Posted by found out about this, a resident of the Vintage Hills Elementary School neighborhood, on Apr 4, 2009 at 8:28 am
the helicopter noise was from training exercises at the Dublin Camp Parks military training center. here's the article and link:
military exercise planned: The United States Marine Corps will conduct a military exercise from 9 p.m. today to 1 a.m. Saturday at Camp Parks Reserve Forces Training Area.
An expedition force from Camp Pendelton will arrive in helicopters from Fort Hunter Liggett in Monterey County to Camp Parks. The exercise includes 13 helicopters and an unspecified number of troops, who will be using blank rounds and star clusters (firecracker-like devices in the air) during the training, said Dan Gannod, the public affairs officer for Camp Parks.
Gannod said the exercise is designed to simulate long distance travel that Marines may experience from their operating base to an objective. The exercise will be contained to the Camp Parks area, but residents may hear the rounds and star clusters going off.
Camp Parks is the training area for the Army's 91st Division (Reserves) and is the only training facility within a short driving distance for 11,000 plus reservists in the San Francisco Bay Area. It was built during World War II and commissioned in 1943 as a Navy Base home to the Navy Seabees. In 1951, it was transferred to the US Air Force and transferred again in 1959 to the US Army.