They were fortunate that Hanford was served by adequate electric power, General Groves explains in Now It Can Be Told: The Story of the Manhattan Project, as Grand Coulee was able to make 20,000 kVA available immediately and could supply their entire power needs by September, 1943:
Within the Hanford site, we had to build over fifty miles of 230,000-volt transmission lines and four step-down substations. Because of the copper shortage, the War Production Board thought that we should use aluminum cables. We encountered considerable difficulty and delay in obtaining any decision from the WPB on this matter and it was not until July, 1943, that procurement could begin. Then only the most vigorous expediting enabled du Pont to obtain the material in time to meet its construction schedules.
Aluminum wiring became popular in the 1960s and 1970s when copper prices soared.
Pros of aluminum wire
Lighter weight. Aluminum is a lightweight material that’s very flexible. Installs are often faster since wire pulls are much quicker in long runs.
Less expensive per pound. Aluminum is considerably less expensive than copper, which makes it more desirable to use in large projects where runs span long distances.
Cons of aluminum wire
Less longevity. Prone to cracking and failure when subject to vibration. Aluminum is also more subject to corrosion than copper, meaning its useful life can be shorter as it becomes brittle and subject to breakage.
Difficult to solder. Aluminum is difficult to solder, limiting its flexibility. Oxidation on aluminum often inhibits soldering.
Larger size. Because aluminum conductors are larger than copper conductors, larger raceways are required (and additional costs).
Potential dangers when use incorrectly. When aluminum is properly installed, it is safe. When it is installed incorrectly, there is a potential risks for fire because expansion and contraction cycles have a larger impact on aluminum and can loosen connections. Normal inspections should be performed.
Terminal points. Aluminum requires an anti-oxidation compound at each terminal point because it is susceptible to oxidation. Oxidation occurs when it comes into contact with moisture and dissimilar metals.
Aluminum conductors must be larger than copper conductors because aluminum is about half as conductive as copper.