Chapter 4—Monitoring Accidental Radiation Releases © 73 Figure 4-9—StandbyAir Surveillance Network Stations vee Bo mea ® e M ontana North Dakota e e e . e | (. cus foe te e 7 an) oe, ° - . . Nebraska a / . 3 lowa Uta , . e Arizona e ° ° Colorad 0 Kansas ° 2 e ° e ® al “yo / :— . _4% setts anf | \ Oklahoma e ° EN A eee Missour, @ Arkansas ° New Mexico 1002" SOO fs 508 e ° ° . eX® “ e fe . neni e South Dakota : e . e Wyoming , *.° e ee o% eote e e e = Neva ‘: ° @ Idaho | y Minnesota Sregon ° e Texas ° Louisiana ~ 86 standbyair surveillance stations are available and samples are collected and analyzed every 3 months to maintain a data base. SOURCE: Modified from Environmental Protection Agency. level for drinking water) of krypton-85, chlorine-36, ruthenium- 106, technetium-99 and iodine-129. Radioactive material from nuclear testing moves through the groundwater at various rates and is filtered by rock and sediment particles. Tritium, however, is an isotope of hydrogen and becomes incorporated in water molecules. As a result, tritium moves at the same rate as groundwater. Tritium is therefore the most mobile of the radioactive materials. Although tritium migrates, the short half-life of tritium (12.3 years) and slow movement of the groundwaterprevents it from reaching the Test Site boundary. No analysis of groundwater has ever found tritium at a distance greater than a few hundred meters from someoftheoldtest sites. None of the water samples collected outside the bounda-