Mass Grading: Controlling Site Runoff on the Ground

Presentation Description : Mass grading sites during overland flow conditions can be the most erosive and challenging sites to manage runoff and minimize offsite sedimentation. Imagine if you started this challenge ill equipped with a “one phase” erosion control plan. A great contractor once told me, “learn to control runoff on your site, OR that runoff will control you” (and you will likely be cleaning it up over the next few days). Learn to put green on the ground in order to keep green in your pocket. Let’s chat with some site contractors about erosion control that works through the use of big berms, big holes, groundcover, and a few other measures.

Full Presentation Abstract: The misconception that an erosion and sediment control plan can be represented with a one phase is short sighted. More than 80% of these plans are destined to fail from the beginning, and if they don’t we can summarize why: 1)Good groundcover, 2)Additional basins dug, 3) Additional runoff conveyance installed, 4)Site is Flat, and/or 5)Great Contractor. I want to focus on the first 3 reasons, as most of our sites have topography and we may not get that great contractor, instead we may need to facilitate the training of a great contractor.
A good erosion and sediment control plan for a mass grading site located in the piedmont will begin with a strong foundation and construction sequence that includes selective clearing/timbering to install vegetated top dewatering basins along the project perimeter, stable temporary runoff conveyances, and a vegetated buffer upstream of perimeter silt fence. The plan would address critical areas on the projects such as temporary stream crossings with smaller storage structures, stable runoff conveyances, vegetation, and stone approaches. Utilize the trees cleared to create single shredded mulch and preserve it onsite to be used as groundcover through the life of construction. The plan should include minimizing the voids and tie-ins along the project perimeter with the mulch preserved during clearing and grubbing. This plan would be supported with necessary calculations and address other items of concern such as stockpiling, materials handling, staging, material laydown, etc. such that the Regulatory agency reviewing the plan has fewer comments and gets a plan that is approvable. Realistically, that approved plan would also address the use of rolled erosion control product on perimeter slopes as this can play a big role in the success of perimeter measures.
What if the “one phase fits all conditions” erosion control plan is approved? These plans can still be implemented in the field and successful, but usually that success is through the determination and implementation of a great contractor. Let’s learn from plan reviewers, inspectors, and contractors what makes or breaks a mass grading site from an erosion control perspective. In NC we are in a wetter climate than some of our counterparts out west. Much of our soil is sandy clay loam, sites have rock that will need to be blasted, and there are buffers and streams that meander throughout many of our mass graded sites. We have learned that if you don’t have adequate erosion and sediment control measures upstream of the project perimeter, our streams will become our sediment basins.
Discussions will focus on mass grading sites but revolve around types of erosion control measures that are effective, including these measures on the erosion control plan submittals, the conflict of prescribing “means and methods”, the role of regulators in this process, typical failures, maintenance requirements, and knowing when to move on to the next tool in your toolbelt.