7.2 Sampling Preparation and Analytical Parameters

Free CESSWI Certified Erosion, Sediment and Stormwater Inspector Study Guide 2026 Exam

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1 Chapter 1: CESSWI Program Overview, Scope of Practice & Professional Ethics

1.1 CESSWI Scope of Practice, Eligibility, and Exam Structure 1.2 Certification Renewal, PDH Requirements, and Audit Policies 1.3 EnviroCert Code of Ethics and Professional Conduct

2 Chapter 2: Federal, State, and Local Stormwater Regulations

2.1 Federal Water-Pollution History and Stormwater Phases 2.2 CWA Sections, Water Quality, and Related Federal Programs 2.3 EPA Construction Permit Coverage and Operational Clocks 2.4 Industrial MSGP and Municipal MS4 Programs 2.5 Regulatory Compliance, Enforcement Mechanisms, and Penalties

3 Chapter 3: Soil Mechanics, Erosion Processes, and Climatic Factors

3.1 Soil Formation, Horizons, and Geomorphology 3.2 Soil Texture, Mechanics, and Revegetation 3.3 Splash, Sheet, Rill, Gully, Channel Erosion, and Slope Movement 3.4 Wind Erosion, Sediment Transport, Climatic Erosivity, and Resource Impacts

4 Chapter 4: Hydrology, Runoff Characteristics, and Drainage Principles

4.1 The Hydrologic Cycle, Watershed Drainage Planning, and Precipitation 4.2 Hydrologic Soil Groups, Disturbed Profiles, and Time Parameters 4.3 Hydrograph Characteristics, Curve Numbers, and Runoff Estimation Equations

5 Chapter 5: Inspection Fundamentals, Duties, and Field Procedures

5.1 Inspector Roles, Scope of Authority, and Core Professional Skills 5.2 Pre-Inspection Document Review and Inspector Support Equipment 5.3 Systematic Field Inspection Sequence, Post-Inspection Meetings, and Follow-Through

6 Chapter 6: Inspection Elements for Active Construction Sites

6.1 Pre-Construction Meetings, Entrance Posting, and On-Site Document Inspections 6.2 Inspecting Active Construction Controls and Diagnosing BMP Failure Modes 6.3 Final Stabilization Verification, Final Inspections, and Notice of Termination

7 Chapter 7: Stormwater Monitoring, Field Sampling, and Chain of Custody

7.1 Permit Monitoring Triggers and Water-Quality Indicators 7.2 Sampling Preparation and Analytical Parameters 7.3 Sampling Locations, Collection Methods, and Field Meter Calibration 7.4 Sample Preservation, Data Recording, Shipping, and Chain of Custody

8 Chapter 8: Inspection Documentation, Reporting, and Map Management

8.1 Inspection Notes and Evidence Procedures 8.2 Objective Findings and Photographic Evidence 8.3 Proper Reporting Techniques and Corrective Action Log Management 8.4 Site Drawing (Map) Management, Compliance Resolution, and Enforcement Records

9 Chapter 9: Professional Communication and Site Safety for Inspectors

9.1 Communication Protocols in Pre-Construction, Post-Inspection, and O&M Meetings 9.2 Dealing with Difficult People, Problematic Sites, and Unpleasant Findings 9.3 Site Hazard Recognition: Physical, Biological, Trenching, and Confined Spaces 9.4 Hazardous Substances, Safety Data Sheets (SDS), Spill Response, and PPE

10 Chapter 10: Stormwater Plan Reading, Map Interpretation, and Site Calculations

10.1 Stormwater Plan Types, Credentials, and Authority 10.2 SWPPP Components and Permit Notifications 10.3 Civil Plan Sets, Legends, Phased Sequencing, and Living Site Maps 10.4 Topography, Contour Lines, Slope Calculations, and Plan Amendments

11 Chapter 11: BMP Framework, Site Planning, and Erosion Control Practices

11.1 Six Functional BMP Categories, Preservation of Vegetation, Phasing, and Tree Protection 11.2 Seeding and Sod Establishment 11.3 Hydroseeding and Hydromulching Inspection 11.4 Mulch and Rolled Erosion-Control Products 11.5 Tackifiers, Soil Binders, Roughening, and Temporary Cover

12 Chapter 12: Perimeter, Linear, and In-Water Sediment Control Practices

12.1 Perimeter & Sheet-Flow Sediment Barriers: Silt Fence, Fiber Rolls, Straw Bales, and Filter Dikes 12.2 Access & Roadside Sediment/Runoff Controls: Stabilized Entrances, Cut-Back Curbs, and Ditch Checks 12.3 In-Water & Dewatering Controls: Temporary Stream Crossings, Turbidity Curtains, and Sediment Bags

13 Chapter 13: Sediment Basins, Traps, and Runoff Conveyance Controls

13.1 Sediment Basins and Traps 13.2 Porous Baffles and Surface Skimmers 13.3 Runoff Conveyances: Diversions, Swales, Pipe Slope Drains, and Rock Check Dams 13.4 Riprap and Gabion Inspection 13.5 Retaining Walls, Outlet Protection, and Wet Ponds

14 Chapter 14: Storm Drain Inlet Protection and Good Housekeeping BMPs

14.1 Storm Drain Inlet Protection: At-Grade, Curb, Block & Gravel, Excavated, Fabric Drop, Gravel Bag, Stone Collar, and Pre-Manufactured 14.2 Good Housekeeping Part 1: Concrete Washout, Equipment Maintenance, Materials Management, and Secondary Containment 14.3 Good Housekeeping Part 2: Stockpiles, Dust Control, Wind Fence, Street Cleaning, Sanitary Waste, and Trash

15 Chapter 15: Post-Construction Stormwater Management BMPs

15.1 Vegetative & Structural Dispersion BMPs: Final Ground Cover, Headwalls, Level Spreaders, Filter Strips, and Riparian Buffers 15.2 Permeable Surfaces and Construction Protection 15.3 Infiltration, Bioretention, and Media Filters 15.4 Detention, Retention & Proprietary BMPs: Dry/Wet Basins, Wetlands, Inline Storage, Catch Basin Inserts, Vaults, and Manufactured Devices

7.2 Sampling Preparation and Analytical Parameters

Key Takeaways Explain This Topic AI

Arrange laboratory bottles, analytical methods, safe access, and delivery before a storm.

Preservation and holding time vary by analyte and approved method.

Check laboratory weekend availability for short-holding-time samples.

Last updated: October 2026

Advanced Planning for Stormwater Sampling Events

Stormwater monitoring cannot be improvised after dark clouds gather over a jobsite. Because qualifying storm events are transient, unpredictable, and frequently occur outside normal weekday business hours, advanced planning the approved practice detail is essential to collect legally defensible samples.

Developing a Written Sampling and Analysis Plan (SAP) / QAPP

Before earth disturbance or monitoring begins, the project team should establish a written Sampling and Analysis Plan (SAP) —often integrated into the SWPPP or accompanied by a formal Quality Assurance Project Plan (QAPP) . A complete SAP specifies:

Exact Monitoring Station Locations: Mapped GPS coordinates and physical descriptions of every permitted outfall ( Outfall-001 , Outfall-002 ), dewatering treatment discharge point, and upstream/downstream receiving water reference stations.

Qualifying Storm Event Criteria: The exact precipitation depth or runoff condition that triggers sampling (for example, a storm producing actual discharge from the outfall, or ≥ 0.25 inch \ge 0.25\text{ inch} ≥ 0.25 inch / ≥ 0.50 inch \ge 0.50\text{ inch} ≥ 0.50 inch of rainfall with at least a 48 - to 72 -hour 48\text{- to }72\text{-hour} 48 - to 72 -hour antecedent dry period, depending on the applicable state permit).

Target Analytes and Approved Analytical Methods: Every parameter to be measured in the field or analyzed in the laboratory, citing approved 40 CFR Part 136 EPA or Standard Methods for the Examination of Water and Wastewater procedure numbers.

Field Personnel Assignments and Safety Protocols: Named primary and backup CESSWI samplers, 24-hour weather tracking assignments, lightning and high-flow abort criteria, and personal protective equipment (PPE).

Quality Assurance / Quality Control (QA/QC) Schedule: Required frequency of field duplicates, equipment rinsate blanks, trip blanks, and daily instrument calibrations.

Pre-Storm Laboratory Coordination and Field Kit Staging

A CESSWI preparing for a forecasted storm event must complete four critical logistical steps before rainfall begins:

Certified Laboratory Coordination & Container Selection: Confirm that the receiving laboratory holds current state or NELAP / TNI accreditation for every requested Clean Water Act parameter. Obtain pre-cleaned, analyte-specific bottle kits directly from the laboratory:

Borosilicate Glass (Amber or Clear Wide-Mouth with PTFE-lined caps): Required for organic compounds, Oil and Grease , and Total Petroleum Hydrocarbons ( TPH \text{TPH} TPH ) because hydrocarbons and organic solvents adsorb onto or leach plasticizers from plastic bottles.

High-Density Polyethylene (HDPE) or Polypropylene: Used for Total Suspended Solids ( TSS \text{TSS} TSS ) , nutrients , general minerals , and trace metals (acid-washed HDPE ensures trace metals do not leach from glass silicates).

Sterile Plastic or Glass with Sodium Thiosulfate ( Na 2 S 2 O 3 \text{Na}_2\text{S}_2\text{O}_3 Na 2 ​ S 2 ​ O 3 ​ ): Required for microbiological bacteria ( E. coli , fecal coliform) to dechlorinate the sample immediately.

Preservatives, Labels, and Custody Supplies: Verify that pre-measured chemical preservative ampoules (such as nitric acid HNO 3 \text{HNO}_3 HNO 3 ​ or sulfuric acid H 2 SO 4 \text{H}_2\text{SO}_4 H 2 ​ SO 4 ​ ) match the bottle labels; stage waterproof labels, indelible ink pens, blank Chain of Custody (COC) forms, tamper-evident Custody Seals , heavy-duty Ziploc bags, bubble wrap, insulated coolers, a temperature blank vial, and a dedicated supply of wet ice .

Holding Time & Weekend/Holiday Receiving Verification: Cross-check the maximum regulatory holding time of every parameter against the laboratory's operating schedule. If a storm occurs on a Friday afternoon and the permit requires a parameter with a 6-hour, 24-hour, or 48-hour holding time (such as bacteria, unpreserved nitrate, or laboratory turbidity), the sample will expire before Monday morning unless the inspector has pre-arranged Friday evening delivery and weekend laboratory reception!

Safe Physical Access to Outfalls: Inspect outfall paths during dry weather to clear brush, install stable stepping stones or safety lines, mount staff gauges, and confirm that samplers will never have to wade into deep, fast-moving channels or climb slick riprap slopes during a storm.

Target Water Quality Constituents and Analytical Parameters

1. Turbidity ( NTU \text{NTU} NTU ) vs. Total Suspended Solids ( TSS \text{TSS} TSS , mg/L \text{mg/L} mg/L ) vs. Settleable Solids ( mL/L \text{mL/L} mL/L )

Sediment is the single largest pollutant by volume generated on construction sites, and permits evaluate sediment in water through three distinct analytical measurements that candidates must never confuse:

Turbidity ( NTU \text{NTU} NTU — Nephelometric Turbidity Units): Turbidity is an optical measurement of water clarity (cloudiness or haziness). A nephelometer (portable field turbidimeter) directs a focused beam of light through a glass sample vial and measures the intensity of light scattered at a 90 ∘ 90^\circ 9 0 ∘ angle by suspended particles in the water column—including fine clay, colloidal silt, finely divided organic and inorganic matter, and microscopic plankton. The higher the concentration of fine light-scattering particles, the higher the NTU \text{NTU} NTU reading.

Total Suspended Solids ( TSS \text{TSS} TSS , mg/L \text{mg/L} mg/L ): TSS \text{TSS} TSS is a gravimetric (mass-per-volume) laboratory measurement (Standard Methods 2540 D / EPA Method 160.2). In the laboratory, a precisely measured volume of well-mixed stormwater is vacuum-filtered through a pre-weighed standard 1.5 μ m 1.5\text{ }\mu\text{m} 1.5 μ m glass-fiber filter . The filter and retained solid residue are dried in an oven at 103 to 105 ∘ C 103\text{ to }105^\circ\text{C} 103 to 10 5 ∘ C until they reach constant weight, cooled in a desiccator, and weighed on an analytical balance. The mass increase divided by the sample volume yields TSS \text{TSS} TSS in milligrams per liter ( mg/L \text{mg/L} mg/L ) .

Settleable Solids ( mL/L \text{mL/L} mL/L ): Settleable solids measure the volume of heavier coarse sand, silt, and flocculated aggregates that settle out of suspension under gravity within 1 hour . A well-mixed 1 -liter 1\text{-liter} 1 -liter sample is poured into a graduated cone-shaped glass vessel called an Imhoff cone (Standard Methods 2540 F). The sample settles quiescently for 45 minutes 45\text{ minutes} 45 minutes , the inspector gently stirs or spins the cone sides with a rod to dislodge clinging particles, and after 15 additional minutes 15\text{ additional minutes} 15 additional minutes ( 60 minutes 60\text{ minutes} 60 minutes total) , the volume of settled sediment at the cone tip is read directly in milliliters per liter ( mL/L \text{mL/L} mL/L ) .

Warning

High-Probability Exam Trap — Turbidity ( NTU \text{NTU} NTU ) Cannot Be Universally Converted to TSS \text{TSS} TSS ( mg/L \text{mg/L} mg/L ): Never assume that 1 NTU 1\text{ NTU} 1 NTU equals 1 mg/L 1\text{ mg/L} 1 mg/L of TSS \text{TSS} TSS or apply a generic multiplier! Turbidity ( NTU \text{NTU} NTU ) is an optical light-scattering property measured instantly in the field, whereas TSS \text{TSS} TSS ( mg/L \text{mg/L} mg/L ) is a gravimetric dry-mass concentration requiring laboratory filtration and drying at 103 – 105 ∘ C 103\text{–}105^\circ\text{C} 103 – 10 5 ∘ C . Fine colloidal clay particles scatter vastly more light per milligram than coarse sand grains (which have high mass/TSS but settle rapidly and scatter comparatively little light). A mathematical conversion between NTU \text{NTU} NTU and TSS \text{TSS} TSS is valid only if a site-specific regression correlation curve has been empirically calibrated by analyzing paired laboratory TSS \text{TSS} TSS and turbidity samples across multiple storm events for that exact site's soil profile.

2. pH ( 0 to 14 0\text{ to }14 0 to 14 Logarithmic Scale)

pH measures the hydrogen ion activity ( pH = − log ⁡ 10 [ H + ] \text{pH} = -\log_{10}[\text{H}^+] pH = − lo g 10 ​ [ H + ] ) of water on a logarithmic scale from 0.0 0.0 0.0 (extremely acidic) to 14.0 14.0 14.0 (extremely alkaline/basic) , with 7.0 7.0 7.0 representing neutral . Because the scale is logarithmic (base 10), a 1.0-unit change in pH represents a 10-fold ( 10 × 10\times 10 × ) change in acidity or alkalinity, and a 2.0-unit change represents a 100-fold ( 100 × 100\times 100 × ) change (for example, water at pH 10.0 \text{pH } 10.0 pH 10.0 is 100 times 100\text{ times} 100 times more alkaline than water at pH 8.0 \text{pH } 8.0 pH 8.0 ).

Acceptable Permit Range: Most federal and state NPDES stormwater permits require discharges to remain between pH 6.0 and 9.0 \text{pH } 6.0\text{ and }9.0 pH 6.0 and 9.0 standard units (s.u.), while stricter state permits (such as California's CGP Risk Level 2/3 NAL) narrow the acceptable range to pH 6.5 to 8.5 \text{pH } 6.5\text{ to }8.5 pH 6.5 to 8.5 .

Construction Sources of High (Alkaline) pH ( > 9.0 to 12.5 + > 9.0\text{ to }12.5+ > 9.0 to 12.5 + ): High pH on construction sites is overwhelmingly caused by calcium hydroxide ( Ca(OH) 2 \text{Ca(OH)}_2 Ca(OH) 2 ​ ) and calcium oxide ( CaO \text{CaO} CaO ) leaching from uncured concrete, mortar, grout, stucco, or shotcrete washout , concrete saw-cutting slurry , lime or cement soil stabilization , fly ash / cement kiln dust , or stormwater percolating through stockpiles and base courses of recycled concrete aggregate (RCA) .

Construction Sources of Low (Acidic) pH ( < 6.0 < 6.0 < 6.0 ): Low pH is typically caused by excavating and exposing acid sulfate soils or pyritic rock (iron sulfide, FeS 2 \text{FeS}_2 FeS 2 ​ , such as marine clays or coal-bearing shales) —which oxidize upon exposure to air and rainwater to form sulfuric acid ( acid rock drainage )—or by spills of masonry muriatic acid ( HCl \text{HCl} HCl ) and vehicle battery acid ( H 2 SO 4 \text{H}_2\text{SO}_4 H 2 ​ SO 4 ​ ).

Immediate Field Analysis Mandate: Under 40 CFR Part 136, pH must be measured immediately in the field (within 15 minutes of sample collection) because carbon dioxide ( CO 2 \text{CO}_2 CO 2 ​ ) degassing, temperature shifts, and chemical reactions inside a closed bottle rapidly alter sample pH.

3. Additional Physical, Chemical, and Biological Parameters

Temperature ( ∘ C ^\circ\text{C} ∘ C ) and Dissolved Oxygen ( DO \text{DO} DO , mg/L \text{mg/L} mg/L ): Both must be measured in-situ or within 15 minutes in the field. Sheet runoff flowing across sun-heated asphalt and unshaded graded pads experiences thermal loading; warm water holds physically less dissolved oxygen, and suspended organic sediment exerts biochemical/chemical oxygen demand, depleting DO \text{DO} DO below the 5.0 to 7.0 mg/L 5.0\text{ to }7.0\text{ mg/L} 5.0 to 7.0 mg/L minimum needed by cold-water salmonids and benthic macroinvertebrates.

Specific Conductance ( μ S/cm \mu\text{S/cm} μ S/cm ) and Total Dissolved Solids ( TDS \text{TDS} TDS , mg/L \text{mg/L} mg/L ): Specific conductance measures the water's ability to conduct an electrical current (standardized to 25 ∘ C 25^\circ\text{C} 2 5 ∘ C ), serving as a rapid field proxy for dissolved ionic salts ( TDS \text{TDS} TDS ), road deicing chlorides, fertilizers, or concrete leachate.

Nutrients (Total Phosphorus, Orthophosphate, Nitrate/Nitrite, Ammonia): Sourced from hydroseeding/turf fertilizers, topsoil stripping, and sanitary waste leaks; excess nitrogen and phosphorus drive cultural eutrophication and toxic algal blooms in receiving lakes and estuaries.

Oil and Grease / Total Petroleum Hydrocarbons ( TPH \text{TPH} TPH , mg/L \text{mg/L} mg/L ): Sourced from leaking equipment hydraulic lines, diesel refueling spills, form-release oils, and asphalt curing/tack coats. Because hydrocarbons float on water and cling tenaciously to plastics, oil-and-grease samples must always be collected as a direct grab in a wide-mouth glass jar —never composited and never pumped through plastic peristaltic tubing.

Total and Dissolved Heavy Metals ( Cu, Zn, Pb, Cd, Cr, Ni \text{Cu, Zn, Pb, Cd, Cr, Ni} Cu, Zn, Pb, Cd, Cr, Ni ): Sourced from galvanized culverts/fencing (zinc), vehicle brake pads (copper), industrial roofs, and contaminated fill soils. Toxicity to fish gills generally increases at lower water hardness and extreme pH.

Summary Comparison of Target Stormwater Monitoring Constituents (40 CFR Part 136)

Constituent / Parameter Standard Units Typical Permit Benchmark / Range Field vs. Laboratory Method Required Bottle / Container Type Chemical & Thermal Preservation Maximum Holding Time (40 CFR 136)

pH Standard Units ( s.u. \text{s.u.} s.u. , 0 – 14 0\text{–}14 0 – 14 ) 6.0 – 9.0 6.0\text{–}9.0 6.0 – 9.0 ( 6.5 – 8.5 6.5\text{–}8.5 6.5 – 8.5 in stricter state permits) Field calibrated glass-bulb pH electrode Clean plastic or glass beaker (or direct in-stream) None (analyze immediately in field) Within 15 minutes (Immediate field test)

Temperature & Dissolved Oxygen ( DO \text{DO} DO ) ∘ C ^\circ\text{C} ∘ C (or ∘ F ^\circ\text{F} ∘ F ) and mg/L \text{mg/L} mg/L Cold-water DO ≥ 5.0 – 7.0 mg/L \text{DO} \ge 5.0\text{–}7.0\text{ mg/L} DO ≥ 5.0 – 7.0 mg/L ; temp per state WQS Field thermistor & optical/membrane DO \text{DO} DO probe Direct in-stream immersion or immediate grab None (analyze immediately in field) Within 15 minutes (Immediate field test)

Turbidity NTU \text{NTU} NTU (Nephelometric Turbidity Units) 50 NTU 50\text{ NTU} 50 NTU (2022 EPA CGP dewatering weekly avg); 250 NTU 250\text{ NTU} 250 NTU (CA NAL) Field nephelometer ( 90 ∘ 90^\circ 9 0 ∘ scatter) or Lab (EPA 180.1) Clean HDPE plastic or glass; scratch-free glass cuvette Cool to 4 ∘ C 4^\circ\text{C} 4 ∘ C ( ≤ 6 ∘ C \le 6^\circ\text{C} ≤ 6 ∘ C ) in the dark if sent to lab Immediate in field preferred; max 48 hours in lab

Total Suspended Solids ( TSS \text{TSS} TSS ) mg/L \text{mg/L} mg/L (dry mass per volume) Benchmark varies by permit/TMDL (e.g., 100 mg/L 100\text{ mg/L} 100 mg/L MSGP) Laboratory gravimetric filtration ( 1.5 μ m 1.5\text{ }\mu\text{m} 1.5 μ m ) & drying at 103 – 105 ∘ C 103\text{–}105^\circ\text{C} 103 – 10 5 ∘ C HDPE plastic or glass bottle (typically 1 L 1\text{ L} 1 L ) Cool to 4 ∘ C 4^\circ\text{C} 4 ∘ C ( ≤ 6 ∘ C \le 6^\circ\text{C} ≤ 6 ∘ C ); no chemical acid 7 days

Settleable Solids mL/L \text{mL/L} mL/L (or mg/L \text{mg/L} mg/L ) Site/state permit specific Field or Lab volumetric 1 L 1\text{ L} 1 L Imhoff cone ( 60 min 60\text{ min} 60 min settling) HDPE plastic or glass bottle ( ≥ 1 L \ge 1\text{ L} ≥ 1 L ) Cool to 4 ∘ C 4^\circ\text{C} 4 ∘ C ( ≤ 6 ∘ C \le 6^\circ\text{C} ≤ 6 ∘ C ) if transported to lab 48 hours

Oil & Grease / TPH \text{TPH} TPH mg/L \text{mg/L} mg/L No visible sheen; numeric limit typically 10 – 15 mg/L 10\text{–}15\text{ mg/L} 10 – 15 mg/L Laboratory hexane extraction / gravimetric (EPA 1664) Wide-mouth borosilicate glass jar with PTFE cap liner (direct grab only) Acidify to pH < 2 \text{pH} < 2 pH < 2 with H 2 SO 4 \text{H}_2\text{SO}_4 H 2 ​ SO 4 ​ or HCl \text{HCl} HCl ; cool to 4 ∘ C 4^\circ\text{C} 4 ∘ C 28 days

Nutrients (Total Phosphorus, Ammonia, NO 3 + NO 2 \text{NO}_3+\text{NO}_2 NO 3 ​ + NO 2 ​ ) mg/L \text{mg/L} mg/L Watershed / TMDL / MSGP sector benchmark specific Laboratory colorimetric / spectrophotometric HDPE plastic or glass bottle Acidify to pH < 2 \text{pH} < 2 pH < 2 with H 2 SO 4 \text{H}_2\text{SO}_4 H 2 ​ SO 4 ​ ; cool to 4 ∘ C 4^\circ\text{C} 4 ∘ C (unpreserved NO 3 \text{NO}_3 NO 3 ​ is 48 hr) 28 days (preserved with H 2 SO 4 \text{H}_2\text{SO}_4 H 2 ​ SO 4 ​ at 4 ∘ C 4^\circ\text{C} 4 ∘ C )

Total Recoverable Metals ( Cu, Zn, Pb, Cd \text{Cu, Zn, Pb, Cd} Cu, Zn, Pb, Cd ) μ g/L \mu\text{g/L} μ g/L or mg/L \text{mg/L} mg/L Hardness-dependent water quality criteria / MSGP benchmarks Laboratory ICP-MS / ICP-AES (EPA 200.7 / 200.8) Acid-cleaned HDPE plastic bottle Acidify to pH < 2 \text{pH} < 2 pH < 2 with nitric acid ( HNO 3 \text{HNO}_3 HNO 3 ​ ) 6 months ; Mercury ( Hg \text{Hg} Hg ) is 28 days

Indicator Bacteria ( E. coli / Fecal Coliform) MPN / 100 mL \text{MPN}/100\text{ mL} MPN /100 mL or CFU / 100 mL \text{CFU}/100\text{ mL} CFU /100 mL Recreational WQS / TMDL / MS4 IDDE thresholds Laboratory membrane filtration or enzyme substrate Sterile plastic or glass bottle ( 100 – 250 mL 100\text{–}250\text{ mL} 100 – 250 mL ) Sodium thiosulfate ( Na 2 S 2 O 3 \text{Na}_2\text{S}_2\text{O}_3 Na 2 ​ S 2 ​ O 3 ​ ) (dechlorination); cool to < 10 ∘ C < 10^\circ\text{C} < 1 0 ∘ C ( 4 ∘ C 4^\circ\text{C} 4 ∘ C ) 6 to 8 hours (up to 24 hours per specific method)

Apply the analytical method and sampling plan

40 CFR 136.3 Table II and its footnotes , checked October 13, 2026, govern preservation and maximum holding times for the applicable Clean Water Act methods. “Nutrients” is not one preservation category: nitrite alone and orthophosphate generally require analysis within 48 hours; preserved combined nitrate/nitrite, ammonia, and total phosphorus commonly allow 28 days. Routine mercury CVAA allows 28 days, whereas CVAFS has method-specific acid preservation and 90 days. Six months is a calendar interval, not always 180 days. Dissolved-oxygen probe readings are immediate, but the Winkler method has different preservation and holding provisions. Microbiological holding limits depend on the approved method and footnotes; do not apply a drinking-water 24-hour allowance to every stormwater test.

Oil-and-grease extraction is not synonymous with total petroleum hydrocarbons; TPH methods and target fractions have their own bottle, preservation, and holding instructions. Use laboratory-supplied bottles and the approved sampling plan. Downstream-to-upstream movement avoids contaminating later stations when wading, but does not override safety, permit locations, timing, or an approved sampling design. Use clean equipment between locations. Calibrate meters at the frequency and number of standards required by the method, instrument, and quality plan; a pH calibration normally brackets the expected sample pH rather than universally requiring all three buffers. A field-quality issue must be documented and qualified with the lab/regulator, rather than declared automatically legally void.