Low Impact Development for Public Works Construction:
Erosion and Sediment Control Compliance
David S. Jenkins, Seattle, Washington
Introduction
Construction is a messy business; in the Puget Sound region of western Washington, with average annual rainfall of 40″ to 60″, it can also be challenging. Uncontrolled erosion from a construction site can generate 10-1000 times the quantity of sediment that occurs naturally from vegetated areas. Most construction in western Washington occurs near wetlands, streams, lakes, or the Puget Sound where sediment loss can reduce beneficial uses, or worse, destroy a salmon stream.
This paper will discuss proven methods that public works professionals can utilise to improve erosion control compliance and reduce project impacts.
Project Scoping
During project scoping, preliminary decisions should be made concerning project-specific erosion control needs: a wetlands rehabilitation project has significantly different challenges than does a 500,000 cubic yard fill embankment. Some questions to ask when scoping a project: Can the project be built around a wetland? Will the project schedule accommodate doing all earthwork during summer months? Will money be saved if additional right of way is purchased to reduce slope gradient and prevent future slides? Is there run off from adjacent properties that could impact the project?
Project Design & Review
During project design, changes may be made that involve adjusting a project schedule to allow more of the earthwork to be done during summer months. Other decisions might include accepting fill material with a very low “fines” content or adjusting contours and grades to reduce erosion potential. New materials and methods including straw wattles, bio-fence, and polyacrylamide should be discussed and included when appropriate. At the 30% design stage, often the TESC plan has not been included and comments may be as simple as making sure there is money set aside for erosion control (typically at least 1% of total project estimate set aside for TESC-Force Account). If appropriate, schedule is discussed if earthwork is planned for winter. Comments at the 60% stage may be more involved such as making sure that roof drainage from a building next to the project does not drain into the work area, or that all storm drains within the project boundary are protected with catch basin inserts, or that vegetated ditches should be used instead of quarry spalls. At 90% stage, all plan sheets and specifications should be in place as well as erosion items listed with estimated quantities.
Contract Specifications
In order to get a bridge built, you must tell someone what you want, what it is made of, and how much you will pay for it. In order to get erosion control work done you must do the same thing. Many contract specifications for erosion control work are taken directly from environmental regulations and permits. Regulatory and permit language is not contract language and may not be enforceable under the contract. When a specification says to do something in a “timely manner”, the contractor gets to decide what a timely manner means. If the specification defines “timely manner” as within 24 hours, it is much clearer and not open to interpretation. For clarity, the specification should just say the work is to be completed within 24 hours. In other words, if you want all bare, un-worked soil covered in a timely manner as the permit requires, write the specification to say something like all bare soil is to be covered daily before end of work. Cover shall be plastic.
Payment
The Contractor should be paid for work performed. Typically, erosion and sediment control work has been “incidental” to the contract and the Contractor has had to figure money into their bid to cover the unpredictability of the weather during the dynamic construction process. As public works contracts take the lowest bidder, there has been little incentive to provide a real monetary figure for erosion control. In addition, a Contractor is penalised if they put in a real number, as they may not get the low bid because someone else bid a dollar for erosion control work.
One payment option is a pro-rated system that provides incentive to do the work on a timely basis. It is set up so that the contractor knows what they must do to get a monthly progress payment for erosion control. 25% is given for an acceptable Contractor’s Erosion and Sediment Control Plan. 50% is pro-rated for the life of the contract, and 25% is paid for a clean and completed site.
CESC Plan
One way to make sure the contractor’s means and methods are addressed is to require the Contractor to develop and submit a Contractor’s Erosion and Sediment Control Plan (CESCP) before earthwork can begin. Spell out the requirements in specifications. The Contractor can utilize the project design and incorporate their operational phasing and scheduling to produce a plan that is tailored to project-specific means and methods. Develop a template that can be given to the Contractor as an electronic file on disc or located on a web site. The template can be formatted in a way that includes all information required or desired with specific questions asked. The Contractor can then spend time thinking about specifics of their project and how to address erosion rather than spend it trying to figure out what exactly the owner wants. This can also assist the developer in reviewing the plan when it is part of the submittal process. Consistency can be developed and predictability increased. In addition, recently developed contract specifications require the contractor with the lowest bid to provide a Contractor’s Erosion and Sediment Control Lead (CESCL) who is responsible for developing a Contractor’s Erosion and Sediment Control Plan (CESCP). The CESCP is developed utilizing the contract plans and specifications, with contractor-specific methods, procedures, and scheduling incorporated. Construction may not begin until the CESCP is approved.
Construction
During construction, Owner Resident Engineers and Inspectors, and the contractor’s Superintendent and ESC Lead, modify existing BMPs or add additional BMPs. These decisions often enhance BMP performance while decreasing project costs. Examples include: use of steel plates or asphalt to reduce offsite tracking of mud at a lower cost than traditional quarry spalls; the Resident Engineer may require an equipment operator to re-grade an area so that water will be directed away from a slope face.
Relationships based on mutual respect and trust make or break a project. On projects where the project inspector, environmental specialist, contractor superintendent, and city inspector have worked together to identify potential problems and find solutions, compliance has been achieved, often at reduced costs.
In addition, Construction Managers can work together to ensure seamless transition between projects. For example, the question might be asked: “What can we do on this project to prevent erosion until your project starts next year?
Dedicated Staff
It may make sense to have someone on staff that is responsible for all erosion and sediment control issues. The Washington State department of Transportation has a Statewide Erosion Control Coordinator and the Port of Seattle has an Erosion Control and Stormwater Engineer to manage all aspects of construction erosion and sediment control. Responsibilities include program development and management, enforcement, environmental liaison, training, inspection and contract administration.
Consultants
Erosion and sediment control consultants can be contracted to work directly with construction staff to identify and correct potential problems before they develop. Hire a consultant that is well experienced in public works contracting, construction, and erosion control. Certified Erosion and Sediment Control Professionals (CPESCs), certified by IECA and the Natural Resource Conservation Service are available.
Integration
Integrating erosion and sediment control means including information in Construction, Design, Inspection, and Landscape manuals. Standard operating procedures and agency policies solidify and legitimise erosion control as an integral part of project design and construction.
Research and New Products
WSDOT maintains a list or new erosion control products as does the International Erosion Control Association. Research on effectiveness of various erosion control methods and products are conducted by the Texas Transportation Institute, WSDOT, Port of Seattle, IECA, and others. New, more effective, products are available; straw bale check dams will be a thing of the past, replaced by materials and methods that work.
Training
Classes in construction erosion and sediment control are available. All inspectors, project engineers, construction managers, contractors, and environmental staff should attend a approved course in construction erosion and sediment control inspection and implementation.
By utilising some or all of these ideas, public works agencies can improve compliance with erosion control and water quality regulations.