Loading...
Numeric Action Levels (NALs) & NAL Exceedances in California 2017-02-15T10:02:22+00:00

Numeric Action Levels (NALs)

The new Industrial General Permit (IGP) provides Numeric Action Levels (NALs) so that permit holders can gauge whether their storm water program is effective in preventing pollutants from discharging in storm water. An NAL exceedance is an indication that the facilities BMPs are not effective in reducing pollutants; however, an NAL exceedance is not a violation of the IGP. The two different types of NAL exceedances are Annual NAL exceedances, and Instantaneous Maximum exceedances.

Annual NAL Exceedance

This occurs when the annual average of all sample results for a given parameter within a reporting year exceed the value in Table 2 of the IGP for that parameter.

Instantaneous Maximum Exceedance

This occurs when two (2) or more sample results for a given parameter within a reporting year exceed the instantaneous maximum value in Table 2 of the IGP for that parameter. Instantaneous Maximum values only apply to the basic parameters; pH, Total Suspended Solids (TSS), Oil & Grease (O&G).

Numeric Action Levels (NALs) and NAL Exceedances

Parameter NAL Values, Test Methods, and Reporting Units

Parameter Test Method Reporting Units Annual NAL Instantaneous Maximum NAL
pH* See Section XI.C.2 pH units N/A Less than 6.0 Greater than 9.0
Suspended Solids (TSS)*, Total SM 2540-D mg/L 100 400
Oil & Grease (O&G)*, Total EPA 1664A mg/L 15 25
Zinc, Total (H) EPA 200.8 mg/L 0.26**
Copper, Total (H) EPA 200.8 mg/L 0.0332**
Cyanide, Total SM 4500–CN C, D, or E mg/L 0.022
Lead, Total (H) EPA 200.8 mg/L 0.262**
Chemical Oxygen Demand (COD) Chemical Oxygen Demand (COD) Chemical Oxygen Demand (COD) Chemical Oxygen Demand (COD)
Aluminum, Total EPA 200.8 mg/L 0.75
Iron, Total EPA 200.7 mg/L 1.0
Nitrate + Nitrite Nitrogen SM 4500-NO3- E mg/L as N 0.68
Total Phosphorus SM 4500-P B+E mg/L as P 2.0
Ammonia (as N) SM 4500-NH3 B+ C or E mg/L 2.14
Magnesium, total EPA 200.7 mg/L 0.064
Arsenic, Total (c) EPA 200.8 mg/L 0.15
Cadmium, Total (H) EPA 200.8 mg/L 0.0053**
Nickel, Total (H) EPA 200.8 mg/l 1.02**
Mercury, Total EPA 245.1 mg/L 0.0014
Selenium, Total EPA 200.8 mg/L 0.005
Silver, Total (H) EPA 200.8 mg/L 0.0183**
Biochemical Oxygen Demand (BOD) SM 5210B mg/L 30

SM – Standard Methods for the Examination of Water and Wastewater, 18th edition
EPA – U.S. EPA test methods
(H) – Hardness dependent
* Minimum parameters required by this General Permit
**The NAL is the highest value used by U.S. EPA based on their hardness table in the 2008 MSGP.

Pursuant to Order 2014-0057-DWQ adopted by the California State Water Resources Control Board. Note that NALs replace prior Benchmarks.

Guidance for Numeric Action Levels (NALs) and NAL Exceedances for Stormwater Discharge in California. NAL Values, Test Methods, and Reporting Units for IGP.
NAL exceedances result in Level I or Level II designation and additional reporting to Regional Board.

Frog Environmental offers consultation on the following topics: Exceedance Response Actions (ERAs), NALs and NAL Exceedances, Annual NAL exceedance, Instantaneous maximum NAL exceedance, Baseline Status, Level 1 Status, Level 1 ERA Evaluation, Level 1 ERA Report, QISP certifying via SMARTS, Level 2 Status, Level 2 ERA Action Plan, Level 2 ERA Technical Report, Industrial Activity BMPs Demonstration, Non-Industrial Pollutant Source Demonstration, Natural Background Pollutant Source Demonstration, Level 2 ERA Technical Report Submittal, Eligibility for Returning to Baseline Status, Level 2 ERA Implementation Extension, and BMPs.