appendix o exposure scenarios and unit dose factors ... - Hanford Site

HNF-5636 Rev. 0
HNF-SD-WM-TI-707 Revision 1
estimate food production per unit garden area, two approaches were considered. The first is
commercial food production in Washington State (WA Department of Agriculture 1994). Values
for production per acre and per square meter are shown on Table 15. "cwt" means 100 pounds.
Bushels of grain were assumed to have a density 70 percent that of water (700 kg/m³). Thus a
bushel of grain is assumed to weigh about 54 lb. The categories used for human consumption are
from Table 13. The average person consumes the amount shown, in kg/y. Based on the average
food production rate, the necessary garden area is 194 m². This total area is mostly needed for
production of grains. This area also requires an efficient gardening operation to succeed.
The second approach to estimating garden size uses garden production estimates published
by the Washington State University (WSU) Cooperative Extension (1980). Values are listed in
Table 16. The document provides estimates of pounds of produce per 10 foot row in a garden.
In addition, it gives recommended row spacings. The spacing was treated as the row width to
compute production per unit area. The same average annual consumption rates from Table 13
were used to determine garden area needs. The WSU production estimates are higher than the
commercial production averages hence the needed garden area is smaller (161 m²). These were
assumed to be optimum values under excellent growing conditions.
For performance assessment gardens, an efficiently planned and maintained garden of 200
m² will be assumed to supply 100% of the garden produce needs of a single adult over a year's
time, or 25% of the garden produce needs of a family of four. Note that this represents a marked
decrease from previous performance assessments. Ingestion doses from the post-intrusion garden
are thus expected to increase due to the higher soil concentration.
Table 15. Commercial Food Production as a Basis for Garden Size.
Type of Produce Yield per acre Yield kg/m²
Garden
Area
Leafy Vegetables 16.5 kg/y 2.35 7.0 m²
Cabbage
Chard
Lettuce 210 cwt 2.35
Spinach
Exposed Produce 38.4 kg/y 1.79 21.5 m²
Apple 17 tons 3.81
Apricots 6.23 tons 1.40
Asparagus 35 cwt 0.39
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