BMP BLAST: Construction Sequence

One of the requirements for stormwater pollution prevention plans (SWPPPs) is to include an implementation schedule for major construction operations. This includes things like clearing, grubbing, excavating, grading, utility installation, and other similar activities.
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The Ohio EPA Rainwater and Land Development manual includes a table of what this general sequence should look like: https://epa.ohio.gov/static/Portals/35/storm/technical_assistance/6-24-09RLDCh8.pdf (pg 13)
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There are steps that should be taken as early in the construction process as possible to avoid problems with sediment and erosion control later in the project. 

Let’s breakdown those crucial early steps:

• Protect your natural areas. As construction activity is commencing, everyone working on the site should be aware of protected forested areas, streams, and wetlands that should not be disturbed. These should be marked off with easily identifiable fencing. If areas that were meant to be left alone get impacted, it can cause harm to sensitive natural areas and may also be in violation of other state and federal permits.
• Construct an area where equipment and vehicles have a clean exit from the site. A proper construction entrance/exit should consist of ODOT #1/#2's aggregate over a geotextile base. The proper aggregate size helps to ensure there will be enough vibration under the tires to kick mud off equipment and vehicles before leaving the construction site. It is best to have this installed as soon equipment and trucks are moving on and off the site to prevent off-site tracking.
• Install perimeter controls around all areas planned for disturbance. Clearing trees (root ball and all), grubbing, and grading work results in exposed soils. That sediment must be contained on the construction site. Perimeter controls need to be up around the entire perimeter of disturbance to help intercept sediment-laden discharges from moving off-site during rain events.
• Construct temporary basins. Basin construction should be part of the initial phase of construction. Basins must be installed and functional before any upslope development. As soon as the basin is dug, apply temporary seeding treatment to ensure embankments are stabilized throughout construction. Doing this early in the process helps to prevent erosion in the basin and sediment storage problems. The basin outlet structure should also have a skimmer device installed as soon as possible for de-watering off the surface of the basin rather than lower depths of water where more sediment is present.
• Follow construction timeline for remaining controls. Other sediment and erosion controls should also be installed as soon as possible. For example, when streets are installed, a sweeping schedule should be established. As new catch basins or street inlets are installed, get inlet protection on them right away. As lot development begins, make sure individual lot controls are in place. When concrete pouring is in full swing, there should be a designated washout area with controls.
• Communicate with your SWPPP inspector! Keep your inspector in the loop when new phases of the project begin in between inspection periods. If there are changes to the timeline or problems with getting certain controls established, let your inspector know so that they can help provide guidance that can help to keep things on track.  

​Generally, the sooner these controls are implemented, the better the outcome for sediment and erosion management. It’s always better to work proactively rather than to have to fix problems that arise from waiting too long to implement or correct controls. 

Phased Disturbance is another tool to keep in mind when developing SWPPPs and generating a construction sequence. This practice minimizes the amount of grading done at one time. Planning smaller earth moving efforts allows for parts of the site to remain undisturbed and stabilized while other parts are being actively worked. Planning disturbance in this way helps reduce the amount of sediment that controls manage at one time, which increases the effectiveness of these practices.

BMP Spotlight Example from the Field: Early Construction Process Communication and Implementation 

Monarch Homes and Diggit Excavating met with Warren Co SWCD at a pre-construction meeting with the City of Lebanon where the requirements and sequence of sediment and erosion controls measures were discussed. Since that meeting, the team has been in constant contact with Warren Co SWCD, proving updates on initial groundbreaking and the control installation timelineas well as any changes to controls being used on the construction site.

As soon as clearing and grading work was set to begin, there was a proper construction entrance in place and silt fence around the clearing boundaries that was supplemented with a mulch berm from the on-site clearing. The basin was dug as part of the first phase as well. The basin will be temporarily stabilized and have a skimmer installed on the outlet once installed. 

​We asked our friends at Diggit Excavating for their take on how communication has helped with the development process from their perspective:
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“At Diggit Excavating we strive to minimize the impact our work has on the surrounding environment. The relationship between community, agency, and contractor is something we take seriously and work hard to cultivate and maintain. Everything as designed on paper is not always perfect in the field but, with proper communication, we can work through any situation to develop practical and real work solutions that help maintain environmental controls. One way we like to accomplish this is by meeting with the agency up front to discuss the project and its environmental requirements to identify specific site constraints and other potential issues before they arise. Warren County has always been very accommodating and great to work with in this regard. Both parties appreciate and encourage this kind of involvement.”
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This is a great example of communication between our agency and developers and contractors on projects and how compliance can begin right out of the gate as a new project begins. This proactive approach helps to avoid many complications later in the construction process. ​