Designing More Contractor-Friendly Plans to Limit Erosion and Sediment Losses

Sediment is tricky stuff. Left undisturbed and protected from the forces of wind and water, billions of tiny soil particles can work for you to help support all types of roads, buildings, and other construction projects. But remove the protective shield of vegetation or pavement and disrupt their cohesion, and these same fine bits of sand, silt, and clay can turn against you, washing and blowing away to undermine the very structure you’re building. The best way to prevent such a rebellion is to attack erosion head-on.

Controlling erosion and sediment at a construction site would be challenging enough if all you had to do was keep disturbed soil from fleeing the scene. But you have to aim your efforts at a continually moving target because topography, wind barriers, vehicle traffic patterns, and other factors that affect your ability to keep soil in place can change from one day to the next, even from hour to hour. And you have to wage your battle without one of nature’s most potent weapons—vegetation. It’s gone as soon as the first blade or bucket bites into the earth. Throw in other complications, such as human nature and profit motives, and you’ve got a real job on your hands.

Controlling erosion while simultaneously building a freeway, an office complex, or other land development project differs from solving an individual erosion problem, such as a receding shoreline or a downcutting channel at a ski resort, in a number of ways.

One of the most obvious differences is the amount of soil that must be protected. A construction project usually disturbs much more soil than that involved with a typical one-time problem (e.g., an eroding streambank). Earthmoving activities at a construction site tend to be very intensive for a short amount of time. In addition to removing soil-protecting vegetation, construction often results in stockpiles of topsoil and spoil that, similar to the exposed terrain, must also be protected from the erosive and polluting effects of wind and water.

Earth work also alters the shape of the site, affecting natural drainage and wind patterns and creating new ones with the potential for more erosion problems. For instance, site development often calls for slopes that are much steeper and longer than nature intended.

“You can exceed the ability of tools, like the Revised Universal Soil Loss Equation (RUSLE), to predict erosion in developing your erosion control plans,” says soil scientist Jim Spotts, CPESC, of HDR/W.L. Jordan Inc. in Atlanta, GA. “For example, RUSLE is applicable for slopes up to about 300 feet in length. After that, its accuracy diminishes.”

Construction equipment and other vehicles can create another problem not found at other sites: compacted soils. With less ability to absorb water, such soils can increase the amount of runoff that must be kept on-site. At the same time, freshly disturbed soil not in the line of construction-vehicle traffic is less cohesive and more erodible than soil in its natural state. That can add to the sediment load in wind and runoff.

Controlling erosion and sediment in that type of situation requires a systematic approach. One that combines sound science and theory with practical measures that can be installed on the ground in a cost-effective manner. In some cases, it might also require educating construction workers about the need to control erosion and sediment in the first place.

“Controlling erosion and sediment at a construction site is a pretty easy concept to understand, if you plan for it,” remarks Dave Sluga, a senior construction engineer with Homes & Narver Inc. in Orange, CA. “You need a good plan to keep up with the dynamics of a construction project. Money can be a big issue. If you don’t have the dollars to implement the plan, complying with erosion and sediment control regulations can be difficult.”

Sluga is part of a team that monitors stormwater management on client projects. As he points out, the sheer volume of work and tight scheduling at a construction site can also be major issues in planning and implementing erosion and sediment control measures.

“The guys out there on a construction site have a lot to do, often in a short amount of time,” he states. “They have a million things to worry about and do the best they can. But when push comes to shove, because erosion or sediment control practices do not affect the overall quality of a project, they tend to put these practices on the back burner.”

Compliance with environmental protection rules and requirements need not be the only motivation for developing a good plan to control erosion and sediment on a construction project

“Conscientious contractors recognize that mud on the road in front of a residential subdivision project can reflect poorly on the project’s quality and affect subsequent home sales,” says Spotts. “On the other hand, an erosion and sediment control plan that leaves the site and streets clean can be a terrific marketing tool that is worth real money.” He then adds, “It’s always cheaper to invest a dollar in preventing erosion than spending more money in reaction to a sediment problem.”

He notes a case in Atlanta several years ago where mud washed from a construction site into a storm drain by runoff created a pond in the street. A motorist was killed when his car hit the water, hydroplaned, and crashed. The accident resulted in a lawsuit in which the court ordered the contractor to pay a seven-figure settlement to the widow.

As Sluga sees it, an effective erosion and sediment control plan does more than indicate where and when various best management practices (BMPs) will be installed. “It also provides specific, reasonable steps that a contractor can bid on and that allow the contractor to build the project profitably,” he says.

Here are some tips for doing just that:

• Think Like a Contractor. In some cases, erosion and sediment control represents change to a contractor – a new or recently imposed requirement that must be planned and budgeted for.“Contractors are used to doing the same thing over and over in the same way,” Sluga notes. “They can build a bridge in their sleep, but they may not understand erosion control. When you start changing the way they do business by requiring them to control erosion and sediment, you affect their bottom line. They tend to resist that kind of change.”Education plays a big role in his erosion and sediment control work with contractors. Besides preconstruction meetings, where he explains the erosion and sediment practices for a project, he offers them ideas for saving money.On one site, for example, he might point out that a minor change in the construction schedule would allow the contractor to install permanent controls now rather than spending money to put down temporary controls several times before finishing that area of the project.

  On another job, Sluga might recommend that the contractor use a chemical stabilizer rather than straw mulch to temporarily protect a fill slope. When the straw decomposed, he explains, it would compromise the integrity of the final slope.

  When possible, he makes use of onsite materials to cut erosion and sediment control costs. He might suggest saving vegetation, such as ice plant, which is removed during clearing operations, for later use as an economical temporary mulch to protect slopes or as an alternative sediment filter around storm-drain inlets.

• Give It Your Best Shot From the Get-Go. Without adequate thought and preparation, your erosion and sediment control plan might not pass muster with regulatory agencies. Waiting for the required revisions can cost the contractor valuable time.“Any delay is critical to a contractor ready to turn a shovel,” says Spotts. “You need a first-rate plan the first time around.”
• Communicate Clearly. One way to increase the effectiveness of an erosion and sediment control plan is to make it easy to understand and implement. Sometimes these plans get so complex that the contractor has trouble interpreting the designer’s intentions. The end result might be poor erosion and sediment control.“I’ve reviewed plans that specify certain erosion and sediment control measures on slopes but don’t tell when to install them,” says Fred Koethke, a senior environmental planner for CH2M Hill in Boise, ID. “I’ve seen a contractor install permanent erosion control–seed, mulch, fertilizer, and tackifier–on top of a temporary one, mulch, because the plan didn’t note that the contractor would first have to remove the temporary mulch to get good soil-seed contact when making the permanent seeding.”Another reason for clearly written plans: The contractor might earn a bonus for completing the job ahead of schedule. In the rush to finish early, a contractor – confused by the plan – might install measures improperly or not at all rather than take the time to clarify things with the designer.
• Write Two Separate Plans. “Project designers need to realize that they are developing erosion and sediment control plans not for themselves or inspectors but for contractors,” emphasizes hydrologist Jerry Fifield, CPESC, of HydroDynamics Inc. in Parker, CO. “Many contractors simply don’t know what is expected of them.”That’s why he develops two sets of plans – one that describes clearly what the contractor does before and during construction and one that explains practices, primarily erosion control, required after construction is completed.More work for the designer? You bet. But Fifield says the improved results are well worth the extra effort.“If we expect contractors to control erosion and sediment properly, we designers have to give them the proper tools,” he says. “You make a book for the contractor so there’s no confusion about what kind of controls to install and when and where to install them. It requires a lot more paper than what has been used traditionally. But as designers, we must write plans that allow contractors to do their job and also provide for sound maintenance and inspection procedures.”

  He suggests that designers include detail sheets and notes that correspond to erosion and sediment controls on each plan view of the project. In addition to instructions on installation and maintenance, the plans should indicate when to remove controls that are no longer needed.

• Communicate Completely. “There has to be continual dialogue among the designer, contractor, and regulatory people,” Fifield stresses. “At the preconstruction meeting, tell the contractor what is expected in terms of erosion and sediment control. Later, if the contractor proposes a change, it should be made only if both the designer and the regulatory agency approve.”If the erosion and sediment control measures you specify aren’t installed properly, they might not work properly. That’s why Sluga suggests keeping the contractor’s entire crew in mind when preparing your plan. For example, if you call for a silt fence, include a drawing that shows laborers how to key it in correctly.The Pennsylvania Department of Environmental Protection requires erosion and sediment control plans to include staging-a written sequence of BMP implementation, earthmoving, and construction activities, such as sediment basin construction and stabilization, temporary stream or wetland crossings, rough grading of the site, and utility construction. The staging coordinates plan maps, construction details, BMP specifications, and construction notes.“Staging is a vital element in implementing an erosion and sediment control plan,” remarks Jeffrey Sholly, senior civil engineer with the department. “Good sequencing tells the contractor how the designer anticipated the way the project’s earth disturbance would progress and the BMPs would protect disturbed areas. Otherwise a contractor might make wrong assumptions, such as grading so that drainage is in the wrong direction before the needed BMPs are installed. The goal is to protect disturbed areas with BMPs in the event of storms until completed areas reach final stabilization. Good staging makes it easier for contractors to balance earthwork, schedule crews, and deliver materials and to submit accurate bids on projects.”
• Focus on Reducing Energy. Spotts notes that wind and water erosion are driven by energy. Reduce energy in the system by installing barriers to reduce wind forces or check dams to slow the velocity of runoff, for example, and you reduce erosion.In some cases, it might even make sense to protect sediment ponds from steady breezes. “Wind as slow as about 3 miles per hour can create a circulation system in the pond that prevents colloidal-size soil particles from settling for a long, long time,” Spotts notes.
• Be Realistic. For a plan to be effective, everyone involved in implementing erosion and sediment control measures must buy into it, Sluga says. It’s not enough to say no particle of soil will leave the site. You should offer precise, rational steps that contractors can bid on and that don’t hinder them from constructing the project.

• Limit Chances for Erosion to Occur. The best plans for keeping soil on-site, say the experts, take active steps to prevent erosion rather than reacting to it with sediment control measures. This includes a wide range of commonsense practices, such as:Minimize the amount of earth disturbed and left unprotected at any time. The less earth you move at any one time, the less earth subject to erosion if the weather suddenly turns against you. But reality has a way of ignoring logic.“Controlling the amount of land disturbed at one time should be a significant part of erosion control efforts, but often it isn’t,” observes Koethke. He favors treating exposed slopes weekly, or more often as weather dictates, with practices like tackified mulch or erosion control blankets. “On cut slopes, we usually treat as we work down, and on fill slopes we start from the bottom as we build up,” describes Koethke.

  Phasing, one way of limiting the risk of erosion, involves breaking a large project into smaller parts. All construction activities, including erosion and sediment control, are completed in one phase before work begins in the next phase. For example, instead of opening up all 9 mi. of a road-widening project, work is done in three 3-mi.-long phases.

  Direct runoff away from exposed soil surfaces and control water that falls onto the site. “Often designers and contractors don’t pay enough attention to grading and other earth-disturbing activities,” Koethke says. “Anticipate where water will flow and collect as the landscape changes. Then protect those areas or control erosion by directing runoff into stabilized channels.”

  Use the correct BMPs. Seldom, in Sluga’s experience, has a single BMP been the best treatment on any one project. “Erosion and sediment control at construction sites isn’t about selecting one BMP as better than another. We get our best results by using a combination of BMPs and adjusting them as needed.”

  “You need the right BMPs for the right job at the right time,” adds Spotts. “Look at various BMPs in use at other construction sites in the area. If they’re not performing well, use better alternatives.”

  Protect inactive areas. In addition to treating disturbed areas, it can pay to prevent access to areas of the site that won’t be developed for some time, if at all.

  Keep current on the latest technologies. Speaking of alternatives, inventive erosion control pros continue to develop new and better ways of keeping soil on a construction site. A product, material, or practice that was most effective for you last year might not be the best available this year.

  Read publications, such as Erosion Control, that cover the erosion and sediment control field. Join the International Erosion Control Association and take part in the various conferences and other professional development opportunities it offers. Update your library of reference texts.

• Cooperate With Mother Nature. It’s difficult to win a battle with her. Often you’re better off in the long run to time earthmoving activities and installation of erosion and sediment control measures to match nature’s mood, even if it means unexpected delays. You might avoid the unexpected costs of cleaning up sediment that has left the site. If high winds are predicted, hold off on grading until after winds subside. Clear land and stabilize slopes before it rains. Schedule seedings to establish plants before winter or the dry season. Arrange for deliveries of materials to avoid mud and rutting.“It’s one thing to specify treated construction entrances with so much stone spread over a given width and length,” says Spotts. “However, it’s also necessary to understand that large trucks can compact that stone into the ground. Once the pores between the stones fill with mud, the entrance won’t drain. As a result, mud can collect on the tires of departing trucks, tracking the mud onto public streets.”
• Include Pay Items for All Erosion and Sediment Control Work in Your Specs. That includes temporary treatments too. “Contractors want to be paid for what they do,” states Koethke. “As long as erosion and sediment control measures are pay items on a project, I have no trouble with contractors installing them. Problems occur when the specifications aren’t clear that the contractors will get paid for this work.”
• Provide Money for Maintenance. It’s almost bound to happen. Someone will drive over a silt fence or damage some other erosion or sediment control device. If money isn’t available to fix or replace it, you could have problems when the next storm strikes. Also, someone has to check the remaining BMPs to see if they’re installed correctly and working properly and to make any needed repairs before the rain begins to fall. They also have to be checked during and after a storm.As Spotts observes, “The best project design can’t counter a poor maintenance program.”
• Keep on Top of Your Plan. Sluga suggests assigning someone with major onsite responsibility to bird-dog implementation of the erosion and sediment control plan. “The people on-site have to be aware of what’s in the plan. Someone has to show them what to do and how to do it. Make sure all subcontractors and others, such as utility relocation crews, know about water-pollution concerns. You might have a sign explaining procedures at a washout pit for the concrete guys, but there’s always someone who didn’t get the message and is washing out the truck’s chute in the wrong place. If you’re dewatering a site, be sure laborers know the water has to be treated before it’s discharged off-site.”In addition, the designer should also visit the site to see how the plan is being implemented. “You can learn if any part of your plan is faulty,” says Fifield. “That could prevent making the same mistake in future plans. It’s all part of working with contractors and not against them.”
• Expect to Change Your Plan. Any number of unforeseen circumstances can affect your erosion and sediment control plan. Perhaps the construction schedule has changed and you don’t yet have access to the area where you plan to build a sediment pond. Now you might need a linear sediment control barrier instead.In excavating to install a box culvert, the contractor might find an unexpected gas line that will take several months to move. In the meantime, it might be necessary to protect the exposed area with riprap or install a pipe to convey water through the excavation. Whatever the reason, it’s smart to be ready with an alternative.“Every single set of design plans for controlling erosion and sediment, whether before or during construction or postconstruction, is always subject to change,” concludes Fifield. “Plans will differ from one job to the next. There’s no such thing as a generic erosion and sediment control plan that will work every time for every project.”