Author: Marc Seelinger

Press Release:

For 10 years, the U.S. Army Engineer Research and Development Center’s (ERDC) Cold Regions Research and Engineering Laboratory (CRREL) has  led research on the development of a national manual and data sheet to identify the Ordinary High Water Mark (OHWM) across the United States.

The national manual was released as an interim draft and describes the OHWM, which is used to define the boundaries of aquatic features for a variety of federal, state and local regulatory purposes.

Dr. Gabrielle David, a CRREL research physical scientist, began working on the manual at its inception, and is the chair of the National Technical Committee for OHWM, a group formed with representatives from the Environmental Protection Agency (EPA), regulators from the U.S. Army Corps of Engineers (USACE) and academia. Recently, members of the committee took the manual’s data sheet into the field, going to several rivers and streams in Vermont to take another critical look at their work prior to releasing the manual.

“This is the first time that we’re publishing something nationally to help improve consistency throughout the nation,” said David. “We’ve built a data sheet because we want to help regulators be more rapid in their decision making, be consistent, and have technical defensibility nationwide.”

David also said that even though the OHWM concept has been in regulation for awhile, there has never been a national technical manual published.

Data Sheet and Manual

“We’re releasing it for a one-year period and asking for public comments so that we can then incorporate that into the final version,” said David. “We want to make sure that we have a data sheet and manual that is as helpful as it can be for regulators and for the public.”

Dr. Tracie Nadeau, an EPA environmental scientist, was also in the field with David and USACE regulators using the data sheet to identify OHWM features. Nadeau said the data sheet and manual will be a major asset to the EPA as they work to enforce the Clean Water Act.

“The data sheet is critical for a lot of reasons,” said Nadeau. “When our folks get out in the field and have to make these decisions about how we’re regulating the waters that are under the protection of the Clean Water Act, the data sheets and user manual help assure that we get really consistent decisions in the field across the country.”

The Clean Water Act establishes the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. The basis of the Clean Water Act was enacted in 1948 and was called the Federal Water Pollution Control Act, but it was significantly reorganized and expanded in 1972. “Clean Water Act” became the Act’s common name with amendments in 1972.

Under the Clean Water Act, the EPA has implemented pollution control programs, such as setting wastewater standards for industry. The EPA has also developed national water quality criteria recommendations for pollutants in surface waters. Section 404 of the CWA establishes a permitting program implemented by USACE, which regulates the discharge of dredged and fill material into the water of the United States.

Applicability

Nadeau said the national manual and data sheet are important for good government, for consistency, and for the defensibility of the decisions that the EPA or USACE makes. She added that the data sheets are a quick “how-to roadmap” of applying the information from the manual.

“So, for us at EPA, we co-administer the Clean Water Act with the Army Corps of Engineers,” said Nadeau. “But EPA actually has to administer all these other programs under the Clean Water Act in its entirety. So, for EPA in particular, we will definitely use these data sheets in the larger manual of how we go out and do a determination of ordinary high-water mark to support lots of programs under the Clean Water Act, because we have to know where the federal government actually has authorities or jurisdiction, so it’s really helpful for the decisions we make around permitting, around national pollution discharge.”

ERDC works with the USACE Regulatory Program, other federal agencies and the academic community to develop regional and national OHWM delineation standards and procedures, as well as to improve OHWM delineation practices across the country. Research scientists test and validate the field indicators and methods used in OHWM delineations and explore new tools, techniques and resources to improve the accuracy, consistency and efficiency of OHWM delineation practices. These efforts have resulted in OHWM delineation manuals, such as the newly released national manual and data sheet, and other technical resources that support both the Corps Regulatory Program and the regulated public.

Sources

Marquis, D. (2023). Press release: ERDC Releases New Data Sheet for Identifying Ordinary High Watermarks. Cold Regions Research Laboratory. Retrieved from https://www.erdc.usace.army.mil/Media/News-Stories/Article/3280392/erdc-releases-new-data-sheet-for-identifying-ordinary-high-watermarks/

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The use of a survey grade level is critical for obtaining accurate measurements of various biological features, biological benchmarks, etc.  This information is used for many purposes including stream restoration, coastal restoration, wetland restoration, and other design purposes.

There are two types of levels used for construction and design. The older of the two is known as the Dumpy level. This level is like a spotting scope with crosshairs. It is highly accurate (despite its name) and has an added advantage of being able to measure distance. However, it does require much more work to operate and is limited to a range of about 30 feet.  It also requires two people to operate.

Laser levels are the other commonly used measuring tool and are a significant improvement over the Dumby levels. The major benefit is that the distance away from the level is pretty much as far as you can see.  This reduces the number of station moves and speeds the process along.  You also only need to have one person to operate the level.

There is a third option which is to use a surveyor total station. This, however, is a complicated process and usually beyond the level of detail needed for most biological assessments.  A corollary to this is the use of GPS. GPS is great for x and y coordinates, but it is often meters off on the elevation (z).

Laser Levels

You do not need to spend a lot of money to purchase a quality laser level. You can often find these for sale in big box home improvements stores and hardware stores.  They are around a couple of hundred dollars. You can also rent one from a survey supply shop for about $20-$30 per day. Survey grade levels are usually in the $500 to $1000 range.  This is worth the investment if this type of work is a regular thing for you.  Also, do not cheap out on the box. The level will get bounced around so you will need a quality instrument case.  This is sometimes a problem with the home center levels.

The laser receiver is usually included with the laser level.  This is a little box that attaches to the survey rod with thumb screws.  It takes batteries and makes a tone when the laser beam from the level hits it.

The level should be placed upon a quality tripod. This is not the same type as you use for a camera. Survey grade tripods are usually made of wood or aluminum and have steel spikes to set it into the ground.  The legs are adjustable so that you can adjust your level. The level should be about chest high when mounted so the tripod needs to be 4-5 feet high when set up.

Next on your shopping list is a survey rod. You want to get the smallest rod that will serve the purposes of the site work you are doing. A 12-foot rod is much better than a 25-foot rod if you only need to go up a few feet. The bigger the rod the more sway you have, and the measurements will be less accurate. However, if you have a steep slope on your site, a bigger rod may be necessary.

You will also need a measuring tape or carpenter’s rule.  It is better to get one that is calibrated to 1/10’s of a foot rather than inches.  The survey rod is always in 1/10’s of a foot, however, make sure you are not using a metric rod.

Set Up

The first thing that you want to do is take a walk around the area that you need to survey. You want to find the best place to set up the level so that you do not need to move it more than necessary. Keep an eye on slope, trees and other obstructions.  The level needs a clear line of sight. You can clear some of the vegetation away, but it is usually easier to find a spot that would require the least amount of work to get your shots. The tripod should be set up above the highest point you are going to survey. You need to include the height of the level receiver on the rod when you are making this estimate. This translates to about 5 feet above your highest point. The level needs to be able to “see” the receiver.  If the level is set is too low it will shoot below the receiver mounted on the rod.  You can move the receiver down, but that would require that you recalculate for those shots.

Keep the level in the box until you are ready to place it on the tripod.  Do not attach it to the tripod and then walk around with it.  It should be boxed when moving it around the site.

Set the legs up on as level a surface as you can. Adjust the legs so that the level mounting plate is fairly level. You can use a hand level to do this or the bubble level on the laser level itself.

The laser level attaches to the tripod by way of a large screw below the mounting plate. Do not tighten this too much until you have leveled the level. There are three or four leveling screws on the level. There is also a glass bubble level on the mounting plate. Adjust the leveling screws so that the level is dead on the level in all directions. This will require that you spin the level around and make adjustments. If you have attempted to level the tripod before you mounted the level, this will go fairly quickly. 

Instrument Height

There is usually a marking on the level where you should measure downwards to the ground. We are also going to determine the height of the instrument using the back site, but you should always measure the distance from the instrument to the ground.

Backsight

You should place a project benchmark somewhere near the level set up. This serves as your project control and can be surveyed for real later if you need to derive actual elevation points from your level runs. This control should be set using a pin, rod, pipe or other relatively permanent makers. Wooden stakes do not work as they can be easily removed or damaged.

The backsight elevation is any number that makes sense. The convention is to set it at 100.  You may come back later in drag control onto the site to determine the actual elevation, but that is not necessary for this type of work.

The laser level indicator should be attached to the rod, usually at the tip. Note the location of the indicator. For example, it is on the rod at 4.5 feet. Most telescopic rods have a height indicator on the back of the rod.  As you raise the rod the height indicator numbers will change.  Be careful to raise the rod in the proper order.  This varies with some rod types so be sure to check with the manufacturer on the use of the rod.

A Direct Elevation Rod or a “ Lenker Rod ” is the most common type and has numbers in reverse order on a graduated strip that revolves around the rod on rollers. Figures run down the rod and can be brought to the desired reading—for example, the elevation of a point or benchmark. Rod readings are preset for the backsight, and then, due to the reverse order of numbers, foresight readings give elevations directly without calculating backsights and foresights.

Turn the laser on and position the rod on the benchmark and raise the rod until you hear a steady tone. You will usually hear a slow chip when you are just below the laser beam and a fast chirp when you go past it.  Note the rod reading. That is your backsight reading. Add the elevation from the benchmark rod reading and you have your height of instrument (HI).

For example, your benchmark is elevation one hundred. Your rod reading on that benchmark is 4.06.  Therefore, your Height of Instrument (HI) is 104.06’.  Your benchmark elevation should be lower than the instrument ground location.  If not, you need to adjust the detector and do some more math. It can be done, but it takes more time.

Now you are ready to go to work on the foresight.

Position the rod directly on the ground at each feature shot. The rod should be straight up and down. There are plumb levels you can attach to the rod to help you. Some laser detectors will also beep at you if you are too far out of plumb.

Raise the rod until you hear that steady tone. Note the rod reading. Make sure that you raised the rod in the right order and that the numbers are being read correctly.  Usually, this is a matter of checking reality.  If your rod reading suddenly jumps by 5 feet from the last point you may have raised the rod sections in the wrong order.

Record each feature and provide some notes. A level book works great for this. This is an example of a level book set up.

Set Up-Example 1

At each feature subtract the foresight (FS) from the Height of Instrument (HI) to derive the elevation.

In this example, we have a 1.28’ difference from mid tide (MT) to Mean High Water (MHW). We can, therefore, assume that our total tidal exchange would be 2.56’ from Mean Low Water (MLW) to MHW.

We would need to check many other points. Usually, for a biological benchmark survey, we would to stationing along a cross-section.  Each feature would be relative to the feature type and its location on the cross-section.  In our example above, the distance from the MT to MHW is 25’.  This is measured by setting a fixed starting point at 0+00 and measuring along that line.

If you need to move the level you will need to calculate a new HI.  Make sure to reference the setup with the data.  Start a new table for a new set up.

Finally, if you need to determine the real elevations of your features survey the benchmark. This will require a surveyor to locate nearby elevation control and drag that onto the site using traverse lines. You can also use high-end GPS for this.  In our example above the real elevation for the benchmark is 456’ NAVD 88.  Our new HI is 460.06.  We need to make sure we cite the vertical data source. In this case, it is North American Vertical Datum of 1988 (NAVD 88). Therefore, our MT is 453.43’ NAVD 88 and the MHW is 454.71’ NAVD 88. You can do this for all the data associated with the benchmark.

One final note

If you are doing level runs for design purposes, you may or may not need a licensed land surveyor to sign off on them.  However, if you are doing any floodplain calculation work you will most likely need the help of a licensed surveyor. Some jurisdictions allow licensed professional engineers to do this as well. This is a matter of state and federal law so be careful and ask questions.

Just how accurate are vegetation inventories? Currently, we are allowed to conduct a visual estimate of percent cover of a given plant species. Based upon the 2020 US Army Corps of Engineers National Wetland Plant List we can determine whether a site has a hydrophytic plant community. Two issues arise from this methodology. The first of course is the proper identification of the plant species. Most wetland biologists put forth a tremendous effort in trying to correctly identify both the genus and species of a given plant. However, the second issue is the estimate of percent cover. This is highly subjective and prone to large error.

The procedure for determining percent cover is a simple guesstimate of looking up into the sky and estimating how much cover each species occupies. Similarly, we also look downwards and estimate the aerial cover of smaller species. The problem lies in the fact that it’s a guess. If you were to have a dozen wetland biologists on a given site, I can almost guarantee that you will have a dozen sets of data. The problem is exasperated by the fact that it is entirely possible for one group of individuals to identify a plant community as being hydrophytic and another group looking at the exact same plant community and find it to be an upland community.

How is this possible? Well quite simply the problem lies in the data collection itself. The current methodology can have variances up to 40%. If you were to go to court and had to defend your data what would be your comfort level given this type of variance?

Fortunately, the US Army Corps of Engineers has published another plant collection methodology. Buried deep in the back of the regional supplements in Appendix B is a procedure called the point intercept sampling method. This procedure is highly accurate and can have a variance of less than 2% among numerous data collectors. As you might suspect it takes a bit longer to do this type of procedure, but the data is rock solid. The following procedure is taken directly from US Army Corps of Engineers regional supplements for wetland delineations. It is highly recommended that you consider incorporating this procedure into your routine wetland delineation methods. As part of our wetland delineation programs, we offer training using this methodology.  Please review the methodology outlined below and let us know your comments.

Appendix B: Point-Intercept Sampling Procedure for Determining Hydrophytic Vegetation

The following procedure for point-intercept sampling is an alternative to plot-based sampling methods to estimate the abundance of plant species in a community. The approach may be used with the approval of the appropriate Corps of Engineers District to evaluate vegetation as part of a wetland delineation. Advantages of point-intercept sampling include better quantification of plant species abundance and reduced bias compared with visual estimates of cover. The method is useful in communities with high species diversity, and in areas where vegetation is patchy or heterogeneous, making it difficult to identify representative locations for plot sampling. Disadvantages include the increased time required for sampling and the need for vegetation units large enough to permit the establishment of one or more transect lines within them. The approach also assumes that soil and hydrologic conditions are uniform across the area where transects are located. Transects should not cross the wetland boundary. Point-intercept sampling is generally used with a transect-based prevalence index (see below) to determine whether vegetation is hydrophytic.

In point-intercept sampling, plant occurrence is determined at points located at fixed intervals along one or more transects established in random locations within the plant community or vegetation unit. If a transect is being used to sample the vegetation near a wetland boundary, the transect should be placed parallel to the boundary and should not cross either the wetland boundary or into other communities. Usually, a measuring tape is laid on the ground and used for the transect line.  Transect length depends upon the size and complexity of the plant community and may range from 100 to 300 ft. (30 to 90 m) or more. Plant occurrence data are collected at fixed intervals along the line, for example every 2 ft. (0.6 m). At each interval, a “hit” on a species is recorded if a vertical line at that point would intercept the stem or foliage of that species. Only one “hit” is recorded for a species at a point even if the same species would be intercepted more than once at that point. Vertical intercepts can be determined using a long pin or rod protruding into and through the various vegetation layers, a sighting device (e.g., for the canopy), or an imaginary vertical line. The total number of “hits” for each species along the transect is then determined. The result is a list of species and their frequencies of occurrence along the line (Mueller-Dombois and Ellenberg 1974, Tiner 1999). Species are then categorized by wetland indicator status (i.e., OBL, FACW, FAC, FACU, or UPL), the total number of hits determined within each category, and the data used to calculate a transect-based prevalence index. The formula is similar to that given in Chapter 2 for the plot-based prevalence index (see Indicator 3), except that frequencies are used in place of cover estimates. The community is hydrophytic if the prevalence index is 3.0 or less. To be valid, more than 80 percent of “hits” on the transect must be of species that have been identified correctly and placed in an indicator category.

The transect-based prevalence index is calculated using the following formula:

PI = FOBL + 2FFACW + 3FFAC + 4FFACU + 5FUPL

FOBL + FFACW + FFAC + FFACU + FUPL

where:

PI = prevalence index

FOBL   = frequency of obligate (OBL) plant species;

FFACW = frequency of facultative wetland (FACW) plant species;

FFAC   = frequency of facultative (FAC) plant species;

FFACU   = frequency of facultative upland (FACU) plant species;

FUPL   = frequency of upland (UPL) plant species.

Over the past several months, several US Army Corps of Engineers (USACOE) districts have started using a new review process called Delineation Concurrence (DC).  A DC provides concurrence that the delineated boundaries of wetlands on a property are a reasonable representation of the aquatic resources on-site. A DC does not address the jurisdictional status of the aquatic resources.  The DC is often an email exchange and does not usually require a site visit.

The DC arose out of the need for the USACOE to streamline its review process with ever shrinking resources.  The need for speed has been a major concern for the Corps as the number of projects under review have increased tremendously.   The DC process is a very simple and quick process, but it has some limitations.

The most significant issue is that the DC does not verify jurisdiction.  This remains with the Approved Jurisdictional Determination (AJD) process.  The DC is like the Preliminary Jurisdictional Determination (PJD) process, but it does not require the field work associated with the PJD.  The DC relies primarily on remote sensing, maps, and other third-party data to concur that aquatic resources are on a site.  Neither of the DC or PJD procedures address the jurisdictional status of the aquatic resources.

The DC process still requires the consultant to preform a full wetland delineation.  The consultants are on the hook for any inaccuracies represented to the Corps.  If a third party challenges a DC, the consultant is the only one that will be defending the aquatic resource data.  The Corps is not providing any “seal of approval” with a DC or PJD.

The main use of the DC is for Nationwide permits.  If the applicant submits a permit request with a Prior Construction Notification (PCN) form, they can also request a DC at the same time.  The Corps is discouraging “standalone” requests and prefers that the JD request be associated with a permit.

This can complicate matters with other regulatory entities and planning boards.  For years the Corps has been training these agencies to require JDs before they issue approvals.  It is going to take some time and a shift in thinking to get these agencies to no longer require JDs.  It may also require formal changes in local ordinances as many municipalities have written the JD requirement into their municipal codes.

It is a reasonable question to ask why the Corps is doing this.  In effect they seem to be backing out of whole JD process.  In fact, they are.

In 2016, the Hawkes case was ruled upon by the Supreme Court of the US (SCOTUS).  That case revealed that JDs are final agency actions that can be immediately appealed in court.  This changed the role of the Corps in the JD process.  They are no longer the final arbiter of what is a jurisdictional aquatic resource.  A federal judge now makes that determination.  The Corps acts as another (well informed) opinion.

There is a fair amount of risk associated with DCs.  If a site has a waterbody on it that the consultant thinks is non-jurisdictional, the consultant is on the hook for that determination.  This is true even if the Corps issues a full AJD.  The liability for the accuracy of the jurisdictional data remains with the consultant and the applicant for DC requests.  In the AJD scenario, the Corps would only become a co-defendant should the determination be challenged.  The Corps makes it very clear that DCs and PJDs are non-binding and do not represent a jurisdictional opinion.

All of this opens the possibility for legal challenges to what is a deemed a jurisdictional aquatic resource under the Clean Water Act.  Any project, big or small, can be challenged by a variety of third-party environmental groups, federal agencies like the EPA or Fish and Wildlife, or other public interest groups.  The accuracy and defense of the site data remains with the consultant, the applicant, and the landowner. 

This leads us into a discussion of whether there should be some sort of licensing or credentialing of aquatic resource delineators.  It would be fair of an insurance company to question the credentials of someone who does this type of work before they issue an Errors and Omissions (E&O) policy or pay on a claim should the consultant be sued.  It is envisioned that it would be some sort of state board would be needed to license aquatic resource delineators.

The Corps has implemented the DC program in over half of the U.S.  Many other Corps Districts are considering it.  It is a useful permitting tool, but it underscores who is ultimately responsible for the jurisdictional determination.  The Corps has made it clear they will no longer assume responsibility.

One of the most fundamental and often confusing topics around soils are hydric soil indicators. There are just so many of them. Each regional supplement also has different indicators. Tweaks are often made that are region or sub-region specific. 

The most basic concept surrounding the hydric soil indicators is that they only apply to hydric soils. Now this may seem a bit obvious, but it is critical to the understanding how they work. Non-hydric soils do not exhibit any of the listed indicators. However, if an indicator is present, it tests positive for hydric soils. Once that happens, it is not usual to find multiple indicators in the same soil profile. If there are no indicators present, the soil is not hydric, and no indicators should have been found. This becomes a bit tricky when dealing with remnant hydric soil as shadows of indicators might be present. However, the soil is not actively hydric. The lack of hydrology indicators may help to confirm this. 

The next topic is, “what is it we are looking for?” The hydric soil indicators are based upon how three groups of elements respond to the presence of water. It is not just the presence of water, but the anaerobic environment the water creates. These element groups are: 

• Carbon 
• Iron and Manganese 
• Sulfur 

The easiest one to spot is sulfur. The soil stinks like rotten eggs. If you have stinky soil, you meet one of the hydric soil criteria. Iron and manganese are also easy to spot. There is a distinct color change from orange red to grey in the case of reduced iron. The anaerobic environment chemically changes the color of the soil. Manganese tends to turn black in this wet environment. However, the problem with these chemicals is that the color change back to the brighter colors in an aerobic environment may not happen quickly or at all in some cases. Consequently, you need to make sure that you have an active reducing environment by cross checking your hydrology indicators. 

Carbon is perhaps the trickiest. A simple explanation is that a significant amount of organic material (a.k.a. carbon) is present due to the lack of oxygen in the environment. The soil microbes are not able to break the organic material down because they need oxygen to do this. The more the soil is subjected to anaerobic conditions, the thicker the layer of undigested carbon becomes. The more organic matter, the more likely the soil is hydric. 

To help organize the indicators, the Corps uses the USDA texture classes. Each indicator is grouped based upon it’s dominate texture. These include sand, loam, and no specific texture.
Sand is the easiest, the texture is sandy like beach sand. All the indicators have this in common. The funny thing about this one is that the presence of organic matter is a big part of the “S” indicators. 

Loam is denoted by the letter “F.” It stands for fine sand or finer. This includes silts and clays. Most of the indicators in the F category related to iron and manganese color changes. 

All soils are the last category and are listed as not specific to any one texture type. Many of the poorly drained organic soil types fall into this category. However stinky soil also is an “A” indicator. These are sort of “other” but with a strong emphasis on organic soils. 

One last thought on this soil overview, many of the indicators have thickness requirements. A given soil feature must be a specified thickness to count. It may also have to occur at a specified depth. Otherwise, the feature does not count. You can also combine features, if present, to meet these thickness thresholds.