In all, seven and a half cubic yards of calcium carbonate, weighing more than 5,000 pounds, were removed from the 96,234 condenser tubes in Unit 1. Shortly thereafter, the same number of condenser tubes in Unit 2 were cleaned using the same method, and more than four cubic yards of calcium carbonate, weighing a little more than 3,000 pounds, was removed. STP personnel believe the tubes in Unit 2 were less fouled because it had been cleaned with metal-bladed mechanical tube cleaners in 2001, whereas the tubes in Unit 1 had been cleaned with nylon brushes that left ridges inside the tubes, promoting faster build-up of debris and scale.
An increasingly popular but still unproven techology involves testing saliva taken from mouth swabs. Saliva testing has the advantage of being less invasive than either urine or blood tests. So far, tests have shown them to be inconsistent and unreliable when it comes to detecting marijuana, but that hasn't stopped them from being used. The sensitivity of saliva tests hasn't been clearly established, but may range from a few hours to a day or more. While it might be supposed that mouthwash is a helpful defense against saliva tests, this isn't necessarily the case, since the tests are supposed to detect drug residues that are exuded from the body's internal mouth tissues into the saliva.
Not surprisingly, no elevated risk was found in the three studies listed at bottom, which looked at urine metabolite levels rather than blood THC. This confirms that urine testing has no bearing on driving impairment. Despite this fact, US Department of Transportation regulations force millions of commercial drivers to submit to random urine testing. The government has never produced convincing scientific evidence that this policy is necessary or effective to protect public safety. But they're the government, so they don't have to provide any evidence!