Washington State Department of Ecology

Physical and Chemical Characteristics
  • Regulations
  • Reuse and Disposal Options Street waste solids contaminant content data is limited and continued regular sampling is needed to verify the recommendations of this guidance.. Current data and regulations suggest that street waste solids from sites that are not obviously contaminated classify as solid waste and can be used, recycled, or disposed of in ways that do not pose a threat to human health or the environment. The following section will outline the reasons for this conclusion and suggest specific use options.

    Physical and Chemical Characteristics

    Catch Basin Solids

    Catch basin solids accumulate from many storms, often over several years. Contamination characteristics result from surrounding land uses (residential, industrial, commercial, agricultural, open space), traffic patterns, property owner habits, illicit connections, and frequency of cleaning. Contaminants may include oil and grease, metals, sediment, and discarded products such as radiator fluids, paints, solvents, and construction materials.

    Analysis of solids samples from 92 catch basins from residential, commercial, and industrial areas showed the following general characteristics. (Serdar, 1993 and Herrara, 1995).


    Table A

    Sampling from 72 sites from all kinds of lands uses in King County (Herrera, 1995) showed Total Petroleum Hydrocarbons (TPH) using EPA 418.1M method with a range of 123 to 11,049 mg/kg (median 1046 mg/kg). Classification as dangerous waste is not influenced by the TPH analysis, but the TPH rusults are substancially above the MTCA cleanup level of 200 mg/kg TPH. It is likely that the high TPH values are the result of analytical interference with natural organic material such as leaves. Robert Carrell of the Ecology's Environmental Investigations and Laboratory Services (EILS) program is working on a method to circumvent this problem.

    Street Sweepings

    Street sweeping can reduce the sediment loadings to the stormwater systems by approximately eight percent (Pitt and Bissonette 1984). Unfortunately, street sweeping is "generally ineffective as a technique for improving the quality of urban runoff" (NURP 1983), since the majority of pollutants are contained in the finer particles that are missed in most street sweeping. High efficiency vacuum systems have potential for collecting the finer particles (TYMCO Inc., 1993)

    The limits to collecting street sweeping waste mean that it is generally coarser (larger than one millimeter in diameter), dryer, and less contaminated than catch basin waste. The more efficient street sweeping is at collecting fine particles, the higher its likely contaminant content. Street sweepings contaminant concentrations from limited sampling (9 samples, reported as 5 average values) in Snohomish County are shown in Table B below (W&H Pacific, 1994):

    Ditch Spoils, Settling Basin Sediment, and other stormwater facility waste

    Data is limited on the contaminant character of ditch spoils, settling basin sediment, and other stormwater facility waste. Contaminant levels are expected to be relatively high because of the fine grained and high organic content sediments trapped in these facilities. Table C (Schueler, 1994) shows comparative metal concentrations (means?) from wet ponds, detention basins, and grassed swales to be similar to that of catch basin solids.


    Regulations

    Solid Waste Classification

    Materials are identified as solid waste under the Department of Ecology's Dangerous Waste Regulations (Chapter 173-303-016 WAC), depending on constituents and end use or disposal methods. Street waste solids will generally classify as solid waste if they are:1) disposed of, 2) "accumulated speculatively" (stored for recycling in excessive amounts), or 3) recycled in ways that pose a "substancial threat to human health or the environment". There are no Department of Ecology regulatory criteria below which street waste solids are not considered solid waste and can be recycled indiscriminately. Even if such criteria existed, associated analytical costs could likely exceed savings from low cost recycling.

    Recycling

    The State's solid waste statute, Chapter 70.95 RCW, prioritizes the need to recycle rather than dispose of waste. All recycling end-uses must be conducted in compliance with specifications required by federal, state or local regulations, or specifications required by a manufacturer or vendor accepting the waste for processing. When considering recycling options for street waste solids, contaminant levels must be considered to insure that the final end-use does not compromise the health of the public or the environment. Until such waste is recycled, it continues to be regulated as a solid waste.

    Dangerous Waste

    Solid wastes are determined to be dangerous waste if they exhibit dangerous waste characteristics or criteria (Chapter 173-303-090 and 100 WAC). Sampling data shows that street waste solids that have passed a precollection screening are not likely to exibit dangerous waste characteristics or criteria. The dangerous waste characteristics most likely applicable to street waste solids are metals using the Toxicity Characteristic Leaching Procedure (TCLP) Table D.


    The dangerous waste criteria most likely applicable to street waste is the persisitence criteria (for PAHs) and carcinogenic criteria [for carcinogenic PAHs and Bis(2-ethylhexyl)phthalate]. The persistence criteria will apply and the waste is classified extremely hazardous waste if the PAH concentration is greater than 1%. This is not likely to occur. The carcinogenic criteria will apply if the concentration of any one designated carcinogenic substance is greater than 0.01% (100 mg/kg) or the total of all carcinogenic substances is greater that 1.0%. Carcinogenic PAHs and Bis(2-ethylhexyl)phthalate are found in street waste in the mg/kg range, but below 100 mg/kg. The carcinogenic substance designation procedure is proposed to be eliminated in current revision of the Dangerous Waster Rules (173-303 WAC)

    Toxic Cleanup Standards

    Juristictions such as the King County Juristictional Health District (Herrera, 1995) have used Ecology's End Use Criteria for Petroleum Contaminated Soils (Table E) and Model Toxics Control Act (MTCA) Method A cleanup levels for soil (Table F) to guide recycling and disposal of street waste solids.

    The End Use Criteria for Petroleum Contaminated Soils appears at first to be the good method for determining end uses for street waste solids, but problems in finding an analytical method that will accurately quantify petroleum content of high organic materials limit its use.


    Class 1 Soil Uses:

    Class 2 Soil Uses: Class 3 Soil Uses: Class 4 Soil Uses: A number of the above uses are not even practical for street waste solids. For example: 'Backfill at the original site' avoids the reason the solids were collected in the first place, and street waste solids often contain too much fine material to function as fill. The presence of contaminants (PAHs and metal principally) in street waste solids, that are not found in petroleum contaminated soil means that the 'End Use Criteria for Petroleum Contaminated Soils' is only a start in finding uses for street waste solids.

    The Model Toxics Control Act (MTCA) Method A cleanup levels for soil (Table F) is good for general direction, but was designed for cleanup (not disposal) and does not account for the effects of the multiple hazardous substances found in street waste. A value of 4.8 mg/kg average concentration of carcinogenic PAHs in catch basin solids from King County reported by Herrara (1995) is higher than the 1.0 mg/kg residential cleanup standard for soil, but lower than the 20.0 mg/kg industrial cleanup standard. This is clear indication that any end uses for street waste solids should be in industrial or commercial areas with little chance for human contact.


    Reuse and Disposal Options

    Sites that fail the Site Inspection

    All liquid and solid waste from sites that fail the Site Inspection shall be considered dangerous waste until testing to show its characteristics or composition are completed and it determined to not be dangerous waste. Dangerous waste shall be managed following the Dangerous Waste Regulations (Chapter 173-303 WAC). Tested solids that are determined by testing to not be dangerous waste shall be considered solid waste and treated as test values indicate.

    Street Waste classified as Solid Waste

    Street waste solids that have passed a visual and historical inspection or dangerous waste analytical tests may be reused and recycled in ways that strongly limit human and environmental contact. Additional treatment such as drying, sorting, or screening may be required depending on the needs and requirements of the end user. Caution should be exercised to avoid creating dangerous waste from the material remaining by concentrating contaminated fines. All street wastes may not reused or disposed of without the knowledge and permission of the final receiver.

    The following suggested reuse and recyle options are considered appropriate for street waste solids treated as solid waste:

    Higher Value Reuse

    Higher value reuse options may be possible for some street waste solids with additional testing, sorting, or quality control. There is the possibility that removal of coarser material will leave fines with higher contaminant concentration that then designate as dangerous waste. Higher value reuse requires evaluation on a case or site basis.

    Reuse of clean road grit as road grit is possible, but no affordable chemical based test exists to determine if road grit is clean. Until a test is developed the following subjective test is recommended to evaluate road grit reuse: it passes the inspection, it is picked up "soon" after use, is from low traffic areas,and is stored under cover. If the street sweeping contains greater than 50% coarse sand (1-4mm), which is indicative of low traffic impact, it may be assumed to be clean. The fines from the street sweeping should be considered as solid waste. A contaminate based test for 'clean' should be used rather than the grain size analysis when one is available.

    Leaves from low traffic areas picked up within two weeks of falling, grass cuttings from swale mowing and other high organic waste that passes the inspection may be used as feed stock for Grade A compost. The compost should only be used for manufacture of industrial/commercial use artificial topsoil because of metal and organic constituents and possible fecal coliform bacteria contamination.

    Inappropriate Uses

    The following are a considered inappropriate uses of street waste solids because of their potential for human and environmental contact. The above lists are not meant to be inclusive and local landowners and juistictional health districts may have have their own restrictions. Alternative testing protocols may be substituted upon approval by the Jurisdictional Health Department.
    Liquids Appendices
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