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Mt. Wilson Update: County Officials to Evaluate Broadcast-Commissioned RF Report

L.A. county officials recommended closing some of the roads necessary to access the transmitter facilities

MT. WILSON, CALIF.: Los Angeles County officials want to evaluate a report that finds radio-frequency emissions on Mt. Wilson compliant with federal standards, according to two broadcast engineers. The County is considering whether or not to continue maintaining some of the access roads to the TV and radio transmitter site that sits above the L.A. Basin. Officials from L.A. County and the U.S.D.A. Forest Service met yesterday with engineers and others affected by the potential road closures.

Fred Volken, a consulting engineer, and Jeremy Howard of KCET-TV both attended. Both reported that county officials wanted to evaluate an RF report from Hatfield & Dawson before making a decision about the roads. Hatfield & Dawson was commissioned by a group of broadcast tenants on Mt. Wilson to take RF measurements. Their engineers this week released a preliminary report stating that RF levels on the roads in question were well within federal limits. Hatfield & Dawson’s final report is expected to be delivered at the end of the month. Two studies previously commissioned by the county found otherwise. Howard said county officials wanted to compare the data of all three studies, and possibly hold another meeting, before making a final determination. He said that RF exposure, and not finances, were the county’s sole concern with regard to maintaining the roads. Both Howard’s and Volken’s reports are posted at Tech Letters.

Aug. 10, 2011Mt. Wilson RF Exposure Levels Found FCC Compliant
Radio frequency levels on Mt. Wilson roads are within federal standards for human exposure, according to a Seattle firm that took measurements. Mt. Wilson, the primary TV and radio transmitter farm for Los Angeles, came under scrutiny recently by L.A. County officials, who commissioned RF studies that indicated excessive levels. The county recommended closing some of the roads necessary to access the transmitter facilities, according to CGC Communicator, which closely follows the activities on Mt. Wilson.

The roads in question, Weathervane Dr. and Video Rd., ring the facilities on the south side, and are maintained by the U.S.D.A. Forest Service. Mt. Wilson tenants were called upon to present their own RF studies to the Forest Service in light of their dependence on those roads. One preliminary report from Hatfield & Dawson in Seattle has been released to the public. It was commissioned by KABC-TV’s vice president of engineering, John K. Holland, with support from KCBS/KCAL-TV, NBC Universal, Univision and Tribune.

Hatfield & Dawson’s safety consultants, Richard Strickland and David Pinion, performed RF measurements July 28 and 29 on the roads and adjacent areas. The highest RF exposure measurement came back at 85.1 percent of the Federal Communications Commission’s maximum for the general public.

“These roadways are fully compliant with the regulatory requirements of the FCC regarding RF radiation, and there are no RF health hazards for anyone traveling or working on the three subject roads,” Strickland and Pinion concluded.

They both noted that a previous report from Aurora Industrial Hygiene dated Oct. 28, 2009, indicated areas of excess RF levels in the area. Strickland and Pinion said the report was flawed in that the maximum exposure limits for UHF stations is higher than those for VHF stations. They also said that spatial averaging was not applied, and that typical sampling techniques inadequate for outdoor evaluation were used.

RF levels on Mt. Wilson have been the subject of scrutiny in the past. Each transmitter was systematically shut down during a July 2002 inspection by FCC field agents, who discovered a hot spot in one of the driveways, CGC said. That inspection led to a $40,000 fine from the FCC for excessive RF levels, according to Radio World.

The FCC hasn’t yet stepped into the current RF debate. A meeting of Mt. Wilson parties and Forest Service officials was scheduled for today.

~ Deborah D. McAdams, Television Broadcast