Disposal options for street sweeping materials Revision as of 21:49, 21 November 2022 by Mtrojan (talk | contribs) (Created page with "There are several options for the disposal of street sweeper waste. Each of these disposal options is listed and described in Table 3 and greater detail is provided below. Whe...")(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff) Disposal options for street sweeping materials

There are several options for the disposal of street sweeper waste. Each of these disposal options is listed and described in Table 3 and greater detail is provided below. When choosing a street sweeping waste disposal option, considerations include financial cost, staff hours, disposal fees, transportation costs, public perception, potential problems, and regulatory requirements, among other things. Dumping the entire load of street sweeping material without screening any items is likely the easiest and least expensive option; however, there are many potential reuse options for street sweeping material that should not be overlooked.

Once collected, street sweeping debris is considered “industrial solid waste” unless screened for trash and debris. In Minnesota, street sweepings not collected from spill sites, hazardous waste cleanup sites or other contaminated areas are not considered hazardous material and do not require testing. Even though testing of street sweepings is not required, the use of the sweepings is restricted in Minnesota (MPCA 2010). Street sweepings are not to be used in the following areas:

• Playgrounds
• Children’s play areas
• Residential yards
• Areas with regular human contact
• Near drinking water wells
• Wellhead protection areas for public drinking water supplies
• Sites with karst features, including sinkholes, disappearing streams and caves

Description of street sweeping disposal options

Solid waste landfills

The beneficial use/reuse of street sweeping materials is encouraged; however, unscreened street sweepings can be disposed of at a permitted solid waste landfill without testing if they are not removed from spill sites, hazardous waste cleanup sites or other contaminated areas. If removed from these sites the material must be tested. Street sweepings that are not screened for trash and debris are considered industrial solid waste and must be disposed of at a permitted solid waste facility that can accept the waste. In addition, unscreened street sweepings must be stored in accordance with Minnesota’s solid waste storage standards (Minn. R. 7035.2855). Disposal in a municipal solid waste landfill is the most common disposal option according to a recent street sweeping disposal survey conducted by (MPCA 2022a) (see section 2.10).

Benefits, Costs and Limitations

The benefit of dumping street sweeping waste directly to a landfill facility is that it is probably the simplest option because the sweepings are disposed of without screening to remove solid wastes.

Unscreened street sweepings must be managed and stored according to Minnesota’s solid waste storage standards before being taken to a municipal or private solid waste facility. Many municipalities are running out of space to store catch basin sweepings and street sweepings at town facilities. In locations where current landfill capacity is an issue, the disposal of street sweeping debris has become more difficult and expensive.

MPCA conducted street sweeping surveys and interviews in 2021 with several Minnesota municipalities to develop case studies. The case studies found that distance to sites can be a limitation when staff must drive materials to sites that are often far, especially if they are private sites. In addition, the cost of disposal has increased because some sites are no longer taking street sweeping materials, resulting in more staff time spent driving materials further. The City of Fridley found that private disposal sites charge two to three times more than traditional disposal sites, such as county compost sites. In the MPCA follow-up street sweeping disposal and leaf management survey, several respondents indicated that the distance to the closest landfill site can be quite far (e.g., an hour away) (MPCA 2022a). This results in an increase in staff time and equipment costs.

The 2021 MPCA street sweeping surveys and interviews were reviewed for disposal cost information and an online search was conducted for general landfill tipping fees and other landfill costs. Costs to bring solid waste (i.e., unscreened waste) or spoils from screened waste to local landfills ranged from $10.00 to $185.83 per ton. Table 4 presents a summary of all solid waste to landfill cost information found in the search. As shown below, costs can vary by an order of magnitude.

Costs to dump unscreened solid waste at landfills

Screening of street sweeping waste

The screening of street sweeping materials to remove trash, leaves and other debris results in a larger choice of disposal options and allows for the reuse some of the materials. Screening separates solid waste (garbage and other debris) from the smaller dirt material, which can be reused several different ways. The solid waste materials screened from the sweepings can be disposed by recycling, composting, or sending to a permitted solid waste facility (for non-recyclable or non-organic trash materials). If street sweepings are screened prior to being stockpiled or stored, they are exempt from Minnesota’s solid waste storage standards.

Once solid waste has been removed from street sweepings, the remaining material can be reused for the following uses without MPCA approval (MPCA 2010):

• Mix with new salt/sand mixture for winter application to roads, parking lots or sidewalks
• Use as Alternate Daily Cover (ADC) material at a permitted solid waste landfill (the landfill must be approved to use street sweepings as ADC).
• Use as material in commercial and industrial development projects, road restoration or construction projects.

Benefits, Costs and Limitations

The benefit to screening street sweeping materials is that some of the material can be reused and, therefore, less of the material needs to be landfilled, resulting in lower costs.

Multiple respondents to MPCA’s 2022 street sweeping disposal survey mentioned that screening, processing and disposing of trash/physical debris is very expensive. The manpower to sift the materials and find a place to put the organics and the untested sweepings left after the screening are an issue. Utilization of the screened material can also be an issue. The screened material can often be utilized for internal city projects, but demand for the screened product can be low. There is often more produced than what can be incorporated into annual operations.

St. Cloud’s street sweepers dump their material directly into dump trucks to be hauled to the city’s compost facility for screening. The screened material is then recycled, composted or landfilled. About 2% of the collected material is trash/debris that gets landfilled (Tom Zabinski, City of St. Cloud, personal communication, November 2022). The remaining screened sweepings are stockpiled at the city’s compost facility for reuse by the city or a 3rd party contractor. St. Cloud’s screening effort involves two front end loaders at $2,380 per day (including fuel, equipment cost, and operator) for five days resulting in a total cost of $11,900 plus the rental cost of a screener, which is about $6,000 per year.

Recycling and compost

Once street sweeping materials have been screened to remove all debris and solid waste, large trash debris can be disposed at a permitted solid waste facility while recyclable material such as paper, plastic, and metal (e.g., aluminum cans) can be taken to a recycling facility. The organic matter that is screened, such as leaves and twigs, can be used as compost. The compost must be properly cured or aged before being reused to ensure the degradation of pathogens and low and medium molecular weight organic compounds. If uncured compost is applied to soils it will continue to decompose, which results in a loss of nitrogen necessary for plant growth.

Other states also allow compost from street sweepings to be reused; however, there are differences in the source of the compost and the allowable uses. For example, in Massachusetts street sweepings used for compost cannot be collected from Urban Center Roads and the compost can be used only along public ways and parking lot areas (MassDEP 2018). The compost must also be kept above the groundwater level, cannot be used in designated "No Salt Areas", cannot be used within 100 feet of a wetland, and cannot be used within 500 feet of a ground or surface drinking water supply.

Benefits, Costs and Limitations

Recycling and composting of street sweeping materials promotes the reuse of materials that would otherwise end up in a solid waste facility. For example, by screening and composting the sweeper materials, St. Cloud diverts over 98% of swept materials to alternative uses and less than 2% of the material is sent to a landfill. St. Cloud’s leaf sweepings are not screened but are stored in a separate area than their other street sweeping debris. The leaf sweeping is then hauled to a local business that produces and sells soil and mulch products.

The use of street sweeping waste as compost or recycling requires that the materials be screened to remove solid wastes (trash and debris). The Indiana Department of Environmental Management (no date) points out that the end uses of street sweeping debris should be limited to industrial or commercial applications with little chance for human contact. While MPCA does not require testing of street sweeping waste for reuse, one respondent to the MPCA 2022 street sweeping disposal survey mentioned that allowing the public to access the resulting compost product requires close management and monitoring of the product on-site and going out.

Responses to MPCA’s 2022 street sweeping disposal survey identified several other limitations of composting and recycling including storage/space, quantity, and expense. Several respondents indicated that there is insufficient space to store compost material, and the space required for separating trash from organics can be a challenge. There is often a lack of demand for composted material as some municipalities produce more compost than the public needs. Finally, it is expensive to screen street sweeping waste to remove garbage, organics and non-organic debris. It is also expensive to transport materials to a recycling facility or a permitted compost site as there are not many permitted compost sites in Minnesota at this time. Bloomington pays $16/ton for disposal of their organics and leaves at a compost facility (Jack Distel, City of Bloomington, personal communication, November 2022). One respondent also mentioned the concern of inadvertently spreading invasive species (e.g., buckthorn or Canadian thistle seed) through compost from street sweeping leaf pickup.

Alternate daily cover

Street sweeping materials can also be used as alternate daily cover (ADC) at permitted solid waste landfills that are approved to use street sweepings as ADC. The permitted landfill should be contacted prior to transportation to ensure that it can accept the material as ADC. When reusing sweepings as cover material, the MPCA recommends using them only on sanitary or demolition landfills that have groundwater monitoring systems. While some states allow street sweeping materials at both lined and unlined landfills, others require that street sweepings only be used for ADC at lined solid waste landfills.

Benefits, Costs and Limitations

As with recycling and composting of street sweeping waste, using it as ADC promotes the reuse of materials. Street sweeping materials can be reused as ADC without MPCA approval after solid waste screening. The City of Mankato sends their leaf pickup to a compost facility where it is screened; however, any material not fit for compost is brought to the landfill for use as daily cover (MPCA 2021a). One respondent to MPCA’s 2022 street sweeping disposal survey stated that they reuse all their street sweeping material, which has greatly reduced their cost of disposal and purchasing daily cover materials.

Limitations of using street sweeping materials as ADC include the necessity of space for covered storage. In addition, when reusing sweepings as ADC material, the MPCA recommends using them only on sanitary or demolition landfills that have groundwater monitoring systems. Sweepings can only be used at facilities approved to accept the material as ADC in Minnesota.

A search for the cost of using street sweeping materials as ADC at landfills found limited information. A case study on alternative disposal options for street sweeping debris in Natick, Massachusetts (Edward J. Collins, Jr. Center for Public Management 2009) found that the cost of disposing the sweeping debris as ADC was approximately $30/ton ($20/ton for disposal and $10/ton for transportation). St. Anthony, MN indicated that they are charged $26/ton (plus fees) for daily cover at their local landfill (Zach Lundberg, St. Anthony Village, personal communication, October 2022). On the other hand, landfills will often take street sweeping waste for free if they use it as ADC. Wisconsin’s Department of Natural Resources (DNR) 2022 solid waste tip fees and landfill tonnage reports indicate that waste approved by the DNR for use as daily cover, dikes, berms, or roads within the landfill is exempt from all fees. Similarly, City of Mankato reported that the landfill does not charge them for daily cover (MPCA 2021a).

Fill dirt, subgrade material, and aggregate in concrete and asphalt

Once street sweeping material is screened for removal of recyclable materials, organic materials, and trash, the remaining sand can also be used for fill dirt and subgrade material in commercial and industrial development projects, road restoration or construction projects. Fill dirt and subgrade material have different uses, but similar costs, benefits, and limitations. Subgrade material is used directly below a paved surface and is placed above the fill dirt. The fill should only be used for an engineered purpose or it is considered disposal of a solid waste without a permit. Examples of the use of fill dirt or subgrade material include use beneath a paved municipal road or parking lot, or for filling potholes covered by asphalt. Another potential use for street sweepings in construction is as an aggregate in concrete or asphalt.

Benefits, Costs and Limitations

This use of street sweeping material diverts a large portion of swept materials to alternative uses. The sweepings may be reused without MPCA approval after solid waste screening. The incorporation of street sweeping sediments into bituminous concrete or asphalt can minimize concerns with contaminant leaching [into groundwater] associated with other reuses such as winter application (Miller et al. 2016).

The City of St. Cloud conducted a cost-benefit analysis to determine the most cost-effective way to dispose of sweeper materials (MPCA 2021a). Results showed that conversion to clean fill for reuse, as well as compost, was most cost effective, despite the staff time, effort and space needed to manage and store sweepings. The cost-benefit analysis indicated the city would save about $75,000 annually with this reuse strategy versus disposing of all non-leaf sweepings at the landfill. St. Cloud screens their debris and separates it into a clean fill pile and a spoils pile. The spoils go to the landfill, but the clean fill is used in city areas in accordance with MPCA’s guidance. Material that is not used for city projects is advertised to contractors who can take the clean fill for free to be used in construction projects.

While St. Cloud has had a positive experience using street sweepings as fill, other municipalities found using street sweeping materials as fill to be a challenge (MPCA 2022a). One town found the soil left after screening to have no compaction because of the organics left in it, and because it is not tested for contaminants, no one wants it for fill. The current composted product, after it is screened for trash, can sometimes be poor quality for topsoil or general fill. This leads to storage and disposal issues. The current screening and processing of material for reuse is costly and yields a product that is not widely useful in construction. St. Anthony Village has found similar issues and are looking for other avenues to use the separated dirt. Contractors are hesitant to take the material for re-use, even with a lab analysis of the material (Zach Lundberg, St. Anthony Village, personal communication, October 2022).

Another downside of using street sweeping materials as fill dirt is that it requires space for covered storage. In addition, MPCA has specific allowable reuse options that limit the areas where fill dirt from street sweepings can be used (MPCA 2010). It cannot be used in playgrounds, children’s play areas, residential yards, regular human contact areas, near drinking water wells, or wellhead protection areas for public drinking water supplies. While MPCA does not require testing of street sweeping materials for use as fill dirt, other states do require that sweeping material be tested to show that the average concentration is below the industrial/commercial direct exposure criteria for heavy metals and semi-volatile organic compounds before use (CDEP 2007).

MPCA has specific separation distances and requirements for cover material when using street sweepings as fill material (MPCA 2010). MPCA requires fill dirt from street sweepings to be at least 200 feet from all surface waterbodies (lakes, rivers, streams, wetlands, intermittent streams, tile inlets, and karst features), a minimum of three feet from groundwater and fractured bedrock, and 50 feet from potable water supplies. Local regulations should also be checked for limits on the depth of the fill that may be applied. The fill area must be seeded with a grass mixture and/or covered with mulch or other cover material to prevent erosion within 7 to 21 days depending on the slope of the area (within 7 days on slopes >3:1; within 14 days on slopes between 10:1 – 3:1; and within 21 days on slopes <10:1).

Winter application

Street sweeping material that has been screened for solid waste can be mixed with a new salt/sand mixture for winter application to roads, parking lots or sidewalks as anti-skid material. There is no need for MPCA approval for this use. When screening sweepings for reuse as a winter application, it is recommended that a ¾-inch mesh be used for the final screening to ensure all the larger debris has been removed before mixing with the new salt/sand mixture. If a municipality chooses to rinse the sweepings to remove the fine particles and debris, so the sand may be reused on roads during the following winter, they should contact local authorities for additional guidance and discharge requirements.

Benefits, Costs and Limitations

As with other reuse options, the use of street sweepings for winter application diverts a large portion of swept materials to alternative uses. The street sweeping materials may be reused without MPCA approval after solid waste screening. The use for winter application requires space for covered storage until the material is needed. MPCA has specific allowable reuse options, which limit the areas where street sweepings can be used for winter application (MPCA 2010). It cannot be used in playgrounds, children’s play areas, residential yards, regular human contact areas, near drinking water wells, wellhead protection areas for public drinking water supplies. While street sweepings can be used for winter application, Massachusetts guidance reminds users that the use of street sweepings as anti-skid material is not a determination of the efficacy of the material for this purpose. A proper engineering review should be done to ensure the material works as intended (MassDEP 2018). One potential concern with reusing street sweeping sediments is that contaminants will become mobile and contaminate nearby surface and groundwater sources (Miller et al. 2016).

Other uses

MPCA specifically supports the reuse of street sweeping waste for fill dirt, ADC, and winter applications, but some additional uses employed in other states include bulking agents, spill cleanup, and energy. In Massachusetts, street sweepings may be used as a bulking material for wastewater treatment plant sludge or septage when the mixed material will be disposed in a permitted lined or unlined sludge or septage landfill (MassDEP 2018). Connecticut allows the use of non-hazardous street sweepings to be used as absorptive material to contain or absorb hazardous materials in emergency spill situations (CDEP 2007). Finally, Tampa, Florida separates the street sweeping dirt from the larger trash and vegetation through screening and sends the solid wastes (trash and vegetation) to Tampa’s waste to energy facility to produce electricity (City of Tampa 2022).

Storage

Street sweeping materials are typically stored before disposal or reuse. Unscreened street sweepings must be stored in accordance with Minnesota’s solid waste storage standards (Minn. R. 7035.2855) (MPCA 2010). If street sweepings are screened prior to being stored, they are exempt from Minnesota’s solid waste storage standards. The stockpiled screened sweepings must be managed in accordance with any best management practices outlined in the storage site’s Industrial Stormwater Permit (if applicable). General MPCA guidance indicates that storage of screened street sweeping materials should occur in an area where erosion and wash-off of the material into wetlands or waterways will be prevented. There should be proper control of stormwater runoff from the site. The material should also be contained for the purpose of preventing contaminant volatilization, leaching, or fugitive dust emissions. More specific recommendations from other states on the storage of screened street sweeping materials include the following:

• Street sweepings shall not be stored less than 100 feet from a wetland or within wetland resource areas including bordering vegetative wetlands and riverfront areas (MassDEP 2018, CDEP 2007)
• Street sweepings shall not be stored within 500 feet of a ground or surface drinking water supply (MassDEP 2018)
• Street Sweepings should be protected from wind and rain to the extent necessary to prevent dust, erosion, and off-site migration (MassDEP 2018). Street sweeping debris should be stored in a covered container or on an impervious surface, covered with a waterproof material (i.e., tarpaulin or 10-mil plastic sheeting) to minimize erosion, dust and runoff. Street sweeping debris should be contained within the area (i.e., by berming the area) (CDEP 2007, IDEM no date).
• Stored street sweepings must be kept at the site where the sweeping occurred (e.g., parking lot) or at an off-site facility run by the agency/municipality (e.g., Department of Public Works) doing the sweeping or contracted by the agency/municipality (MassDEP 2018). Sites for storing and processing street sweepings should be sized to handle the expected volume of material to be collected and allow for any testing or processing necessary for reusing the material (CDEP 2007). Possible storage options include an empty salt storage shed; a municipal site where sand and salt are normally handled; or a paved/impervious area.
• Municipalities may want to limit the height of storage piles, to the extent space allows, to no higher than 10 to15 feet, as stockpiles higher than that will be difficult to cover and manage for dust and erosion control (CDEP 2007).
• The stored materials should be used within one year.

MPCA’s 2022 street sweeping disposal survey found that finding space to store street sweepings is a common challenge for municipalities. The need for additional land to handle and store the material is sometimes a problem.

Testing

In Minnesota, street sweepings not collected from spill sites, hazardous waste cleanup sites or other contaminated areas are not considered hazardous material and do not require testing; however, testing should be conducted if it is suspected the sweepings will not meet hazardous waste criteria or if local testing requirements exist (MPCA 2010). Street sweeping debris does not typically contain hazardous levels of contaminants unless the street sweeping debris originates from hazardous waste cleanup sites or areas where spills of hazardous substances have occurred (IDEM no date).

While street sweepings can reused without MPCA approval after solid waste screening, determining costs for local disposal options may require paying for initial laboratory testing to ensure debris do not contain contaminants. Lakeville, MN, stockpiles their street sweeping materials and brings it to a landfill in the spring where it is tested for contaminants and used for daily cover. The city pays $15,000 per year for disposal and testing (Kelly Perrine, City of Lakeville, personal communication, October 27, 2022).

Roseville, MN encountered a barrier during early development of their street sweeping program related to material testing (i.e., when should collected street sweeping material be tested, how often, and what to do with contaminated materials) (MPCA 2021a). After years of operations, Roseville found the spring sweepings were almost always contaminated, primarily with diesel range organics. Due to the low cost-benefit of screening collected material and limited storage capacity for screened material, Roseville now landfills all material collected during spring street sweeping efforts. Sweepings collected outside the spring season have not been found to be contaminated.

Some states require testing of street sweeping materials. For example, Massachusetts requires that street sweepings sent to a Reclamation Soil Facility be sampled and analyzed as required by the facility’s Soil/Fill Management Plan and demonstrate that the street sweepings meet the facility’s acceptance criteria (MassDEP 2018). Unless specifically addressed in a facility’s Soil/Fill Management Plan, a minimum sampling frequency of 1 sample per 100 cubic yards is required for characterization of street sweepings collected from roads in urban centers. Street sweepings originating from non-urban center roads may be sampled at a minimum of 1 sample per 500 cubic yards. Regardless of its point of origin, if the total quantity of street sweepings is less than 100 cubic yards, a minimum of one composite sample is required for characterization of the material.

Street sweepings and leaf management survey

MPCA conducted a survey of stakeholders who conduct street sweeping, mostly at the municipality level, in 2022. The survey included several questions as well as space for respondents to include additional comments on challenges their street sweeping programs face. Ninety-eight percent of the survey participants were from a local city, while 1% were from a county and 1% from a town or township. The results are summarized below and were used to inform some of the costs, benefits and limitations for the disposal options presented in this document.

Thirty eight percent of respondents manage their street sweeping waste by sending it to a landfill (unscreened). Twenty six percent of respondents always screen the street sweeping debris and utilize the organic portion, while 20% only screen and use the organic portions at certain times of the year. Sixteen percent do something other than the choices provided in the survey. The respondents that answered “other” give their street sweepings to contractors who use the material as they see fit or they store and stockpile it for compost.

Survey participants were asked if they utilize the organic portion of their street sweepings and how is it used. The use of the organic materials is evenly split with 32.1% of the respondents composting and using as cover (e.g., at landfills, construction sites, etc.). Thirty two percent (32.1%) give or deliver the organic material to another entity (e.g., composting facility) and 30.2% make compost that is available for residents. The remaining respondents (5.7%) have other uses for their organics including compost, temporary cover, disposed of at a landfill, and clean fill available to residents. Finally, survey participants were asked if they were to significantly increase the amount of organic material collected from sweeping, would management of the material be a big challenge. 43.3% of respondents said it would be somewhat of a challenge, while 25.8% said it would be a big challenge, 19.6% said it would not be a challenge, and 11.3% were not sure.

Waste management survey

While taking unscreened street sweeping materials to a solid waste landfill may be the simplest option for disposal, there are multiple reuse options for municipalities that will result in the benefits of keeping cities looking clean, the storm drains open, and preventing excess phosphorus and sediment in ponds and rivers. The most common disposal options in Minnesota are taking the unscreened street sweeping materials to a landfill or screening and using the materials for compost or fill. The largest overall issues for Minnesota street sweeping stakeholders (MPCA 2022a) are the cost of dealing with street sweeping disposal, storage space for materials, and lack of demand for screened materials (e.g., fill, compost). Still, some stakeholders do not have trouble finding places to take their street sweeping waste and have room to increase their street sweeping programs.