Part V. Chesapeake Bay Total Maximum Daily Load Compliance
9VAC25-151-400. Chesapeake Bay total maximum daily load compliance.
A. Chesapeake Bay TMDL Compliance. EPA's Chesapeake Bay TMDL (December 29, 2010) includes wasteload allocations for VPDES permitted industrial stormwater facilities as part of the regulated stormwater aggregate load. EPA used data submitted by Virginia with the Phase I Chesapeake Bay TMDL Watershed Implementation Plan, including the number of industrial stormwater permits per county and the number of urban acres regulated by industrial stormwater permits, as part of their development of the aggregate load. Aggregate loads for industrial stormwater facilities were appropriate because actual facility loading data were not available to develop individual facility wasteload allocations.
Virginia estimated the loadings from industrial stormwater facilities using actual and estimated facility acreage information and total phosphorus (TP) and total nitrogen (TN) loading rates from the Northern Virginia Planning District Commission (NVPDC) Guidebook for Screening Urban Nonpoint Pollution Management Strategies (Annandale, VA November 1979), prepared for the Metropolitan Washington Council of Governments. The loading rates used were as follows:
TP - High (80%) imperviousness industrial; 1.5 lb/ac/yr
TN - High (80%) imperviousness industrial; 12.3 lb/ac/yr
Actual facility area information and TP and TN data collected for facilities subject to Part V of this permit will be used by the department to quantify the nutrient and sediment loads from those VPDES permitted industrial stormwater facilities.
1. Facilities that obtained coverage under the 2019 industrial stormwater general permit that demonstrated compliance with the Chesapeake Bay TMDL loading rates.
Owners shall maintain documentation of their demonstration of compliance with the Chesapeake Bay TMDL loading rates with the SWPPP and shall continue implementing any BMPs that may have been developed as part of that demonstration.
Documentation may include:
a. Calculations submitted to the department indicating that reductions were not necessary;
b. A completed TMDL Action Plan, including a description of the means and methods, such as management practices and retrofit programs that were utilized to meet the required reductions;
c. Other means accepted by the department indicating compliance with the Chesapeake Bay TMDL loading rates.
2. Facilities that obtained coverage under the 2019 industrial stormwater general permit that did not demonstrate compliance with the Chesapeake Bay TMDL loading rates shall submit a demonstration to the department.
a. Owners of facilities that submitted a Chesapeake Bay TMDL action plan during the 2019 industrial stormwater general permit term that did not achieve reductions by the end of the 2019 permit term shall update and resubmit their action plan to the department for approval no later than 60 days following coverage under this general permit. Permittees shall achieve 10% of the remaining reductions by December 31, 2024, and all remaining reductions by December 31, 2025. An annual report shall be submitted to the department by June 30 of each year describing the progress in meeting the interim and final reductions. A final report to demonstrate compliance shall be submitted to the department no later than January 10, 2026. Documentation of compliance with the Chesapeake Bay TMDL loading rates shall be maintained with the SWPPP.
b. Owners of facilities that completed four samples for each outfall for TN and TP during the 2019 industrial stormwater general permit term that did not submit calculations by the end of the 2019 permit term shall utilize the procedures in Part V D to calculate their facility stormwater loads. The permittee shall submit a copy of the calculations, and a Chesapeake Bay TMDL action plan if required under Part V E, no later than 60 days following coverage under this general permit to the DEQ regional office serving the area where the industrial facility is located on a form provided by the department. Reductions, if applicable, shall be achieved by December 31, 2025, and an annual report shall be submitted to the department by June 30 of each year describing the progress in meeting the required reductions until such time that the demonstration is completed. The demonstration shall be submitted to the department no later than January 10, 2026. Documentation of compliance with the Chesapeake Bay TMDL loading rates shall be maintained with the SWPPP.
c. Owners of facilities registered prior to July 1, 2022, that did not complete four samples for each outfall for TN and TP by the end of the 2019 industrial stormwater general permit term shall monitor their discharges for TN and TP to characterize the contributions from their facility's specific industrial sector for these parameters. Total nitrogen is the sum of total Kjeldahl nitrogen (TKN) and nitrite + nitrate and shall be derived from the results of those tests. After the facility is granted coverage under the permit, samples shall be collected during each of the first four quarters of permit coverage. Samples shall be collected and analyzed in accordance with Part V B. Monitoring results shall be reported in accordance with Part V C and Part II C, and retained in accordance with Part II B. Calculations utilizing the procedures in Part V D, and a Chesapeake Bay TMDL action plan if required under Part V E, shall be submitted no later than 60 days following the completion of the fourth quarterly monitoring period to the DEQ regional office serving the area where the industrial facility is located on a form provided by the department. Reductions, if applicable, shall be achieved by December 31, 2025, and an annual report shall be submitted to the department by June 30 of each year describing the progress in meeting the required reductions until such time that the demonstration is completed. The demonstration shall be submitted to the department no later than January 10, 2026. Documentation of compliance with the Chesapeake Bay TMDL loading rates shall be maintained with the SWPPP.
Facilities may use the applicable sampling data collected during the 2019 industrial stormwater general permit term to satisfy all or part of the four monitoring periods requirement in accordance with Part V A 2 c.
d. Owners of facilities registered after June 30, 2022, that did not complete four samples for each outfall for TN and TP by the end of the 2019 industrial stormwater general permit term shall monitor their discharges in accordance with Part V A 3.
Facilities may use the applicable sampling data collected during the 2019 industrial stormwater general permit term to satisfy all or part of the four monitoring periods requirements in accordance with Part V A 3.
3. Facilities that obtain initial coverage under the 2024 industrial stormwater general permit, but are not newly constructed facilities as identified in 9VAC25-151-60 C 13.
Owners of facilities in the Chesapeake Bay watershed that obtain initial coverage under the 2024 industrial stormwater general permit shall monitor their discharges for TN and TP to characterize the contributions from their facility's specific industrial sector for these parameters. Total nitrogen is the sum of total Kjeldahl nitrogen (TKN) and nitrite + nitrate and shall be derived from the results of those tests. After the facility is granted coverage under the permit, samples shall be collected during each of the first four quarters of permit coverage. Samples shall be collected and analyzed in accordance with Part V B. Monitoring results shall be reported in accordance with Part V C and Part II C, and retained in accordance with Part II B. Calculations utilizing the procedures in Part V D and a Chesapeake Bay TMDL action plan if required under Part V E shall be submitted no later than 60 days following the completion of the fourth quarterly monitoring period to the DEQ regional office serving the area where the industrial facility is located on a form provided by the department. Reductions, if applicable, shall be achieved by two years following the end of the fourth quarterly monitoring period, and an annual report shall be submitted to the department by June 30 of each year describing the progress in meeting the required reductions until such time that the demonstration is completed. The demonstration shall be submitted to the department no later than the 10th of the month directly following the two year period. Documentation of compliance with the Chesapeake Bay TMDL loading rates shall be maintained with the SWPPP.
B. Monitoring instructions.
1. Collection and analysis of samples. Sampling requirements shall be assessed on an outfall by outfall basis. Samples shall be collected and analyzed in accordance with the requirements of Part II A.
2. When and how to sample. A minimum of one grab sample shall be taken from the discharge associated with industrial activity resulting from a storm event that results in a discharge from the site providing the interval from the preceding storm event discharge is at least 72 hours. The 72-hour storm interval is waived if the permittee is able to document that less than a 72-hour interval is representative for local storm events during the sampling period. In the case of snowmelt, the monitoring shall be performed at a time when a measurable discharge occurs at the site. For discharges from a stormwater management structure, the monitoring shall be performed at a time when a measurable discharge occurs from the structure.
The grab sample shall be taken during the first 30 minutes of the discharge. If it is not practicable to take the sample during the first 30 minutes, the sample may be taken during the first three hours of the discharge, provided that the permittee explains why a grab sample during the first 30 minutes was impracticable. This information shall be submitted in the department's electronic discharge monitoring report (e-DMR) system and maintained with the SWPPP. If the sampled discharge commingles with process or nonprocess water, the permittee shall attempt to sample the stormwater discharge before it mixes with the nonstormwater.
3. Storm event data. For each monitoring event, except snowmelt monitoring, along with the monitoring results, the permittee shall identify the date of the storm event sampled; rainfall total (in inches) of the storm event that generated the sampled runoff; and the interval between the storm event sampled and the end of the previous storm event discharge. For snowmelt monitoring, the permittee shall identify the date of the sampling event.
4. Monitoring periods. Quarterly monitoring shall be conducted in each of the following three-month periods: January through March, April through June, July through September, and October through December.
5. Documentation explaining a facility's inability to obtain a sample (including dates and times the outfalls were viewed or sampling was attempted), of no rain event, or of deviation from the 72-hour storm interval shall be submitted with the e-DMR and maintained with the SWPPP. Acceptable documentation includes National Climatic Data Center (NCDC) weather station data, local weather station data, facility rainfall logs, and other appropriate supporting data.
6. Representative outfalls may be used in accordance with Part I A 2 f.
C. Reporting monitoring results.
1. Reporting to the department. The permittee shall follow the reporting requirements and deadlines in Table 400-1 if required by Part V A 2 or A 3:
Table 400-1 Monitoring Reporting Requirements | |
| Quarterly Chesapeake Bay TMDL Monitoring | Submit the results by January 10, April 10, July 10, and October 10 |
2. Permittees shall submit results for each outfall associated with industrial activity according to the requirements of Part II C.
3. Significant digits. The permittee shall report at least the same number of significant digits as a numeric effluent limitation or TMDL wasteload allocation for a given parameter; otherwise, at least two significant digits shall be reported for a given parameter. Regardless of the rounding convention used by the permittee (i.e., five always rounding up or to the nearest even number), the permittee shall use the convention consistently and shall ensure that consulting laboratories employed by the permittee use the same convention.
D. Calculation of facility loads.
Permittees required to collect nutrient and sediment data in accordance with Part V A 2 or A 3 shall analyze the data collected to determine if pollution reductions are required. The permittee shall average the data collected at the facility for each of the pollutants of concern (POC) (e.g., TP and TN) and compare the results to the loading rates for TP and TN presented in Part V A.
The following formula may be used to determine the loading rate:
L = 0.226 x P x Pj x (0.05 + (0.9 x Ia)) x C
where:
L = the POC loading rate (lb/acre/year)
P = the annual rainfall (inches/year) - The permittee may use either actual annual average rainfall data for the facility location (in inches/year), the Virginia annual average rainfall of 44.3 inches/year, or another method approved by the department.
Pj = the fraction of annual events that produce runoff - The permittee shall use 0.9 unless the department approves another rate.
Ia = the impervious fraction of the facility impervious area of industrial activity to the facility industrial activity area.
C = the POC average concentration of all facility samples (mg/L) - Facilities with multiple outfalls shall calculate a weighted average concentration for each outfall using the drainage area of each outfall.
For total phosphorus, all daily concentration data below the quantitation level (QL) for the analytical method used shall be treated as half the QL. All daily concentration data equal to or above the QL for the analytical method used shall be treated as it is reported.
For total nitrogen, if none of the daily concentration data for the respective species (i.e., TKN, nitrate, or nitrite) are equal to or above the QL for the respective analytical methods used, the daily TN concentration value reported shall equal one half of the largest QL used for the respective species. If one of the data is equal to or above the QL, the daily TN concentration value shall be treated as that data point is reported. If more than one of the data is above the QL, the daily TN concentration value shall equal the sum of the data points as reported.
Calculations shall be submitted to the department within 60 days from the end of the last monitoring period that satisfies the monitoring requirements in Part V A 2 or A 3. Calculations shall be submitted to the DEQ regional office serving the area where the industrial facility is located, on a form provided by the department, and maintained with the facility's SWPPP.
Alternative calculations may be accepted on a case by case basis by the department to accommodate facilities with outfalls that rarely discharge.
E. Chesapeake Bay TMDL action plan requirements. For permittees required to submit calculations in accordance with Part V D, if the calculated facility loading rate for TP or TN is above the loading rates for TP or TN presented in Part V A, then the permittee shall develop and submit a Chesapeake Bay TMDL action plan to the department.
The Chesapeake Bay TMDL action plan shall be submitted on a form provided by the department to the regional office serving the area where the industrial facility is located within 60 days following the completion of the fourth quarterly monitoring period. A copy of the current Chesapeake Bay TMDL action plan and all facility loading rate calculations shall be maintained with the facility's SWPPP. The Chesapeake Bay TMDL action plan shall include:
1. A determination of the total pollutant load reductions for TP and TN (as appropriate) necessary to reduce the annual loads from industrial activities. This shall be determined by multiplying the industrial average times the difference between the TMDL loading rates listed in Part V A and the actual facility loading rates calculated in accordance with Part V D. The reduction applies to the total difference calculated for each pollutant of concern; and
2. The means and methods, such as management practices and retrofit programs that will be utilized to meet the required reductions determined in Part V E 1 and a schedule to achieve those reductions by the applicable deadline set in Part V A 2 or A 3. Pollutant reductions may be achieved using a combination of the following alternatives:
a. Reductions provided by one or more of the BMPs from the Virginia Stormwater BMP Clearinghouse listed in 9VAC25-875-590, approved BMPs found on the Virginia Stormwater Clearinghouse website, or BMPs approved by the Chesapeake Bay Program. Any BMPs implemented to provide the required pollutant reductions shall be incorporated in the SWPPP and be permanently maintained by the permittee;
b. Implementation of site-specific BMPs followed by a minimum of four stormwater samples collected in accordance with sampling requirements in Part V B that demonstrate pollutant loadings have been reduced below those calculated under Part V D. Any BMPs implemented to provide the required pollutant reductions shall be incorporated in the SWPPP and be permanently maintained by the permittee; or
c. Acquisition of nonpoint source credits certified by the board as perpetual in accordance with § 62.1-44.19:20 of the Code of Virginia.
Statutory Authority
§ 62.1-44.15 of the Code of Virginia; § 402 of the Clean Water Act; 40 CFR Parts 122, 123, and 124.
Historical Notes
Dervied from Virginia Register Volume 40, Issue 15, eff. July 1, 2024; Errata, 40:22 VA.R. 1892 June 17, 2024.