By H. Keith DuBois, P.G.
Limited Reuse Soils (LRS) are soils that contain contaminants at levels above naturally occurring background concentrations, are not determined to be hazardous wastes, and which are not associated with a release of oil or hazardous materials regulated under Env-Or 600 Contaminated Site Management. Transportation infrastructure construction and maintenance related LRS typically encountered on municipal projects consist of street wastes (i.e. street sweepings, roadside ditching soils, catch basin sediments, etc.) and soils removed from within and adjacent to roadways. LRS are managed as a solid waste under the New Hampshire Solid Waste Rules, specifically Env-Sw 903 Contaminated Soils, if they are removed from the site of origin. Soils containing elevated concentrations of naturally occurring metals solely due to the natural mineral content of the soil (i.e. arsenic) are not considered to be subject to regulation under the solid waste rules.
Municipalities annually generate thousands of cubic yards of soil and sediment associated with transportation infrastructure construction and maintenance. Soils excavated within or adjacent to roadways often contain contaminants related to roadway runoff and past construction activities. These contaminants generally consist of various metals such as arsenic and lead, polycyclic aromatic hydrocarbons (PAHs), salt, and minor amounts of petroleum hydrocarbons. Most of these contaminants are associated with asphalt abrasion and degradation, tire wear and vehicle drippings (minor contributor). Evidence of pavement abrasion is commonly observed along roadways during or immediately following the plowing season. Contaminants can be incorporated within the shallow roadway soils through the use of ground asphalt as roadway sub-base. Roadway soils in historic urban areas can contain other contaminants such as coal waste. Therefore, municipalities are encouraged to conduct due diligence for projects that traverse highly industrialized or commercialized areas or that are located near known contamination sites. In these cases, pre-excavation soil sampling and analysis is appropriate. In some cases, funding may be available for disposal of contaminated soils that are clearly associated with a known contamination site. It is important to remember that all generators of excess soils are liable for the content and reuse of their soils and are required to conduct a waste determination prior to shipping such soils out of the work zone for disposal or reuse. In many cases the waste characterization can be based on generator knowledge and visual screening.
Should Municipalities be Concerned with LRS?
The primary contaminants typically associated with these LRS are PAHs. PAHs are a group of compounds that are associated with the incomplete combustion of petroleum hydrocarbons such as coal, wood, charcoal, tobacco and oil. The refining process for various petroleum products results in the presence of PAHs in the products. This includes the petroleum used to produce asphalt. The U.S. Department of Health and Human Services has determined that some common PAHs may reasonably be expected to be carcinogens. The most likely modes of human exposure to PAHs are inhalation of PAH-containing smoke and dust and to a lesser extent direct contact with contaminated soils. Certain vegetables such as tomatoes are known to take up PAHs from contaminated garden soils. Once contaminated soils leave a project site they are no longer under the municipality’s control and can end up as construction fill at industrial, commercial or residential developments with contaminant concentrations in excess of the health based Soil Remediation Standards (SRS). If not screened for obvious evidence of gross contamination, contaminants could be present at levels above corresponding leaching based SRS. Some contractors blend excess soils from numerous projects to manufacture loam for uncontrolled distribution. Uncontrolled distribution of LRS can result in widespread low-grade environmental degradation. Also, runoff can carry the contaminants into waterways and negatively impact surface water quality, drinking water quality and the biota present in lakes, rivers and streams.
So What Does One Do with LRS Generated From Municipal Transportation Infrastructure Projects?
LRS can be disposed of in solid waste landfills or used as daily cover material at solid waste landfills. NHDES acknowledges our society regularly makes risk based decisions, well maintained roadways are a necessity for a healthy and functioning economy as well as public safety, and filling up available landfill space with LRS and replacing it with clean fill is not the best use of our natural and financial resources. New Hampshire Department of Environmental Services (NHDES) recently approved a waiver for the New Hampshire Department of Transportation (NHDOT) to use transportation infrastructure related LRS within the confines of their roadway systems provided: (1) all trash, litter, leaves and other debris are removed from the LRS prior to reuse; (2) the LRS is placed in a manner that does not result in the erosion of LRS to surface water; (3) the soils generated are screened for evidence of gross contamination in accordance with procedures reviewed and approved by NHDES; (4) the LRS is managed in accordance with best management practices (BMPs) and a Soil Management Plan reviewed and approved by NHDES; (5) the LRS is not reused in proximity to drinking water supplies; and (6) identified grossly contaminated soils are appropriately managed and disposed of at a properly permitted facility. This management approach keeps the LRS within already impacted areas that are likely to continue to be impacted, does not result in a significant increase in the potential for human health or environmental impacts, does not introduce LRS contaminants to non-impacted areas, reduces the consumption of available landfill capacity, reduces the consumption of natural resources, minimizes the carbon footprint of transportation infrastructure projects and reduces financial and environmental liability.
State to “Test Drive” Waiver Process Before Imposing New Rules
The goal for NHDES is to develop a standard set of BMPs and conditions for NHDOT and municipal reuse of roadway related LRS in the roadway system within the confines of a general permit established by future revision of the New Hampshire Solid Waste Rules. However, NHDES intends to “test drive” the concept under the NHDOT waiver for three to five years before proposing rule revisions to assure that the process is logistically feasible. In the meantime, NHDES will entertain waiver requests from municipalities wishing to proceed in a similar manner to NHDOT. Any such municipal waiver applications would need to include municipality specific screening procedures and best management practices contained within a generic or project specific Soil Management Plan. Alternatively, municipalities may propose alternative uses of LRS at municipal projects in the context of a project specific waiver request. However, NHDES staffing resources make quick responses problematic. Therefore, parties requesting a waiver should plan accordingly.
How Do Other States Manage Roadway-related LRS?
Is NHDES making a mountain out of a mole hill?
A review of how other states are managing transportation infrastructure related LRS indicate the NHDES approach is similar to approaches developed by other states. The Massachusetts Department of Environmental Protection (MADEP) established pre-approved uses of street wastes from non-urban areas and considers other options for approval. However, sampling and laboratory analysis are required in support of other than pre-approved uses. The MADEP pre-approved uses of non-urban street wastes include use as daily cover at lined and unlined permitted solid waste landfills and use as fill in public ways provided the fill is: (1) from a non-urban source; (2) placed beneath a road surface or as fill along the side of the road within the public way; (3) not placed in residential areas; (4) not placed below the groundwater surface; (5) not used in “No Salt Areas”; (6) not placed within the 100 foot buffer zone of a wetland or within wetland resource areas including bordering vegetative wetlands and riverfront areas; and (7) not used within 500 feet of a ground or surface water drinking water supply. These specific requirements for use as fill in public ways are similar to the BMPs contained in the Street Waste Waiver issued to the NHDOT by NHDES. The MADEP also allows non-urban street sweepings to be used as an additive to compost but restrictions and conditions apply.
The Vermont Department of Environmental Conservation – Agency of Natural Resources has published a guidance document that lays out a rather labor and document intensive process for allowing reuse of PAH-impacted LRS at certain development projects. However, this document does not appear to address street sweepings and other street wastes.
The Delaware Department of Transportation disposes of all street wastes in landfills but is currently evaluating other beneficial uses of LRS.
The New Jersey Department of Environmental Protection (NJDEP) regulates street sweepings as a solid waste, provided they do not meet the definition of a hazardous waste, and requires landfilling of all non-hazardous street wastes unless they are used for a NJDEP-approved beneficial reuse such as fill for potholes, embankment material for emergency road repairs, containment/absorption medium for hazardous materials spill response, sub-base fill for roadways, soil mix additive for pavement materials, deicing/anti-skid material (a.k.a. traction sand), landfill cover material and other approved one time uses in accordance with NJDEP site specific approval. However, these beneficial uses require laboratory analyses to demonstrate the wastes meet specified soil quality requirements. Minnesota, Ohio and Indiana also regulate street wastes as solid waste and have established lists of beneficial reuses with State approval that are similar to those presented above. In all cases, including New Hampshire, each state requires the removal of trash, litter, leaves, and other debris prior to any reuse of LRS other than disposal within a permitted landfill.
Specific information regarding the management of street wastes and other LRS for the remaining states was not easily discernable. Ireland, Great Britain and certain Nordic countries have well-established requirements for soil washing and recovery and recycling of the grit for reuse as construction fill and traction sand provided the washed product meets certain analytical standards. NHDES has fielded initial inquiries from municipalities about using this approach; with their intent being not only reusing the materials for their own purposes but potentially as an income stream.
NHDES recommends that all municipalities review their current procedures for managing transportation infrastructure related LRS to assure that they are in compliance with the New Hampshire Solid Waste Rules and are not participating in, or contributing to, the uncontrolled distribution of contaminated soils.
H. Keith DuBois, P.G., is Assistant Director of the Waste Management Division at the New Hampshire Department of Environmental Services. Keith can be reach by phone at 603.271.4978 or by email at firstname.lastname@example.org.
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