\fDT Montana Wetland Assessment Method May 25. 1999 



provides discussion and instructions for completing each of the fields on the form. 



The COE Regulatory' Division must consider impacts to wetland ftmctions and values when evaluating Section 404 pennit 

 apphcations. Functions are self-sustaining properties of a wetland ecosystem that exist in the absence of society, and relate to 

 ecological significance without regard to subjective human values (COE 1995). Groundwater discharge is an example of a wetland 

 function. Values are benefits that derive from either one or more functions and the physical characteristics associated with a wetland 

 (COE 1995). The value of a given wetland function, or combination of functions, is based on human judgment of the worth, ment. 

 importance, or quality attributed to those functions. 



The following functions and values are evaluated by this method: 



Habitat for federally listed or proposed threatened or endangered plants or animals 



Habitat for plants or animals rated S 1 , S2, or S3 by the Montana Natural Heritage Program 



General wildlife habitat 



General fish/aquatic habitat 



Flood attenuation 



Long and short-term surface water storage 



Sediment/nutrient/toxicant retention and removal 



Sediment/shoreline stabilization 



Production export/food chain support 



Groundwater discharge/recharge 



Umqueness 



Recreation/education potential 



The form assesses and assigns each of the 12 fiinctions and values ratings of "low", '"moderate", or "high" (or, in some cases, 

 "exceptional"), and scores each on a scale of . 1 (lowest) to 1 (highest) "functional points". The scoring scale for each function and 

 value is similar to that of HGM, although HGM does not generalh consider values and not all of the variables considered by HGM 

 with respect to a given function were included in this method. 



Functional points are summed on the data form and expressed as a percentage of the possible total; functions that do not apply to a 

 given wetland are assigned a rank of "NA" and are not included m point totals. This percentage is then used in conjunction with other 

 cnteria to provide an overall wetland ranking into one of four categories. Category I is the highest overall ranking a wetland can 

 receive, followed by Categorv II. Category III, and Category IV. Functional points can be multiplied by the total existing or expected 

 (post-project) acreage in the assessment area (AA) to determine the total "functional units" existing. ex"pected to be lost or expected to 

 be gained at a given site. Wetland categories and functional units are further discussed in the latter portion of this section. 



When completing fields 14A through 14L (the functions and values assessment portion of the form), if it is the evaluator's best 

 professional opinion that a rating for a particular function is inadequately represented on the form due to specific site conditions, it is 

 appropriate to override the calculated value and note the justification in the comment space provided. It is important to note. howe\er, 

 that this should be treated as the exception rather than the rule. 



Generally, it is appropnate to assess wetlands, or assessment areas (AAs). indi\idualh' on separate data forms. Howe\er, it is also 

 appropnate to address several AAs on one data form if the AAs are very s imil ar with respect to size, composition, exposure to 

 disturbance, and other features. Several very similar roadside ditch wetlands along a proposed highway project would comprise an 

 example of when several AAs could be assessed on one data form. AAs that differ enough from one another such that they would 

 result in different ratings for various fiinctions and values should be assessed on separate data forms. 



Several attributes throughout the form are rated by working through matrices. Variables used within these matrices are addressed in a 

 dichotomous, "top to bottom" fashion, resulting in an assignment of functional points and a rating for each evaluated function. An 

 example based on the matrix used to evaluate flood attenuation is provided below. In this example, estimated wetland acreage subject 

 to floodmg is at least 10 acres. > 75 percent of the flooded wetland is forested, scrub-shrub, or both, and the site contains an 

 unrestricted outlet, receiving a score of .9 and a rating of "high" for this function. 



