Authorities in Montgomery County did some expensive weed whacking recently, cutting about $1 million in high-grade grass from the region's marijuana black market and shutting down an operation they say brought about 3,670 pounds into the area over the last year.

Eight men were charged Thursday after detectives searched a South Philadelphia warehouse on Sigel Street May 7 and allegedly found 271 pounds of marijuana and $450,000.

The investigation, dubbed "Operation Weed Whacker," began last September when Montgomery County narcotics detectives began looking at high-grade marijuana trafficked into Whitpain Township. By November, detectives learned the source of marijuana in Montgomery County was allegedly Dennis Frederick of Delaware County and his brother, Jeffrey Frederick of Philadelphia.

Last month, the detectives from county Prosecutor Risa Ferman's office got approval for a wiretap on the cell phones of the Frederick brothers. They then allegedly tracked the supply line to a California man, Charles Sadrin, who authorities now say routinely shipped truck containers full of pot into the region.

"Sadrin routinely shipped large orange tool boxes from Sacramento, California to Delaware County via a freight service," the prosecutor's office said in a statement. "The investigation revealed Sadrin himself picked up the containers using a rented pickup truck, delivered them to Dennis Frederick at a garage on the 1100 block of Sigel Street, Philadelphia, and then returned the empty containers to Sacramento via the freight service."

Freight records show Sadrin shipped more than 3,673 pounds of marijuana from January 2012 through April 22, 2013, according to authorities. At $4,000 a pound in street value, the pot had an estimated value of $14.6 million.

The big bust May 7 took place after detectives learned through the wiretap that three containers of pot were arriving in Philadelphia that day.

Subsequent arrests the same day resulted in a total of 400 pounds, nearly $700,000 in cash, four firearms, seven vehicles and 30 cell phones.

Along with the Frederick brothers and Sadrin, authorities also arrested Ernest Peterkin, 24, of the 1900 block of Montrose Street, Philadelphia, Jeffery Frederick, 32, of the 1700 block of Memphis Street, Philadelphia, Stanislav Dubovsky, 26, of the 1100 block of Hewson Street, Philadelphia, Martin Williams, 31, of the 700 block of Christian Street, Philadelphia, Earl DeSantis, 45, of the 800 block of South Avenue, Secane, Delaware County, and John Walker, 29, of the 200 block of Seneca Street, Delaware County.

All the defendants were scheduled to have preliminary arraignments Thursday afternoon.