METHODOLOGY


HUMMOCK ELEVATION MEASUREMENT


Establishment of Benchmarks

 A benchmark was established in the Agrifos site by driving a 5-foot long (1.5m),
 /4-inch (0.64 cm) steel rebar into the ground at a central point between the hummocks
 after construction. Four-foot (1.2m) lengths of -inch (0.64cm) steel rebar were driven
 into the center of each hummock leaving a six-inch section above ground. Elevations,
 based on a surveyors benchmark elevation, were taken at the top of each rebar by
 surveyors during the as-built site survey. Benchmarks were established in the Cargill site
 using 5-foot (1.5m) lengths of -inch (0.64cm) steel rebar. Rebar was driven into the
 center of each hummock leaving 1-foot (30.5cm) of rebar exposed above ground.
 Elevations were taken at the top of each rebar relative to the surveyors' benchmark. No
 benchmark was established in the Iluka site, as survey information was not available.


 Elevation Measurements

 A tape measure was stretched across the length and width of each hummock
horizontally from the center rebar to establish major and minor transects along the
centerline. A typical hummock with transects is shown in Figure 5.5. Stake flags were
placed at 30.5cm intervals to serve as permanent sampling locations in the Agrifos and
Iluka wetlands. Permanent sampling locations were set up at 61cm intervals in the Cargill
wetland because of larger hummock sizes. Heights were taken with a laser level placed at
the benchmark point between the hummocks. The readings were given in feet and inches
to the nearest tenth of an inch. Height measurements were taken at each sampling point.
Height was also taken at the top of each rebar to provide a relationship with the
benchmark elevation relative to mean sea level (MSL).

 The top of the rebar was considered the zero point. Each hummock height was
subtracted from the height at the top of that hummock's rebar to give a difference in
height in feet at each point. The difference in height was subtracted from the known
elevation at the top of the rebar to get the elevation above sea level. Elevation versus
distance was then plotted using the Excel 97 spreadsheet.

 Cross sectional areas along the major and minor transects were generated for each
hummock (Figures A1-A35) by using multiple applications of Simpson's 1/3 Rule and
Simpson's 3/8 Rule (Chapra and Canale 1988).