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Native Plant Synoptic Garden
10
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(see Figure 3) fog can mediate daily water stress; as a result many of Western Washington’s
plants are adapted to these specific conditions.
Wind
Using data
collected at Sea-Tac
International Airport and
at Boeing Field by the
Western Regional Climate
Center, Figure four shows
the average monthly wind
speeds from the years
1992 to 2002. The
average annual wind
speed is 8 mph at Sea-Tac
Airport and 6.7 mph at
Boeing Field. The
average wind direction for
both measuring stations is south, but July through September, the winds generally come from a
northerly direction (WRCC, 2004). Believing this to be true for the Arboretum as well, the
northerly winds would aide in mitigating high summer temperatures at the northern end of the
arboretum. This aid is further enhanced since there is not a lot of wind obstruction north of
Arboretum Drive.
Soils
SPEED (mph)
9
8
7
6
5
4
3
2
1
0
8.8
8.6
8.4
6.7
6.6
7
8
7.2
8
7.1
7.8
7.2
7.4
6.8 7.2
6.5
JANUARY
FEBRUARY
Soil samples taken from portions of the proposed site were sent to the Soil and Plant
Tissue Testing Lab at the University of Massachusetts (UMASS) for analysis; a copy of this
analysis can be found in Appendix A. Figure five illustrates data collected by group members
who took three different soil samples with a soil corer to measure bulk density and the
MARCH
FIGURE 4:
AVERAGE WIND SPEEDS FOR THE SEATTLE AREA
gravimetric water content or percent moisture. Sample A was located within the upper bowl area
of the proposed valley bottom area, sample C was also taken at the northern end of the proposed
lower valley bottom area, and sample B was taken from the trail along the western ridge of the
APRIL
MONTH
MAY
JUNE
JULY
AUGUST
SEA-TAC AP BOEING FIELD
SEPTEMBER
7.1
6 6
OCTOBER
7.3
NOVEMBER
8.1
6.6
DECEMBER
8.9
6.8