2008 Site Environmental Report for Pantex Plant

2008 Site Environmental Report for Pantex Plant
Humidity averages are low, occasionally dropping below 20 percent in the spring. Low humidity moderates
the effect of high summer afternoon temperatures, permits evaporative cooling systems to be very effective,
and provides many pleasant evenings and nights.
Severe local storms are infrequent throughout the cool season, but occasional thunderstorms with large hail,
lightning, and damaging wind occur during the warm season, especially during the spring. These storms are
often accompanied by heavy rain, which can produce local flooding, particularly of roads and streets.
Pantex Plant is located in an area with a relatively high frequency of tornados: an average of 14 tornadoes
each year occurred in the 20 counties of the Texas Panhandle during the period between 1950 and 2000
(DOCb). While the threat of tornadoes is real, tornado occurrences in Amarillo are generally rare.
Tornadoes are most common from April to June. There were 12 tornadoes reported over the Texas
Panhandle during the 2008, close to the average, but 50 fewer than those that were observed during the very
active year of 2007 (DOCc).
The normal annual mean temperature in Amarillo is 13.9˚C (57˚F), while the normal annual rainfall for
Amarillo is 49.9 cm (19.65 in.) (Department of Commerce [DOCc]). The year 2008 was slightly wetter
than normal in the area of the Pantex Plant, as the official Amarillo Airport National Weather Service
(NWS) rain gauge recorded 57.0 cm (22.44 in.) of precipitation. 2 This amount is approximately 14 percent
above the normal. Snowfall totaled 18.0 cm (7.1 in) at the NWS, or only 40 percent of normal. The
potential gross lake surface evaporation in the area is estimated to be about 178 cm (70 in.) or 350 percent
of the average annual rainfall. The mean temperature at the Amarillo NWS during 2008 was slightly (0.4˚C
[0.8˚F]) above normal.
The Pantex Plant maintains a meteorological monitoring station located on the northeast corner of the site.
The monitoring station is an instrumented 60-m (197-ft) tower located approximately 3.7 km (2.3 mi) north
of the Zone 12 production area. The tower is equipped with two sets of sensors, located at the 10- and
60-meter (33- and 197-foot) levels. Wind speed, wind direction, and temperature sensors are located at
both levels and a relative humidity sensor is located at the 10-m (33-ft) level. A barometer measures the
atmospheric pressure on the tower approximately 1.8 m (6 ft) above the tower base. A pyranometer
(instrument that measures insolation or incoming solar radiation) and a tipping bucket rain gauge are
located adjacent to the tower at approximately 1 m (3.3 ft) above ground level. Sensor measurements are
taken every 2-8 seconds. The tower’s datalogger calculates and stores 15-minute averages of the data.
Every 15 minutes, the system uploads the meteorological data for the latest 15-minute interval to a standalone
personal computer located in the Operations Center.
The frequencies of wind direction and speed during 2008 at the Pantex Plant are illustrated by the “wind
roses” in Figure 1.3. As usual, Figure 1.3(a) indicates a large percentage (nearly 50 percent) of the winds
blew from the southeast through southwest during the year. A secondary maximum (almost 8 percent) of
winds from the north-northeast is primarily a result of cold air masses impacting the Texas panhandle
during the cold season. Wind direction and speed frequencies vary by season: Northwesterly winds are
most frequent during winter [Figure 1.3(b)], wind direction frequency is most bi-modal during spring
([Figure 1.3(c)] and the vast majority of winds are from the southern sector in summer, including over 40
percent from the south and south-southwest directions [Figure 1.3(d)]. In addition, wind speeds are highest
in winter and spring and lowest in summer and autumn.
2 Precipitation includes the liquid water equivalent from snowfall.
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