How To Do Stormwater SamplingA guide for industrial facilities

Washington StateDepartment of Ecology

December 2002 (rev. 1/05)

Publication #02-10-071

The Department of Ecology is anequal opportunity agency and does notdiscriminate on the basis of race, creed,color, disability, age, religion, nationalorigin, sex, marital status, disabledveteran's status, Vietnam Era veteran'sstatus, or sexual orientation.

If you have special accommodationneeds or require this document inan alternative format, please callMelinda Wilson at (360) 407-6401.The TTY number is 7-1-1 or1-800-833-6388. Email may be sent tomewi461@ecy.wa.gov

Table of Contents

Introduction

Advance Planning for Stormwater Sampling . . . . . . . . . . . . . . page 1

Deciding What To Sample . . . . . . . . . . . . . . . . . . . . . . . . . . . page 1

Selecting a Laboratory to Test Your Sample . . . . . . . . . . . . . . . . . page 1

Contacting the Lab in Advance . . . . . . . . . . . . . . . . . . . . . . . . page 1

Deciding How You Will Take The Sample . . . . . . . . . . . . . . . . . page 3

Collecting Oil and Grease Samples. . . . . . . . . . . . . . . . . . . . . . page 3

Determining which Discharges to Sample . . . . . . . . . . . . . . . . . page 4

Selecting Sampling Points . . . . . . . . . . . . . . . . . . . . . . . . . . . page 5

Obtaining Supplies for Sampling. . . . . . . . . . . . . . . . . . . . . . . page 6

Planning Just Prior to Stormwater Sampling . . . . . . . . . . . . . page 7

Being Prepared. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 7

Choosing the Storm Event . . . . . . . . . . . . . . . . . . . . . . . . . . . page 7

Conducting Sampling at Your Facility . . . . . . . . . . . . . . . . . . page 9

Checklist for Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 9

How to Fill Sample Bottles. . . . . . . . . . . . . . . . . . . . . . . . . . . page 9

Keeping Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 10

Determining if the Sampled Storm EventMet the Recommended Criteria . . . . . . . . . . . . . . . . . . . . . . . page 11

When the Sampled Storm Doesn’t Meet the Recommended Criteria . page 12

Special Sampling Considerations . . . . . . . . . . . . . . . . . . . . page 13

Sampling as Stormwater Discharges from a Pipe . . . . . . . . . . . . . page 13

Sampling from a Manhole . . . . . . . . . . . . . . . . . . . . . . . . . . page 13

Sampling from a Drainage Ditch or Swale . . . . . . . . . . . . . . . . . page 14

Sampling Sheet Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 14

Sampling from a Stormwater Detention Pond or other BMP . . . . . . page 15

Ecology Wants to Hear from You . . . . . . . . . . . . . . . . . . . . . . page 15

Appendix - Proper and Improper Methods of Sampling . . . . . . page 16

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 18

Introduction

The Industrial Stormwater General Per-mit requires that your facility con-

duct at least quarterly visualmonitoring and sampling of storm-water and report the sampling resultsto Ecology. These requirements are out-lined in the permit under Section S4.MONITORING REQUIREMENTS. Thisguide supports the sampling portion ofthe general permit but does not substi-tute for it.

The purpose of this guide is tohelp those who operate facilities dotheir own sampling by more fully de-scribing the steps and procedures tobe followed. This guidance will leadyou to be able to sample in a way thatwill provide you and Ecology withmeaningful results.

Sources of pollutants that may en-ter surface water, sediments, orground water can be identified bysampling stormwater discharges. Theresults of sampling will be helpfulwhen developing your Stormwater

Pollution Prevention Plan (SWPPP),determining if your existing plan isadequate, and when implementing orassessing Best Management Practices(BMPs).

Some effort is required up front toprepare for sampling in a way thatwill meet requirements and provideuseful data. What follows is a step-by-step procedure of what you needto do to gather and report data thatwill represent the quality of storm-water leaving your facility. The stepsare organized to guide you throughthe process from start to finish ofstormwater sampling.

This guidance is an update to “How todo Stormwater Sampling” which wasoriginally developed by Ecology’sEnvironmental Assessment Program in2002. The update was made in accordancewith the modified The IndustrialStormwater General Permit whichbecame effective in January 2005.

The purpose of this

guide is to help

those who operate

facilities do their

own sampling.

Advance Planning forStormwater Sampling

Deciding WhatTo SampleBefore beginning your sampling,you’ll need to determine the specificpollutants (water quality parameters)you are required to sample and testfor. Ecology has listed these parame-ters on your permit cover sheet. Yourparameters are based on:

� the standard set of parameters forall facilities,

�your facility’s primary StandardIndustrial Code (SIC Code),

�whether your facility discharges toan impaired (303 (d) listed) waterbody, and

�any requirements that apply towater cleanup plans (TMDLs).

All facilities must monitor for turbid-ity, pH, zinc, and oil and grease. Oiland grease are grouped together as asingle parameter tested in the labwith a single analysis. Turbidity canbe measured directly in the field us-ing a handheld meter, or sampled andanalyzed in the lab. pH must be mea-sured in the field using either a cali-brated pH meter or pH paper. Youcan get pH paper from a distributorof scientific/laboratory supplies orthrough the same laboratory that willbe doing your sample analysis. Zinc,oil and grease and other parametersrequired by the permit (other thanturbidity and pH) are measured bysending bottled samples to a labora-tory for analysis.

Selecting a Laboratoryto Test Your SampleHaving identified the parameters youwill need tested, the next step is to se-lect a laboratory to perform the tests.You are required to select a lab ac-credited by Ecology. Accreditation as-sures Ecology that the lab is able to doquality testing using the analyticalmethods specified under MonitoringRequirements in your permit. A list oflabs can be found on Ecology’swebsite: www.ecy.wa.gov/pro-grams/eap/labs/lablist.htm.

Contacting the Labin AdvanceYou should contact the lab well aheadof time. They will be providing youwith the sampling bottles you’ll need.For some water quality parameters,such as oil and grease, it is not onlydesirable but necessary to collect thesample directly into a specially-cleaned container, so you will need tohave bottles from the lab on hand be-fore you sample. You can also askyour lab to send pH paper along withyour sample bottles.

Discuss with the lab the analyticalmethods they will use, as specified inthe sample parameter tables includedin S4. D of the general permit. The labwill provide you helpful informationand explanations that go beyond thescope of this guide. If you must meetdischarge limits listed in S3, Dis-charge Limitations, you should care-fully review them with the lab.

Advance Planning for Stormwater Sampling Page 1

All facilities must

monitor for

turbidity, pH, zinc,

and oil and grease.

Contact the lab

well ahead of time.

Issues you may want to coverwith the lab include:

The type and size of bottle that willbe supplied for each water quality pa-rameter to be sampled and tested.

How full to fill the bottle.

Any safety concerns with materialssupplied by the lab.

What you need to know about pre-serving your samples: Make a note ofthe parameters for which bottles willhave preservative inside. For sometests, a preservative is necessary. Thepreservative is a substance that stabi-lizes certain chemicals at the time ofsampling so that a valid test can bedone later. It is critical that you use thecorrect bottles because tests requiringpreservative will not be valid withoutthe correct preservative. In some cases,the wrong preservative will interferewith a test. It is important not to losethe preservative that comes in the bot-tles supplied by the lab.

The kind of labels the lab will supplyfor the bottles and how the labelsshould be filled out. The labels or tagsyou use to identify the samples youtake must be waterproof, and if youwrite on them, the writing must bewaterproof also.

A description of forms or other pa-perwork to submit to the lab with thesamples and how to fill them out.

Whether the lab will supply pH paperas well as sample bottles, tags or labelsfor the bottles, and blank forms.

How bottles and other supplies fromthe lab will be delivered to you.

The holding times for each water qual-ity parameter to be sampled and tested.A holding time is the maximum timeallowed between taking the sample anddoing the lab analysis. If you exceedholding time, the sample analysis is notacceptable.

How and when you will deliversamples to the lab. Plan with the labhow you will get the samples to themin time to begin analysis before theparameter with the shortest holdingtime reaches that holding time. Thefastest way to deliver samples to thelab may be to do so in person, but itmay be possible to ship samples(cooled in picnic coolers) and stillmeet holding times. If you deliversamples in person, you can pick upbottles and supplies for the next quar-ter at the same time.

The table (left) shows typical sam-pling information for the three waterquality parameters that must be mon-itored under the Industrial Storm-water General Permit. Theinformation you obtain from your labmay differ somewhat from this:

In many cases, the preservativeslisted above come pre-measured in thesampling bottles and there is no needto check pH. Ask your lab about this.

Sampling requirements tend to usescientific words and units of measure.Temperature is measured in degreesCelsius, “C”. Thermometers that wetypically use in the United Statesmeasure temperature in Fahrenheit,“F” and 4º C is about 39° F. But foryour purposes, “Cooling to 4º C”means putting the samples oncrushed ice or packed with blue ice in

Page 2 Advance Planning for Stormwater Sampling

ParameterBottleType

MinimumSampleRequired

HoldingTime

Preservation

Turbidity

500 mLwide-mouthedpoly

100 mL 48 hours Cool to 4º C

Total Zinc

1liter (L)bottlecleanedaccordingto protocol

500 mL 6 monthsHNO3 to pH<2

Cool to 4º C

Oil andGrease

1L glassjar

750 mL(jar ¾ full)

28 daysJar preservedin lab within24 hours ofarrival to lab.

HCl to pH<2

Cool to 4º C

Typical Sampling Information

Ask questions -

your lab can

help you.

an ice chest so they will be kept justabove freezing. Metric units are usedto measure weight, volume and dis-tance. Liquid volumes do not use“quarts” and “cups” but use mea-sures such as liters, “L” and milliliters“mL”. Chemicals use their own scien-tific notation. Nitric acid for exampleis HNO3. Be sure to have the lab ex-plain any words or expressions thatyou do not understand.

Deciding How YouWill Take The SampleSection S4.A.1 of the Industrial Storm-water General Permit states that agrab, time-proportionate, or flow pro-portionate sample may be taken. Agrab sample is a single sample“grabbed” by filling up a container, ei-ther by hand or with the container at-tached to a pole. It is the simplest typeof sample to collect and it is expectedthat most Permit holders will chooseto collect grab samples. The generalpermit recommends that grab samplesbe collected within the first hour afterstormwater discharge begins.

As we will discuss in the next sec-tion, oil and grease samples must becollected as grab samples. Some Per-mit holders may choose to better rep-resent water quality parameters otherthan oil and grease by collecting time-proportionate or flow-proportionatesamples. These samples consist of anumber of subsamples taken at inter-vals rather than a single grab sample.The general permit recommends thattime-proportionate and flow-propor-tionate samples be started within thefirst 30 minutes after discharge begins,and be taken over a two-hour period.

A time-proportionate sample is onemade up of a number of small samples(subsamples) of equal volume collectedat regular time intervals combined intoa single large sample. A flow-propor-tionate sample is one made up of anumber of subsamples where eachsubsample is collected in such a way as

to represent a given amount of storm-water discharge. Time-proportionateand flow-proportionate samples pro-vide the advantage of including a num-ber of smaller samples (subsamples) inthe sample so that the stormwater dis-charge is better represented than with agrab sample. Time-proportionate andflow proportionate samples can be col-lected either by hand or with auto-mated equipment. Collecting them byhand is somewhat difficult and collect-ing them with automated equipmentinvolves additional expenses. Addi-tionally, flow-proportionate samplingrequires some knowledge of how tomeasure fluid flow. A reference for au-tomatic stormwater sampling is thebook Automatic Stormwater SamplingMade Easy (Thrush and De Leon, 1993)published by the Water EnvironmentFederation. It can be purchased atwww.wef.org.

Collecting Oil andGrease SamplesThe general permit requires that oil andgrease samples be collected by all per-mit holders. Because of the particularway oil and grease samples must becollected, this requirement may governyour overall approach to sampling.

For some parameters other than oiland grease, it is possible to sample indifficult situations by filling a containerand transferring it to the sample bottleto be sent to the lab. Oil and greasesamples, however, must be collectedfrom the stormwater source directly.The sample cannot be transferred fromanother container because oil andgrease tends to stick to the inside sur-faces of containers. Since you mustsample directly into the oil and greasebottle (grab sample), taking grab sam-ples may be the easiest way to collectadditional samples for the other param-eters. Take samples by collecting storm-water directly from the discharge intothe bottles supplied by the lab, fillingeach bottle one after another.

Advance Planning for Stormwater Sampling Page 3

Oil and grease

samples must be

collected directly

into the bottle you

send to the lab.

Because oil and grease samplescannot be transferred between contain-ers, a sample cannot be formed fromseparate grab samples combined to-gether. If more than one oil and greasesample is desired from a sampling siteduring a storm event, additional oiland grease grab samples must be col-lected and analyzed separately.

Because oil and grease samplesmust be collected directly and notthrough the tubing of an automaticsampler, those using automatic sam-plers will still have to grab oil andgrease samples by hand.

Determining whichDischarges to SampleThe first step in selecting samplingpoints is to consider the areas drain-ing your facility. The site map in yourSWPPP should show the drainage ar-eas. Areas of particular concern arethose where raw materials or finishedproduct are exposed to rainfalland/or runoff, and areas where leak-ing fluids such as petroleum productsand hydraulic fluids have the poten-tial to enter stormwater runoff.

The next step is to determinewhere the runoff from each drainagearea is discharged from your facility.If there are separate drainage areaswith separate discharge points,stormwater sampled at one dischargesampling point may not represent thefacility’s stormwater quality overall.

Section S4.A.5 of the IndustrialStormwater General Permit describesthe requirements for selecting sam-pling points:

“Sampling must be conducted to capturestormwater with the greatest exposure tosignificant sources of pollution. Each dis-tinct point of discharge offsite must besampled and analyzed separately if activi-ties and site conditions that may pollutethe stormwater are likely to result in dis-charges that will significantly vary in theconcentration or type of pollutants. Where

pollutant types do not vary, the Permitteemay sample only the discharge point withthe highest concentration of pollutants.However, the SWPPP must include docu-mentation on how these determinationswere made and in the description of eachpoint of discharge, including the relativequantity (volume) of discharge and pollut-ants likely to be found.”

If your facility discharges stormwatercollected over areas that are used forsimilar activities and have similar siteconditions, and there is reason to be-lieve pollutant types will be similar insuch areas, a single sampling point canbe used to represent several dischargepoints. For example, if a facility hasseparate discharge points but the in-dustrial activities are similar, you cansample at just one of the dischargepoints. The site chosen must be the onewhere there is reason to believe thepollutant concentration is highest (theworst case). For example, select thedischarge that drains an area withgreater use and/or more equipmentactivity. Determining where to samplecan be approached as a logical deduc-tion, or you may want to take samplesat multiple sites and use the results todetermine sampling location. Docu-mentation of how sampling sites werechosen is required in the SWPPP, asdescribed above in the general permit.

If your facility has multiple dis-charge points from areas with differ-ent uses or activities, you need todetermine if that will result in signifi-cant differences in the type of pollut-ants that may be discharged. Forexample, if one portion of the site isused to store raw materials and dis-charges separately from another por-tion of the site where finishedproduct is stored, it may be necessaryto take separate samples. Some initialsampling and analysis may be neces-sary to make this determination. Ecol-ogy expects that most facilities will beable to choose a single sample loca-tion for their site.

Page 4 Advance Planning for Stormwater Sampling

Making a determination ofwhether a discharge is likely to havestormwater quality that differs fromother discharges and require separatesampling requires a review of the sitemap in the SWPPP with considerationto sources of pollutants in each drain-age area. This should be followed upwith an on site assessment of activi-ties, sources and quantities of pollut-ants in each drainage area. Thisinformation will help you documentyour decision as to whether two ormore drainage areas can be repre-sented by a single sample site.

Selecting Sampling Points�Pipes discharging your facility’sstormwater offsite.

�Ditches carrying your facility’sstormwater offsite.

�Manhole access to storm sewer’scarrying your facility’s stormwater, soyou can lower a sample bottleattached to a pole into the manhole.In general, manhole access on yourproperty may be simpler and saferthan access off property and morereadily verifiable as carrying onlyyour facility’s stormwater.

These three types of sampling pointsare not too difficult to access and theflow within them tends to be fastenough, with enough turbulence, to al-low you to collect well mixed, represen-tative samples. In some cases, portionsof industrial stormwater runoff leave asite as sheet flow. Specific approachesto sampling of pipes, ditches, man-holes, grated storm drains, and sheetflow will be covered in the final sectionof this guide manual.

Make sure your sampling pointswill provide for sampling only thestormwater that comes from your fa-cility. If the stormwater in a pipe(storm sewer) contains other dis-charges, move your sampling pointupstream to a point where the flow isfrom your facility only. Also check to

see that there is no base flow in thestorm sewer during dry periods. Re-port in your SWPPP the presence ofany base flow and measure or esti-mate its flow rate. If it is not possibleto sample only flow from your facil-ity, document the reason for this andprovide information concerning thesource of the flow you are sampling.

If possible, the stormwater your fa-cility samples should not be a mixtureof your facility’s stormwater withother water. Some examples of situa-tions where a sample would be of amixture of water sources, situations inwhich you should not sample:

Examples of mixed water sourcessituations in which you shouldnot sample:

A ditch that carries additional storm-water from properties upstream. Inthis case, the stormwater from yourfacility is mixed with other water andyou should find a location or loca-tions where your facility’s stormwateralone can be sampled.

A stormwater sewer or pipe (culvert)discharges to a creek or other receiv-ing water, the pipe being partiallysubmerged where it discharges intothe receiving water. In this case, thisfinal discharge point will not be ableto be used as a sampling point be-cause the stormwater flow is mixedwith the receiving water.

A manhole that carries stormwater,not only from your facility but fromother stormwater sources as well. Ifyou are grabbing a sample from amanhole but from the point where astorm sewer from your facility ends ata municipal manhole, make sure thatthe flow in that pipe is entirely fromyour facility, that the pipe is not sub-merged or partly submerged and thatyou are otherwise not prevented fromcollecting stormwater from your facil-ity only. If you are not sure that astorm sewer carries only flow fromyour facility, the municipality may

Advance Planning for Stormwater Sampling Page 5

Base flow here

refers to any water

in the ditch that is

not a direct result

of stormwater

runoff. Ground

water seepage into

the ditch, for

example, would add

base flow.

Manhole access can

be a good sample

point if it can be

accessed safely and

the stormwater is

solely from your

facility. Do not

climb into the

manhole. Use a

sample bottle

attached to a pole

to take the sample.

have storm sewer plans to help youdetermine this. Contact the munici-pality beforehand to discuss samplingfrom the manhole and associatedsafety issues, particularly for man-holes in areas with vehicular traffic.

It is important to sample flow fromonly your facility if possible becauseotherwise it cannot be determinedwhat the sample actually represents. Ifyou discharge stormwater to a storm-water conveyance system that includesstormwater from other sources, youneed to sample before your storm-water commingles with stormwaterfrom other sources. However, if storm-water runs onto your property in anuncontrolled fashion (for example,sheet flow) from adjacent property,into areas of industrial activity on yoursite so that it becomes a part of thestormwater discharge from your site,this should be included in your sampleof stormwater discharge. If you areconcerned about this offsite source,you may want to sample that storm-water where it enters your property. Ifthe results show significant pollution,you may want to provide Ecologywith a narrative description of the con-tributing site and sample results todocument the relative contribution ofthe other property or upstream source.

It is a good idea to observe thesampling point(s) you have chosenduring actual stormwater runoff con-ditions to see how readily stormwatercan be sampled there. Keep in mindthat changing tides and flow condi-tions in receiving waters, includingflood stages may occur during stormevents. This may cause a pipe that isdischarging your facility’s storm-water to become submerged or partlysubmerged, preventing you fromsampling during some conditions.

Obtaining Suppliesfor SamplingThe supplies you will want to haveon hand before sampling include:

�Sampling bottles from the lab,including a few extra of each type.

�When needed, a pole to holdsample bottles and filament strappingtape.

�Powder-free disposable nitrile orlatex gloves (sold by medical andlaboratory suppliers). Do not usepowdered gloves as the powder maycontain metals that could contaminatemetals samples such as zinc.

�Foul-weather gear.

�One or more picnic coolers(depending on the number of samplesto be stored and transported orshipped).

�A bound notebook to serve as afield book for keeping recordsconcerning sampling. Notebooks withwaterproof pages are available forthese field notes at office supplystores. The information to be includedin the notes will be described in the“Keeping Records” section of thisguide.

Page 6 Advance Planning for Stormwater Sampling

Practice sampling

before you do

the real thing.

Take time to

get ready for

sampling.

Planning Just Prior toStormwater Sampling

Now that the bulk of the planningfor sampling is complete, there

are a few things to keep in mind be-fore deciding to actually begin sam-pling.

Being PreparedIt is important to assemble everythingthat will be needed for the samplingevent ahead of time because opportu-nities to sample during storm eventsoften come with little advanced no-tice. Complete the identification tagsand Lab Services Required form.Place the tags, lab form, field note-book, permanent ink pen, meter, andpH paper in the cooler with the sam-ple bottles. Have re-sealable plasticbags or other means on hand to keepthe pH paper dry. If you are using aturbidity meter or pH meter, be pre-pared to protect them from the rain.Have foul-weather gear ready andavailable. It will be necessary to keepsufficient ice on-site or plan to pur-chase ice that day.

Choosing the Storm EventNow you are ready to sample. Suc-cessful sampling is first and foremosta matter of being at the right stormevent at the right time. What followsis some guidance on how to do that.

The general permit recommends thatthe storm event to be sampled mustmeet the following two conditions:

1. Be preceded by at least 24 hours ofno greater than trace precipitation.

2. Have an intensity of at least0.1 inches of rainfall (depth) of rain ina 24-hour period.

If the above criteria can’t be met, thepermittee must still collect and submitstormwater sampling results in accor-dance with the general permit. Apermittee is required to sample onlyonce in a sample collection period anduse its best efforts to achieve the aboverecommended sample collection crite-ria. If a sample is taken and the recom-mended sample collection criteria arenot met, the permittee is not requiredto conduct additional sampling forthat sample collection period.

Success in collecting grab samplesrequires being ready to go as soon asthe decision is made to sample during aparticular storm event. It is especiallyimportant to be at-the-ready becausethe permit recommends that grab sam-ples be collected during the first hour ofstormwater discharge. Note that thepermit recommends that the sample betaken within the first hour after dis-charge from your facility to a point offsite, not from when rainfall begins.

You will increase your chances ofmeeting the second recommended cri-terion for rainfall intensity at a mini-mum of effort if you evaluate weatherforecasts before deciding whether ornot to sample a particular rain event.

Planning Just Prior to Stormwater Sampling Page 7

Sample during

a hard (intense)

rain event.

If your facility is located in an areathat is covered by a standing snowpack for days at a time during a yearof normal precipitation, you may alter-natively sample a snowmelt event dur-ing the winter or spring quarter. Therecommended sampling conditions fora snowmelt event are as follows:

1. It is preceded by at least 24 hoursof no greater than trace precipitation.

2. The snowmelt is generated bya rainfall or warm weather melt-producing event on a standing snowpack of at least one inch in depth.

3. The sample is collected duringthe first hour of discharge from yourfacility that was produced by themelting snow.

Keeping up with the weather forecastand planning so that sampling can becarried out on short notice are thekeys to successful sampling.

Local forecasts, including televisedsatellite and radar images can give anindication of the expected intensity ofcoming storms. The National WeatherService is an excellent source ofinformation on upcoming storms. Italso includes local current radar and

satellite images. Their website:http://www.wrh.noaa.gov/seattle.A number of commercial websites,such as http://www.weather.com/and Yahoo also provide weatherinformation and forecasts.

When evaluating a weather fore-cast, consider indications of expectedintensity, for example “90% chance”rather than “50% chance” and “rain”rather than “showers.” Over the tele-phone, National Weather Service per-sonnel can often provide estimates ofanticipated rainfall amounts. In addi-tion to intensity, consider the pre-dicted duration of the storm. It will bevery helpful to spend time observingrain events at your site with attentionto how rain intensity relates to storm-water discharges from your site, be-fore you begin sampling.

Once the decision has been madeto attempt to sample a storm event,the personnel who will be samplingshould be notified and they shouldprepare to sample. If it does rain, theyshould be at the sampling sites beforestormwater begins discharging sothey can document the time of dis-charge and be ready to sample.

Page 8 Planning Just Prior to Stormwater Sampling

Check

weather

forecasts.

Conducting Samplingat Your Facility

After you have selected a stormevent and it begins raining, the

personnel conducting the samplingshould prepare their equipment andgo to the sampling site(s). They willbe collecting grab samples at the sam-pling site(s), placing the samples inpicnic coolers containing ice, andkeeping notes in a field book.

Sampling for the first time may re-quire working out some difficulties,but after performing these dutiesonce, future sampling will not be dif-ficult.

Checklist for SamplingBecause stormwater sampling is not adaily part of the workload of a facil-ity, it is a good idea to keep a check-list of things to have prepared beforesampling and to do during sampling.You can make the checklist by jottingdown the things you did for the firstsampling event to remember for sub-sequent sampling events. Update thischecklist, if necessary, based on theexperience you gain with each sam-pling event.

How to Fill Sample BottlesThis section and an illustrated appen-dix at the end of this guide describehow to collect a sample properly. Col-lecting a grab sample can be as simpleas holding a bottle under the storm-water falling from a pipe and fillingthe bottle properly. Still, the persondoing the sampling must use care inapplying the principles outlined be-low so that the sample will be repre-sentative of the water being sampled.

Simple principles of goodgrab sample collection:

Wear disposable powder-free gloveswhen sampling.

Grab samples with the stormwaterentering directly into bottles sup-plied by your lab rather than bytransferring the samples from a con-tainer that may not be clean. Metalcontamination of ordinary containersis common and household detergentsoften contain phosphorus, a testedparameter for some industries. Again,transferring the sample from anothercontainer is not an option for oil andgrease samples under any circum-stances.

When holding the sample bottleyour lab has provided, keep yourhands away from the opening in or-der to prevent contaminating thesample.

Always hold the bottle with itsopening facing upstream (into theflow of water) so that the water entersdirectly into the bottle and does notfirst flow over the bottle or yourhands.

Sample where the water has amoderate flow and, if possible, someturbulence, so that the stormwaterdischarge will be well-mixed andthe sample will be representative.Sampling in still water should beavoided. Include in your field booka note about the sample location andhow briskly the water appears to bemoving.

Sample from a central portion of thestormwater flow, avoiding touchingthe bottom of channels or pipes so asnot to stir up solid particles.

Conducting Sampling at Your Facility Page 9

Have your

sampling kit

ready to go.

Do not rinse or overfill the bottles.The bottles supplied by your lab forsome parameters (ammonia andphosphorus) will include smallamounts of liquid preservative (gen-erally a few drops). Fill the bottle toabout ½ inch of the top (not quite full)to ensure that no preservative is lost.

As soon as the sample is collected,cap the bottle and label it. It is impor-tant that the bottles are labeled cor-rectly so that the lab will be able toidentify samples by sample site andensure proper preservation for eachparameter. It is a good idea to placesample bottles in re-closable bags.Place the samples in a picnic coolerpartially filled with ice. Plan to main-tain ice in the picnic cooler until thesamples arrive at the lab. Rememberto make certain that the samples willbe delivered to the lab soon enoughfor the lab to meet holding times.

Oil and grease samplingraises additional concerns:

Oil and grease floats on water sosampling it requires special attention.Oil and grease samples must be col-lected directly into the sample bottlessupplied by the lab because oil andgrease tends to stick to the sides ofcontainers. Do not rinse the samplingbottles beforehand or pour the samplefrom another container. Do not fill thebottle completely and do not pour outsome of the sample if the bottle isoverfilled by mistake. If you do over-fill a bottle, use a new bottle insteadto collect your sample. Because youonly get one try at filling an oil andgrease bottle, it is a good idea to haveplenty of extra bottles on hand.

Oil and grease samples should becollected as the stormwater falls froma pipe or from a running, turbulentstream of flow when possible so thesource will be well mixed. When thesamples must be collected from a wa-ter surface, the person holding thebottle should plunge it below the sur-

face in a sweeping arc and then bringit upwards through the water surfaceagain, so the water surface is brokentwice by the mouth of the bottle. Besure to note in your field book howyou collected your samples as this isespecially important for the oil andgrease sample.

Keeping RecordsSection S5. of the general permit spec-ifies requirements for reporting andrecordkeeping. In order to complywith the requirement that lab reportsinclude sampling date and samplinglocation, you will need to supply thisinformation to the lab when submit-ting samples. You can do this by us-ing the sample location as the fieldstation identification on your labels orsample tags.

You should purchase a notebookfor use in the field. Water resistant“rite in the rain” notebooks serve thepurpose well. Information is availableat www.riteintherain.com.

Section S5.C. requires that you re-cord the date, exact place, method,and time of sampling or measure-ment, and the individual who per-formed the sampling or measurement(the section also specifies some re-quirements for lab record keeping).Record these in your field book:

�Time rainfall began

�Sampling location (when there ismore than one)

�Date of sampling

�Time of sampling (and time youcompleted sampling if different)

�How you collected the sample(for example, “from a ditch by hand”or “from a manhole with the bottleson a pole”)

�name of the sampler(s)

�number, types (parameters) ofsamples collected

Page 10 Conducting Sampling at Your Facility

Take notes!

Writing down

your observations

at the time of

sampling is

importatnt.

� field measurement results(such as pH)

�unusual circumstances that mayaffect the sample results.

Entries in the field book should bemade with ink. If you make an errorin the field book, cross it out ratherthan whiting out or erasing. Numberthe pages of the field book consecu-tively. To ensure that the bound fieldbook is a complete record, do not ripout pages from it.

It is desirable in addition, thoughnot required by the general permit, torecord the following information foreach storm event sampled:

�number of dry days before theday the sample was collected, ora statement that there was at leastone day of no greater than traceprecipitation before sampling.

� inches of rain during a 24-hourperiod

� time of sampling as well as date

�date and time the rainfall began

�date and time the discharge beganat the sampling site

�duration of the storm in hours

� inches of rainfall during the storm

The information you record for thefirst two items above (number ofpreceding days of no greater thantrace precipitation and inches of rainduring a 24-hour period) will serveto document that you met thoserecommended criteria for samplingspecified in the general permit.

Determining if theSampled Storm Event Metthe Recommended CriteriaSection S4.A. recommends that the stormevent be preceded by at least 24-hours ofno greater than trace precipitation. Dur-ing times of clear weather, it may be obvi-ous that this criterion has been met.When it is cloudy, you can verify thatthere has been no precipitation (includingovernight) by installing a simple, inex-pensive rain gauge at your site.

The same section of the permit alsorecommends that the storm have a rain-fall intensity of at least 0.1 inches of rain ina 24-hour period. This does not mean thatthe rainfall must last for a full 24 hours,only that from the time it begins rainingto the time you stop sampling, the rainfallbe of the recommended intensity orgreater. To determine this, you shouldobserve and record the time it began rain-ing as well as the time you stopped sam-pling. What the storm does after you stopsampling is of no concern. In addition tothe times rainfall began and samplingended, your rain gauge will give you allof the information you need to easily cal-culate the rainfall intensity.

An example rainfallintensity calculation:

Rainfall begins at 9:35 AM (you emptythe rain gauge beforehand)

Stormwater discharge at your samplingsite begins at 10:05

You complete sampling at 10:30

Your rain gauge shows 0.01 inches ofrain when you stop sampling

Rain intensity= 0.01 inches / 55 minutes= 0.00018 inches/minute= 0.00018 inches/minute

x 60 min/hrx 24 hrs/24 hrs

= 0.26 inches/ 24 hours

The criterion for rain intensity is0.1 inches / 24 hours. 0.26 is greaterthan 0.1, so the storm event you sampledmeets the recommended criterion.

Conducting Sampling at Your Facility Page 11

A simple, inexpensive rain

gauge mounted on a post. A

rain gauge such as this one

provides accurate readings

at the low rainfalls often as-

sociated with the period

from the beginning of rain-

fall to the end of sampling.

The gauge can be removed

and the water that has col-

lected in it dumped out be-

tween rains.

If you do not have a rain gauge,you will have to rely on rainfall datafrom other sources. The NationalOceanographic and AtmosphericAdministration (NOAA) posts dailyrainfall records on their website:http://www.wrcc.dri.edu/state_climate.html. (Note that there isan underline between “state” and“climate,” but no space, in this webaddress). The data posted is only forthe previous day, so you will have tomake sure you don’t miss the internetposting. A disadvantage of relying onthis data is that it is a measure ofnearby rainfall but not that from yoursite. A further disadvantage is that itgives you only daily (24-hour) rainfalldata and, while this may indicate arainfall of less than 0.1 inches in somecases, you may have had sufficientrainfall intensity at your site to meetthe recommended criterion of thegeneral permit, had you measured itwith a rain gauge.

When the Sampled StormDoesn’t Meet theRecommended CriteriaThere may be times when you start tosample but the rainfall intensity turnsout not to meet the recommendedcriterion of the general permit. Ordespite your best efforts, you areunable to collect grab samples duringthe first hour of a storm event thatmeets the recommended criterion forpreceding dry conditions. When thishappens, the general permit statesthat the permittee must still collectand submit stormwater samplingresult, and must include anexplanation with the monitoringreport identifying what recommendedcriteria were not met and why.

Page 12 Conducting Sampling at Your Facility

Get the best

sample you can.

Special Sampling Considerations

Safety should be the primary con-sideration in sampling. Samples

should never be collected in a waythat compromises the safety of thesampler. In cases where a physicalhazard such as a trip hazard or whensampling near deep water bodies,samplers should work in pairs. Donot wade in water where the esti-mated depth in feet times the velocityin feet per second is equal to orgreater than 8, as swift currents canlead to drowning accidents. Be awareof the slip hazard common near thebanks of water bodies and decidewhether a bank is too steep to negoti-ate safely. Safety comes down to indi-vidual judgment. Never put yourselfin a position you consider to be un-safe.

Collecting grab samples of storm-water is basically a simple process butan important one since getting goodresults depends on proper sampling.Samples can be collected easily insome locations, but not all stormwaterdischarges are as readily sampled asthe flow in a ditch or from a pipe fall-ing into a receiving water. Below aresome situations you may encounterand suggested approaches for han-dling them. Because oil and greasesamples must be collected directlyinto the bottle supplied by the lab wewill consider only methods for col-lecting samples directly by hand orwith a bottle attached to a pole. Whensampling in these or other situations,keep in mind the steps outlined in thesection, How to Fill Sample Bottles.

Sampling as StormwaterDischarges from a Pipe intoa Receiving WaterIf stormwater is being dischargedfrom your facility through a pipe intoa ditch, creek, or other receiving wa-ter, it can be readily sampled as itfalls from the pipe before it reachesthe receiving water if the dischargepipe is safely accessible and not sub-merged. Hold the bottles with thebottle opening facing upstream (intothe flow and be sure not to overfillthem. You may need to fasten the col-lection bottles to a pole to reach thepipe. Attaching a bottle to a pole isdescribed in the section below, Sam-pling from a Manhole.

Sampling from a ManholeWhen sampling from the manhole ofa municipal storm sewer, rememberto contact the municipality before-hand. Discuss sampling being sure tocover safety concerns. Open a man-hole with a hook or pick axe, exercis-ing care not to drop the manholecover on hands or feet. You shouldnot, under any circumstances, enterthe manhole unless trained to safelyenter confined spaces, but you cansample the flow in a manhole fromabove ground by taping the samplingbottles, one at a time, to a pole andlowering the pole into the manhole.

Each bottle can be fastened to thepole by holding the bottle against itand wrapping tape tightly around thebottom and the top of the bottle as youhold the bottle firmly to the pole. Fila-ment strapping tape works well forthis purpose as it is waterproof andstrong. If the flow in the storm sewer isshallow, the bottle may have to be po-sitioned horizontally with the bottle’sopening somewhat higher than its bot-tom. When sampling in a manhole, be

Special Sampling Considerations Page 13

Don’t take risks -

know how to

sample safely.

careful not to scrape the bottle againstthe sides of the pipe to avoid pickingup extras solids in your sample.

Collecting into bottles with oil andgrease samples with a pole is done byplunging the bottle on the pole belowthe water surface and back upwards.This must be done as a single motionand only once. Because you only getone try at getting a good oil and greasegrab sample, it may take some practiceand extra bottles to collect the amountof sample you need without overfill-ing the bottle. Collecting samples otherthan oil and grease into bottles withpreservative can be done by quicklyplunging the pole into the flow repeat-ing if necessary until the bottle ismost but not all of the way full. If youoverfill the bottle, remove it, tape aclean bottle to the pole, and try again.Be sure, when collecting samples witha pole, to follow clean principles bykeeping the pole downstream of thebottle while sampling.

Sampling from aDrainage Ditch or SwaleIf a drainage ditch carries stormwaterflow from your facility offsite, and ifit carries no flow other than the flowfrom your facility, you can sample thewater in the ditch simply by placingthe bottle where the flow is free, withthe bottle opening facing upstream. Ifyou cannot reach a freely flowingportion of the ditch by hand, you mayneed to attach the bottles, one at atime, to a pole for sampling. Followthe procedure outlined in the section,How to Fill Sample Bottles.

If the flow is carried in a small ditchor swale, you can install a barrier devicein the channel or deepen a small area soyou can gain enough depth of flow tosample directly into the bottles. Makesure to allow for sufficient time after dis-turbing the bottom so that the solids re-sulting from muddying the water willnot become part of your sample.

Sampling Sheet FlowIt is not always possible to samplestormwater runoff in locations suchas ditches or pipes where the flow isconcentrated. Sometimes thepermittee has no choice but to selectsample locations for which sheet flowis sampled before it becomes concen-trated. Approaches to sampling sheetflow are described below and illus-trated in the figures that follow.

In some cases, a stormwater dis-charge from a facility is not concen-trated at any point and leaves theproperty in the form of sheet flow asit runs off a work area or driveway orgrassy area. In this case the flow maybe too shallow for the collection bottleto be filled with sample. It is oftenpossible to find a way to collect thestormwater runoff in these situations.

One way to concentrate sheet flowis to excavate a small basin in an exist-ing ditch or other location wherestormwater runoff flows. Another ap-proach is to install a barrier device ortrough, gutter, or ditch to interceptand concentrate stormwater flow. Aswith other sample sites, the flowshould be moving and somewhat tur-bulent so the samples will be well-mixed. Be sure that any excavationyou do does not expose the storm-water to be sampled to newly workedsoil surfaces that the runoff may erode,increasing the solids in your samples.You may want to consider lining thetrough, gutter, or ditch with plastic. Besure not to introduce materials (suchas metals that include zinc) that maycontaminate the samples. Sheet flowon paved areas can be concentratedand collected by constructing smallbumps, similar to speed bumps.

Another way to collect samplesfrom sheet flow is to use a specialperistaltic hand pump to pump sam-ples from shallow surface flows. Thismethod is of limited use for collectingthe samples required by the general

Page 14 Special Sampling Considerations

When sampling from a man-

hole, use a pole to safely

sample from above ground.

Avoid touching the sides of

the manhole or pipes with

the bottle to prevent con-

tamination. Place the open-

ing of the bottle upstream so

that the flow enters the bot-

tle directly.

permit as it cannot be used to collectoil and grease samples.

Roger Bannerman of the Wiscon-sin Department of Natural Resourceshas developed simple devices to grabsamples of sheet flow from paved ar-eas, rooftops, and lawns. Though thedevices are intended to be used forsimple, automatic sampling, pouringa container of collected sample intoother sample bottles, the ways inwhich they intercept and concentrateflows can be adopted for direct grabsampling.

The following figures illustrate themethods of sampling sheet flow dis-cussed above:

Sampling from aStormwater Detention Pondor other BMPWhen stormwater from a facilitydischarges after flowing through adetention pond or other treatmentsystem, sample as the stormwaterflows out at the discharge point.Ponds may hold stormwater for atime before discharge begins.Sample within the first hour,preferably 30 minutes from whenthe pond begins to discharge.

Special Sampling Considerations Page 15

Runoff entering a catch basin can sometimes

be collected directly into bottles by removing

the grate and allowing the runoff to fall into

the bottles.

Overland flow from vegetated areas can be

sampled by constructing a shallow ditch to

intercept the runoff and a deepened area to

place bottles to catch the runoff.

Overland flow on paved areas can be sam-

pled by constructing asphalt or concrete

bumps to collect and concentrate the flow. A

box positioned below ground surface in the

paved area or the edge of an unpaved area

can provide a place to collect samples di-

rectly into bottles.

Deepening an existing ditch can allow sam-

ples to be collected directly into bottles in

some cases. Be careful not to stir up solids

from the sides or bottom of the ditch.

Ecology Wants to

Hear from You

If you have suggestions

on how Ecology can

improve this guidance

document, have

developed innovative

sampling techniques,

or just want to

comment on

stormwater sampling,

please contact

Joyce Smith:

Email (preferred):

josm461@ecy.wa.gov

Telephone:

(360) 407-6858

Mail:

Washington State

Dept of Ecology

PO Box 47600

Olympia WA 98504-7600

Appendix - Proper and ImproperMethods of Sampling

Do not touch openings of bottles. Keep bot-

tles clean to prevent contamination.

Do not allow bottle lids to touch ground.

Keep lids clean to prevent contamination.

Do not sample in stagnant areas with little

flow. Do not stir up bottom sediments or al-

low foreign materials to enter the sample

bottle. (Do be careful to grab a clean sample

in cases where stormwater runoff is shal-

low.) If the runoff is so shallow that it is not

possible to sample without the sample being

contaminated in the process, then find an al-

ternative way to sample.

Do attach a bottle to a pole for sampling in

manholes or when a hand sample would be in

stagnant water. A boathook is used in this

example and the bottle is attached to it with

filament strapping tape.

If the water is too shallow to sample with

the bottle upright on the pole, try taping it

on sideways, but tilted up slightly.

Page 16 Appendix - Proper and Improper Methods of Sampling

Do not sample with the bottle opening facing

downstream, when using a pole or sampling

by hand. Water flowing past your container,

pole, or hand and into the container can be

contaminated by such contact.

Do sample with the opening of the bottle

facing upstream, into the flow so the water

will enter directly into the bottle. This is

true when sampling either by hand or with a

pole. Do sample water that is rapidly flowing

rather than stagnant.

Do not allow water to overfill the bottle,

particularly not for sample bottles with pre-

servative. Oil and grease samples should be

collected from water falling into the bottle

when possible, or otherwise in a single

swoop.

Do collect samples without overfilling the

bottles.

Appendix - Proper and Improper Methods of Sampling Page 17

References

Bannerman, R.T.; Owens, D.W.;Dodds, R.B.; Hornewer, N.J., 1993.Sources of Pollutants in WisconsinStormwater, Wat. Sci. Tech. Vol. 28.No. 3-5, pp 241-259.

Colorado Department of PublicHealth and Environment; WaterQuality Control Division; ColoradoDischarge Permit System, 1996.CDPS Stormwater SamplingGuidance Document.

Dodson, Roy D., 1995. Storm WaterPollution Control: Municipal, Industrial,and Construction NPDES Compliance,1999, 1995. Second Edition.McGraw-Hill.

Ecology, 2005. The Industrial Storm-water General Permit: A National Pollut-ant Discharge Elimination System andState Waste Discharge General Permitfor Stormwater Discharges Associatedwith Industrial Activities. State ofWashington Department of Ecology,January 14, 2005.

Ecology, 2000, 1999. Field Operationsand Safety Manual: EnvironmentalAssessment Program, Washington StateDepartment of Ecology, Environmen-tal Assessment Program, UpdatedAugust 2000.

New Jersey Department of Environ-mental Protection Division of WaterQuality, 1998. General Sampling andReporting Guidance for PAS andADI Form.

Thrush, Cindy and De Leon, Dana B.,1993. Automatic Stormwater SamplingMade Easy, Water EnvironmentFederation.

United States EnvironmentalProtection Agency, 1992. NPDESStorm Water Sampling Guidance.EPA 833-B-92-001.

Waschbusch, R.J.; Selbig, W.R.;Bannerman, R.T., 2000. Sources ofPhosphorus in Stormwater and StreetDirt from Two Urban Residential Basinsin Madison, Wisconsin, 1994-95.National Conference on Tools forUrban Water Resource Managementand Protection Proceedings, February7-10, 2000, Chicago, IL.

Wisconsin Department of NaturalResources Bureau of WaterManagement Municipal WastewaterSection – Storm Water Unit, 1994.Wisconsin’s Guidance for IndustrialStorm Water Monitoring.

Torno, Harry C., 1995. StormwaterNPDES Related Monitoring Needs,American Society of Civil Engineers.

Page 18 References