in conjunction with the other techniques that we utilize.”

Sacramento, CA–based Thunder Mountain Enterprises Inc. has been in business for over six years and employs upwards of 60 people in the development and implementation of comprehensive soil and water management services. Activities include the installation of erosion and sediment control products, the design of stormwater pollution prevention plans (SWPPPs), chemically enhanced treatment of stormwater, pond construction, and the restoration of native habitats, landscapes, and streams.

Photo: Thunder Mountain Enterprises

Thunder Mountain Enterprises combines sediment control with restoring native habitats, landscapes, and streams.

“We try to meet the growing needs of landowners, developers, contractors, and industrial facility owners in managing water, soil, and onsite pollutants, and to help these clients understand and meet the requirements of today’s complex environmental laws,” explains Beth Smiley, who is a co-owner of the company and handles sales and training activities. Both owners of the company are Certified Professionals in Erosion and Sediment Control. “We have developed an analytical approach to the business, which combines biotechnology, site hydrology, soil science, and advanced erosion control technology with construction expertise,” adds Smiley.

“Proactive erosion control planning is always our first priority, but realistically, even with a strong erosion control effort, soil fines are mobilized during peak rain events, particularly on dynamic or active sites. Once in suspension, very fine colloidal clay particles can be very challenging to filter out, which has driven the development of new technology that helps allow construction to continue during the wet season. Thunder Mountain conducts soil tests to determine particle size in order to specify technology that will clean runoff enough to meet the legal requirements. Some colloidal clays too small for mechanical removal in the construction environment can stay in suspension for years unless advanced treatment methods are used.”

During the 2006 rainy season, Thunder Mountain installed and operated 10 chemically enhanced treatment systems (CETS) for stormwater on sites with fine clay particles, including a 166-acre residential development in Lincoln, near Sacramento, CA. Thunder Mountain designed the SWPPP incorporating a CETS using a natural biopolymer derived from crab and shrimp shells. Washington state–based Natural Site Solutions supplied the product, Chitosan.

Thunder Mountain has worked with other industry experts to build “electrocoagulation” systems capable of treatment without using chemicals but have been unsuccessful in treating the large flow-through volumes required on many sites. Like electrocoagulation, Chitosan changes the charge on colloidal particles, causing them to attract one another, coagulate, and flocculate, rather than repel and stay in suspension indefinitely. This process causes most of the sediment to drop out during residency in ponds or tanks, and the remainder is removed in mechanical filters along with any residual polymer. Natural Site Solutions provides acute and chronic toxicity data that show the polymer is not harmful to delicate animal or plant life at the dosages used. Thunder Mountain performs residual tests in the field while operating CETS in order to ensure that no polymer is released with the stormwater.

Photo: Superior Sandbag Systems

The Port of Long Beach uses continuous sandbags both for perimeter control and the top and toe of a steep slope.

Thunder Mountain chemically enhanced treatment systems are typically designed to handle flows ranging between 500 and 2,000 gallons per minute, and can be applied to construction-site agricultural or industrial runoff. “Typically we test for turbidity [cloudiness of the water] and pH before and after treatment, and then we do a final colorimetric test to ensure the process is working,” adds Smiley.

Kevin Stumpff, president and owner of Windswept Organix Inc. in the Phoenix, AZ, suburb of Chandler, says his company has to deal with sediment control on almost every job it works on. “We are a full-service erosion control and environmental contracting firm and we specialize in SWPPP work, dust control, and stabilizations, primarily in Arizona, Nevada, Utah, and New Mexico,” says Stumpff. “Because of the NPDES requirements, we are always aware of sediment and where it is going. In most projects, we are working for developers in the residential and commercial sectors, and for government, and we get involved right from the beginning with the environmental and compliance issues.”

Once sediment is moving, Stumpff notes that they use a variety of techniques and products to stop it, but his main day-to-day tool is the FilterSoxx line of products from Filtrexx International LLC. “The Filtrexx products are one of our primary tools, but they are not the only tool we use. We will use them in conjunction with rock bags, silt fence, and hydroseeding. We use whatever combination will work for the situation, but we have found the FilterSoxx give us a lot of options as they come in varying sizes, including 8 inches, 12 inches, 18 inches, 24 inches, and 30 inches.”

According to Stumpff, the primary benefits of the product are longevity, durability, cost-effectiveness, and filtration properties. The products are made onsite, so customization is possible, including various material flow rates, pollutant removal additives, flocculants, and so on. “These products have a long life cycle due to their UV rating,” adds Stumpff. “This keeps clients from having to pay excessive maintenance or replacement costs during the dry periods. Filtrexx FilterSoxx filter out pollutants far better than any other products I have seen in action. They are EPA approved and reasonably priced, and since they are biodegradable, the mulch can be left onsite, which reduces your removal cost. All of these benefits translate into increased profits for our clients.”

In addition to perimeter control and inlet protection, Stumpff says the FilterSoxx can be used in nine other unique applications. “They can be used for inlets, concrete washouts, temporary diversion, and even in channels so that it creates a high-flow channel and replaces riprap, but at a far lower cost. These are all effective when you want a temporary solution, and these products are easier to maintain. You can also use it to bioengineer retaining walls and stabilize streambanks, and you can even get vegetation to grow out of the FilterSoxx to make them part of the permanent landscape. This is especially useful in greener parts of the country.”

Stopping sediment from moving is also important to Devin Davis, a manager at Running Creek Investments LLC in Parker, CO, which is located just south of Denver. The company is currently in the first phase of Spring Valley Ranch, which is a three- to four-phase project (the number of phases has not been finalized yet) that will see 1,800 residential lots developed in the Denver suburb. Some of the lots surround the Spring Valley Golf Course, which is an operating course, so Davis says they have to ensure sediment created when the lots are cleared doesn’t move onto the course.

“The area is fairly flat, but we do have some rolling hills and some contour changes, so we have to be careful, and we monitor what is happening. We also have to act quickly once the clearing happens, and we generally install a perimeter silt fence and install a straw mat or a heavier-duty mat as soon as possible. We contract the mat work to Colorado Lining International in Parker as they supply the mat and do the installation, and they supply straw wattles that are pinned perpendicular in the ditches. They also brought in a subcontractor to do hydroseeding for us.”

To date, Davis says they have been very pleased with the results. “We could use a little more rain this spring to get everything to germinate, but last year when we did get heavy rain, the products all did the job and sediment movement was minimal.”

For Barry Regan, a superintendent at Calgary, AB–based Top Notch Construction Ltd., a current job required a different kind of product to prevent sediment movement. Top Notch, which has about 220 employees, has been working on both the north side and the south side of McGregor Reservoir, which is about 60 miles (100 kilometers) south of Calgary. The company is now constructing a two-lane vehicle bridge over the reservoir so that the water level can be raised. To prevent silt movement when crews are working in the water, Regan says they use turbidity curtains from Layfield Geosynthetics and Industrial Fabrics Ltd. in Edmonton, AB, and Applied Geo-Environmental Solutions Inc. in Calgary. The floating silt curtains stop the silt from moving throughout the water system.

“You put the curtain about 25 meters [75 feet] away from where you are digging,” explains Regan. “The curtain is on a cable, which is bolted to posts on each end, and the posts are anchored in the water. The bottom of the curtain is fitted with a three-eighths-inch chain to hold it down, and a diver has to go out and install the anchors and pull the curtain tight. Floats on the top of the cable keep the curtain in place.”

The curtains come in 50-foot lengths and in depths from 6 to 38 feet. Regan says workers can attach as many curtains together as they need to for the job at hand. The curtains were specified as part of an “Eco Plan,” which Regan says is required by Environment Canada on any job that may have sediment movement. “They have checked the upside and the downside of the turbidity curtains, and the particles that get through are minimal,” he adds.

The Port of Long Beach, CA, the second busiest port in the United States and the 12th busiest port in the world, has been looking at methods of sediment control and other stormwater issues in the port area.

Photo: Altitude Training Associates

Emphasizing erosion control on a project, says Altitude Training Associates, makes sediment less of an issue.

Recently, Irvine, CA–based Superior Sandbag Systems performed the sediment and erosion control work in two areas of the port. In one instance, the port is using continuous sandbags for perimeter control and around an area where the recycled asphalt was contained; in the second area, the port uses the continuous sandbags at the top and the toe of a steep slope, which was covered with visqueen barriers in order to prevent runoff during the heavy rains.

“We look after stormwater pollution issues port-wide, including 300 acres that we are preparing for future development,” explains Howard Morlock, principal construction inspector for the port. “For us, sediment is an area that we don’t want to have a problem with in both the developed and undeveloped areas within the port. We look at preventative measures and maintenance programs to prevent stormwater pollution in the harbor waters and to control dust within the port boundaries. Right now we have a stormwater plan in place that includes some temporary solutions, and we have recently hired a consulting firm to come up with long-term mitigation solutions for us,” he says.

“We like using the continuous sandbag method because it is all recyclable material, so we can reuse the crushed rock the sandbags are filled with if conditions change,” adds Morlock. “The bags are also continuous, meaning that we don’t have any gaps or seams, and the work can be accomplished at a faster pace, which keeps the labor costs down. This has been a very inexpensive option for us, and so far, everything has worked exceptionally well, especially the slope covered in visqueen layers. We wanted the slope protected because we knew it was subject to extreme erosion and we didn’t want the sediment moving to our tenants’ sites, which are adjacent to the slope.”

Superior Sandbag Systems has been able to run bags to a maximum of 240 feet in one loading, but a new, larger hopper now allows the company to make up to 450 feet of bag without stopping. The process is operated onsite with the sandbag material extended in 6,000-lineal-foot rolls. By using a two-person crew, the bags are laid in place at the same rate as they are filled. The crews can fill and place 240 lineal feet in 90 seconds. Due to the weight of the filled sandbags (75 pounds per lineal foot), joins are generally not required, but if the sections do need to be joined, the installing team can use a sleeving technique. A total of 4,200 lineal feet of sandbag was installed in the two sites Superior Sandbag Systems completed at the Port of Long Beach.

Scott Olson, owner of Altitude Training Associates in Cheyenne, WY, takes a different approach than most people when it comes to sediment control. “Contractors tend to focus too much on sediment removal and not enough on erosion control, so what I have been trying to teach them in our courses is that if they put more emphasis on erosion control practices and administration for a project, they will have far less sediment to deal with,” explains Olson, whose company primarily presents training programs in environmental management and compliance and worker health and safety throughout Wyoming and Colorado. “An example of this is construction phasing. Most contactors tend not to phase well when protecting water quality. They strip off an entire phase of a development at one time, removing all of the vegetation, which creates an environment that is susceptible to sediment movement. This is often done to achieve what they think are cost savings as they want to clear as much of the phase as they can while they have the equipment onsite, but what we always propose is that they evaluate the cost of removing the sediment and the cost of addressing the stormwater regulations when they have problems. The only way to do this is to develop effective BMPs for erosion control.”

The typical kinds of things Olson recommends in BMPs include fairly obvious processes such as finishing a job and getting the stabilization completed right away through practices such as mulching, blankets, revegetation, bonded fiber matrix application, and surface roughening. He also recommends opening up as little bare soil as possible, especially during the wettest time of the year. “These are all straightforward solutions, and the contractors are generally not surprised by these when we teach our courses, but most of the time, they are under extremely tight construction time schedules, which makes it difficult to execute these BMPs,” Olson explains. “They are bidding against other contractors, so they have to keep the time frame short; the owners of the property have unrealistic expectations; and the way projects get managed makes it difficult for site people to execute the BMPs. If people responsible for the project take what they think is the easy route, which is often silt fence around the perimeter of the project, they end up fighting it the entire time. The bottom line is it takes money to execute any selection of BMPs, but a carefully thought-out plan to protect the soil from erosion, and the use of sediment removal practices when necessary, can work effectively. The important message we have to get to contractors is that they have to do a better job of estimating for BMPs and put an administrative structure in place to handle BMPs. Basically, it has to be a way of doing things, not just things to do.”

Author Bill Tice is based in Blaine, WA.

EC - July/August 2006