Corporal Newkirk mentions Florence Chadwick and the swimming of the English Channel as Sergeant Carter is preparing to descend into the well. At the time this episode is set (1943 or 1944), Florence Chadwick had not yet swum across the English Channel. This occurred on August 8, 1950.
The towers in the water treatment plant had flashing lights. This would not occur in war time due to blackout to avoid aerial attacks. Also Newkirk, Kinchloe and Carter are standing too close to the fence to throw the explosives so far into the plant compound.