Improving the EPA Multi-Sector General Permit for Industrial Stormwater Discharges (2019) / Chapter Skim
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2 Pollutant Monitoring Requirements and Benchmark Thresholds
2 Pollutant Monitoring Requirements and Benchmark Thresholds
Pages 21-44
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ways to improve pollutant monitoring requirements, Consequently, some industrial groups submitted including industrial activities not currently covered by more information than others, causing monitoring data the MSGP, industry-wide benchmarks, and sector- submittal discrepancies among some sectors. The result specific monitoring requirements.
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However, they benchmark monitoring compliance and provide impor- provide insight into the sectors and pollutants with tant context for the committee's findings. More than frequent elevated discharge concentrations.
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, based on the limited available data on industrial sites, copper, and TSS, and 81 percent of the samples a lower threshold of eight reported results was used. exceeded eight times the benchmark for copper.
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24 IMPROVING THE EPA MULTI-SECTOR GENERAL PERMIT TABLE 2-3 NetDMR 2015 MSGP Data According to the Percentage of Results Above Benchmarks NO2+ Sector Al NH3 As BOD5 Cd COD Cu CN Fe Pb Mg Hg pH TP Se Ag TSS Turb Zn NO3 A1: Sawmills A2: Wood A3: Log storage A4: Hardwoods B1: Paperboard B2: Pulp mills C1: Agricultural C2: Industrial inorganics C3: Cleaning, cosmetics C4: Plastics C5: Medicinals D1: Asphalt E2: Concrete E3: Glass F1: Steel works F2: Iron/steel foundries F3: Nonferrous metals F4: Nonferrous foundries G1: Copper ore G2: Other ores H: Coal mines J1: Construction sand J2: Stone J3: Clay mineral mining K: Hazardous waste L1: Landfills L2: Landfills, not MSW M: Automobile salvage N1: Scrap recycling O1: Steam electric P: Transportation, postal Q: Water transportation R: Ship and boat building S: Air transportation T: Sewage treatment U1: Grain mill products U3: Meat, dairy, tobacco Y1: Rubber Y2: Misc. plastics AA1: Fabricated metals AA2: Fabr.
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POLLUTANT MONITORING REQUIREMENTS AND BENCHMARK THRESHOLDS 25 TABLE 2-4 Categorization of NetDMR Data Based on the Percentage of Results Above Eight Times the Benchmark NO2+ Sector Al NH3 As BOD5 Cd COD Cu CN Fe Pb Mg Hg TP Se Ag TSS Turb Zn NO3 A1: Sawmills A2: Wood 81% 13% A3: Log storage A4: Hardwoods B1: Paperboard B2: Pulp mills C1: Agricultural 13% 25% C2: Industrial inorganics C3: Cleaning, cosmetics C4: Plastics 16% C5: Medicinals 50% D1: Asphalt E2: Concrete 17% E3: Glass F1: Steel works F2: Iron/steel foundries F3: Nonferrous metals 14% 12% F4: Nonferrous foundries 50% 30% G1: Copper ore G2: Other ores H: Coal mines 95% 95% 55% J1: Construction sand J2: Stone 11% J3: Clay mineral mining K: Hazardous waste 83% L1: Landfills L2: Landfills, not MSW 17% M: Automobile salvage N1: Scrap recycling 13% 26% 18% 13% O1: Steam electric P: Transportation, postal Q: Water transportation 12% 61% 12% R: Ship and boat building 81% S: Air transportation 16% T: Sewage treatment 10% U1: Grain mill products U3: Meat, dairy, tobacco 13% Y1: Rubber 23% Y2: Misc. plastics AA1: Fabricated metals 46% AA2: Fabr.
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The submission of the MSGP data was not mandated until committee identifies industrial activities not currently 2016. Several parameters have data from only one per- covered by the MSGP, discusses the value of industrymittee and, in some cases, at only one outfall; therefore, wide benchmark monitoring, and analyzes sectorthe data are too limited to assess any trend between specific pollutant monitoring requirements.
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• Timber lots, The committee recommends a suite of water quality • Fuel storage and on-site fueling, parameters for benchmark monitoring by all industrial • Vehicle maintenance (e.g., school bus transporta- sites that must do stormwater sampling, including tion facilities) , those that currently only do visual monitoring.
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water quality parameters can provide indications of Turbidity measurements have also been suggested SCM absence, neglect, or failure, which can lead to as an indicator for suspended solids. However, TSS high concentrations of potential pollutants.
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Monitoring requirements for leaks can also lead to petroleum hydrocarbon contamiSector M are TSS, total aluminum, total iron, and total nants in stormwater, including PAHs, which have been lead, whereas Sector N1 is required to monitor for these shown to be highly toxic to aquatic life (Incardona et parameters and also total copper, total zinc, and COD. al., 2011; Abdel-Shafy and Mansour, 2016; McIntyre et As discussed earlier in this chapter, Sector M does not al., 2016)
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data, but the 2015 MSGP does not include any benchmark monitoring requirements for this sector. Although Need for Periodic Monitoring Reviews benchmark monitoring is not required nationally, some Sector P monitoring data have been reported in EPA's These examples show that monitoring requireNetwork Discharge Monitoring Report (NetDMR)
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Scientific advances that identify cost-effective monitoring surrogates should also be considered. Application of Water Quality Criteria This level of analysis should be adequate to substantiate Many of the current benchmark thresholds were the addition of benchmark monitoring requirements derived from aquatic life criteria (see Table 1-3)
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EPA decided not to substantially specific rationale for protecting against chronic effects weaken the benchmark based on concerns about near- of iron from intermittent events. coastal freshwater discharges flowing quickly into sensitive saline waters, which had a saltwater acute Updating Benchmarks to Match Aquatic Life Criteria aquatic criterion of 69 µg/L (EPA, 2008b)
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constituents, which could have implications for the MSGP benchmark monitoring requirements. For Developing New Benchmarks to Better Characterize copper, the most recent aquatic life criteria (EPA, 2007)
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Using nonhazardous materials, to be observed in industrial stormwater discharges. general site cleanliness, and creating no-exposure Therefore, the committee recommends that magnesium s cenarios will greatly minimize pollutant discharge be removed as a benchmark monitoring requirement.
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Therefore, the analysis only included Results i nfluent/effluent data pairs where the influent exceeded the benchmark threshold. As with the 2015 MSGP data To highlight examples of the results of this analysis, analysis, for a data set to be included, each site consid- the SCM treatment performance for two pollutants, ered had to have a minimum of eight storm events.
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from the International site evaluation, many site owners noted that their filter Stormwater BMP Database were able to meet the total media were proprietary mixes developed by a vendor iron benchmark concentrations for at least 50 percent and optimized for their site pollutants. In the Interof the monitored storm events, but the average influent national Stormwater BMP Database, all media filters concentrations were substantially lower in this data set are placed into a single category, even though the per(see Figure 2-4)
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FIGURE 2-2 International Stormwater BMP Database comparison of influent and effluent concentrations for total suspended solids (TSS)
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NOTE: BM = benchmark; BR = bioretention; DP = dry detention ponds; MF = media filters; n = number of storm events sampled; RP = wet retention ponds; WB = wetlands.
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In the site-level industrial The International Stormwater BMP Database proevaluation (Clark and Pitt, in press) , at least one treat- vides a larger data set, but it includes many nonindustrial ment SCM was capable of meeting benchmarks for at sites, and on average it has much lower pollutant influleast 50 percent of storm events for TSS, aluminum, ent concentrations than the site-level industrial data.
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With median inflow iron concentrations determine that certain benchmarks cannot be achieved ranging from 1,500 to 3,500 µg/L, two of the three with existing treatment technology combined with treatment SCMs in the BMP Database met the iron appropriate site management and pollution prevenbenchmark for at least half of the storm events, while tion strategies. It does appear, however, that some type none of the four industrial sites/treatments (with of treatment train approach, where an initial SCM median inflow concentrations of 8,500 to 19,000 handles part of the pollutant load followed by a second µg/L)
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. Additional NELs a large percentage of samples with high discharges for industrial stormwater could be developed based (eight times the benchmark levels)
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EPA efforts for industrial stormwater would strengthen The committee reviewed several sectors where data the value of the BMP Database. suggest that stormwater pollutants are common, but For water quality-based criteria, rigorous treat- little or no benchmark monitoring is required.
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typically measure acute end points following exposure of aquatic life to consistent pollutant levels for short Additional monitoring data collection on the periods of time, and measure chronic end points follow- capacity of SCMs to reduce industrial storm ater w ing exposure of aquatic life to consistent pollutant levels pollutants is recommended to inform periodic for longer periods of time. Given the episodic nature of reviews of the benchmark thresholds and identify stormwater flow and the likelihood of instream dilution sectors for which new national effluent limits could and attenuation, aquatic life criteria based on short- help address treatment attainability.
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Several sectors For benchmarks based on aquatic life criteria, the can be identified in recent MSGP data with recurrent additional high-quality data collected can be used to high-concentration discharges. However, the decision assess the feasibility of achieving the benchmarks with to develop new numeric effluent limits would need current technology and practices.
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