“Today, a general consensus of literature reports two major national and global sources of PAHs in the environment: 1) incomplete combustion of organic matter, especially common, nonpoint activities that utilize modern emissions controls (e.g., cars) or less common activities with no emissions control (e.g., tire fires); and
2) releases of petroleum, including oil spills and illegal dumping. Major sources include forest fires, motor vehicle emissions, open burning, domestic fireplaces, and spills and dumping of petroleum products. (page 47)
“Our estimates indicate that transportation-related activity (i.e., on-road and off-road engine exhaust, tire wear, and motor oil disposal and leakage) is the source category contributing most greatly to total loadings of PAHs”. (page 27)
Study determined that refined tar based sealer to be a minor source of PAHs to the NY/NJ harbor watershed (less than 1% total contribution). (pages 21 & 26)
NYAS reconsidered and dropped PAH loading estimate recommended by COA.
NYAS rejected COA photographic sealer wear-off estimation.
NYAS saw flawed conceptual study design and flawed statistical analysis (errors in calculations) in the COA studies.
Crane, J., Grosneheider, K., Wilson, C., Contamination of Stormwater Pond Sediments by Polycyclic Aromatic Hydrocarbons (PAHs) in Minnesota-The Role of Coal Tar-based Sealcoat Products as a Source of PAHs. Minnesota Pollution Control Agency, March 2010.
”Stormwater ponds are filling up with contaminated sediments throughout Minnesota and my cities have not included the cost of removing these sediments in their budgets. One pollutant, PAHs, are a concern in these sediments”.
”Most cities have slowed there maintenance of their stormwater ponds after the “discovery of high levels of PAHs” in the sediments. Cities need to periodically need to remove these sediments otherwise the stormwater ponds will not operate effectively. Many of the stormwater ponds are over 15 years old and are filling with sediment”. According MPCA guidance document “Stormwater Detention Ponds”, MPCA recommends that the detention pond be built with a capacity of 25 years of storage. Futhermore, it states “Urbanization will increase the runoff volume that occurs from each storm event, overloading the natural drainage systems that had adapted themselves to the pre-existing conditions. The frequency of bank-full and over-bank events usually increases with urbanization of the watershed”.
Cities have requested a solution from the Minnesota Pollution Control Agency (MPCA).
Local news media have started to cover the issues therefore increasing public awareness and expectation for action.
According to MPCA, U.S. Geological Survey have provided clear and compelling evidence regarding the magnitude of this problem, particularly from pavement dust and stormwater runoff of driveways and parking lots treated with refined tar based sealcoat products. This is all without any information from PCTC regarding their studies.
MPCA assumption is the same as USGS and COA, in that the source of the majority of environmental PAHs is from refined tar pavement sealer.
In the 2009 Minnesota legislative session, a restriction of refined tar-based sealcoats by state agencies was implemented beginning July 1, 2010. In addition, the State of Minnesota will make grant funding available in state fiscal year 2011 for municipalities to implement best management practices (BMPs) to treat or clean-up contaminated sediments in their stormwater ponds. This funding will only be available to local governments that have adopted an ordinance restricting usage of coal tar-based sealcoat products. This is the copy of the legislation H.F. No. 1973. It should be noted that Minnesota legislation or MPCA never consulted with industry prior to issuing this restriction nor allowed industry to be represented as a stakeholder in the formulation of this document.
This is a diagram of a typical wet detention stormwater pond:
Source: Crane, J., Grosneheider, K., Wilson, C., Contamination of Stormwater Pond Sediments by Polycyclic Aromatic Hydrocarbons (PAHs) in Minnesota-The Role of Coal Tar-based Sealcoat Products as a Source of PAHs. Minnesota Pollution Control Agency, March 2010. Page 6
MPCA was aware of Pavement Coating Technology Council from conversations with the City of White Bear Lake, MN but yet never contacted the organization for their input.
The report incorrectly states that NYAS PAH study identified refined tar base sealer as major contributor of PAHs into the NY/NJ harbor watershed (see other studies section).
The primary references used were the USGS and COA studies (see COA Studies and USGS studies section).
On page 50 of the study, MPCA discusses the cost of Minnesota businesses to switch from refined tar to asphalt. The analysis most of which revolved around comparing the cost of 275 gallons tote of asphalt based sealer vs. refined tar based sealer. This would be more of an analysis of a snapshot cost to the consumer than a reflection of any business related cost (including any additional capital outlays, opportunity costs, tank cleaning, etc.). The industry organization, PCTC could have perhaps aided in putting together a more realistic evaluation of this analysis.
Similar to the COA and USGS studies, MPCA assumes that 100% of the environmental PAHs are from refined tar based pavement sealer.
MPCA performed an aquatic ten-day Hyalella azteca and ten-day Chironomus tentans toxicity tests at two of the sites indicated no toxicity to C. tentans and slight to moderate toxicity to H. azteca at one site (Polta et al. 2006). However, it was not reported whether this toxicity was statistically significant and therefore inconclusive.
Σ PAH13 was the analysis that MPCA performed in the Area of Concern (AOC) of the St. Louis River.
The MPCA covered a great deal on environmental forensics but actually performed very little in this study. One noteworthy item is that on page 24, table four lists an inventory of recommend PAHs to be analyzed to determine their sources (ΣPAH42). First MPCA analyzed Σ PAH13 which is actually insufficient to utilize even as a method of screening (See Environmental Forensics under About Coal Tar). The only other environmental forensics method utilized is the single component ratios for two different groups of compounds. Since MPCA utilized only two of the many environmental forensics tools available, especially considering the fact that there are may other sources of PAHs in the environment, it is necessary to use more of the tools that are available. Therefore, MPCA did not prove that the major source of the PAHs in their watershed is derived from refined tar based pavement sealer.
PAH Forensic Evaluation by PCTC
-PCTC asked leading expert on PAH forensics whether RTBS are a significant source of PAHs in urban sediments. PAH forensics used to identify sources of PAHs in the environment based on detailed evaluation of PAH chemistry.
-PAH forensic techniques routinely used in legal proceedings to apportion responsibility for environmental PAH contamination
PAH Forensic Evaluation of Minnesota Pond Sediments:
-Use published data to compare wider range of potential sources and urban sediments RTBS, RTBS-sealed parking lots, roof dust atmospheric particles, soil and highway runoff. Sediments from across the country including a fifty sample study from Minneapolis and data from White Bear Lake’s Varney Pond.
-Apply six environmental forensic methods PAH source ratios, double ratio plots, histograms, ring number fractions, chemical correlation, and principal component analysis. Methods used depend on type of analytical data available.
-PAH Double Ratio Fingerprint
The PAH source ratios of sediments collected from Varney Pond in White Bear Lake and ten ponds in Minneapolis are inconsistent with RTBS or particles from RTBS-sealed parking lots.
-Principal Component Analysis (PCA)
PCA is a statistical approach that considers the concentration profiles of all the individual PAHs. The results indicate clear differences between urban sediment and RTBS samples.
PAH Forensic Evaluation of Minnesota Pond Sediments
The results of this evaluation:
1) Does not support the general hypothesis that refined tar-based sealants are a significant source of PAHs in urban sediments.
2) Indicate that refined tar-based sealants are not a significant source of PAH in Minnesota pond sediments.
HF3456 & 2009 Law: Only Impact is on small businesses:
-Little to no impact on current or future sources or concentrations of PAHs in Minnesota pond sediments.
-Two manufacturing facilities in Minnesota.
-Customers include hundreds of small contractors throughout MN and neighboring states. Many small contractors heavily invested in RTBS technologies/equipment.
-In the study, Fernandez, M., Hutchinson, CB.1993. Hydrogeology and Chemical Quality of Water and Bottom Sediment at Three Stormwater Detention Ponds, Pinellas County, Florida. U.S. Geological Survey Water Resources Investigations Report 92-4139. it states; “The bottom sediments from the 1 year old Seminole pond contained undesirable concentrations of 1 trace element and 7 organic compounds; the sediment sample from the 20 year old Clearwater pond contained detectable concentrations of 4 trace elements and 16 organic compounds; and the sediment sample from the 30 year old Largo pond contained detectable concentrations of trace elements and 23 organic compounds. These results indicate that contaminants accumulate in the pond sediments and constituent diversity increases as a function of the age of the pond. The limited data indicates that the pond bottom sediments are not toxic to aquatic life”. (pages 25-26)
-In the study; Kamalakkanna, R., Zettel, V., Goubatchev, A., Stead-Dexter, K., and Ward, N. Chemical (polycyclic aromatic hydrocarbon and heavy metal) levels in contaminated stormwater and sediments from a motorway dry detention pond drainage system. J. Environ. Monit., 2004, 6, 175-181.
Chemical (polycyclic aromatic hydrocarbons – PAH and heavy metal) levels in stormwater and sediment samples collected from the London Orbital (M25) motorway drainage dry detention pond at Oxted, Surrey, UK were determined.
The dry detention pond at Oxted, Surrey, UK is located approximately 50 m south of the London Orbital M25 motorway, between junctions 5 and 6. Rainfall runoff from an approximately 2.24 km (76160 m2) stretch of the motorway discharges into the pond. The motorway has an average traffic density of 120 000 vehicles per day. The road surface is constructed of conventional asphalt.
Vehicular traffic on roads and motorways has dramatically increased during the last couple of decades, thereby contributing to potential chemical pollution problems.8 Run-off water (or stormwater) contains many chemical constituents, including heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Pt, Sb, V and Zn), organo-metallic species, polycyclic aromatic hydrocarbons (PAHs), fuels (petrol and diesel), lubricating and transmission oils, grease, corrosion-preventing and anti-freezing agents.
ΣPAH16 were 10,200 ppb dry weight.
Refined tar based sealer is not sold in the UK.
Conclusion: The results raise some serious concerns about the chemical contamination
pattern of the motorway drainage media, and in particular the accumulation of PAHs in drainage sediments beyond the treatment facilities.
Finally in the study; Weinstein, J., Crawford, K., Garner, T., Chemical and Biologicals Contamination of Stormwater Detention Pond Sediments in Coastal South Carolina. South Carolina Sea Grant Consortium & South Carolina Department of Health and Environmental Control. July 2008.
Stormwater ponds are a common management practice to protect the water quantity and quality of runoff entering natural receiving waters. However, the sediment which accumulates in the ponds must periodically be removed in order to maintain pond efficiency. The purpose of the current project was to characterize the chemical and biological contaminants in stormwater pond sediments here in coastal South Carolina.
In this project, the 16 individual PAH analytes that the U.S. Environmental Protection Agency (US EPA) considers to be “priority pollutants” were analyzed. Levels of the sum of these PAH analytes (ΣPAH16) were significantly higher in the sediments of commercial ponds (24,371.6±6,415.7 ng/g) (mean ± standard error) compared to that of reference (1,276.7±695.7 ng/g), low density residential (508.6±129.5 ng/g) and high density residential ponds (956.2±432.1 ng/g). These levels of PAHs are generally on the same order of magnitude as those of other suburban stormwater ponds reported in the literature. In general, there was no consistent pattern in PAH levels with regard to sampling location (inlet or pond center) among the various land use classifications. Isomer ratio analysis suggested that the predominant source of PAHs in these stormwater ponds were pyrogenic (e.g., derived from combustion); however, many ponds had a PAH signature consistent with mixed petrogenic (e.g., uncombusted fuel), and pyrogenic sources.
Commercial stormwater ponds had significantly higher levels of PAHs compared to ponds associated with other land uses. Sediment levels of ΣPAH16 in these commercial ponds ranged from 570 to 63,689 ug/g with an average level of 24,372 ug/g. These levels are generally similar to those reported in other studies involving commercial stormwater ponds. For example, in a study of a variety of stormwater detention ponds, wetlands and swales in Minneapolis, MN, sediment levels of total PAH (13 analytes) in commercial stormwater ponds ranged from 5,007 to 26,230 ug/g with an average level of 16,771 ug/g (Polta et al., 2006). A commercial stormwater pond in Ontario, Canada and a highway stormwater pond in Surrey, UK also had total PAH levels (16,370 and 10,200 ug/g, respectively) similar to those reported in the current study. However, the levels reported here are generally an order of magnitude less than those reported for certain commercial ponds in Clearwater and Largo, FL, which had total PAH levels of 592,000 ug/g and 7,161,000 ug/g, respectively (Fernandez & Hutchinson, 1993). These high levels of PAHs are probably related to their age (20 and 30 years, respectively) and the fact that they had not had sediment removed as part as routine maintenance (Fernandez & Hutchinson, 1993).
Recommendations: In coastal South Carolina, the majority of stormwater ponds have been constructed in the past 15 years likely due to regulations established in 1991. If homeowner’s associations, property management firms and local governments are following recommendations for sediment removal every 10 years, then the overwhelming majority of existing stormwater ponds have not had accumulated sediment removed. Given their age and history, it is quite likely that many of the existing ponds will need to have sediment removed in the next 5-10 years to maintain efficiency. More likely, however, the need for sediment removal will only become apparent when the stormwater pond becomes very shallow and performance has already significantly degraded.