EPA 832-B-09-003
Industrial Stormwater
Monitoring and Sampling Guide
March 2009
Final Draft

Industrial Stormwater Monitoring and Sampling Guide

All photos are courtesy of Tetra Tech, Inc. Sampling illustrations in Section 2 are courtesy of Washington
Department of Ecology's guide on How To Do Stormwater Sampling: A guide for industrial facilities
(available at http://www.ecy.wa.gov/pubs/0210071.pdf)
                                        Final Draft
                                  Prepublication Copy

                  A formatted version of this guide will be available in April, 2009.

Industrial Stormwater Monitoring and Sampling Guide

               Industrial Stormwater Monitoring and Sampling Guide
1.  Introduction to Stormwater Monitoring and Sampling                                      1
2.  Preparation for Monitoring                                                             3
  2.1 Determine Where Stormwater Is Discharged From Your Property                         4
  2.2 Determine Where You Will Collect Samples                                            5
  2.3 Determine Which Types of Monitoring Requirements Apply At Each Outfall                 12
  2.4 Determine if Your Facility is Subject to Impaired Waters Monitoring Requirements          17
  2.5 What Type of Storm Events Qualify for Monitoring                                      20
  2.6 Select the Monitoring Team                                                          21
  2.7 Select a Laboratory to Analyze the Samples                                            22
  2.8 Document Monitoring Procedures in Your SWPPP                                       23
3.  Conduct Monitoring                                                                   24
  3.1 What to Have In Place Prior to Collecting Stormwater Samples                            24
  3.2 Collect Stormwater Samples                                                         27
  3.3 Record Information for Each Monitoring Event                                         29
  3.4 Quality Assurance Considerations                                                     30
  3.5 Conducting Visual Assessments of Stormwater Discharges                                33
4.  Evaluate Monitoring Results                                                            34
  4.1 Evaluating Quarterly Visual Assessment Results                                         34
  4.2 Evaluating Benchmark Monitoring Results                                             35
  4.3 Effluent Limitation Guideline Monitoring Results                                        37
  4.4 Specific Pollutants and Control Measure Options                                        38
5.  Record-Keeping and Reporting                                                          40
  5.1 Reporting Monitoring Data                                                          40
6.  Train Personnel                                                                       42
7.  References                                                                           42
Appendix A - 2008 MSGP Industrial Stormwater Monitoring Form                              43
Appendix B - 2008 MSGP Visual  Monitoring Form                                            44
Appendix C - 2008 MSGP Industrial Stormwater Collection Form                                45

Industrial Stormwater Monitoring and Sampling Guide

The Industrial Stormwater Monitoring and Sampling Guide ("guide") is a how-to primer for industrial
facility operators on how to conduct visual and analytical monitoring of Stormwater discharges.  The
target audience is operators of facilities subject to the U.S. Environmental Protection Agency's (EPA)
2008 Multi-Sector General Permit (2008 MSGP) or a similar State-issued industrial Stormwater permit.
The information presented will also be useful to anyone interested in industrial Stormwater monitoring.
The procedures presented in this guide, specifically related to monitoring methodology and quality
assurance, will help ensure that Stormwater samples yield usable information.

The 2008 MSGP covers specific industrial activities (see Appendix D of the 2008 MSGP, available at
www.epa.gov/npdes/msgp) in States, territories, and Indian Country lands where EPA is the National Pollutant
Discharge Elimination System (NPDES) permitting authority (i.e., in those States or territories not authorized to
issue NPDES permits themselves - see Appendix C of the 2008 MSGP).

This guide does not impose any new legally binding requirements on EPA, States, or the regulated
community, and does not confer legal rights or impose legal obligations upon any member of the public.
In the event of a conflict between the discussion in this document and any statute, regulation, or permit,
this document would not be controlling.

Monitoring vs. Sampling.  In this guide, "sampling" refers to the actual, physical collection and analysis of
Stormwater samples. The term "monitoring" refers to both sampling and visual observations of Stormwater
discharges, including the related preparation and documentation tasks.

Interested parties are free to raise questions and objections about the substance of this guide and the
appropriateness of the application of this guide to a particular situation. EPA and other decision makers
retain the discretion to adopt approaches on a case-by-case basis that differ from those described in this
guide where appropriate.

1.   Introduction to Stormwater Monitoring and Sampling

Most industrial Stormwater permits require  installation and implementation of control measures to
minimize or eliminate pollutants in Stormwater runoff from your facility. The control measures you
choose for your facility must be documented in your facility-specific Stormwater Pollution Prevention
Plan (SWPPP). The results of your Stormwater monitoring will help you determine the effectiveness of
your control measures, and overall Stormwater management program. Evaluation of your Stormwater
management program will include inspections, visual assessments, and monitoring (i.e., sampling) of
specified Stormwater discharges.  Regular Stormwater inspections and visual assessments provide
qualitative information on whether there are unaddressed potential pollutant sources at your site, and
whether existing control measures are effective or need to be reevaluated. Stormwater sampling
provides quantitative (i.e., numeric) data to  determine pollutant concentrations in runoff and, in turn,
the degree to which your control measures are effectively minimizing contact between Stormwater and
pollutant sources, and the success of your Stormwater control approach in meeting applicable discharge
requirements or effluent limits.

The following are the types of industrial Stormwater monitoring requirements typically included in
industrial general permits:

Industrial Stormwater Monitoring and Sampling Guide
    •   Visual Assessments of Discharges. Permittees are required to regularly and frequently (e.g.,
       quarterly under the 2008 MSGP) take a grab sample during a rain event and assess key visual
       indicators of stormwater pollution - color, odor, clarity, floating solids, settled solids, suspended
       solids, foam, oil sheen, and other qualitative markers of pollution. The findings of these
       assessments are used to trigger further facility inspections and corrective actions to modify
       problems found at the site.

    •   Indicator or Benchmark Sampling. Stormwater samples are collected from a site's discharge
       points (or outfalls) for laboratory analysis and the results are compared with benchmark
       pollutant concentrations as an indicator of the performance of stormwater control measures. A
       benchmark pollutant concentration is a level above which a stormwater discharge could
       adversely affect receiving water quality (and control measures must be evaluated) and, if below,
       the facility is not expected to have an impact on receiving water quality. This type of monitoring
       differs from "compliance monitoring" (see below) in that exceedances of the indicator or
       benchmark levels  are not considered violations, but rather  "red flags" that could point to a
       problem at the site with exposed pollutant sources or control measures that are not working
       correctly.  For instance, the 2008 MSGP includes "benchmarks" that are based to a large degree
       on EPA's aquatic life criteria.  Where the average of samples taken over four consecutive
       quarters exceed the applicable benchmark concentration of a particular pollutant, the permittee
       is required to investigate whether the higher pollutant levels can be attributed to some
       pollutant source or faulty control measure(s), and to address such problems through corrective
       action and possibly further monitoring.

    •   Compliance Sampling.  Where a facility is subject to one of the Federal effluent limitation
       guidelines (ELGs) addressing limits on stormwater runoff, sampling is required to determine
       compliance with those limits. Table 1 provides a list of the  current applicable effluent limitation
Table 1. Applicable Effluent Limitations Guidelines
(2008 MSGP Part 2.1.3)
Regulated Activity
Discharges resulting from spray down or intentional wetting
of logs at wet deck storage areas
Runoff from phosphate fertilizer manufacturing facilities that
comes into contact with any raw materials, finished product,
by-products or waste products (SIC 2874)
Runoff from asphalt emulsion facilities
Runoff from material storage piles at cement manufacturing
Mine dewatering discharges at crushed stone, construction
sand and gravel, or industrial sand mining facilities
Runoff from hazardous waste landfills
Runoff from non-hazardous waste landfills
Runoff from coal storage piles at steam electric generating
40 CFR Part/Subpart
Part 429, Subpartl
Part 418, SubpartA
Part 443, SubpartA
Part 411, SubpartC
Part 436, Subparts B, C, or D
Part 445, SubpartA
Part 445, Subpart B
Part 423

Industrial Stormwater Monitoring and Sampling Guide

       These limits are required to be included in all general industrial permits. Typically, permits
       require corrective action and further sampling when an effluent limitation is exceeded. An
       exceedance of an applicable effluent limitation guideline constitutes a violation of the permit.

    •   Monitoring Requirements for Discharges to Impaired Waters - General industrial permits may
       have special monitoring requirements for facilities that discharge pollutants of concern into
       impaired waters.

For an explanation of these monitoring requirements in the 2008 MSGP see Part 6.2.  Part 8 of the 2008 MSGP
includes the benchmark and effluent limitation guideline monitoring requirements for each of the industrial
sectors affected by such requirements.
2.  Preparation for Monitoring
This section describes the information you will need before monitoring. While this guide is meant to be
a general primer for anyone interested in industrial stormwater monitoring, Section 2 follows the
organization of the 2008 MSGP. Many State general permits are very similar to the 2008 MSGP. It is
EPA's hope that this format will be of use to permittees in most states.  However, if you are subject to a
State industrial general permit, you should compare your permit's monitoring requirements to the
requirements reflected in this guide to ensure that you are following all applicable State requirements.

In general, preparation is critical to make sure that industrial stormwater monitoring is conducted
properly and in a timely manner. Most of this information should have been collected previously for the
purposes of submitting your permit application or Notice of Intent (NOI), and in developing the
monitoring procedures section of your stormwater pollution prevention plan (SWPPP).  However, this
guide reviews some of the steps necessary to develop this information, such as the site map component
of the SWPPP, in case facilities have not already done so. If you have already completed any of these
steps in this section, you can skip to the next application section or subsection in this guide. For more
information on how to develop a SWPPP, refer to EPA's guide Developing Your Stormwater Pollution
Prevention Plan: A Guide for Industrial Operators, available on EPA's website at

If you have already submitted your NOI, the following documents will serve as good resources for
information that you will need prior to monitoring:

   •  A copy of your NOI or application submitted to EPA or a State, and your assigned permit
       registration number.

   •  A copy of the EPA/State response to your NOI/permit application submission if it includes
       specific details pertaining to your monitoring (e.g., pollutants required to be monitored,
       frequency of monitoring, benchmark or compliance sampling requirements, etc.).

   •  A copy of your applicable permit, including the accompanying fact sheet.

   •  A complete copy of your SWPPP, which must include a detailed site map of your facility with
       locations of all stormwater monitoring points, and a description of the procedures you or your

Industrial Stormwater Monitoring and Sampling Guide

       stormwater pollution prevention team will follow when conducting monitoring and visual

2.1 Determine Where Stormwater Is Discharged From Your Property

If you have not already done so, walk the grounds and perimeter of your facility during a storm event to
identify where runoff discharges from the site (known as "outfalls"). Outfalls are locations where
stormwater exits the facility property, including pipes, ditches, swales, and other structures that
transport stormwater. If possible, walk outside the boundary of your facility to identify outfalls that may
not be apparent from within your site.
         Stormwater discharges to the slot drain and is conveyed offsite through a valvedpipe.

You should note where:

    •   Concentrated stormwater exits your facility (e.g., through a pipe, ditch or similar conveyance).
       These outlets are usually good sampling points.

    •   Dispersed runoff (i.e. sheet flow) flows offsite (e.g., through a grassy area or across a parking
       lot).  Note whether concentrated flows commingle with the sheet flow.

    •   Storm drain inlets or catch basins are located. Try to determine where the storm drains send
       your runoff (e.g., to your municipal separate storm sewer system [MS4], to a combined sewer
       system, to the separated sanitary sewer, or directly to a nearby waterbody).

Industrial Stormwater Monitoring and Sampling Guide

    •   Authorized non-stormwater discharges commingle with stormwater prior to discharge (such
       commingled discharges may be covered under your permit).

    •   Areas where stormwater might enter your facility from neighboring facilities and commingle
       with your stormwater discharges.

Terms to Know:

Combined Sewer System:  Combined sewer systems are sewers that are designed to collect rainwater
runoff, domestic sewage, and industrial wastewater in the same pipe. Most of the time, combined
sewer systems transport all of their wastewater to a sewage treatment plant, where it is treated and
then discharged to a water body. During periods of heavy rainfall or snowmelt, however, the
wastewater volume in a combined sewer system can exceed the capacity of the sewer system or
treatment plant. For this reason, combined sewer systems are designed to overflow occasionally and
discharge excess wastewater directly to nearby streams, rivers, or other water bodies.

MS4:  A conveyance or system of conveyances (including roads with drainage systems, municipal streets,
catch  basins, curbs, gutters, ditches, man-made channels, or storm drains) which are owned and
operated by a ... public body (created by or pursuant to State law) having jurisdiction over disposal of
sewage, industrial wastes, stormwater, or other wastes ... that discharges to waters of the United States;
designed or used for collecting or conveying stormwater; which is not a combined sewer; and which is
not part of a publicly owned treatment works (POTW). [40 CFR 122.26(b)(8)].

Mark these locations on your facility site map, which will be included as part of your SWPPP, and label
each outfall location with unique identifiers to differentiate them.  For example, you may decide to
name the different outfalls according to where the stormwater is being discharged, such as MS4-1, MS4-
2, etc. for outfalls discharging to the MS4 or ST-1,  ST-2, etc. for outfalls discharging directly to  an
adjacent stream. Using unique identifiers will help you to coordinate monitoring requirements.

In addition to marking the outfalls on the map, you will need to determine the drainage area for each
discharge point. If your facility is large and has significant changes in  elevation, a topographic map may
be necessary. However, if your facility is small and relatively flat, the best way to define the drainage
area for each outfall is an on-the-ground visual assessment, preferably during a rain event.  Sketch the
basic drainage areas on the map for each outfall. Knowing the drainage area for each outfall is helpful
when  your sampling indicates problems at that outfall. You can focus your efforts on the industrial
materials and activities in that drainage area, instead of the entire site, to identify what may be causing
the problem.

2.2 Determine Where You Will Collect Samples

Now that you have determined the different points of discharge from your site, you will need  to select
the exact locations from which you will be collecting your stormwater samples. Note that Part of
the 2008 MSGP  requires industrial operators to document in their SWPPPs the location where samples
will be collected. Generally, industrial stormwater permits require that you sample stormwater
discharges prior to the stormwater leaving your facility, and at a location downstream from all of your
industrial materials and activities. The reason behind requiring such a location is so that the sample is

Industrial Stormwater Monitoring and Sampling Guide
representative of your facility's discharge, taking into account the types of pollutants that may be
contained in runoff from the property.

Appropriate sample locations include:

    •   Underground pipes that collect stormwater from drop inlets and convey stormwater to an
       offsite location (e.g., street, curb or MS4). Be sure you collect only the stormwater discharging
       from your facility and not the baseflow in the pipes that is being discharged from facilities
       upstream. Do not enter underground locations to collect samples. Use a pole with a sampling
       container attached at the end to collect the sample.
    •   Open ditches, gutters or swales that carry stormwater from your facility to an offsite location.  If
       these conveyances contain runoff from another facility, it is important to note that in your

       Facility driveways and other street access points; and

Industrial Stormwater Monitoring and Sampling Guide
    •   Outlets discharging offsite from onsite stormwater detention ponds or other types of structural
       control measures. It is important to sample at the OUTLET of your structural control measures,
       as opposed to the INLET of such structures, in order to determine the quality of the water after
Where to Sample When There Are Multiple Discharge Points

You are required to monitor all outfalls that receive stormwater discharges from your industrial activity.
See Part 6.1.1 of the 2008 MSGP. If you have multiple stormwater discharge points at your facility, you
need to identify which outfalls are associated with industrial materials and activities, and monitor those
outfalls. Understanding the hydrologic connection between your outfalls and the parts of your facility
that drain to those points, and the pollutants associated with the industrial activities in these areas, will
assist you in designing a monitoring program that is representative of the pollutants being discharged
from your site. Developing such an  understanding will also help later on when you begin to assess your
sampling results and determine where improvements could be made to your stormwater control
measures. The site map you prepare (see Part 5.1.2 of the 2008  MSGP) will help you understand the
correlation  between your areas of potential pollutant sources, the direction of stormwater flow from
those areas, and the discharge points.

Industrial Stormwater Monitoring and Sampling Guide

Note that you are not required to monitor at outfall locations that receive stormwater flow only from
unregulated areas of your site (i.e., there are no industrial materials or activities in the drainage area).
For instance, a hypothetical facility may have two outfalls, one that receives discharges from an area
where industrial materials are handled and stored, and a second outfall that receives discharges from an
unregulated parking lot used by employees. In this scenario, the industrial permittee would only collect
samples from the first outfall because it discharges stormwater associated with industrial activity.
Alternatively, if the site's second outfall (e.g., the outfall receiving runoff from the parking lot) also
drains areas of the facility with regulated industrial activities, then this outfall would also need to be
sampled. In this situation, sampling for this outfall should be done at a location prior to where the two
flows commingle so that you are capturing the industrial portion of the flow. See Part 6.1.2 of the 2008

Where to Sample if Outfalls Are Substantially Identical

If your facility has two or more outfalls whose  discharges are "substantially identical," some industrial
stormwater permits,  including the 2008 MSGP, allow you to monitor the discharge at just one
representative outfall and apply the results to  the other substantially identical outfalls.  EPA defines
"substantially identical" in the 2008 MSGP as follows:

       "... two or more outfalls that you believe discharge substantially identical effluents, based on the
       similarities of the general industrial activities and control measures, exposed materials that  may
       significantly contribute pollutants to stormwater, and runoff coefficients of their drainage areas
       ...."  See Part 6.1.1 of the 2008 MSGP.

The flexibility provided to permittees to sample at just one location, which is considered representative
of all substantially identical  outfalls, is an exception to the rule stated above that samples must be taken
from all outfalls at a facility. Note that this exception does not apply to compliance monitoring (effluent
limitation guideline monitoring), which must be conducted at each outfall to which the effluent
guideline applies.

In choosing which of the substantially identical outfalls from which to sample, you should select the
outfall that has been  observed to have the  most consistent flow. To use the substantially identical
outfall exception, you must document in your  SWPPP how the two or more outfalls are substantially
identical, based on the above definition.  You will  need to document the following information:

    •   The locations of the outfalls;
    •   Estimated size of the drainage area (in square feet) for each outfall;
    •   General industrial activities conducted in the drainage area of each outfall;
    •   Control measures being implemented  in the drainage area of each outfall;
    •   Why the outfalls are expected to discharge similar stormwater; and
    •   An estimate of the runoff coefficient of the drainage areas (0.0 no runoff potential to 1.0 all
       precipitation runs off).

The runoff coefficient is the ratio of excess  runoff to the amount of precipitation for a given time over a
given area, with a 0 (zero) runoff coefficient meaning no runoff potential and 1.0 (one) meaning a
completely impervious surface and all stormwater runs off. The runoff coefficient is related to the
amount of impervious surfaces (buildings, pavement, sidewalks, etc.) versus pervious surfaces (grass,

Industrial Stormwater Monitoring and Sampling Guide

graveled areas, etc.) at the site. The more impervious surface a facility has, the larger the runoff
coefficient. Light industrial facilities typically have a runoff coefficient between 0.50 and 0.80 and heavy
industrial facilities typically have a runoff coefficient between 0.60 and 0.90.

Here is an example where a facility could take advantage of the "substantially identical outfalls"
exception:  a metal recycling facility with a large scrap metal pile has three separate outfalls that are
each connected by their own drainage ditch to different portions of the same pile, and the runoff that is
discharged is managed using the same type of control measure in each drainage area.  In this scenario,
the facility's operator can use the "substantially identical outfall" exception because the industrial
activities at the site are all the same, the runoff flows through exposed areas that presumably contribute
the same type of pollutants, and the drainage area has the same or similar runoff coefficients.  Note that
the substantially identical outfall exception could not be used if there were in fact differences in any of
the required components defined above.

If your permit does allow you to use a substantially identical outfall exception, make sure you carefully
review the type of monitoring for which this exception applies. For instance, while the 2008 MSGP
allows permittees to  use the substantially identical outfall exception for benchmark and visual
assessment samples, the permit prohibits use of this exception for compliance monitoring (e.g., for  use
in showing compliance with numeric effluent limitation guidelines). Therefore, if a facility permitted
under the 2008 MSGP is subject to a numeric limit based on an EPA effluent limitation guideline, it
would have to monitor all outfalls at the site receiving flows from the applicable industrial activities. See
Part of the 2008 MSGP.

Where to collect a sample

Sampling Sheet Flow

In some areas of your facility it may be difficult to obtain a sample  because the runoff drains as sheet
flow before it becomes concentrated enough for sampling. If the flow is too shallow to directly fill a
collection bottle, you can overcome this by:

         o  Concentrating the sheet flow by excavating a small depression in an existing ditch or other
            location where stormwater runoff flows.
            Installing a trough, gutter or ditch to intercept and concentrate stormwater flow.

Industrial Stormwater Monitoring and Sampling Guide
         o  Installing "speed" bumps to convey and concentrate a large area of sheet flow.
                            Collecting a sheet flow stormwater sample.

You should make these modifications during a period when rain is not forecast so any pollutants
generated can be cleaned up before a storm hits. Also, if you dig a ditch or disturb the earth in some
way, line the disturbance with concrete or plastic so that you do not contaminate your stormwater
samples with sediment or other pollutants.

Sampling from a Pipe
                                                                   When collecting any type of
                                                                   stormwater sample it is
                                                                   imperative that the sample is
                                                                   collected before the
                                                                   stormwater reaches the
                                                                   receiving water.
For runoff flowing through a pipe into a ditch or receiving water, you
should sample the outflow directly from the pipe.  For hard-to-reach
pipes, it may be necessary to fasten a collection bottle to a pole (see
Sampling from a Manhole in Table 2 below).

Sampling From  a Drainage Ditch or Swale
If your stormwater is discharged via a drainage ditch or vegetated swale, take a grab sample from a
consistently flowing part of the ditch / swale.  If the ditch / swale is too small or shallow, install a barrier
device in the channel or deepen a small area so you are able to sample directly into the bottles. Allow
sufficient time to pass after disturbing the bottom so that any solids stirred up do not contaminate your

 Industrial Stormwater Monitoring and Sampling Guide
 Sampling From a Stormwater Detention / Retention Basin or Other
 Treatment Device

 If it is necessary for you to sample from a detention or retention basin, do so
 at the outfall of the structure. Collecting samples from stagnant or slowly
 moving water inside a pond will not yield a representative sample as the
 pollutants might not be adequately mixed. Stormwater basins may hold
 Stormwater for long periods of time. Collect your sample within 30 minutes
 from when the  pond begins to discharge.

 Potential Sampling Issues

 Depending on the location of your monitoring points, you may encounter
 additional challenges beyond deciding which sampling technique to employ at
 each site. Table 2 identifies some Stormwater sampling problems common to
 industrial facilities and guidance for how EPA suggests you address them if they occur at your site.

	Table 2. Solutions to Typical Stormwater Sampling Problems	
 Run-on from Neighboring Properties
Ideally, your Stormwater samples will contain only runoff from
your site. However, Stormwater from a neighboring facility can
"run on" and commingle with your own regulated discharge,
possibly adding contaminants not found at your facility.  You are
responsible for any and all pollutants discharged from your site
irrespective of the pollutants' origin and whether the other facility
has permit coverage. This responsibility includes run-on
discharges from neighboring properties if this discharge
commingles with your own regulated discharge. To accommodate
Stormwater run-on, EPA requires as part of the SWPPP site
description that you document the locations and sources of run-
on. As part of this documentation, if you collect and analyze
samples of the run-on, you will need to report all such findings in
your SWPPP.	
 Stormwater from industrial areas
 commingles with Stormwater
 discharges from non-industrial areas
 or areas not regulated under the
 MSGP before it reaches the surface
 water body or MS4.
Attempt to sample the industrial Stormwater discharge before it
mixes with Stormwater from non-industrial areas.
 Adverse Weather Conditions
High tides and high flow or flood conditions can cause Stormwater
conveyances to reach maximum capacity, pipes to become clogged
or submerged, and other unrepresentative flow situations. High
flows could also be dangerous, so you should use your best
professional judgment when selecting sampling locations.  In some
cases you may need to sample at a point before the intended
outfall location.
 There are numerous Stormwater
 outfalls in one area.
Construct an impound channel or join together flows by building a
weir or digging a ditch to collect discharge at a low point for
sampling purposes. This artificial collection point should be lined
with plastic to prevent infiltration and the introduction of

Industrial Stormwater Monitoring and Sampling Guide

The outfall is inaccessible (examples
include underwater discharges or
unreachable discharges such as a
pipe discharging out of a cliff).
A facility has many sampling
locations making it difficult to collect
all of the samples during the first 30
minutes of discharge, as required by
the 2008 MSGP.
A stormwater sample location is
beneath a manhole.
Stormwater from more than one
industry type is commingled.
sediment. Or, alternatively, sample at several locations to
represent total site runoff.
Go upstream of the discharge until a sample can be taken (i.e., to
the nearest manhole or inspection point). You may need to
sample at several locations to best represent runoff from this
discharge point if you cannot access an upstream location.
Have a sampling crew ready when storms are forecast so that all
outfalls can be sampled during the first 30 minutes. Also,
automatic samplers may be used to collect samples within the first
30 minutes, triggered by the amount of rainfall, the depth of flow,
flow volume or time.
For accessibility and safety, use a sampling pole to collect samples
from a manhole. Before a person can enter a manhole to collect a
sample, they must be trained in confined space entry.
You must comply with monitoring requirements for all applicable
sectors and SIC codes.
2.3 Determine Which Types of Monitoring Requirements Apply At Each Outfall

The next step in preparing for monitoring at your site is to determine the type of monitoring
requirements that correspond to each outfall. The type of monitoring requirements to which you are
subject will differ according to your permit.  Different monitoring requirements may also apply to
individual outfalls on your property based on the type of industrial activity discharging to that point, and
even the receiving water to which you are discharging.  Using your permit, determine the type of
monitoring requirements to which your specific facility  is subject, and document in your SWPPP the
specific monitoring requirements that applies to each outfall, including the frequency of monitoring and
the specific parameters that must be monitored.

Recall that it is not necessary to monitor an outfall if it does not have any industrial activity associated
with it (e.g., discharge from an employee parking lot that does not commingle with stormwater runoff
from an area of industrial activity) or if the outfall does  not drain to a surface water (i.e. the outfall
drains to a sanitary sewer or combined sewer system).

The following applies to the types of monitoring required under the 2008 MSGP. If you are not subject
to the 2008 MSGP, consult your State permit to determine your monitoring requirements.

    •  Visual Assessments (Part 4.2 of the 2008 MSGP) - All 2008 MSGP permittees are required to
       collect samples of their stormwater discharge for visual inspection. The following qualitative
       characteristics must be assessed:

              floating solids;
              settled solids;
              suspended solids;
              oil sheen; and

Industrial Stormwater Monitoring and Sampling Guide

              other obvious indicators of stormwater pollution.

       Visual assessments must be conducted at all outfalls, although if several outfalls are
       "substantially identical" then  only one visual assessment must be conducted on the set of
       outfalls. The sampling frequency for visual assessments under the 2008 MSGP is quarterly. The
       monitoring quarters are: January 1 - March 31, April 1 - June 30, July 1 - September 30, and
       October 1 - December 31.

    •   Benchmark Monitoring (Part  6.2.1 of the 2008 MSGP) - This type of analytic monitoring applies
       to certain industrial sectors regulated under the 2008 MSGP. Permittees subject to these
       requirements must take periodic grab samples of their stormwater discharge to compare the
       concentrations of key indicator pollutants to their corresponding benchmark concentrations.
       The benchmark values are based in large part on EPA's aquatic life water quality criteria and are
       meant to serve as indicators of how well a facility's stormwater control efforts are working. If a
       particular benchmark is exceeded, this indicates to a permittee that there may be a problem at
       the site, such as a spill, exposed pollutant source, or a faulty control measure, and triggers a
       required review of the potential problem to determine what corrective actions are necessary.
       For example, a total suspended solids (TSS) concentration found in a benchmark sample of
       greater than 100 mg/L, which is the applicable benchmark concentration for TSS, would require
       a facility to re-evaluate and potentially revise control measures implemented to control dust,
       soil erosion, or other sources  of suspended solids.  Note that the exceedance of the benchmark
       is not a violation (because benchmarks are typically not enforceable limits), but the failure to
       conduct the follow-up investigation and applicable corrective actions would be a violation of the

Be sure to update your SWPPP  and site map whenever you change or add new control measures.
Control measure maintenance activities must be documented (preferably in a log), and such records
must be kept with your SWPPP and stormwater file.

       Determine whether you are subject to any  benchmark monitoring requirements based on your
       particular industrial sector or  subsector.  The benchmark monitoring requirements differ based
       on the sector or subsector under which a particular facility falls.  Note that not all sectors are
       subject to this type of monitoring. Appendix D in the 2008 MSGP provides the Standard
       Industrial Classification (SIC) code and activity codes categorized by sectors and subsectors. Use
       Appendix D to link your industrial activities with their associated SIC code sectors / subsectors.
       Your facility will have a primary industrial activity and associated SIC or activity code (which is
       the major determinant of your permit requirements), and, possibly, additional secondary
       sectors / subsectors with additional requirements for which you must comply. Next, using Part
       8 of the 2008 MSGP, under your particular sector or subsector, determine whether you are
       subject to any benchmark monitoring requirements, and the corresponding benchmark that
       applies. Consider the following example: if you operate a gold mine (subsector G2) you are
       subject in Part 8.G.8.2 to the following benchmark monitoring requirements:

Industrial Stormwater Monitoring and Sampling Guide
Tables. Subsector G-2.
(Discharges may be subject to
requirements for more than one
Subsector G2. Iron Ores; Copper Ores;
Lead and Zinc Ores; Gold and Silver Ores;
Ferroalloy Ores, Except Vanadium; and
Miscellaneous Metal Ores (SIC Codes
1011, 1021, 1031, 1041, 1044, 1061, 1081,
1094, 1099)
(Note: when analyzing hardness for a
suite of metals, it is more cost effective to
add analysis of calcium and magnesium,
and have hardness calculated than to
require hardness analysis separately)
Total Suspended Solids (TSS)
Hardness (as CaCO3; calc. from
Ca, Mg)1
Total Antimony
Total Arsenic
Total Beryllium
Total Cadmium1
Total Copper1
Total Iron
Total Lead1
Total Mercury
Total Nickel1
Total Selenium
Total Silver1
Total Zinc1
Benchmark Monitoring
Cutoff Concentration
100 mg/L
6.0-9.0 s.u.
no benchmark value
0.64 mg/L
0.15 mg/L
0.13 mg/L
Hardness Dependent
Hardness Dependent
1.0 mg/L
Hardness Dependent
0.0014 mg/L
Hardness Dependent
0.005 mg/L
Hardness Dependent
Hardness Dependent
       Based on this table, you then know the pollutant parameter for which you must conduct
       benchmark monitoring, and the corresponding benchmark concentration against which you will
       compare each individual grab sample. Each sector or subsector subject to benchmark
       monitoring requirements includes a similar table in Part 8 of the 2008 MSGP.

       After you have determined which (if any) benchmark sampling requirements apply, document in
       your SWPPP which outfalls are subject to such requirements, the frequency of monitoring, and
       the parameters that must be analyzed. If your facility has multiple outfalls, be aware that there
       may be different requirements for different outfalls depending on the type of industrial activity
       conducted in the drainage area of each outfall. You are only required to conduct benchmark
       monitoring for those outfalls with discharges from the specific sectors / subsectors that are
       affected by such requirements. Where an  outfall includes no discharges from those sectors or
       subsectors for which benchmark monitoring requirements apply, then no benchmark samples
       need to be taken at that outfall.

       The required benchmark monitoring frequency under the 2008 MSGP is quarterly. The
       monitoring quarters, beginning with the first quarter on April 1, 2009 are: April 1 - June 30, July
       1 - September 30, October 1 - December 31 and January 1 - March 31.

       Exceptions for Inactive and Unstaffed Sites (Part of the 2008 MSG) -The requirement for
       benchmark monitoring does not apply to inactive and unstaffed facilities, providing there are no
       industrial materials  or activities exposed to stormwater. This exception only applies to
       benchmark monitoring requirements and not to the other types of monitoring described above.

Industrial Stormwater Monitoring and Sampling Guide

       To claim this special exemption, you must note on the next quarterly benchmark monitoring
       report that your facility is inactive and unstaffed, and you must keep an inactive and unstaffed
       certification onsite (see Part The requirement for conducting a quarterly visual
       assessment also does not apply inactive and unstaffed sites, as long as there are no industrial
       materials or activities exposed to stormwater. If you are invoking the exception for inactive and
       unstaffed sites, maintain a signed and certified statement onsite with your SWPPP stating that
       the site is inactive and unstaffed, and that there are no  industrial materials or activities exposed
       to stormwater.

       Hardness-Dependent Benchmarks (Appendix J of the 2008 MSGP) -The benchmark values of
       some metals are dependent on the level of hardness in  your receiving waters (see 2008 MSGP,
       Appendix J). Hardness is a characteristic of water that results from the presence of dissolved
       salts, especially calcium sulfate or bicarbonate, and is usually reported as carbonate,
       noncarbonate or calcium + magnesium (Ca  + Mg). If you are required to monitor for a  hardness-
       dependent pollutant, you must first determine the hardness of your receiving water before you
       can establish the corresponding benchmark concentration.

    •   Effluent Limitations Monitoring (Part 6.2.2 of the 2008  MSGP) - Eight of the 2008 MSGP's 29
       industrial sectors are required to  monitor to determine  if they comply with EPA-defined effluent
       limitation guidelines. These monitoring requirements are included in Part 8 of the 2008 MSGP.
       Effluent limitation guidelines are legally enforceable limitations that must not be exceeded in
       stormwater discharges.

       Similar to the benchmark monitoring requirements, samples only need to be taken at those
       outfalls with discharges from the specific activities that  are subject to effluent limitation
       guidelines; otherwise these requirements do not apply.  As stated previously, permittees subject
       to these monitoring requirements must take samples at all applicable outfalls, and no
       exceptions are given for substantially identical outfalls.  However, if you are required to monitor
       a pollutant both for benchmark and effluent limitation guideline purposes, you only need to
       take one sample for both requirements.
When monitoring requirements overlap, e.g., TSS once per year for an effluent limit and once per quarter for
benchmark monitoring, you may use a single sample to satisfy both monitoring requirements (i.e., one of your
four quarterly benchmark samples would be used for your yearly effluent limit sample).
       Table 4 identifies the industrial activities that are subject to effluent limitation guideline
       monitoring requirements and the associated sampling parameters.  Effluent limitation guideline
       samples must be taken once per year (see Part 8 of the 2008 MSGP for the numerical values of
       each effluent limit).

                 Table 4. Required Monitoring for Effluent Limitations Guidelines
Regulated Activity
Discharges resulting from spray down or
intentional wetting of logs at wet deck storage
Runoff from phosphate fertilizer manufacturing
Where in
2008 MSGP
Part 8.A.7
Part 8.C.4
Effluent Limit Parameters
debris, pH
total P, fluoride

Industrial Stormwater Monitoring and Sampling Guide
Regulated Activity
Runoff from asphalt paving and roofing emulsion
Runoff from material storage piles at cement
manufacturing facilities
Mine dewatering discharges at crushed stone,
construction sand and gravel, or industrial sand
mining facilities
Runoff from hazardous waste landfills
Runoff from non-hazardous waste landfills
Discharges from coal storage piles
Where in
2008 MSGP
Part 8. L 10
Effluent Limit Parameters
total suspended solids (TSS), oil
and grease, pH
biochemical oxygen demand
(BOD5), TSS, ammonia,
alpha terpineol, benzoic acid, p-
cresol, phenol, total recoverable
zinc, pH, aniline, naphthalene,
pyridine, total recoverable
biochemical oxygen demand
(BOD5), TSS, ammonia,
alpha terpineol, benzoic acid, p-
cresol, phenol, total recoverable
zinc, pH
       Determine whether you are subject to any effluent limitation guideline monitoring
       requirements.  Document in your SWPPP which outfalls are subject to such requirements, the
       frequency of monitoring, and the parameters that must be analyzed.

       Impaired Waters Monitoring (Part 6.2.4 of the 2008 MSGP) -The 2008 MSGP requires facilities
       to monitor, at least in the first year of permit coverage (and yearly thereafter depending on the
       sample results  in the first year), for the presence of any pollutant causing an impairment to their
       receiving water. This requirement is triggered regardless of whether the particular pollutant is
       used or stored  at the industrial site; however the facility may be able to discontinue monitoring
       after the first year if the pollutant is not present in the sample and is not expected to be present
       in any discharge. In advance of conducting this monitoring, you should already have a good idea
       of whether the pollutant will be found in your discharge. When you developed your SWPPP,
       you conducted a complete inventory of your site to determine what pollutants or pollutant
       constituents could be discharged in stormwater runoff. See Section 3.1 of EPA's guide,
       Developing Your Stormwater Pollution Prevention Plan: A Guide for Industrial Operators,
       particularly the discussion about conducting an "Inventory of Materials and Pollutants". Using
       this inventory from your SWPPP, you will be able to determine if any materials stored or used at
       your facility could contribute to impairment of your receiving water.

       The next section of this guide includes specific steps to help you determine if you are subject to
       impaired waters monitoring requirements. After following those steps, document in your
       SWPPP which outfalls are subject to impaired waters monitoring requirements, the frequency of
       sampling, and the parameters that  must be monitored.

       State /Tribal Monitoring Requirements (Part 6.2.3 of the 2008 MSGP) -The 2008 MSGP
       includes a number of additional monitoring requirements that are  unique to individual  States

Industrial Stormwater Monitoring and Sampling Guide

       and/or Indian Country lands. These requirements are set out in Part 9 of the permit. These
       requirements may include additional or more frequent benchmark monitoring requirements,
       alternative benchmark thresholds, or additional parameters that must be monitored to establish
       compliance with applicable water quality standards.

       Based on the State or Indian Country land in which they are located, each 2008 MSGP permittee
       must consult the applicable Part 9 section to determine what, if any, additional monitoring
       requirements apply. If you are subject to such requirements, you must document in your
       SWPPP which outfalls are subject to these provisions, the frequency of applicable sampling, and
       the parameters that must be monitored

    •   Additional Monitoring Required by EPA- It is possible EPA may require additional monitoring
       (see 2008 MSGP Part 6.2.5).  You will be notified by the Agency if additional monitoring is

2.4 Determine if Your Facility is Subject to Impaired Waters Monitoring Requirements

If you are required by your industrial stormwater permit to monitor for pollutants that cause
impairment to your receiving water, you must first identify the receiving waters (e.g. ditch, creek,
intermittent stream, lake, arroyo, etc.) into which your facility discharges stormwater and mark them on
your site map.  Note that you will have already identified your receiving waters if you filed an NOI to be
covered by the 2008 MSGP.

    A.  Identify Your Receiving  Water(s)

There are several ways to identify your receiving
waters. Your receiving water may be a lake,
                                               Do these monitoring requirements apply
                                               runoff to a waters of the United States.
                      .    ,     ,                to me if I discharge into a dry ditch?
stream, nver, ocean, wetland or other             yes jffhe ^ eventua,,y comeys the
waterbody, and may or may not be located
adjacent to your facility. Your facility might
discharge directly into its receiving water, or indirectly to the receiving water by discharging first
through an MS4, ditch, or other conveyance.

If the discharge from your facility does not discharge into an underground storm sewer system, you can
use your site map and local topographic maps to pinpoint the closest waterways. Using the contours on
the topographic map and your facility's outfall locations, determine the direction stormwater runoff
flows from your facility. Once you know the direction of flow, you should be able to identify the
receiving waters into which you discharge.

Industrial Stormwater Monitoring and Sampling Guide
Sample section of a U.S.G.S. quadrangle map, with arrows showing direction of flow.

After identifying where your stormwater enters a waterbody, identify any additional interconnected
waters for at least one linear mile downstream from the entrance point of your discharge (in case there
are concerns about impacts to these downstream waters).

Resources to help you identify receiving waters:

     •   EPA's Water Locator Tool (available at www.epa.gov/npdes/stormwater/msgp) allows you to
         locate nearby receiving waters and impaired waterbodies within a 10 mile radius of your

     •   EPA's Enviromapper (www.epa.gov/enviro/emef) enables you to find nearby waterbodies by
         entering your facility's zip code, address, facility name or identification number,  EPA Region,
         watershed, or latitude/longitude data. Additional  information on the location of impaired
         waterbodies can also be obtained.

     •   Topographic maps, which can be obtained from the U.S. Geological Survey (USGS) at
         http://topomaps.usgs.gov/ordering  maps.html, or through a retailer.

If your stormwater drains into an MS4, you will likely need to contact the operator of the system  (e.g.,
the local public works department, the highway department, etc.) to identify the first receiving water
your stormwater is released to after entering the MS4. Some MS4s have their storm sewer
infrastructure maps available online.

Remember, the MS4 into which your facility's stormwater discharges is NOT your receiving water. The first
waterbody that the MS4 discharges to after receiving your stormwater is the receiving water for your facility.

Industrial Stormwater Monitoring and Sampling Guide

    B.  Determine if Your Receiving Water is Impaired and Whether a TMDL Has Been Completed

Once you have identified your receiving water(s), you will need to find out if the waterbody is impaired,
and, if so, whether a total maximum daily load (TMDL) has been approved or established.

    •   Water quality impairment status. You need to determine whether your facility's receiving
       water is listed by your State as impaired and/or has an approved or established Total Maximum
       Daily Load (TMDL). EPA's Water Locator Tool (available at
       www.epa.gov/npdes/stormwater/msgp) will help find impaired waters within a 10 mile radius
       of your facility. Another place to check is EPA's website on Water Quality Assessment and TMDL
       information  (www.epa.gov/waters/ir) or you can also contact your State water agency
       (cfpub2.epa.gov/npdes/contacts.cfm?program id=6&type=STATE).

"Impaired waters" are streams, rivers, and lakes that do not currently meet their applicable designated uses and
water quality standards. States, territories, and authorized tribes are required underthe Clean Water Act to
compile lists of known impaired waters, called 303(d) lists. Stormwater discharges to impaired waters may
trigger additional control measures and monitoring requirements. For facilities subject to EPA's 2008 MSGP, see
Part 2.2 for a more detailed discussion of water quality-based effluent limitations and conditions for discharging
to impaired waters.

If your receiving water is impaired, use EPA's Water Locator Tool or Water Quality Assessment and
TMDL website, or a State agency to help you determine:

    •   For what pollutant(s) is the water impaired? Make a separate list of all pollutants that have
       caused your  waterbody to be impaired.

    •   Has an approved TMDL been completed for each of the pollutants? Some TMDL documents
       include information suggesting the type of monitoring that should be conducted to improve the
       understanding of the impairment or to demonstrate achievement of applicable wasteload
       allocations (WLAs).

    C.  Determine What Monitoring Requirements Apply

Having determined the pollutants that cause the impairment, you should now consult your permit to
determine the type of monitoring that must be conducted, the frequency of monitoring, and whether
any exceptions apply to certain pollutants. As discussed in Section 2.3 above, this  must all be
documented in your SWPPP so that it is clear which requirements apply to which outfall.

The 2008 MSGP lists several exceptions to and clarifications of the requirement to monitor for each
impairment pollutant. In Part of the 2008 MSGP, the permit clarifies that no monitoring is
required when a waterbody's biological communities are impaired but no pollutant is specified as
causing the impairment, or when a waterbody's impairment is related to hydrologic modification,
impaired hydrology,  or temperature. The permit also clarifies that monitoring is only required for
pollutants for which  a standard analytical method exists as defined in 40 CFR Part 136.  In addition,
certain exceptions exist that enable the permittee to be excused from sampling after the first year if it is
found either that:

Industrial Stormwater Monitoring and Sampling Guide

    •   The pollutant for which the waterbody is impaired is not detected above natural background
       levels in the discharge, and it is documented that the pollutant is not expected to be present
       above natural background discharges; or

    •   The pollutant for which the waterbody is impaired is not present and not expected to be present
       in the discharge.

Both the parameters that must be sampled and the frequency of monitoring for impairment pollutants
may be subject to State- or Indian Country land-specific requirements. Therefore, each 2008 MSGP
permittee must also consult Part 9 of the permit when determining which impaired waters sampling
requirements apply.
2.5 What Type of Storm Events Qualify for Monitoring
In addition to understanding which monitoring requirements apply and where, it is also critical to
develop an understanding of what type of discharge event you will be sampling.  Under the 2008 MSGP,
two preconditions must be met before a storm or snowmelt event is considered adequate to be
monitored (see Part 6.1.3 of the 2008 MSGP).

   •   The storm / snowmelt event must create an actual discharge from your site ("measurable storm
       event"). This storm event will vary based on numerous factors at your site, the most obvious
       being the actual size and duration of the storm event.  However, the amount of impervious
       surface at your facility will impact this as well.  If your facility is covered mostly by grass or
       another type of vegetation with only a small amount of paved surfaces or roofs, it will take a
       larger storm to create a discharge from your site than it would at a facility that is entirely paved.
       Another factor affecting whether and how frequently you have a measurable storm event will be
       how frequently rain occurs at your facility and the size  of the most recent storms. Saturated soil
       will generate a stormwater discharge more quickly than dry soil; however, VERY dry soil can also
       become compacted and become nearly impervious to rain, thereby converting precipitation to
       runoff quickly as well. You will need to pay attention to your facility's particular characteristics
       to develop an understanding of what type of rain events or snowmelt results in a discharge.

   •   At least 72 hours must have elapsed since the previous measurable storm event (unless you are
       able to document that less than a 72-hour interval is representative for local storm events during
       the sampling period, or if you are monitoring snowmelt consistent with Part 4.2.1 [quarterly
       visual assessments] or Part 6.2.1 [benchmark monitoring] of the 2008 MSGP).

In order to properly characterize rain events at your facility, it is a good idea to begin by documenting
each event as part of your facility's routine maintenance activities. You can purchase a simple rain
gauge and keep a notebook handy in order to document the dates on which rain occurred and the
amount of rain that fell. You should also consider documenting whether or not an  actual discharge from
your facility occurred for each rain event.  Tracking rainfall amounts and discharge  information will help
you to better predict which storm events will be measureable and result in a discharge.

In order to be prepared to take advantage of storms that will result in a "measurable storm event":

   •    Be familiar with local precipitation trends, storm patterns, and seasonal variations.

Industrial Stormwater Monitoring and Sampling Guide
    •   Check weather forecasts so you can prepare to sample upcoming precipitation events.

    •   In addition to your local television news and the Weather Channel, you can get weather
       information online from http://www.wrh.noaa.gov (National Weather Service) and

Note:  You should try to collect both benchmark samples and visual monitoring samples concurrently so you can
compare visual observations with the laboratory results, and reduce your field activities burden.

What To Do If You Are Unable To Sample - EPA acknowledges there may be times you are  unable to
complete required monitoring.  The following are guidelines on how you should deal with such times.

    •   Areas with Intermittent Stormwater Runoff- If your facility experiences limited rainfall for
       extended periods of the year (i.e., in arid or semi-arid climates), or freezing conditions that often
       prevent runoff from occurring, then the quarterly monitoring events may be distributed during
       seasons when discharging does occur. If you are unable to collect four samples in  one year
       because of insufficient runoff, document this fact in your SWPPP and continue quarterly
       monitoring until you have collected four samples.

    •   Snowmelt Sampling - If you are located where appreciable snow is common, one of your
       samples must include the capture of snowmelt discharge. If, however, you experience
       prolonged subfreezing temperatures, you may only be able to acquire a sample once over two
       quarters. You will then have to complete the monitoring requirements as above.

    •   Adverse Weather Conditions - When adverse weather prevents sampling per your monitoring
       schedule, you must sample during the next qualifying storm event.  Adverse conditions are
       those that are dangerous or create inaccessibility for personnel, caused by such things as
       flooding, high winds, electrical storms or situations that otherwise make sampling  impractical
       (e.g., drought or extended frozen conditions).

2.6 Select the Monitoring Team

Identify the members of your facility's pollution prevention team (which you identified in your SWPPP)
who will collect samples and conduct visual assessments of discharges. To be considered as a member
of the monitoring team, applicable staff must be familiar
with the SWPPP, especially the site plan, the layout of the
facility, potential pollutant sources, and the monitoring
and reporting program. They also need to possess the
knowledge and skills to assess conditions and activities
Ideally, the pollution prevention
team consists of at least one
individual from each shift so that
a team member is always
present during normal operating
that could impact Stormwater quality at your facility, and
be able to evaluate the effectiveness of control measures.
Typically, monitoring staff are based near the site to enable them to be available on short notice to
sample storm events.

It is also important that monitoring staff understand and follow all quality assurance quality control
(QAQC) techniques and procedures to ensure that the data is good.  You should discuss these
techniques with your laboratory prior to taking samples and properly train all sampling staff.

Industrial Stormwater Monitoring and Sampling Guide
2.7 Select a Laboratory to Analyze the Samples

Your stormwater samples will need to be analyzed for the parameters you identified in section 2.3 by a
qualified laboratory. Labs must use the approved methodologies found at 40 CFR Part 136 and return a
report with chemical concentrations including data quality assurance information.

EPA recommends that you select a laboratory that is a participant in the EPA's Discharge Monitoring
Report - Quality Assurance (DMRQA) Program, and, if possible, be approved by the National
Environmental Laboratory Accreditation Program (NELAP).  NOTE: for ELG compliance monitoring,
participation in DMRQA is a minimum requirement.
       Things to discuss with the laboratory
       •  What type and size of bottle will be provided for each test?
       •  How full do I fill the bottle?
       •  Are there any safety concerns with materials provided by the lab?
       •  What is the best way to preserve the samples?
       •  What kind of labels will be supplied and how should I fill them out?
       •  Will the lab deliver the supplies or do I need to pick them up?
       •  What are the maximum holding times for each water quality parameter to be sampled?
       •  Will the lab provide pH paper? Samples need to be tested for pH within 15 minutes of
          collection to be valid, typically in the field.
       •  Will the lab pick up the samples from my facility or do I need to deliver them?
       •  Can you walk me through filling out the chain-of-custody forms?
       •  Is the quantitation limit for each  parameter less than the  benchmark or effluent
          limitation concentration?*
      * The quantitation limit is the minimum concentration of a parameter that the lab can accurately
      report using a particular method.

    •   A comprehensive list of NELAP-approved laboratories can be found at www.nelac-

    •   To ensure your chosen laboratory is eligible and reliable, you may want to request
       documentation showing they are certified to analyze environmental samples, and evidence they
       participate in DMRQA or other performance evaluation testing results.

You should ask the laboratory about any additional services and products they offer.  Such as:

    •   pre-labeled bottles and pre-printed chain-of-custody forms;

    •   training on sample collection, documentation and data interpretation;

    •   sampling and courier services; and

    •   complete sampling kits which include bottles, packing materials, bottle labels, coolers and chain-
       of-custody forms;  many laboratories provide free sampling kits.

Industrial Stormwater Monitoring and Sampling Guide
2.8 Document Monitoring Procedures in Your SWPPP

Ensure your monitoring procedures are correctly documented in your SWPPP (see 2008 MSGP Part The required information includes:

    •  The monitoring requirements that specifically apply to your facility.

    •  Information related to the substantially identical outfall exception, if you will use it.

    •  Your sampling procedures.

    •  Your procedures for performing quarterly visual assessments of stormwater discharges. This
       SWPPP element includes the routine facility inspections and comprehensive site inspections
       required by the 2008 MSGP (see 2008 MSGP Part 4.1 and 4.3, respectively).

Figure 1 is an example of a completed  MSGP Industrial Stormwater/Snowmelt Monitoring Summary
Form. You should fill out this form (Appendix A) with the sampling locations and monitoring
requirements that apply to your facility and include a copy in your SWPPP.

Benchmark lewis and ELGs
tr -—«

oil and

Benchmark Level


Dili ly Max



instant Min Max

&- *


Sample Summary
Outfall Identifier
t,S). OQl-A
i.a,. oot-A
t.Oj. ooi-B
e.g. ooi-B
Industry Sector (SIC)
SatfejSCCfcDF ^5 (.S^C
Srttejeter ea (sic
I/fi£iAfl rt^V
ist wn i?f rtt^rtth
1st wfe of mfliAth


Irotv (6P.A Mfthnst SOO.^1


Figure 1.  Example MSGP Industrial Stormwater/Snowmelt Monitoring Summary Form with monitoring
requirements, sampling locations and industry sectors.

Industrial Stormwater Monitoring and Sampling Guide
3.  Conduct Monitoring

This section describes sampling preparation, choosing the right storm event to monitor, how to collect
stormwater samples, how to conduct quarterly visual assessments, quality control considerations, and
how to report the results.

The information contained in this section is not specific to monitoring for the 2008 MSGP or any particular
general industrial permit.

3.1 What to Have In Place Prior to Collecting Stormwater Samples

Preparation is essential, especially if you are in a climate where measureable storm events are

    •   In-Office Preparations - Your in-office preparations should include the following:

       •   Contacting the lab well ahead of time so that you have the sample bottles before a
           measurable storm event.

       •   Paying attention to weather forecasts so that you are tracking patterns that are likely to
           result in a measurable storm event.

       •   Knowing who your monitoring personnel are and how to contact them when a measurable
           storm event is expected.

       •   Having sampling gear assembled and checked for readiness.

       •   Preparing sample bottle labels using waterproof ink with the following information (if not
           already done by the lab):

              •   Facility name and address
              •   Sample location identifier (e.g., Outfall 001)
              •   Name or initials of sampling personnel
              •   Parameter and associated analytical method (e.g., TSS, Method # 0160.2; consult
                  with your contract laboratory for analytical method numbers)
              •   Sample type (generally will be "grab" samples)
              •   Sample preservation notes
              •   Date and time after completing sampling event

       •   Having chain-of-custody forms ready for use.

The chain of custody form is a document that travels with the sample from collection through analysis. Each
individual that handles the sample will place their name, date, and time on the chain-of-custody form. The form
is used to maintain the integrity of the sample by providing documentation of the control, transfer, and analysis
of samples (see Section 3.4 below for a more detailed discussion of chain-of-custody).

Industrial Stormwater Monitoring and Sampling Guide

    •   Sampling Supplies - Collect the following supplies and keep them ready for quick use:

           o  Clean, sterilized sample bottles, sized appropriately for
                                                                    For rinsing sample bottles,
                                                                    use only distilled water
   the parameter to be analyzed (many labs provide the
   appropriate bottles or will tell you what size to get).
   Glass must be used for oil and grease samples; plastic
   containers can be used for other parameters.  Use Teflon or aluminum-lined caps.

o  If bottles are new but not pre-cleaned, they must be pre-conditioned before use by
   filling with water for several days (the duration can be reduced by using a dilute solution
   of hydrochloric acid).

o  Additional glass or clear plastic bottles suitable for visual assessments.

o  Visual monitoring forms (see example in Appendix B).

o  Clipboard and site-specific monitoring checklist.

o  If needed, a pole (sold at field supply stores) on which to attach sample bottles and
   attachment clips or strapping tape to secure the bottle to the pole.

o  Safety equipment, including first aid kit.

o  Hand sanitizer solution.

o  Carrying case for sampling equipment or backpack for carrying equipment to remote

o  Powder-free disposable nitrile or latex gloves (sold by medical and laboratory suppliers
   or may be provided by your contract laboratory). Do not use powdered gloves as they
   may contaminate your samples.

o  Indelible pens / markers that can write on wet surfaces.

o  Foul-weather gear including footwear appropriate for the conditions at your sampling
   locations (e.g., non-slip boots).

o  Sturdy cooler and ice or ice packs for stowing and preserving your samples en route to
   the lab (the lab may provide an appropriate container).

o  Field notebook or field forms for your sampling records (waterproof notebooks are
   available at office supply stores).

o  pH paper and appropriate chemical preservatives for adding to sample bottles (obtain
   from your laboratory).

Industrial Stormwater Monitoring and Sampling Guide
               Preparing sampling supplies.

       Optional or as-needed supplies:

           o  Sodium bicarbonate (for safety reasons if using acid preservative additives)

           o  A graduated stick to measure water depth for determining safe / wade-able sampling
              access locations (if a sampling pole will be used, you can modify it with depth markings)

           o  Mosquito repellent

           o  Flashlight in case of sudden loss of light or darkness under storm conditions

           o  Flagging tape for marking access to remote or overgrown locations

           o  Camera, used for:

                    •  Recording evidence of potential pollutants or sampling conditions.
                    •  Especially useful  if different people will do the sampling throughout the
                       permit term.
                    •  Pictures of sample appearance along with the visual inspection records can
                       help "normalize" visual assessments.
                    •  Pictures of the sampling  location can help you find the same spot for
                       subsequent sampling events.

Industrial Stormwater Monitoring and Sampling Guide
  Develop a stormwater sampling checklist to ensure consistency and continuity across sampling events.  Since
  stormwater sampling is not a regular part of a facility's workload, a checklist of things to have prepared
  before sampling, sampling activities, and sampling locations will help you remember from quarter to
  quarter. You can make the checklist by noting the things you did for the first sampling event to remember
  for future sampling events. Keep the checklist updated as you gain experience with sampling.
3.2 Collect Stormwater Samples

Contact the lab prior to collecting stormwater samples so they know to expect the samples and have
adequate staff available to conduct the analyses within the applicable holding times (the lab may offer
courier service).  Inform them of the pollutant parameters for which your samples will be analyzed.
              A stormwater grab sample is collected directly into the sample container.

Follow the protocol below to obtain an accurate grab or manual sample. A grab sample is a single
sample "grabbed" by filling up a container, either by hand or attached to a pole. Obtaining accurate
data is vital to your ability to assess how your stormwater control measures are performing.

    •   Wear disposable powder-free gloves for sampling; never touch the inside of the lid or bottle.
       For oil and grease: fill the glass sample bottle directly from
       the discharge; never collect in a container first and then
       transfer to the sample bottle because oily residue will collect
       along the inside of the first collection bottle and make the
       sample inaccurate.
Remember, oil and grease
must be collected directly into
the glass sample bottle.

Industrial Stormwater Monitoring and Sampling Guide
    •   If you have problems accessing the stormwater discharge point (e.g., access is too far or
       dangerous), use a pole or other appropriate sampling apparatus.

    •   Sample only stormwater discharging from your facility (i.e., do not sample from puddles, ponds
       or retention basins).

    •   Sample from a turbulent section in the central part of the flow; avoid touching the bottom or
       sides of the stormwater conveyance.

    •   Fill the sample bottle nearly to the top (meniscus almost at the rim) by holding the opening into
       the flow of water; do not rinse or overfill the bottles.
           Sample bottles labeled with location, date, time, sample collector, analysis, and
                                       preservative type.

While stormwater samples are typically grab samples, in some situations the use of an automatic
sampler may be appropriate. Automatic samplers are mechanical devices that monitor site conditions
and collect a sample when needed. The automatic sampler can be set up well in advance of a storm, or
set up as a permanent installation, and the technician can retrieve the sample after the storm when
conditions are favorable. Advantages of automatic samplers include low labor costs, convenience, and
safety - personnel are not out in the storm trying to collect one or more samples. The major
disadvantage is cost; automatic samplers are expensive. Secondarily, the automatic sampler cannot
collect visual observations, and they cannot be used for collection of certain measurements.

After the samples have been collected:

   •   Place the samples in a sturdy cooler partially filled with ice.  As a general rule, samples should be
       kept at approximately 39°F (4°C) until the cooler is delivered to the lab.
       Put a completed chain-of-custody form enclosed in a re-
       sealable plastic bag inside the cooler.  If you have several
pH has a 15 minute
holding time; therefore,
the sample must be
analyzed within 15
minutes of collection.

Industrial Stormwater Monitoring and Sampling Guide

       coolers complete a separate chain of custody form for each cooler.

    •   Deliver the samples to the lab (e.g. drive, arrange same-day pick-up by the lab, or use an express
       / overnight service) as soon as possible, bearing in mind the holding times for each parameter
          Stormwater samples packed for delivery to the lab, note the chain of custody forms
                                      attached to the lid.

3.3 Record Information for Each Monitoring Event

For each individual sample collected, you should note the following information:

    •   The sample / outfall identifier.

    •   The duration between the storm event you sampled and the end of the previous storm event
       that resulted in a discharge of Stormwater from your site (i.e., a "measurable storm event").

    •   The date and duration of the storm event sampled.

    •   Rainfall measurement or estimate (in inches).

    •   Estimate of the total volume of the discharge sampled from the outfall.

You should record this information on a Stormwater Collection Form (see appendix C for an example).

Industrial Stormwater Monitoring and Sampling Guide
3.4 Quality Assurance Considerations

The following actions must be followed explicitly. Quality assurance (QA) helps maintain the accuracy
and integrity / legal defensibility of your monitoring results by documenting the stewardship of your
samples, by minimizing biases in sampling and lab procedures, and by helping to assess the accuracy and
precision of the lab's analyses.

Holding Times and Sample Preservation

Samples that cannot be delivered to the lab on the same day may need to be preserved, often by
cooling to 4°C (i.e., in an ice bath) and/or with added chemical preservatives (laboratory-supplied
bottles may already include preservatives).  If your samples need to be analyzed for more than one
parameter you may need to bottle  more than one sample at an outfall using different preservatives.  In
addition, you  should be aware of the maximum holding time allowed for a particular parameter before
which the sample must be analyzed. Following is a table with typical preservation and holding
requirements for benchmark  parameters and additional potential pollutants of concern (the latter will
not have a numeric value in parentheses). Work with your laboratory service  providers to develop a list
of containers to optimize "sharing" of containers across different parameters. Not all laboratories
provide the same container types for the different parameters. Laboratories frequently provide pre-
completed custody records and seals, and will provide pre-labeled sample bottles for ease of use in the
field as part of their routine "value-added" services. Pre-completed  custody records and labels require
only time, date, and  samplers' initials in order to complete this critical documentation. Your laboratory
may also have additional sampling, sample handling, or shipping instructions helpful to your sample
collection personnel. NOTE: Whenever possible, minimize the amount of lead  time sample containers /
kits are outside of the laboratory. Extended storage of pre-preserved containers for some analytes may
present opportunity for blank contamination, even under ideal storage conditions.

                          Table  5. Sample Preservation and  Hold Times
(Benchmark Level, mg/l
or as specif led)
Aluminum, Total Recoverable
Antimony, Total Recoverable
Arsenic, Total Recoverable
Beryllium, Total Recoverable
Biological Oxygen Demand,
Cadmium, Total Recoverable
(0.0005 - 0.0053)*
Chemical Oxygen Demand,
Cool to 42 Additional
N HN03 (nitric acid) to pH<2
Y H2S04(sulfuricacid)topH<2
N HN03topH<2
N HN03topH<2
N HN03topH<2
Y None
N HN03topH<2
Y H2S04topH<2
N HN03topH<2
Holding Time
6 months
28 days
6 months
6 months
6 months
48 hours
6 months
28 days
6 months
500 ml HOPE
500 ml HOPE
500 ml HOPE
500 ml HOPE
500 ml HOPE
1L HOPE or glass
500 ml HOPE
100 ml HOPE or
500 ml HOPE

Industrial Stormwater Monitoring and Sampling Guide
(Benchmark Level, mg/l
or as specif led)
Copper, Total Recoverable
Cyanide, Total
Hardness (as CaC03)
Iron, Total Recoverable
Lead, Total Recoverable
Magnesium, Total Recoverable
Mercury, Total Recoverable
Nickel, Total Recoverable
Nitrate + Nitrite Nitrogen
Oil and Grease
Phenols, Total Recoverable
Phosphorous, Total
Radium, Total Recoverable
Radium, dissolved
Selenium, Total Recoverable
Silver, Total Recoverable
Total Suspended Solids, TSS
(50 NTU)
Zinc, Total Recoverable
Cool to 42 Additional
N HN03topH<2
Y NaOH (sodium hydroxide) to
pH >12, refrigerate in dark
HN03 or H2S04to pH <2
(method dependent)
N HN03topH<2
N HN03topH<2
N HN03topH<2
N HN03topH<2
N HN03topH<2
Y H2S04topH<2
Y HCIorH2S04to pH<2
N None
Y H2S04topH<2
Y H2S04topH<2
Field-filtered HN03 to pH <2; if
not field filtered - none
N HN03topH<2
N HN03topH<2
Y None
Y store in the dark
N HN03topH<2
Holding Time
6 months
14 days; 24 hours if
sulfide present
28 days
6 months
6 months
6 months
6 months
28 days
6 months
28 days
28 days
15 min (Field test)
28 days
28 days
6 months
Field filtered,
preserved 6months;
if not field filtered,
filter on receipt,
preserve to pH <2 6
6 months
6 months
7 days
6 months
6 months
500 ml HOPE
100 ml HOPE
100 ml HOPE
500 ml HOPE
500 ml HOPE
500 ml HOPE
500 ml HOPE
500 ml HOPE
200 ml HOPE
1L Boston round
50 ml
500 ml HOPE
500 ml HOPE
500 ml HOPE
500 ml HOPE
200 ml HOPE
100 ml HOPE
500ml HOPE
500 ml HOPE
Landfill Parameters
Alpha Terpineol
Benzoic Acid
7 days to extraction
40 days to analysis
7 days to extraction
40 days to analysis
7 days to extraction
40 days to analysis
7 days to extraction
1L Amber glass
1L Amber glass
1L Amber glass
1L Amber glass

Industrial Stormwater Monitoring and Sampling Guide
(Benchmark Level, mg/l
or as specif led)

Cool to 42 Additional


Holding Time
40 days to analysis
7 days to extraction
40 days to analysis
7 days to extraction
40 days to analysis


1L Amber glass
1L Amber glass
*These values are hardness dependent.

Field Blanks

Field blanks are distilled or de-ionized water samples prepared when you are collecting stormwater
samples. Field blanks are prepared, in the field, after cleaning the sampling equipment but before
collection of water quality samples. Blanks are prepared by pouring distilled de-ionized water into each
scoop, dipper, etc. used for sample collection and then into sample bottles as if they were actual field
samples. The field blanks are processed and analyzed in an identical manner as the stormwater
samples. If the lab detects any contamination in the blanks, your sampling results could be considered
tainted (either from contamination or errors in sampling or analysis). Collection and analysis of field
blanks is not required by the 2008 MSGP; however, field blanks are used for quality control to assess
whether contamination was introduced during sampling, and may prove useful in interpretation of

Chain of Custody Forms and Procedures

Samples must be traceable from the point of collection until the sampling results are reported. To do
this, document who is in possession of the samples using the chain of custody procedures below. One
person should be responsible for the care and custody of the samples, and for generating the chain of
custody record until the samples are properly transferred or relinquished to the laboratory. Chain of
custody tasks include:

    •    Ensure that the sample labels are properly filled in.
    •    Complete the chain of custody form with the date, time, parameter and sample locations for
        each sample, and sign the form.
    •    During the transfer of custody of the samples, both the persons relinquishing and receiving the
        cooler (including lab personnel) must record the date and time on the chain of custody form and
        sign it.
    •    Record the shipping method, courier name(s), and other pertinent information as remarks on
        the chain of custody form.
    •    The original chain of custody form remains with the samples and a copy must be provided to the
        facility for inclusion in project records.

Chain of custody records are critical to ensure that no tampering occurs between sample collection and
analysis. Your analytical service provider may provide training or written instructions to assist in your
completion of accurate custody records. This is another key area where many laboratories invite the
opportunity to work with their clients as part of their value-added services.

Industrial Stormwater Monitoring and Sampling Guide
3.5 Conducting Visual Assessments of Stormwater Discharges
All facilities covered by the 2008 MSGP must perform quarterly visual assessments, irrespective of benchmark

Visually inspecting Stormwater samples from a measurable discharge at your sampling outfalls is an
inexpensive way of assessing the performance of your control measures. The sample should be
collected and analyzed in a colorless glass or plastic bottle. It is recommended that you take
photographs of the discharges at the time of observation in case more than one person is doing the
assessments and because photos can be helpful in determining the effectiveness of your control
measures and any need to make changes to control measures.

Assess the general appearance, as an indicator of contaminants, of your discharges for these

    •   Color- If the discharge has an unusual color, such as  reddish, brown, or yellow hue, this may
       indicate pollutants or suspended sediment.

    •   Odor- If the discharge has a noticeable odor, for instance if it smells like gasoline fumes, rotten
       eggs, raw sewage, or solvents odor, or has a sour smell, this could be indicative of pollutants in
       the discharge.

    •   Clarity- If the discharge is not clear, but is instead cloudy or opaque, this could indicate
       elevated levels of pollutants in the discharge.

    •   Floating solids - If you observe materials floating at or near the top of the bottle, take note of
       what the materials appear to be.

    •   Settled solids - You should wait about a half hour after collection, then note the type and size of
       materials that are settled at the bottom of the bottle.

    •   Suspended solids - Particles suspended in the water will affect its clarity,  and color and could be
       attributable to pollutant sources at your facility.

    •   Oil sheen -You  should check the surface of the water for a rainbow color or sheen; this would
       indicate the presence of oil or other hydrocarbons in  the discharge.

    •   Foam - You should gently shake the bottle and note  whether there is any foam.

    •   Other obvious indicators of Stormwater pollution.

To record your visual monitoring results you can use the optional "Quarterly Visual Monitoring Form" in
Appendix B (or a comparable one of your own).

Industrial Stormwater Monitoring and Sampling Guide
4.   Evaluate Monitoring Results

The primary purpose of any industrial stormwater monitoring program, consisting of analytic chemical
monitoring and visual assessments, is to provide feedback on the performance of your selection and
implementation of control measures. 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 provides an
indicator that modifications or additions to the site's control measures need to be considered to
improve the effectiveness of your stormwater program.

The following will aid you in interpreting your monitoring results and revising your control measures, if

4.1 Evaluating Quarterly Visual Assessment Results

For anything but colorless and odorless stormwater in your discharge, you should investigate what area
of your site or what specific pollutant sources are contributing to the contamination of your  site's
runoff. To search for the source of pollutants, you should move upstream from the discharge point. You
should scrutinize your exposed industrial materials and activities (material handling equipment,
industrial machinery, raw materials, finished product, wastes, or products that are stored, used or
created onsite, etc.). Examine where material
handling activities occur, such as: storage,
loading and unloading, and material
transporting.  Be aware, the source could be
from an ongoing activity or the result of a spill or
other infrequent occurrence.  In looking at your
samples, consider the following:

    •  When there is a distinct color or odor,
       are the abnormalities associated with
       any raw materials, chemicals or other
       materials used at the site?

    •  Muddiness or sediment may have been
       picked up from areas where there is disturbed earth or other unpaved areas lacking  adequate
       control measures.

    •  Foam or oil sheen may be the result of a leak or spill of materials.

    •  Cloudiness indicates suspended solids such as dust, ash, powdered chemicals, and ground up
       materials. Determine whether you use any of these materials and whether they are exposed to

Clean up all sources of potential contamination, make changes to your control measures, and update
your SWPPP, as  necessary.

 Industrial Stormwater Monitoring and Sampling Guide

 4.2 Evaluating Benchmark Monitoring Results

 The analysis of your benchmark monitoring results can yield valuable information about the
 characteristics of your runoff and how well your control measures are working.  Once you have received
 your lab results for your benchmark samples, compare these concentrations to the benchmark values
 that apply to your facility. The 2008 MSGP requires that you conduct four benchmark samples in your
 first year, and then compare the average value to the applicable benchmark. If the average
 concentration of your samples exceeds the benchmark, then you are required under the permit to
 evaluate whether changes to your control  measures are necessary.  See Parts and 3.2.  However,
 prior to the completion of the four samples,  if one or more sample results makes an exceedance of the
 benchmark mathematically certain, you are required to conduct this evaluation  without waiting for the
 results of the remaining benchmark samples.

 Table 6 will help you decide a course of action depending on the results of your  benchmark samples.

	Table 6. Evaluation of Benchmark Monitoring Results	
      Does the average of your four quarterly benchmark samples for any pollutant exceed the applicable
                                   benchmark concentration? OR
  If you have not vet completed your four quarterly benchmark samples, does the total value of your samples
  already make an exceedance of the benchmark mathematically certain  (e.g.. the sum of the concentration of
                   your samples exceeds four times (4X) the benchmark concentration)?
 You must evaluate whether modifications to the
 stormwater control measures used at your site are
 necessary. You will need to consider whether there is a
 problem in the selection, design, installation, and/or
 operation of applicable control measures.  Follow the
 evaluation and corrective action process in Parts 3.2,
 3.3, and 3.4.

 An exceedance of a benchmark does not necessarily
 mean that your control measures are insufficient.
 Continue reading below for additional items to consider
 as you proceed.
Sample results below benchmark limits provide an
indication that your control measures are working as
intended to minimize the discharge of pollutants.

Although your samples indicate properly functioning
control measures, you should continue to note
changes to your site that may affect the quality of
stormwater runoff, and to link such changes to your
future monitoring results.

You are still required to meet all requirements in the
permit affecting the implementation and
maintenance of your control measures, despite the
good results of your benchmark monitoring.
 If benchmarks were exceeded:
        Did you sample correctly?
            Did you start with clean sample collection jars and were the samples preserved and
            submitted to the lab within the allotted time frame?
            Did you properly sample the discharge flowing from the site or did you collect the sample
            from a low spot or stagnant pool?

Industrial Stormwater Monitoring and Sampling Guide
       Was anything atypical going on at the site prior to or during the storm? Atypical activities could

       •   A leak or spill that was not adequately cleaned up.
       •   Construction, painting and paving activities.
       •   Having a large amount of material (raw materials, wastes or products) recently delivered or
           being prepared for shipment.

       Did you observe anything during visual inspections that may have indicated that stormwater
       runoff would have been exposed to pollutants? If so, are control measures in place to address
       the pollutant sources?
The more the benchmark was exceeded, the greater your facility's problems may be, necessitating a
more robust response. For example, if your results for TSS were over the benchmark value by a
relatively small amount (e.g., TSS values of 110 to 150 mg/L, compared to the 100 mg/l benchmark level
assigned to TSS), then simply performing additional housekeeping measures (e.g., frequent sweeping)
may reduce the values below the benchmark of 100 mg/l by the next storm. However, an exceedance
above 150 mg/l may warrant new or supplementary control measures (assuming your control measures
are performing as designed) that more effectively reduce the potential for sediment in discharges (e.g.,
installing storm inlet filters, seeding / stabilizing disturbed areas, implementing dust and debris
controlling procedures). TSS values exceeding benchmarks by orders of magnitude  indicate a serious
problem, and may require structural control measures (e.g., paving, installing berms around piles of
loose material, placing operations under cover, placing grassy swales or basins in the discharge flow
path to trap sediment).

Until your visual observations and sampling results show that pollutants are not found in your
discharges or are present in concentrations below benchmark values, the pollution prevention team
should engage in an iterative process in which control measures are selected, implemented, evaluated
and modified until determined to be completely effective.

Industrial Stormwater Monitoring and Sampling Guide
There may be circumstances where benchmark values cannot be reasonably achieved because of local natural
background concentrations (see 2008 MSGP Part In such cases, EPA allows for benchmark exceedances.
For example, high natural background levels of iron in soils or groundwater could cause exceedances of a
benchmark value. This provision exempts facilities from further control measure evaluation and benchmark
monitoring when natural background levels are solely responsible for the exceedance of a benchmark value.

To make this determination, natural background pollutant concentrations must be greater than the
corresponding benchmark value, and there is no net facility contribution of the pollutant (i.e., average
concentration detected in runoff from all monitored outfalls over four separate events minus the average
natural concentration of the parameter for four separate events does not exceed zero).

For example, if the natural background concentration of TSS from an undisturbed watershed is 200 mg/L, an
exemption from further benchmark monitoring / control measure evaluation is available if the average of your
four benchmark samples  is equal to or lower than 200 mg/L. There are additional requisites for claiming a
natural background level exemption, including documentation. Details of these are contained in the 2008 MSGP
in Part and the Fact Sheet.

4.3 Effluent Limitation Guideline Monitoring Results

What happens if your facility is subject to numeric effluent limits (for ELG compliance monitoring) and
your stormwater sample exceeds the  effluent limits for one or more parameters? Within 24 hours of
receiving the lab report you must prepare a corrective action report, including:

    •   Identification of the condition triggering the need for corrective action review;
    •   Description of the problem identified; and
    •   Date the problem was identified.

Within 14 days of receiving the lab report, you must document the following information:

    •   Summary of corrective action(s) taken or to be taken;
    •   Notice of whether any modifications to your control measures and any related changes to your
        SWPPP are necessary as a  result of this discovery or corrective action;
    •   Date corrective action initiated; and
    •   Date corrective action completed or expected to be completed.

You must submit these  reports with your annual  report and retain a copy onsite with your SWPPP

The 2008 MSGP requires that you conduct follow-up monitoring within 30 calendar days of
implementing corrective actions (or during the next qualifying runoff event, should none occur within 30
days, see Part 3 of the 2008 MSGP). Monitoring must be performed for any  pollutant(s) that exceeded
the effluent limit. If the results from the follow-up monitoring exceed the effluent limit(s), you are
required to submit an Exceedance Report to EPA no later than 30 after receipt of your lab results. The
exceedance report must include:

    •   NPDES permit tracking number;
    •   Facility name, physical address, and location;
    •   Name of receiving water;
    •   Monitoring data from this  and the preceding monitoring event(s)

Industrial Stormwater Monitoring and Sampling Guide
    •   An explanation of the situation; what you have done and intend to do (should your corrective
       actions not yet be complete) to correct the violation; and
    •   An appropriate contact name and phone number.

In addition to preparing the Exceedance Report, you must continue to monitor, at least quarterly, until
your stormwater discharge is in compliance with the effluent limits or until EPA waives the requirement
for additional monitoring.

4.4 Specific Pollutants and Control Measure Options

All facilities need to gear their control measures toward their specific pollutants of concern, as
determined by the materials and activities onsite.  Below is a brief discussion of some of the most
common pollutants and control measure options.
       Total Suspended Solids (TSS).
       Small sediment particles are
       easily suspended and carried by
       surface water flows. These
       particles may be blown onto the
       site from unpaved areas within
       or adjacent to your facility as
       well as being tracked in  on the
       tires of vehicles.  Excess
       particles may be self-generated,
       particularly in the concrete,
       asphalt, scrap recycling,
       automobile salvage, and mining
       sectors.  See the discussion
       above for control measure
       options for controlling TSS.
       Oil and Grease. Often, oil and grease may be observed as a film, sheen or discoloration on the
       top of a discharge or receiving water. But such a surface anomaly may not be obvious, in which
       case detection by a lab would be the only way. This could be a pollutant of concern for any
       facility, especially if there are exposed vehicles or equipment. Therefore, it is vital that due
       diligence regarding "reportable quantity" (RQ) spills or leaks be observed.  Basically, an RQfor oil
       is any quantity of oil that causes a film, sheen or discoloration on a receiving water surface (and
       for which there are separate reporting requirements to regulatory agencies). If detected you
       must find the source and mitigate it. Start with the vehicle / equipment maintenance and
       storage areas or where shipping / receiving and the like are done.  Above ground storage tanks
       and waste storage are other likely sources.

       Available control measures range from regularly monitoring these areas and applying an
       absorbent material (choose a bio-based absorbent like Nature's Broom, not a clay-based
       material) as soon as an oil  leak or spill is observed. Consider coverage of and secondary
       containment for storage areas where oil  or grease are stored, transferred or disposed of. An oil
       water separator downstream of the area(s) most likely to contain oil or grease could provide
       enough treatment to reduce oil and grease to  acceptable levels in the discharge.

Industrial Stormwater Monitoring and Sampling Guide
       pH. pH values below benchmark range
       indicate that acidic substances are
       exposed to stormwater. In this case you
       need to determine whether any of your
       industrial processes use acids and if so,
       where. Does your facility do plating, or
       are lead-acid batteries used or stored
       on-site? If acids are being used to clean
       parts, for example, where are the parts
       stored after being treated with the acid?
       Where are waste acids stored and how
       are they disposed? Which operations
       could expose acids to  stormwater?  Coal
       piles are also a source of acidified
       High pH values indicate that a base or alkaline material (such as lye) is exposed to stormwater.
       Cement and some cleansers can produce high pH values.

       Control measures applicable to controlling pH include housekeeping (sweeping and cleaning
       areas where materials that affect pH could be exposed to stormwater); overhead coverage and
       disposal of waste materials in covered receptacles. Low or high pH runoff can be collected and
       neutralized by adding an appropriate agent to neutralize pH values to the 6.0 - 9.0 range.
       Alternatively,  flow can be directed to come in contact with a neutralizing substance (e.g., acidic
       coal pile runoff directed to flow through a limestone channel).

       Chemical Oxygen Demand (COD). COD is the amount of dissolved oxygen in water consumed by
       the chemical breakdown of organic and inorganic matter (i.e., COD is not a specific component in
       the discharge). Therefore, a high COD value indicates elevated quantities of pollutants in runoff,
       especially carbon.  Examples of facilities that handle materials which could cause high COD levels
       include the wood and paper product industries. Control measures applicable to controlling COD
       levels are the  basic stormwater ones: good housekeeping  and covering materials with the
       potential to allow carbon or other organic materials to be carried by stormwater.

       Metals. Metals originate from many sources and consequently a number of industries must
       monitor for metals, including facilities such as wood preservative and agricultural chemical
       makers, mines, and foundries.  Depending on a facility's activities, metals can be found in a
       dissolved form and/or adsorbed to particles or sediment.  It is because both the dissolved and
       particulate forms can occur at the same time is why stormwater discharges are analyzed for
       "total recoverable metals." After identifying those operations that could expose stormwater to
       metals  sources, implement control measures capable of reducing metals concentrations,
       including good housekeeping (sweeping and disposing of metal wastes in covered containers),
       covering / shielding operations, and directing run-on away from any critical outdoor areas.  Ion
       exchange techniques can also be employed to remove dissolved metals.

Industrial Stormwater Monitoring and Sampling Guide
5.   Record-Keeping and  Reporting

It is important that accurate record-keeping of monitoring activities become a standard operating
procedure at your facility.  You need to be able to show that monitoring and sampling events not only
meet all permit requirements, but are defensible and abide by all QA/QC procedures. It is always
preferable to document too much as opposed to too little when dealing with any sort of permit
compliance.  Create easy to use log  books for keeping track of rain events.  Be sure that your site map is
up to date and easy to understand.  Develop simple instruction sheets for recording sampling, visual
assessments, or other monitoring activities. The instructions should be kept in logical locations (e.g. in
sample kits, in the SWPPP notebook) and updated as needed.

When possible, use standardized forms such as those provided  in the appendices of this monitoring
guide to record your monitoring activities. This will provide consistency in information reported.
Example forms are provided in this guide in Appendix A (2008 MSGP Industrial Stormwater Monitoring
Form), Appendix B (2008 MSGP Visual Monitoring Form), and Appendix C (2008 MSGP Industrial
Stormwater Collection Form).

If possible, regularly transfer sampling records and sample results into databases or spreadsheets.  This
will provide back-up records for hard-copy logs or forms as well as providing an easy way to analyze your
sampling data.

5.1 Reporting Monitoring Data

Each state industrial Stormwater permit has different requirements for how monitoring data should be
reported. Facilities subject to EPA's  2008 MSGP must submit to EPA all monitoring data collected no
later than 30 days after receiving complete lab results for all monitored outfalls. You must submit even if
your facility is reporting "no discharge" or a change in status from "active and staffed" to "inactive  and

Facilities must use the online eNOI system (www.epa.gov/npdes/eNOI) to report results. EPA's
Electronic Notice of Intent (eNOI) system is an online electronic permit application  system that enables
Stormwater entities to submit NOI forms to EPA. eNOI  also allows registered eNOI users to report
discharge monitoring data and submit annual reports and other reporting information to EPA.

If you cannot access eNOI, the paper MSGP Discharge Monitoring Report (MDMR) reporting form
(available at www.epa.gov/npdes/stormwater/msgp) can be submitted to the appropriate address
identified in the 2008 MSGP (Part 7.6.1).

Even if you submit monitoring data  via eNOI, the paper MDMR form can help ensure you have the
information you need to complete all the required fields. Rather than go line by line through the MDMR,
which the instructions do, this Guide will highlight the information needed to fill out the MDMR.

You will need the following information to submit monitoring data via eNOI and complete the MDMR, at
a minimum:

    1.  Permit tracking number
    2.  The facility SWPPP

Industrial Stormwater Monitoring and Sampling Guide
    3.  Monitoring records
    4.  Lab reports
    5.  Corrective actions

Permit Tracking Number - The permit tracking number is a unique identifier assigned to your facility by
EPA. EPA tracks report submittals using the Permit Tracking Number rather than facility name or
address. Thus, if you do not include the Permit Tracking Number you may not get credit for submitting

Facility SWPPP- The facility SWPPP includes several pieces of information needed for the MDMR,

    •   The number of stormwater outfalls.
    •   Which, if any, of the outfalls discharge substantially identical effluents.
    •   Alternative monitoring periods, if the facility is located in an area of irregular stormwater runoff.

Monitoring Records - Detailed monitoring records will make completing the MDMR easier.  As
previously discussed, monitoring records must include:

    •   The date(s) of all monitoring events during the MDMR reporting period.
    •   Any stormwater outfalls that did not have a discharge during the MDMR reporting period.
    •   Whether the discharge resulted from rainfall or snowmelt.
    •   The duration of the storm event.
    •   The number of inches of rainfall from the monitored storm event(s).
    •   The number of days since the previous measurable storm event, which may or may not be the
       previous monitored measurable storm event.

Lab Reports-The lab will provide a detailed report with the results of your stormwater analyses and
detailed QA/QC data to verify that the results are accurate. For each parameter the lab will typically
report one of three results to be reported on the MDMR.

    1.  The measured concentration to be compared against the benchmark or effluent limitation
    2.  BQL or below quantitation limit means that the parameter is present at some amount greater
       than zero but less than the quantitation limit but the method used is not precise enough to give
       an exact concentration. Report BQL and the numeric quantitation limit on the MDMR.
    3.  ND or not detected means that the parameter was not detected in the sample. Report ND and
       the detection limit on the MDMR.  Note that the ND level is typically three to five times less than
       the quantitation limit.

Other lab reports you may need include receiving water hardness results if any of your required
parameters are hardness dependent, and data on natural background pollutant levels if you are claiming
that an exceedance of a benchmark limit is due to natural background conditions.

Corrective Actions - The 2008 MSGP requires you to implement corrective actions if the lab report
indicates an exceedance of one or more numeric effluent limits or if the average of four quarterly
samples exceeds the applicable benchmark. You must document discovery of effluent limit(s) or

Industrial Stormwater Monitoring and Sampling Guide

benchmark concentration(s) exceedances within 24 hours of receiving the lab report, including the
condition triggering the need for corrective action review; a description of the problem; and the date
the problem was identified. Within 14-days of receiving the lab report you must summarize the
corrective action that was taken or will be taken, including a description of the corrective action; start
and end dates; and whether the SWPPP will be modified.  You can submit the corrective action report(s)
via eNOI or along with the paper MDMR form.

6.  Train  Personnel

You must train your stormwater pollution prevention team in the proper procedures for sample
collection, visual assessments, tracking and reporting. Trainings should be  held regularly to update staff
on any permit or SWPPP changes.  New employees that become members  of the stormwater pollution
prevention team should be trained in general stormwater awareness as well as the following
monitoring-specific topics:

    •   How to anticipate a measurable storm event.
    •   Where to monitor.
    •   How to collect and document the collection of stormwater samples including the assembling of
       "field blank" samples.
    •   How to perform and document visual assessments.
    •   How to handle and send the samples to the lab.
    •   How to interpret the results.
    •   How to keep accurate and complete records and report appropriate information to the
       permitting authority.

7.  References

APHA (American Public Health Association). 1998. Standard Methods for the Examination of Water and
       Wastewater, 20th Edition. American Public Health Association, 20th Edition.

Ecology. 2002. How To Do Stormwater Sampling: A Guide for Industrial Facilities. Publication #02-10-
       071. State of Washington Department of Ecology, Olympia, Washington.

"EPA Administered Permit Programs: The National Pollutant Discharge Elimination System." Code of
       Federal Regulations Title 40, Pt. 122.

"Guidelines Establishing Test Procedures for the Analysis of Pollutants." Code of Federal Regulations
       Title 40, Pt. 136.

USEPA (U.S. Environmental Protection Agency). 1992. NPDES Storm Water Sampling Guidance
       Document. EPA 833-8-92-001. U.S. Environmental Protection Agency, Office of Water,
       Washington D.C.

USEPA (U.S. Environmental Protection Agency). 2008. NPDES Multi-Sector General Permit for
       Stormwater Discharges Associated with Industrial Activity (MSGP). U.S. Environmental
       Protection Agency, Washington D.C.

Industrial Stormwater Monitoring and Sampling Guide

Appendix A - 2008 MSGP Industrial Stormwater Monitoring

                         MSGP Industrial Stormwater/Snowmelt Monitoring Summary Form
Name of Facility:
Permit Tracking Number:
Benchmark Levels and ELGs
Industry _ .. ^ ^
Sector Pollutant

Benchmark Level

Daily Max


Instant Min/Max

Sample Summary
Outfall Identifier

Industry Sector




Pollutants to sample (Method)

MSGP Sample Collection Form

Industrial Stormwater Monitoring and Sampling Guide

Appendix B - 2008 MSGP Visual Monitoring Form

                     MSGP  Quarterly Visual  Assessment Form
                                 (Complete a separate form for each outfall you assess)
Name of Facility: Perm
Street Address: City:
Outfall Number:
"Substantially Identical Outfall"? u No
it No.:
(State: |ZipCode:
u Yes (identify substantially identical
Substitute Sample?: u No u Yes (identify quarter/year when sample was originally
scheduled to be collected):
Person(s)/Title(s) collecting sample:
Person(s)/Title(s) examining sample:
Date & Time Storm or Snowmelt
Date & Time Sample Collected:

Date & Time Sample Examined:

Nature of Discharge: u Rainfall u Snowmelt
Rainfall Amount: inches
Previous Storm Ended > 72 hours Before Start of This Storm? u Yes u No* (explain):
Floating Solids
Settled Solids**
Suspended Solids
Oil Sheen
Foam (gently shake sample)
Other Obvious Indicators of
Storm Water Pollution
u None u Other (describe):
u None u Musty u Sewage u Sulfur u Sour u Petroleum/Gas
u Solvents u Other (describe):
u Clear u Slightly Cloudy u Cloudy
u Opaque u Other (describe):
u No u Yes (describe):
u No u Yes (describe):
u No u Yes (describe):
u None u Flecks u Globs u Sheen u Slick u Other (describe):
u No u Yes (describe):
u No u Yes (describe):

* The 72-hour interval can be waived when the previous storm did not yield a measurable discharge or if you are able to document (attach
applicable documentation) that less than a 72-hour interval is representative of local storm events during the sampling period.
** Observe for settled solids after allowing the sample to sit for approximately one-half hour.

Sampling not performed due to adverse conditions: D No   D Yes (explain):	
Sampling not performed due to no measurable storm event occurring that resulted in a discharge during the monitoring quarter:
D No   D Yes (explain):  	

Detail any concerns, additional comments, descriptions of pictures taken, and any corrective actions taken below
(attach additional sheets as necessary).
Certification by Facility Responsible Official (Refer to MSGP Subpart 11 Appendix B for Signatory Requirements)

I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a
system designed to assure that qualified personnel properly gathered and evaluated the information submitted. Based on my inquiry of the
person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted
is, to the best of my knowledge and belief, true, accurate, and complete. I am aware  that there are significant penalties for submitting false
information, including the possibility of fine and imprisonment for knowing violations.
A. Name
B.  Title
C. Signature_
D. Date Signed_

Industrial Stormwater Monitoring and Sampling Guide

Appendix C - 2008 MSGP Industrial Stormwater Collection

                                              MSGP Industrial Stormwater/Snowmelt Discharge Collection Form
Name of Facility:
Person(s)/Title(s) collecting sample:
Permit Tracking Number:
Outfall Numbers/Sample Locations:
Discharge Information
Nature of
Discharge (circle one): Rainfall or Snowmelt
Rainfall Amount (inches):
Date of Discharge Sampling:
Date & Time Storm Began:
Date & Time Storm Ended:
Date & Time of Previous Measurable Storm Event:


Sampled by:
Received by:
Sample Identification/Outfall


Preservative (Y/N)

Number of Containers

Relinquished by:
Received by:
Type of Analyses Required


Sample Collection Information
Date & Time Sample Collection Began:
Date & Time Sample Collection Ended (if different):

Shaded area for laboratory use only

Received by:
Received by:
Laboratory Log Number

The 72-hour interval can be waived when the previous storm did not yield a measurable discharge or if you are able to document (attach applicable documentation) that less than a 72-hour interval is representative of
local storm events during the sampling period.
Detail any concerns, additional comments, descriptions of pictures taken, and any corrective actions below (attach additional sheets as necessary).
Certification by Facility Responsible Official (Refer to MSGP Subpart 11 Appendix B for Signatory Requirements)
I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gathered and
evaluated the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the
best of my knowledge and belief, true, accurate, and complete.  I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations.
A. Name
                                                                                              B. Title
C. Signature_
C. Date Signed_
     MSGP Sample Collection Form