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Sampling Platforms
Building a platform
Installing a platform
This page provides detailed instructions on sampling platforms and how to build them.
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Because the SET measures elevation change of soft, unconsolidated wetland sediments, you need to minimize your impact to the immediate area around the benchmark pipe or rod you install. This is usually accomplished by constructing a wooden sampling platform.
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Most of the platforms that we construct are "permanent" and remain at the study site indefinitely. There are situations where you may not be able to use a permanent platform. Some managers may not allow them. In these circumstances, the use of a portable platform can be used. A portable platform consists of planks with "milk crates" or "step stools" attached to the bottom to elevate the planks above the marsh surface (see 3 photos below). These are carried to the site, along with a 3rd plank for sampling and are removed when finished. This makes for a lot of work when you have to sample but it will minimize your impact in the sampling area. We have also had sites where we only installed the teeth and brought the planks with us each time.
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When circumstances necessitate, you can also get away without using a platform. We have not used platforms in areas where it's very difficult logistically to transport the lumber and build them. Also in other sites where a platform would be too visible. For this to be successful, the site has to have relatively firm sediments. You need to be very careful and consistent in how you approach the SET pipe and stand for sampling.
Building a sampling platform:
Platforms are usually constructed out of treated lumber consisting of 2 planks (2"x10"x8' or 2"x10"x10') supported by 2 “teeth” which are pounded into the ground. The teeth are constructed out of 2, 2x4's bolted to a 32" crosspiece. The crosspiece is made out of a 2x4 or a 2x6.
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The length of the legs on the teeth will vary depending on where you are installing them. In shallow ponds or in unconsolidated sediments, you may need 8' long legs. You may also need to add a second crosspiece to the tooth to stabilize it further. In firm or very firm marshes, you will need legs 4' or less. Be sure to have the 2 vertical legs stick up above the crosspiece a few inches. This will provide a guide to keep the planks from sliding off the tooth.
The 2 planks on a platform are spaced about 8 feet apart (See below diagram). A third plank (10' is ideal) is laid across the other 2 planks to access the area around the SET pipe. The platform is laid out with the SET sampling sites located between the two planks. Feldspar plots, if used, are located around the outside of the platform.
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NOTE: The deep and Shallow RSET's are smaller and requires less platform area than the original design SET. The above instructions are for the original SET. You can scale down these platforms and still have plenty of room for the rod SET.
Installing a sampling platform:
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Step
1 - Install the Front Two Teeth
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| Step 1- Insert the front two teeth. They will be about 6-8 feet apart. Use a sledgehammer to knock them into the substrate. Crosspieces should be about 1-2 feet above the surface. Possibly higher if you are in a pond. | |
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| Step 2 - Lay Planks | |
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| Step 2: Lay planks on each tooth. The far end of the plank will be laying on the marsh (or on the pond bottom). Make sure they are perpendicular to the tooth. | |
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| Step 3 - Install the Back Teeth | |
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| Step 3: Walk out onto the plank with a tooth in your hands ready to install. Be careful, this is a tricky maneuver and you may be likely to slip. Have another person steady the board you are walking on. This same person can pass you the sledgehammer once you're at the end of the plank. While standing on the plank, knock the far tooth into the ground. Do the same for the other side. All four teeth are now in the ground. | |
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Step 4: Walk back to the end of the plank and step off. Pull the board back and lay it on top of the far tooth. You are finished! Bolts: Be sure to tighten the bolts on the crosspieces. Planks: If you are leaving the planks on the platform, you might consider nailing them down. This will keep them from floating away and getting stolen (hopefully). |
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U.S. Department of the Interior, U.S. Geological Survey, Patuxent Wildlife Research Center
URL: http://www.pwrc.usgs.gov/ | Last Updated: 14 February 2003
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