Fixmell WPA 



CllBatic setting. The net annual precipitation balance for the 

 Furnell WPA (from the MAPS database) is -19 inches, showing Furnell 

 to be the least evaporatively intense of the plains sampling sites. 

 Monthly average precipitation for the Gold Butte climatic station 

 shows a broad summer peak with a maximum in June. The 3-year 

 moving averages for the Gold Butte station appears to show roughly 

 cyclical peaks with a period of 6 to 11 years. The moving average 

 has been mostly near or above the long-term mean since the mid 

 1980s; in 1993 (the year prior to sampling) the annual total 

 exceeded the long-term mean by more than 10 inches. 



Geologic setting. The Furnell WPA site is underlain by calcareous 

 till deposited in a prominent end moraine complex. The moraine 

 marks the terminus of a late Pleistocene glacial lobe which 

 occupied the gap in the Sweet Grass Hills. Till underlying the 

 sample site appears relatively loose-textured with a matrix of fine 

 sand and silt. 



Bedrock beneath the till cover is sandstone and shale of the late 

 Cretaceous Eagle Formation and Claggett Shale, regionally intruded 

 by the alkaline intrusive complex underlying the Sweet Grass Hills. 

 There are producing and shut in natural gas wells within a few 

 hundred meters of the site. 



Hydrologic type. The Furnell site is a small glacial kettle 

 lacking surface drainage at water levels represented by the samples 

 analyzed. Shoreline features and drainage development indicate 

 outflow from the pond occurs at pond stage roughly 3 feet higher 

 than that observed in August 1994. Ground-water outflow may 

 occur, based on topographic position and the character of 

 underlying glacial sediments. 



Basin characteristics. The Furnell site is very small but has an 

 intermediate catchment to wetland area ratio among hydrologically 

 similar sites. The basin has a relatively flat bottom and a 

 maximum depth of approximately 1.5 feet at water levels observed 

 in August 1994. The pond has two prominent slope breaks appearing 

 to correspond to periods of higher stage; the upper feature 

 probably relates to an upper stage controlled by surface outflow. 

 The outflow channel is a grassy swale with poorly defined meander 

 patterns shown by vegetation; outflow appears to have occurred 

 relatively recently and may occur on a regular seasonal basis. 

 Water chemistry. The Furnell site contains water of a dilute 

 calcium/potassium - bicarbonate character. The proportionately 

 high potassium concentration is unusual among the sampled wetlands. 

 Equilibrium calculations indicate moderate supersaturation with 

 carbonate species. 



Water column concentrations of trace elements were either below 

 detection limits or (for arsenic and boron) near detection limits 



