WI DNR Field Procedures Manual
Intranet Edition

Scope

The goal of this section is to describe proper general procedures for sediment sampling and the use of common sediment sampling equipment. Sound sediment sampling techniques that are followed for all sampling efforts throughout the state will improve the quality of data received from sediment surveys in the State of Wisconsin. Effective and proper use and cleaning of sampling equipment is important to the safety of field staff and quality assurance and control of samples. Study goals may require that additional or alternate equipment or procedures be used than are discussed here. Any procedure changes should be based on sound scientific and practical reasons and should ultimately help further the goals of the study, without the loss of quality assurance and control.

Equipment and Supplies

Below is a suggested list of equipment needed for most sediment sampling efforts. This list suggests equipment that may be necessary for your project and should not be considered exhaustive. Equipment that is specific to a specialized type of sampling may be included only in the section describing the particular type of sampling.

Basic Sediment Sampling Procedures

1. Preparation

   1. Sampling Plan - Sampling strategy decisions should be made well before going into the field, and should be designed to collect quality data that will best answer the questions or meet the goals of the study or monitoring program. Decisions should be made ahead of time about what sites, how many replicates at each site (sampling strategy), and what chemical analyses will performed on the samples (see 701.1 Planning a Sediment Survey and WDNR 1990). This will help ensure that appropriate and quality samples are collected.
   2. STORET stations - Every site that is sampled in Wisconsin should have a STORET station number assigned to it so that chemical data about the site will automatically be added into the STORET database. After site locations are decided upon, each site should be checked to see if a STORET station number exists for it. This number should continue to be used if the sites are really the same. A STORET number must be assigned (before samples are sent to the lab for processing) to each new site in a project. Location information including section, township, range and longitude and latitude will be needed to establish the station (see 3000.1 Field Positioning Methods). To establish a STORET station, call Carol Tiegs at (608) 267-7659.
   3. Field Staff - All field staff working at a site should understand the basic goals of the study the samples are for and the basic methods to be used to assure that quality samples are collected.
   4. Safety - All field staff should be aware of and fully understand the possible physical and chemical safety hazards posed by any site they will be working at. Precautions should be taken to prevent exposure to contaminated sediments (see 701.2 Safety).
   5. Equipment - Make all the preparations necessary to obtain suitable collecting equipment, protective clothing, vehicle and boat if necessary. Test and calibrate any equipment (according to manufacturers instructions) that will be used to take field measurements, etc. This way, a malfunctional pH meter can be detected in time to be repaired or replaced. Always check that the batteries are good and take extras! Record in the field notebook information about the instrument tests and calibrations including: dates, results and person testing the equipment. It may help to label sample containers for each site ahead of time. Field conditions can sometimes make scribbling on jars difficult, and wet conditions make tape not sticky and permanent markers not so permanent.
   6. Cleaning Equipment - All equipment should be cleaned before going into the field and between sites to prevent contaminating sediment samples. Equipment should be washed with clean scrub brushes using a non-phosphate detergent that leaves no residue when rinsed such as Alconox® powdered or Liqui-nox liquid detergent (Liqui-nox is the EPA standard detergent for sampling apparatus). To properly clean equipment, wash apparatus thoroughly with detergent, then rinse 5-6 times with tap water and 3 times with deionized/distilled water if it is available. Rinse the apparatus with site water before taking the first sediment sample.
   7. Field Observations - Take turbidity or Secchi readings first, before the sediment is stirred up. Record all field measurements and observations. Also see 701.3 on field observation and measurements.
2. General Procedures in the Field

   1. Turn on any equipment that needs to warm up (like a DO meter) first or before reaching the site.
   2. Make sure all equipment is clean and ready to use.
   3. When working from a boat, two or three anchors or spuds driven into the sediment in shallow water will help stabilize boat in breezy, open water conditions.
   4. Each grab or core attempt, whether for a composite sample or replicates, should be taken from undisturbed sediment at the site. Avoid disturbing sediments with a boat motor or by walking on the site. Approach sites from downstream to avoid suspending sediment into the water column over the site.
   5. Have container ready to accept entire sample quickly upon retrieval.
   6. Label every sample container with a permanent marker on labelling tape on the side of the jar or wherever the label will not come off accidentally. Information on the label should include: STORET #, District code (e.g., SED, WD, NWD, etc...), Field #, replicate #, date, collector name and analysis type (organic, inorganic).
   7. Record all site information in a field notebook or on fieldsheets before leaving site. Information usually includes: field measurements, time and date, persons collecting samples, number and types of samples taken including field blanks, etc., labels assigned to each sample, and any general observations. Keep records of all samples, how they were labelled and any blanks or controls that are submitted for analysis.
3. Collecting Composite Samples

   Composite samples are generally used to estimate the average concentration of the individual samples that make up the composite. Multiple grabs or cores for a composite sample should be taken from a relatively homogeneous sediment deposit (i.e., all grabs should be of similar sand/silt content). In some cases, composite samples are needed to generate sufficient sample volume for all analyses. It is best to know the rough boundaries of the sediment deposit or "site" before sampling.

   Place each grab or core into a single mixing bowl (made of suitable material), remove any large objects such as sticks, leaves or stones, etc.. and stir thoroughly with a spoon to homogenize. A single grab or core should be mixed at least two minutes. Multiple grab or core samples should be mixed five minutes or longer if necessary.

   Fill sample jars with the sediment mixture by placing one spoonful sequentially into each jar until the jars are full (see section on sample containers). This subsampling system assures that each sample container contains a sample as similar as possible to the other containers.

4. Collecting Replicate Samples

   Replicate samples can be obtained at different stages of the sampling for different purposes depending on the objectives of the study. A study plan should describe where and how much replication is necessary. The procedures described here are for collecting distinct field replicate samples where the object is to determine the variability within a deposit and compare one field site to another.

   When collecting replicate samples to statistically compare sediment deposits, sample sites within each deposit should be randomly located for statistical comparisons to be valid.

   Be sure each sample is taken from an undisturbed area of sediment

   If the replicate samples are fairly similar, the equipment need only be rinsed with site water between samples. But, if the replicates are not similar, and some contain significantly more fines than others, than the core tube or dredge may need to be washed with a non-ionic detergent (see equipment) and rinsed in between samples to prevent cross-contamination and to keep replicate samples independent for valid statistical analysis of the data. Use a tub of water in the boat to wash equipment to prevent getting detergent in the site water while sampling.

Procedures for Core and Grab Sampling Devices

Sediment samples are most commonly collected using a coring device or dredge or grab. The type of collecting equipment chosen will depend on sediment texture, site location (depth and current velocity), analyses to be performed and study goals. See References for more detailed discussion of the pros and cons of various sampling devices.

1. Piston Corer

   1. Preparation and Scope

      A corer allows excellent quantitative and qualitative sampling to a specified sediment depth with little disturbance of the sediment water interface. Samples can be separated or stratified by depth or color/texture to analyze distinct layers of sediment, although the sediment along the side of the core may smear as the core penetrates, slightly distorting the stratification of the sediment.

      A corer may not be able to penetrate and/or retain very sandy substrates. Coring in high clay-content sediments where grabs won't work is possible if the water is not too deep, but may be difficult with a push corer and may require the use of a slide hammer or vibrating corer.

      A large bore corer will provide a larger volume of sediment per attempt. This is important if discreet sample replicates are desired, and enough sample must be collected for a specific analysis or test. Even with the large bore core tube, samples may need to be composited to obtain enough sediment volume for the required analyses and/or tests.

      A hand-operated, 3 inch diameter core sampler with an optional piston and extensions for deeper water can be effectively used in soft sediments with some silt/clay content in water up to ~30 ft deep (see Figures 701.4 A and B for a diagram of the coring device and its use). Core samplers may not be able to penetrate or retain very sandy sediments. Each district should have one of these coring devices with an acrylic core tube. A stainless steel core tube is also available for use from Central Office (call Tom Janisch 266-9268).

   2. Collection Procedure

      This procedure can be used for a push corer with or without a piston. A piston may not be necessary in high clay sediments. Disregard directions for use of the piston if piston will not be used.

      1. Assemble the corer. Adjust the piston (the nut on the bottom adjusts piston diameter) so that it just fits snugly. If the piston is too loose, it will not stay in place until the corer reaches the sediment. If too tight, the piston will not move sufficiently when the corer is being pushed into the sediment, and compaction of the sediment core may occur.
      2. Position the piston at the bottom of the core tube (open end), with the rope attached and threaded through the core head.
      3. With the piston in place, let the core tube fill with water from the top, then lower the corer slowly and vertically to the sediment. If the piston falls out the bottom or moves up the core tube before reaching the sediment, tighten piston slightly and try again.
      4. With the bottom edge of the corer and the piston in contact with the sediment in a vertical position, push the core tube into the sediment while maintaining some tension on the piston rope. The piston should remain at the sediment surface while the core tube moves into the sediment. In difficult sediments, it may be necessary to actually pull on the rope as the corer is pushed into the sediment. The object however is to maintain the piston in a fixed position at the sediment-water interface without compacting the sediment.
      5. In hard or clay sediments where it is difficult to push the corer into the sediment by hand, a slide hammer designed specifically for the core sampler should be used. Do not pound on the core head or extension tubes with a hammer or anything else as this could break or damage the core head or other parts, and is generally less effective than the slide hammer.
      6. After core is pushed to desired depth, pull up the corer slowly while maintaining the position of the piston by holding the piston rope in place. Even with the piston, some sediment may be lost from the bottom of the corer if the sediment is sandy. To help prevent sample loss, bring the corer into a horizontal position as it reaches the surface. A plug can also be inserted into the bottom of the sampler before removal from the water.
      7. Place the corer on the work surface (boat or ice) over the receiving container. The sediment core can be extruded from the top or bottom of the core tube, depending on the purpose of the sample and study goals. Generally, cores collected for macroinvertebrate work should be extruded out the bottom, and cores collected for chemical analysis should be extruded out the top of the core tube if only part of the segment is needed to reduce contamination of the sample segment from other layers.
      8. To extrude through the bottom, remove the sampler head, insert a pole through the top and push down on the piston eyebolt. Extrude the core into a waste container until the desired length of core remains, then extrude the remaining sediment into the sample container. To extrude through the top, remove the sampler head and place an extrusion pole and rubber plug at the bottom of the sampler and push sediment out through the top slowly. A premarked acrylic or polycarbonate (clear) core tube is helpful for measuring core lengths.
2. Grab Samplers

   1. Preparation and Scope

      Grab samplers rely on their own weight and gravity to penetrate the sediment as well as the leverage from the closing of the jaws. For this reason, they are not as efficient in water flowing over one meter per second. They normally take a discreet "bite" of sediment to a fairly consistent and measurable depth. Grabs often cause a shock wave upon descent which may disturb very fine sediment at the sediment-water interface.

      Many grabs and dredges such as the petite Ponar and Ekman dredge are available and used by DNR staff. These two can be hand operated from a suitably sized boat, preferably flat-bottomed. The Ponar is better suited to sampling hard or sandy sediments because of the greater ability to penetrate. The Ekman is more suited to sampling in soft sediments in low flow waters. Neither grab will effectively sample hard clays where a coring device or shovel such as a sharpshooter spade can be used.

      Have a sample tub ready to receive sediment that is large enough to receive the entire contents of the sampler.

      Understand and be careful of the closing mechanism and moving parts on a sampler. It is easy to pick up a grab the wrong way and pinch fingers.

   2. Collection Procedure

      1. Set closing mechanism and lower grab slowly to substrate, being careful to avoid a shock wave caused by too rapid of a descent near the sediment.
      2. Initiate closure mechanism of grab. This is usually a messenger sent down the rope or a sharp pull on the rope.
      3. When it feels like the grab has closed and contains sediment, raise grab at a steady rate and immediately position over large bucket. If jaws are not completely closed due to obstructions, discard entire grab contents away from sampling area and try again. Make sure to move the sampling site at least several feet away from the previous attempt(s) to avoid sampling a disturbed area.
      4. If the study dictates careful sampling for metals analysis, the middle portion of the sample not touching the metal grab can be collected with a teflon or plastic spoon, and the rest of the sample discarded.
      5. Empty entire contents of grab into mixing bowl if sample needs to be mixed.
      6. Place appropriate volume of sediment into sample container.

Quality Control Measures

Sediment samples should be collected from the reference or control sites first whenever possible to reduce the chances of cross-contamination from other sites.

All samples in a study should be handled identically, including using the same sampling equipment, stirring times, etc.

When collecting samples for chemical or toxicity tests, take appropriate measures to prevent contamination from other sources such as vehicle and boat motor exhaust or associated contaminants and other contaminated sites. The person operating the boat motor should either not handle sediment samples or make sure to put on clean gloves to prevent contamination from the motor.

References

Baudo, R., Giesy, J., and H. Muntau, (Eds.). 1990. Sediments: Chemistry and Toxicity of In-Place Pollutants. Lewis Publishers, Boca Raton, FL.

EPA. 1992. Sediment classification methods compendium. Office of Water, Washington, DC. EPA 823-R-92-006.

EPA. 1985. Sediment sampling quality assurance user's guide. Environmental Monitoring Systems Laboratory. Las Vegas, Nevada. EPA/600/4-85/048.

EPA. 1994. Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated Contaminants with Freshwater Invertebrates.

Green, Roger H. 1979. Sampling design and statistical methods for environmental biologists. John Wiley & Sons. New York. 257 pp.

Klemm, D.J., P.A. Lewis, F. Fulk, and J.M. Lazorchak. 1990. Macroinvertebrate field and laboratory methods for evaluating the biological integrity of surface waters. Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH 45268. EPA/600/4-90/030.

WDNR. 1990 (draft). Quality Assurance Guidance for Inplace Pollutant Monitoring Activities. Unpublished document on file at Office of Technical Services, Bureau of Water Resources Management.