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Data Interpretation


Analysis of sampling and monitoring results can yield valuable information about the characteristics of the airport’s runoff and how well control measures are working. Visual evidence of pollution in a stormwater sample, a spike in the concentration of a benchmark pollutant, or the exceedance of a numeric effluent limitation can serve as indicators that modifications or additions to control measures need to be considered to improve the effectiveness of the airport’s stormwater program.

Laboratory reports should be reviewed as soon as possible to identify potential errors in sampling, handling, analysis, or reporting. Analytical results should be compared to any applicable permit limits or benchmark values.  Exceedances of these values can indicate that best management practices (BMPs) need to be evaluated, often as a permit compliance requirement.  Be sure to review the airport’s stormwater permit for exceedance reporting timelines and follow-up requirements.

The following resources can be used in reviewing and evaluating stormwater quality data. Always refer to the specific permit or regulatory requirements applicable to your facility.

ACRP Resources
ACRP Research Report 166: Interpreting the Results of Airport Water Monitoring
 This report is a resource for understanding, diagnosing, and interpreting airport water quality monitoring results.

Other Stormwater Resources
Industrial Stormwater Monitoring and Sampling Guide  This guide explains how to conduct visual and analytical monitoring of stormwater discharges. It can be used by facilities required to comply with Multi-sector General Permit (MSGP) monitoring requirements as well as facilities subject to other state or federal-issued industrial stormwater permits.  Chapter 4 provides a discussion regarding evaluating monitoring results.

Urban Stormwater BMP Performance Monitoring  This manual was developed as part of the International Stormwater BMP Database project to provide guidance regarding stormwater BMP monitoring. It presents protocols and standards for collecting, storing, analyzing, and reporting stormwater BMP monitoring data to support understanding of the function, efficiency, and design of urban stormwater BMPs.

Caltrans Stormwater Monitoring Guidance Manual This manual was prepared for the implementation of the Caltrans Stormwater Monitoring Program; however, the guidance on standardized procedures for sample collection, sample analysis, and data reporting are applicable to most stormwater monitoring programs.

Caltrans Construction Site Monitoring Program Guidance Manual This manual was prepared for the implementation of the Caltrans Construction Site Monitoring Program; however, the guidance on standardized procedures for sample collection, sample analysis, and data reporting are applicable to most construction site monitoring programs.

Environmental Protection Agency (EPA) 2015 Multi-sector General Permit The MSGP regulates stormwater discharges associated with specific categories of industrial activity.  Many of the requirements, including visual monitoring, apply to all categories.

Industrial Stormwater Fact Sheet – Sector S: Vehicle Maintenance Areas, Equipment Cleaning Areas, or Deicing Areas Located at Air Transportation Facilities Stormwater discharges associated with specific activities at air transportation facilities are regulated in accordance with the requirements of Sector S of the MSGP. Sector S Sections 7 and 8 describe benchmark values and effluent limitations application to airports.

Guidance on the Industrial Stormwater Permit for the Air Transportation Sector (Sector S)  This document prepared by the Minnesota Pollution Control Agency provides additional guidance for complying with Sector S requirements of the MSGP.

Guidelines Establishing Test Procedures for the Analysis of Pollutants Under the Clean Water Act; National Primary Drinking Water Regulations; and National Secondary Drinking Water Regulations; Analysis and Sampling Procedures This final rule promulgates procedures for the analysis of pollutants for compliance with the Clean Water Act and Primary/Secondary Drinking Water Regulations.

Technical Report for the Florida Statewide Airport Stormwater Study  This report describes a statewide study of pollutants found in airport stormwater.  It includes tables of water quality parameters and test methods, as well as results of storm event samples collected at a wide range of airports.

NCHRP Report 767: Measuring and Removing Dissolved Metals from Stormwater in Highly Urbanized Areas This report summarizes concerns about current methods used to determine dissolved metal content in stormwater, reviews previous studies of the treatment of dissolved metals, and proposes prototype conceptual designs for metals treatment. Appendix A provides practical guidance for measurement of dissolved metals in stormwater runoff.

Clean Water Act National Pollutant Discharge Elimination System Compliance Monitoring Strategy The Compliance Monitoring Strategy provides recommended minimum frequencies for compliance monitoring activities that, from a national perspective, EPA believes constitute a strong and balanced compliance monitoring program that should be reflected in all approved state National Pollutant Discharge Elimination System and pre-treatment programs, as well as in all EPA direct implementation activities.


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