NPDES Storm Water Sampling Guidance Document DISCLAIMER
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United States Office Of Water EPA 833-8-92-001 Environmental Protection (EN-336) July 1992 Agency EPA NPDES Storm Water Sampling Guidance Document DISCLAIMER This document was issued in support of EPA regulations and policy initiatives involving the development and implementation of a national storm water program. This document is agency guidance only. It does not establish or affect legal rights or obligations. Agency decisions in any particular case will be made applying the laws and regulations on the basis of specific facts when permits are issued or regulations promulgated. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. FOREWORD Pollutants in storm water discharges from many sourcesan largely uncontrolled. The National Water Quality Inventory, 1990 Report to Congress provides a general assessmentof water quality based on biennial reports submitted by the States under Section 305(b) of the Clean Water Act. The report indicates that roughly 30% of identified cases of Water quality impairment reported by the States are attributable to storm water discharges. sampling data from storm water discharges is an important tool which provides information on the types and amounts of pollutants present. This data can then used to identify pollutant sources and to develop storm water pollution prevention plans and best management practices priorities to control these sources. This manual is for operators of facilities that discharge storm water associated with industrial activity and operators of large and medium municipal separate storm sewer system. This manual describes the basic sampling requirements for NPDES storm water discharge permit applications and provides procedural guidance on how to conduct sampling. Many of the conceptsin this guidance may also be applicable to sampling requirements contained in NPDES storm water permits. This document was issued in support of EPA regulations and policy initiatives involving the development and implementation of a national storm water program. This document is agency guidance only. It does not establish or affect legal rights or obligations. Agency decisions in any particular case will be made applying the laws and regulations on the basis of specific facts when permits arc issued or regulations promulgated. This document is expected to be revised periodically to reflect advancesin this rapidly evolving area. Comments from users are welcomed. Send comments to the U.S. Environmental Protection Agency, Office of Wastewater Enforcement and Compliance, 401 M Street, SW, Mailcode EN-336, Washington, DC 20460. Michael Cook, Director Office of Wastewater Enforcement and Compliance TABLE OF CONTENTS TABLE OF CONTENTS Page 1.INTRODUCTION...........................................................................................1 1.1 PURPOSE OF THIS MANUAL. .............................. 2 1.2 ORGANIZATION OF THIS MANUAL ........................... 2 2. BACKGROUND FOR STORM WATER SAMPLING . 5 2.1 BENEFITS OF SAMPLING .................................. 5 2.2 INDUSTRIAL FACILITY APPLICATION REQUIREMENTS ............. 6 2.3 MUNICIPALITIES' APPLICATION REQUIREMENTS ................. 7 2.4 APPLICATION SUBMITTAL DEADLINES ........................ 8 2.5 WHERE TO SUBMIT APPLICATIONS ........................... 8 2.6 WHO MUST SAMPLE ..................................... 9 2.7 WHEN SAMPLING IS REQUIRED ............................. 15 2.7.1 STORM EVENT CRITERIA ............................. 15 2.7.2 OBTAINING RAINFALL DATA .......................... 18 2.7.3 DETERMINING REPRESENTATIVENESS ................... 22 2.7.4 LOGISTICAL PROBLEMS WITH WHEN TO SAMPLE ........... 23 2.7.5 WHEN INDUSTRIAL FACILITIES MUST SAMPLE ............. 24 2.7.6 WHEN MUNICIPAL FACILITIES MUST SAMPLE .............. 28 2.7.7 USE OF HISTORICAL DATA. ........................... 29 2.8 WHERE TO SAMPLE STORM WATER DISCHARGES . 29 2.8.1 INDUSTRIAL FACILITIES ............................. 30 2.8.2 MUNICIPALITIES ................................... 30 2.8.3 LOGISTICS OF WHERE TO SAMPLE ...................... 31 2.9 STAFFING CONSIDERATIONS . 31 3. FUNDAMENTALS OF SAMPLING . 35 3.1 TYPES AND TECHNIQUES OF SAMPLING . 35 3.1.1 SAMPLE TYPE VERSUS SAMPLE TECHNIQUE ............... 36 3.1.2 SAMPLE TYPE: GRAB AND COMPOSITE SAMPLES ........... 36 3.1.3 SAMPLE TECHNIQUE: MANUAL VERSUS AUTOMATIC SAMPLING ....................................... 39 TABLE OF CONTENTS TABLE OF CONTENTS (Continued) Page 3.2 OBTAINING FLOW DATA . 41 3.2.1 MEASURING FLOWRATES . 41 3.2.2 ESTIMATING FLOW RATES . 49 3.2.3 MEASURING TOTAL FLOW VOLUMES FOR THE SAMPLED RAIN EVENT . 58 3.2.4 ESTIMATING TOTAL FLOW VOLUMES FOR THE SAMPLED RAIN EVENT . 58 3.2.5 REPORTING STORM WATER DISCHARGE FLOW RATES AND VOLUMES . 67 3.2.6 MEASURING RAINFALL . .. .. 67 3.3 GRAB SAMPLE COLLECTION . 68 3.3.1 HOW TO MANUALLY COLLECT GRAB SAMPLES . 68 3.3.2 HOW TO COLLECT GRAB SAMPLES BY AUTOMATIC SAMPLER . 70 3.4 FLOW-WEIGHTED COMPOSITE SAMPLE COLLECTION . 70 3.4.1 HOW TO MANUALLY COLLECT FLOW-WEIGHTED COMPOSITE SAMPLES . 75 3.4.2 HOW TO COLLECT FLOW-WEIGHTED COMPOSITE SAMPLES BY AUTOMATIC SAMPLER . 80 3.5 SAMPLE HANDLING AND PRESERVATION . 81 3.5.1 DECONTAMINATION OF SAMPLE EQUIPMENT CONTAINERS . 82 3.5.2 SAMPLE PRESERVATION AND HOLDING TIMES . 83 3.6 SAMPLE VOLUMES . .... 88 3.7 SAMPLE DOCUMENTATION . 88 3.8 SAMPLE IDENTIFICATION AND LABELING . 93 3.9 SAMPLE PACKAGING AND SHIPPING . 93 3.10 CHAIN-OF-CUSTODY PROCEDURES . 94 TABLE OF CONTENTS TABLE OF CONTENTS (Continued) Page 4. ANALYTICAL CONSIDERATIONS ................................. 97 4.1 INDUSTRIAL REQUIREMENTS ............................... 97 4.1.1 INDIVIDUAL APPLICANTS ............................ 98 4.1.2 GROUP APPLICANTS ............................... 101 4.2 MUNICIPAL REQUIREMENTS .............................. 102 5. FLEXIBILITY IN SAMPLING ................................... 105 5.1 PROTOCOL MODIFICATIONS ............................... 105 5.2 PETITION FOR SUBSTITUTING SUBSTANTIALL Y IDENTICAL EFFLUENTS .......... .. .............................. 105 5.2.1 OPTION ONE: NARRATIVE DESCRIPTION/SITE MAP ......... 106 5.2.2 OPTION TWO: USE OF MATRICES TO INDICATE IDENTICAL OUTFALLS ...................................... 107 5.2.3 OPTION THREE: MODEL MATRICES .................... 107 5.3 ALTERNATE 40 CFR PART 136 METHOD ...................... 116 5.4 LACK OF METHOD IN 40 CFR PART 136.. ..................... 117 6. HEALTH AND SAFETY ....................................... 119 6.1 GENERAL TRAINING REQUIREMENTS ........................ 119 6.2 NECESSARY SAFETY EQUIPMENT ........................... 120 6.3 HAZARDOUS WEATHER CONDITIONS ........................ 120 6.4 SAMPLING IN CONFINED SPACES ........................... 120 6.4.1 HAZARDOUS CONDITIONS IN CONFINED SPACES ........... 121 6.4.2 SPECIAL TRAINING REQUIREMENTS .................... 121 6.4.3 PERMIT SYSTEM .................................. 121 6.5 CHEMICAL HAZARDS ................................... 122 6.6 BIOLOGICAL HAZARDS .................................. 122 6.7 PHYSICAL HAZARDS .................................... 122 iii July 1992 TABLE OF CONTENTS LIST OF EXHIBITS Page Exhibit 2-1. Form 2F Application Requirements.. ......................... 7 Exhibit 2-2. Part 2 Group Application Sampling Requirements.................. 8 Exhibit 2-3. Municipal Application Sampling Requirements .................... 9 Exhibit 2-4. Permit Application Submission Deadlines....................... 10 Exhibit 2-5. NPDES Storm water Program Permitting Authorities............... 11 Exhibit 2-6. Industrial Facilities Which Must Submit Applications for Storm Water permits ............................................ 16 Exhibit 2-7. Decision Chart for Storm Water Sampling ...................... 20 Exhibit 2-8. Rain Zones of the United States.. ........................... 21 Exhibit 2-9. Example of 50 Percent Variance From Average Rainfall.. ............ 22 Exhibit 2-10. Logistical Problems of Sampling ............................ 25 Exhibit 2-11. Checklist for Conducting Dry Weather Evaluations 27 Exhibit 2-12. Solutions to Sample Location Problems....... ............. 32 Exhibit 3-1. Sample Type vs. Sample Technique.......................... 36 Exhibit 3-2. Automatic Sampler..................................... 40 Exhibit 3-3. Comparison of Manual and Automatic Sampling Technique............ 42 Exhibit 3-4. weirs ............................................. 44 Exhibit 3-5. Suppressed Flow over the Weir Crest......................... 45 Exhibit 3-6. Flumes ............................................ 46 Exhibit 3-7. Palmer-Bowlus Flume ................................... 47 Exhibit 3-8. Example Calculation of Float Method for Unimpeded Open Channel Flow ... 51 Exhibit 3-9. Example Calculation of Float Method for Estimating Drain Flow Rates ..... 52 Exhibit 3-10. Example Calculation of Bucket and Stopwatch Method for Estimating Flows ............................................. 54 Exhibit 3-11. Example Calculation of Slope and Depth Method for Estimating Flow Rates ............................................. 55 Exhibit 3-12. Typical "c" Coefficients for 5- to 10-Year Frequency Design Storms ...... 57 Exhibit 3-13. Example Calculation of Runoff Coefficient/Flow Depth Method for Estimating Flow Rates ................................... 59 Exhibit 3-14. Example Calculation of Runoff Coefficient Rainfall Depth Method for Estimating Flow Rates ................................... 61 Exhibit 3-15. Example Calculation of Total Runoff Volume