Avoid Costly Construction Washout: Key Erosion Control and Stormwater Measures

When building on parcels of land featuring slopes or other challenging topography, owner, developer, and contractor concerns must extend beyond getting the site foundation-ready. Especially given recent surges in heavy rainfall and extreme weather events, these concerns include attaining knowledge of site conditions and building in a responsible construction sequence to avoid costly washouts and minimize unwanted impacts. Below, we offer some broad guidelines for effective early construction project erosion control and stormwater measures, as well as some unfortunate examples of what occurs when these measures are not properly put in place.

Preconstruction Priorities

In the preconstruction planning and design phase, as the project team focuses on permitting, it is imperative to conduct appropriate soil testing. This will reveal the land’s natural drainage patterns, determine the number of soil tests that must be performed, and provide critical information as to the types of structure and foundation the site can accommodate.

Before sitework begins, mandated erosion controls must be installed around the perimeter as well as at targeted areas within the boundaries of the property; the specifics of these internal controls will vary depending on the size and grading of the parcel, as well as the presence of any internal resource areas such as water features.

As the project moves to Phase One development – which, depending upon the site, could include removal of trees and vegetation for entry drive clearance – stormwater management measures should be installed. Typically, these will include surface basins (which some contractors use as temporary sediment basins during construction) and the installation of erosion control barriers upstream from the basins to manage runoff.

Next, the contractor must prepare the site for Phase Two. If land must be cleared of trees and other vegetation, it is important to do so by starting at upper elevations of the slope(s) and working downward from there to retain a lower erosion buffer during the process. Erosion control measures can then kick into high gear with rough grading and placing new loam and land-stabilizing grass and vegetation seeds. At the same time, any additional erosion barriers that may help keep the topography intact – such as coir logs, silt fencing, and biodegradable erosion blankets – should be installed at this point.

Barriers to Certification (and How to Avoid Them)

While these measures are not overly complex, many projects experience costly delays due to lack of careful attention to ground cover and stormwater. As no two projects are identical, Meridian Associates prepares Operations and Maintenance (O&M) manuals adhering to official state erosion and sediment requirements as well as local regulations. Owners, developers, and contractors who follow this manual safeguard against unexpected site surprises and/or delays in certification.

Conversely, overlooking these stormwater and erosion control elements is short-sighted, as one Massachusetts developer recently learned when attempting to fast-track nature’s germination process on a parcel of land by hydroseeding without preparing the very sandy ground with loam. The hydroseed sprouted grass for a brief period but without adequate watering it did not hold up in the sandy environment. As a result, the local municipality shut the project down multiple times until seed planted in line with O&M manual instructions successfully took root.

While these measures are not overly complex, many projects experience costly delays due to lack of careful attention to ground cver and stormwater. Owners, developers, and contractors who follow this manual safeguard against unexpected site surprises and/or delays in certification.

Likewise, a residential development team recently found itself spending a significant amount of time and resources on “reverse engineering” a problematic slope. When rough-grading the hillside in the fall, the only erosion control measure put in place was a single staked strawbale at the base of the slope. Come spring thaw, silt and sediment washed off the property and onto abutting lands. The hillside was eventually stabilized with retroactive erosion control measures including a diversion swale, additional strawbales, a row of siltation fencing, additional topsoil compacted to specifications, and biodegradable mesh erosion control blankets saturated with hydroseed.

Project owners can avoid problems like those above by engaging expert site/civil design support up front to produce an effective construction sequence and help ensure project success. Do it once and do it right.

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