Blog – Washington Stormwater Center

Sampling Stormwater from an Outlet Pipe

Sampling stormwater from an outlet pipe is often the easiest scenario to sample for your stormwater permit requirements. In most cases, the pipe is easy to identify, provides ample concentrated flow, and usually can be sampled without the need for special tools. That said, there are still several things to keep in mind to ensure that sampling goes smoothly and you get good-quality results.

1. Safety
Outlet pipes are often located on the outskirts of our property in areas that are infrequently trafficked and see little to no maintenance. These pipes can be located on steep slopes, be overgrown with blackberries, or be located right on the edge of a water body. No matter the situation, you should always take time to consider your safety when approaching a sampling event.

As mentioned in our Sample Handling article, sampling with a helper can be a great way to ensure that sample bottles are handled properly. In cases of sampling an outlet pipe, having a helper can also add an important element of safety. A helper can help reduce the weight of equipment having to be carried down a steep slope, they can help you navigate a muddy or bramble-covered area, and they are an extra pair of eyes on the less traveled areas of your facility who can get help in an emergency.

Other sampling safety considerations:

Clear a path to your sample location. During a dry day, clear any blackberries or other brush from around your outlet pipe to prevent trip hazards and to make sampling a much more pleasant experience.
Consider wearing a life jacket if sampling near a water body. Steady rainfall can quickly turn even a modest creek into a dangerous situation.
Remember your site safety procedures. Some areas may require a hard hat, safety glasses, boots, or a high visibility vest to access. Always follow your facility?s safety procedures when sampling.
Consider permanently changing your sampling point. If your sample point is inaccessible due to safety, it is a good idea to reach out to Ecology to change your sampling point to somewhere you can access safely. This isn?t as easy as just deciding to sample elsewhere, it will require a sample point update form, documentation, and approval from Ecology.
Remember, you are not required to sample during unsafe conditions. Don?t brave it out during a lightning storm, or in flood conditions. Document these conditions to the best of your ability and wait until the next sampling opportunity. If no such opportunity presents itself, you can report the unsafe conditions on your DMR.
2. Clean Your Sample Point

During site inspections, and before taking your sample, make sure you take a few seconds to remove any trash, accumulated debris, or other material from your outlet pipe. This material can have a significant impact on your sample results and can prevent you from getting an accurate picture of what is happening at your facility. You don?t want this material to end up in your sample bottle, as it can impact sampling results for things like turbidity or other parameters depending on the situation. For example, as organic material breaks down, it can leave a sheen on the surface of water that is easily mistaken for an oil sheen.

3. Create Access to Sample

Clearing blackberries and other debris was mentioned in the safety section to avoid trips and falls, but creating sample access also helps with the integrity of the sample you are taking. Clearing space to visually inspect your outlet pipe allows you to identify and avoid any potential contamination issues. It also helps create a more comfortable sampling environment. Nobody wants to be poked in the back by blackberry thorns while trying to sample, and this scenario may make you lose focus on the sampling and lead to accidental contamination caused by poor sample handling techniques.

Some outlet pipes may be too close to the ground to easily fit a sample bottle. This should be identified early and taken care of on a dry day well before sampling. This may be remedied by simply moving a couple of rip-rap stones away from the outlet. In other cases, a small depression may need to be dug around the outlet pipe. Make sure this depression is stabilized, and that the disturbed dirt doesn?t cause turbidity issues downstream. Lining the depression with river-rock is a simple and long-lasting solution that uses natural materials. Other solutions may include using plastic products such as sheeting or even a plastic bucket or section of large-diameter pipe.

4. Sample Handling

As with any sampling scenario, sampling from an outlet pipe requires meticulous sample handling procedures. Many of these procedures are discussed in detail in our Sample Handling post, but highlights include:

Avoid contaminating your sample by wearing clean gloves and changing them frequently.
Work with your lab to ensure you are using the correct bottles, that you have any preservatives that you need, and that you know what your hold times are.
Keep your samples on ice from the time you sample until you drop them off at the lab.
Keep the lid on your sample bottle for as long as possible, and avoid allowing anything but stormwater to enter your bottle.
Check that your bottle labels match your COC and sample locations to avoid any mixups.
Take notes of sampling conditions.
Keep all data, notes, and other materials organized.

Sampling Stormwater from a Catch Basin

Sampling stormwater out of a catch basin is a common scenario that many facilities face when sampling for their ISGP. With multiple stormwater inputs, hard-to-reach sampling points, and heavy coverings, catch basins can be an extremely intimidating scenario to tackle. This article will help arm you with the proper tools and techniques to make catch basin sampling a breeze.

1. Accessing your Catch Basin Safely

The catch basin grate or lid can be very heavy. A simple grate hook is an excellent tool for sliding off smaller coverings. If you have back problems, need to remove a larger covering, or want to prevent injury potential, you may consider investing in a specialized grate lifter. Several models are available, but most are some form of large lever that allows you to safely and securely remove your grate or lid. Remember when removing rectangular lids they can be easily dropped into the catch basin, so make sure your removal method is secure, and never attempt to climb into a catch basin to retrieve a lost lid without proper training.

The open hole in the ground that is left when opening a catchbasin can present a significant safety hazard on your site. Never leave an open catch basin unattended. Since catch basins are often located near heavily trafficked areas, it may be a good idea to close off the area and temporarily route traffic around the area you are sampling.

Confined space training is required for anyone attempting to enter a catchbasin. Do not attempt to enter a catch basin without proper training. Luckily there are sampling poles and other tools available to allow you to safely and effectively sample your basin without the need to climb in.

2. Identify your Sample Point

A catch basin can have multiple stormwater inputs that act as potential sampling points. One catch basin may have 3 pipes coming in, the bottom sump, and water flowing in over the top. That is 5 potential points to sample in a relatively small area. It is important to identify which of these sampling points is representative of the area of your facility you need to sample. Suppose we want to sample the area immediately around our loading dock, for example. In that case, we might need to dig up the as-builts to identify that the central pipe comes in from our loading dock, the pipe on the left comes in from a neighboring facility?s parking lot, and the pipe on the right comes in from the roof.

When you identify which of these pipes is the correct one, take a picture and keep it with all of your sampling supplies. Sometimes it can be months between sampling events, and it is easy to forget.

Avoid sampling from the catchbasin sump. The sump of a catchbasin is where the sediment and a certain volume of water are pooled. It is advised to not take your stormwater sample out of this area if possible for 2 reasons:

The sump could contain water that isn?t from your facility. As mentioned in the example above, you could have water coming into a catchbasin that is from a neighbor?s facility. You have no control over what types of pollutants could be coming off of their facility, and you don?t want to take the hit for someone else?s pollution.
The sump tends to accumulate pollutants. Since the sump acts as a settling area for sediment across multiple rain events, the water in the sump likely contains a higher level of pollutants that are associated with the settling of sediment and other bound contaminants such as metals. Do make note of the sediment levels in your sump, however, as these should be removed once they reach 60% of the sump volume.
3. Use Proper Tools and Handling Techniques
As with any sampling scenario, catch basin sampling requires proper sample handling techniques. Using gloves and changing them frequently is a great way to avoid accidental contamination of a sample. We mention several simple sample handling techniques that will help with quality assurance in our Sample Handling post. What makes a catch basin unique is the need to sample below ground level in an area that is hard to reach.

Sampling poles make this much easier. A sampling pole will allow you to securely attach a sample bottle, and get it into the stream of flowing water while standing a safe distance away from the open basin. When using a sample pole, you must avoid potential contamination risks. Have firm control of the pole, and don?t let the open bottle touch the sides of the catchbasin. Our Sampling Kit post described the importance of having extra bottles on hand. This is even more important when sampling with a sample pole, as you have less control of the bottle an can easily drop or otherwise contaminate it. Don?t miss a sample, or turn in a potentially contaminated sample because you didn?t have a spare bottle on hand.

Cleaning around the lip of your catch basin is an important step if you are sampling stormwater that is flowing in from the top. Sediment, moss, and stormwater contaminants can accumulate in this area, and can make the difference between a clean sample and a benchmark exceedance.

Preservatives can also be a little tricky to deal with when sampling a catchbasin. If your bottles are pre-loaded with preservatives, you want to avoid inverting your bottle and losing that preservative. A sample pole may be a little unwieldy the first couple of times you use it, so it might be a good idea to sample your non-preservative bottles first to get the hang of it. You may also discuss with your lab the possibility of adding a preservative after you sample. This should be a last resort, as this option can get confusing quickly.

Sampling from a catchbasin can be an intimidating proposition at first, however, it isn?t much different from any other sampling scenario once you know the proper techniques. Safety is the most important consideration to make. Protect your back by using the proper tools to open up the catch basin, and protect others by directing traffic away from this open pit. Sampling from the correct point in your catchbasin prevents benchmark exceedances caused by your neighbors, and using proper sample handling techniques prevents exceedances caused by you.

Sampling Stormwater Sheet Flow

Sheet flow is one of the most challenging sampling scenarios you can face for the Industrial Stormwater General Permit. The biggest challenge comes from getting enough volume in your sample bottle to allow your lab to analyze your sample properly. If you are faced with a sheet flow sampling scenario, there are several strategies that you can use to make sampling easier.

1. Choose your Location Wisely
Sometimes the easiest way to sample sheet flow is to simply find an alternative sampling location. Look closely at your site and look for a substantially identical alternative. Perhaps this flow gets congregated into an outlet pipe or ditch. Use these alternative locations as long as they collect water from the same areas of your facility and represent the same potential pollutant loads.

If there isn?t an alternative, you will want to optimize what you have to work with. Usually, the challenge is getting the bottle under the water, so we need to use the terrain to our advantage. If sheet flow cascades down into a catchbasin, remove the lid and use that point to capture the water as it cascades down (as we mention in the Catchbasin Sampling Post, we want to avoid sampling from the sump if possible).

Look for things like curbs, speedbumps, or dips in the pavement. Water can accumulate in these spaces allowing us enough concentrated flow samples. In some cases, we may need to build up a small dam to concentrate the flow enough to sample. We have demonstrated how to build this in our long-form sampling video below:

2. Choose your Sample Containers Wisely
When sampling sheet flow, you want to give yourself the best chance to collect adequate volume. This is nearly impossible when sampling with a narrow-mouth bottle. Talk with your lab and discuss potential alternatives with them. In some circumstances, you may be able to sample using a secondary container to assist in taking your sample. A ziplock bag is a great option for this, as it can be laid flat and capture water from a wide area with minimal volume needed. Plastic or glass wide-mouth sample jars may also be sufficient secondary containers.

Some analytes, such as Total Petroleum Hydrocarbons, don?t allow for the use of secondary containers. If you find yourself in this scenario, ask your lab if they have any wide-mouth bottles that you can collect your sample in. Also, confirm the minimum volume they need for analysis- there is a good chance that you will be unable to fill the bottle completely.

3. Use Proper Sample Handling Techniques
We want to handle our sampling equipment properly to avoid contaminating our samples. As with any sampling scenario, this means simple things like:

Wearing clean gloves and changing them often
Keeping our samples stored on ice
Using the proper preservatives as identified by our lab
Staying organized with our labels, COC forms, and data.
With sheet flow sampling, we often have one additional consideration: the cleanliness of our secondary container. Talk with your lab about the use of a secondary container. Explain your situation. For many parameters, a brand-new ziplock bag will be sufficiently clean. This is ideal, as these bags are inexpensive and come in giant packs. Other parameters may require samplers to wash equipment using special procedures to ensure quality. These cleaning procedures can be as simple as soapy water and a thorough rinse, and as complicated as needing acids and solvents applied in a specific order. Many labs will offer equipment cleaning as an optional service.

This cleanliness expands beyond just the secondary container. Plastic sheeting used to build a dam to sample from should also be adequately clean, as any material coming into contact with stormwater could be a vector for contamination. Don?t let a dirty container or sheet of plastic be the difference between acceptable water quality and a benchmark exceedance.

For more video content covering a wide range of stormwater topics, please visit our YouTube page!

Posted in Industrial Permit

pH Stormwater Sampling

1. Equipment Considerations
There are several equipment options for pH measurements in the field:

Handheld, portable pH meters offer a high degree of accuracy and precision but are the most expensive of the options considered here. Some of these have data-logging capabilities, which can make things like source evaluation and long-term monitoring a breeze. The steep price tag usually keeps these meters reserved for only the most rigorous testing needs.

pH hand-held ?pens? are commonly used by industrial permittees. While these pens don?t offer all of the features that pH meters offer, they are suitable for most purposes. These pens are simple to use and provide accurate results.

pH test strips are another common method of testing and are cheap and straightforward to use. pH strips are coated with a chemical indicator; when dipped in water, they change color depending on the pH. The resulting color is visually matched against a reference chart (provided by the manufacturer) to determine the pH value. For purposes of the ISGP, strips should be within a narrow range and give the precision of +/- 0.5 s.u.

2. Calibrating and storing equipment
pH meters and hand-held pens should be calibrated frequently. In most cases, the calibration procedure requires you to insert your meter into one or a series of calibration standards while running a calibration function within the device. Exact procedures will vary from instrument to instrument, so follow the manufacturer?s instructions for your specific device. Calibrations are relatively quick and simple to perform and ensure the quality of your measurements. Therefore, we recommend performing these calibrations before every sampling event. If you have a lot of samples, you may also consider periodically measuring the pH of the buffer solutions to check that your instrument?s calibration has not drifted. Re-calibrate as needed.

It is also important to check the quality of your calibration standards. These standards can come in sizes ranging from single-use sachets to large bottles. Only buy enough for what you can use in a year, as these standards have a limited shelf life. Check and make note of the expiration dates of these samples so you can have fresh supplies ordered in time for your next sampling event.

pH probes should also be stored in a storage solution. This solution is usually a mixture of KCl and water and keeps the probe moist and in the ionic conditions required to keep it functioning properly. These storage solutions have a little longer shelf life than the calibration standards but should be replaced as needed. It is a good idea to keep extra solutions on hand just in case you knock over the storage container.

4. Sampling for pH
When measuring pH in the field, make sure you have a clean sampling bottle or container dedicated to this measurement. This step is easily forgotten, as in most cases your lab provides you with bottles for your other parameters. It can be very easy to forget your bottle, and tempting to just dip your test probe or test strip into a bottle intended for another parameter. Doing so will risk cross-contamination of samples collected for other lab analyses. If using a pH meter or pen, further avoid cross-contamination by rinsing the probe between each sample.

Once you have collected your water sample in the bottle designated for pH, take the pH measurement as soon as possible following sample collection. pH will change over time as carbon dioxide from the air dissolves in the water, therefore the maximum amount of time between sample collection and pH testing should be 15 minutes.

5. Organization
It is easy to lose track of your pH measurements during the hustle and bustle of a sampling day. This is often the only parameter not measured by the lab and sent to you in a nicely organized lab report. Before going out into the field, you should have a dedicated place to record your results in the field and a procedure to organize those results and enter them into your Discharge Monitoring Report.
1. Equipment Considerations
There are several equipment options for pH measurements in the field:

Turbidity Sampling

urbidity is the measurement of the cloudiness of our stormwater generally caused by material that washes off the landscape and becomes suspended in our stormwater. Turbidity is easy to measure and the equipment is relatively inexpensive, so it is one of the few water quality analyses that we can do in-house. This article aims to show you the proper sampling and measurement techniques to ensure accurate turbidity results.

1. The Equipment
The device used to measure turbidity from our stormwater is called a turbidimeter. Turbidimeters can come in several form factors from large benchtop units commonly found in a dedicated laboratory to small battery-powered units that are water-resistant and field-friendly. These smaller units are what are commonly used for sampling for your stormwater permits, and are fairly simple to operate. These units come with dedicated sampling cuvettes that hold the water sample for analysis and are sized to specifically fit your unit. Your unit will also require calibration standards that come in their own dedicated cuvettes. Other dedicated Turbidity equipment may include oil for your sample cuvettes and a microfiber cloth. Both of these are used to reduce false readings from smudges and scratches on your sampling cuvette.

2. Equipment Calibration
Calibrating your equipment is a critical step in ensuring quality results from your turbidity sampling. This process may vary slightly depending on the turbidimeter you have, however, most processes involve running a calibration program that analyses multiple calibration standards and adjusts its readings accordingly. This process doesn?t take much time and should be done frequently. If you are sampling quarterly, you should calibrate your equipment before every sampling event. If you are sampling more frequently, a simple verification that your readings match your calibration standard may be sufficient between calibrations.

3. Taking your reading
Your turbidity reading is measured by quantifying the amount of light that is scattered in your sample. The more turbid the sample, the more light will be scattered. This reading is measured in Nephelometric Turbidity Units or NTU. A higher NTU reading correlates to cloudier (more turbid) water. It is critically important that your sampling cuvette is clean and free of scratches or fingerprints. A muddy fingerprint or scratched cuvette can easily cause more light refraction resulting in a reading that is falsely reading higher NTU values. This could easily lead to benchmark exceedances and costly corrective actions.

Make sure your sampling cuvette is free of smudges and fingerprints by cleaning it with a microfiber cloth and holding it by the cap as opposed to touching the glass where the reading will be taken. Many turbidity kits will come with silicone oil that is intended to coat the sample cuvette to smooth out any imperfections. Check your manufacturer?s instructions on the specific sampling protocols.

pH Stormwater Sampling

1. Equipment Considerations
There are several equipment options for pH measurements in the field:

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