Earlier this year, NEBRA collaborated with the Green Mountain Water Environment Association (GMWEA) to share a “success story” write up about the approved use of manufactured topsoil (MFT) for Vermont Department of Transportation (VTrans) improvement projects. That story was about a specific VTrans project at the Park-and-Ride at Exit 12 on Interstate Route 89 in Williston. Shortly after publishing the success story, NEBRA learned that VTrans had become concerned about per- and polyfluoroalkyl substances (PFAS) and instituted a temporary moratorium on the use of biosolids-based MFT. This concern was generated by conversations VTrans was having with their peer agency at the Department of Environmental Conservation (DEC) about the recent PFAS testing that had been done on biosolids. After many conversations with stakeholders, and review of extensive data, VTrans lifted the moratorium. Here is more on that story.

MFT is a terrific use for biosolids and residuals (see partial list of Benefits)! Last year, NEBRA member Resource Management, Inc. (RMI) secured approval from the Vermont Recycled Materials Working Group and VTrans to use its own blend of MFT for various industrial projects, like parking lots and improvements at the airport.

BENEFITS OF MANUFACTURED TOPSOIL

• Uses renewable recycled resources • Sustainable and locally sourced • Increase nutrient cycling by adding valuable nutrients to the soil, and not landfills • Provides economic benefit to the public and end users • Virtually no soil loss on 3:1 and steeper slopes • High water-holding capacity • Reduces erosion potential • Creates a long-term nutrient-balanced vegetative medium • Eliminates need to strip native topsoil • Is designed to be a low phosphorous soil to protect water quality

RMI’s MFT blend is comprised of biosolids from the South Burlington water resource recovery facility (for slow-release nitrogen), paper fiber from Soundview Paper Mill, wood ash from McNeil Biomass Power Plant in Burlington, and some sand. The mix is made up of 5 parts paper fiber, 5 parts sand, 1 part biosolids, and ½ part wood ash blend. The material is screened and put in a windrow to mature for 3 months allowing microbial activity to create a homogenous topsoil product.

For the Exit 12 Park & Ride project, the finished MFT product was taken from the mixing site and trucked over to the nearby job site where it was spread with conventional construction equipment and seeded. Within a few days the grass was sprouting (see collage of photos from the project, courtesy of RMI). Within a few weeks the site was green and the grass was establishing a robust vegetative cover to complete this site conversion.

Interstate Route 89, Exit 12 Park-and-Ride Improvements in Williston, VT (courtesy of Resource Management, Inc.)

However, what started out as enthusiasm about the results of the approved MFT specification, soon turned to disappointment as VTrans rescinded its previous approvals for using MFT in April of this year. What VTrans called a “temporary moratorium” was based on concern about public perception initially, and not as much on science or risk of PFAS in the MFT.

The beneficial use community rallied around this issue. Soundview Paper in particular was very concerned about losing this primary outlet for its residuals. GMWEA members and Soundview Paper raised concerns about the decision, and multiple meetings and conversations ensued. Upon review of extensive PFAS data and the overall MFT program, the VTrans team once again felt confident to support the use of MFT at roadside projects. In May, VTrans resumed allowing the use of the biosolids-based manufactured topsoil for roadside construction projects, with a new requirement for testing the MFT for PFAS. To be able to continue to use MFT on VTrans projects, contractors are required to test the first 500 cubic yards of the stockpiled MFT for PFAS, initially, and then every 1,000 cubic yards going forward. Results are being compared to 2019 background concentrations for soils as established by the UVM, Sanborn, Head and Associates study: Microsoft Word - PFAS FINAL REPORT_03-24-19.docx (vt.gov). According to sources at RMI, to date all material tests have met this screening standard.

While this was a temporary disruption in the construction season, RMI and several Vermont contractors have been able to meet the new testing requirements and MFT is again being used on VTrans projects throughout Vermont. Increasing our knowledge of product quality and sharing information with state regulatory agencies is essential for continued beneficial use! NEBRA and its members are on the forefront of these initiatives.