Expert challenges Gregg Township data center sound plan

Allenwood, Pa. — The third continuance of a township data center ordinance hearing in Union County focused on testimony from an acoustical expert witness for the township, and sharp cross-examination from the developer's attorney.

Testimony centered on dueling interpretations of the township's noise ordinance and the sound measurements meant to determine whether PNK Group's proposed data center campus would comply.

The Sept. 14 meeting at the Warrior Run Area Social Hall began at 5 p.m. with an audience of about 150 residents of Gregg Township and neighboring communities. Again, many attendees wore red to signal opposition to PNK Group's development. As people filed into the social hall, several carried anti-development yard signs, and homemade handheld signs expressing similar sentiments.

Expert witness for township

The township’s special counsel, Attorney Brett Flower, introduced acoustical expert witness John Michael Spencer. Special solicitor Richard Shoch moderated.

Spencer testified for more than an hour on behalf of Gregg Township. Spencer, who holds a bachelor's degree in acoustics and music from the University of Hartford and a master's in acoustics from Penn State, told the board he has over 30 years' experience in acoustical consulting. He also said he has worked on data center noise ordinances for several other Pa. municipalities, including Conewago, Silver Spring, and Butler townships.

Spencer walked the board through the mechanics of Gregg Township's existing ordinance, which contains two separate noise provisions:

Section 15.9.1.2, an "ambient" standard that bars new noise from exceeding the average intensity of existing background sound at a property's boundary line, andSection 15.9.4, which sets hard-cap maximum sound levels using an older system of octave bands dating to a 1955 Chicago ordinance.

Spencer testified that PNK Group's proposed curative amendment, which would replace those provisions, has problems.

He said the amendment incorrectly converts the ordinance's old octave-band levels to modern ones, eliminates the ambient noise provision entirely and adds an exception for generator operation that does not exist under current law.

While Spencer said the amendment's octave-band caps are more stringent in some respects, he said the overall proposal was "significantly less stringent" than existing law because it drops the ambient standard.

Sound measurements

Spencer presented a report, dated the day of the hearing, summarizing 48-hour sound measurements he conducted at two locations:

One along the boundary between the commercial-manufacturing zone and the village district to the south,and the other on Poplar Avenue in a rural residential district.

Also recorded were shorter, 30- to 40-minute spot checks at two additional sites, including one near Clyde Peeling's Reptiland. Spencer said he took that last reading after hearing community concern for the zoo's animals.

Using the L90 metric, which Spencer testified is the sound level exceeded 90% of the time and the measure most associated with community annoyance, he found nighttime background levels as low as 28 decibels near the village district and 29 decibels on Poplar Avenue. He said those levels are typical of quiet rural Pa.

PNK Group's proposed curative amendment would set a minimum limit of 45 dBA for "sensitive receptors," about 17 decibels above that measured background, Spencer testified. He said a 10-decibel increase is generally perceived by the human ear as a doubling of loudness, and told the board that, in his professional opinion, sound levels permitted under the proposed ordinance would have a significant negative impact on nearby residents.

Spencer also testified that meeting the objective numeric standards of a noise ordinance does not necessarily mean a project has no health, safety, or welfare impacts.

Equipment and mitigation

Spencer identified chillers and roughly 38 proposed diesel backup generators, each about 3 megawatts, as the primary sources of concern.

He testified that moving generators indoors, an idea PNK Group raised at an earlier hearing, would require large silenced openings for cooling airflow — in the range of 100,000 to 120,000 cubic feet per minute per generator — and said he could not assess the sound impact of that approach without a completed design.

He recommended pairing ambient-based standards with hard caps to prevent what he called "sound ratcheting," in which repeated developments in the same zone each add to the background level until only the hard cap remains meaningful.

Cross-examination

PNK Group attorney Michael Wiley cross-examined Spencer at length, opening by noting the company had received Spencer's report only upon arriving at the hearing and had no advance opportunity to review it.

Wiley established that only two of Spencer's four measurement locations — the two with full 48-hour data — included detailed charts in the report. The other two were shorter spot checks reflected only in summary tables.

Much of the cross-examination focused on methodology. Wiley got Spencer to confirm that one of the low nighttime L90 readings, 28 decibels, came from an hour that also included a passing truck with a "Jake brake" that peaked at 56 decibels for about one second. Spencer maintained that L90 is a standardized statistical metric, not a discretionary one, and that such events are included in, not excluded from, the calculation.

Wiley also pointed to the ordinance's ambient provision, Section 15.9.1.2, relies on the LEQ metric rather than L90, and that LEQ captures the average intensity of all ambient sound, including passing traffic. Under LEQ, Spencer's first set of location data showed a nighttime average of 42 decibels and a daytime average of 46 decibels.

Wiley said that, according to a right-to-know request PNK Group submitted to the township, there is no record the township has ever enforced Section 15.9.1.2. Spencer said he was not aware of the origin of that section's language, distinguishing it from Section 15.9.4.1's more traceable lineage to the 1955 Chicago ordinance.

Wiley also had Spencer confirm that several buildings and neighboring Route 15 lie in a direct line between the Poplar Avenue measurement site and the commercial-manufacturing district, and that measurement results can vary day to day based on weather and traffic conditions.

On mitigation, Spencer testified walls and berms are effective noise-control measures, but said vegetative buffers require roughly 300 feet of dense forest before providing any meaningful acoustic attenuation, calling most vegetative buffers a visual rather than acoustic solution, in an "out of sight out of mind" fashion.

Flower declined to redirect after Wiley's cross-examination concluded.

More to come

This story covers the first part of tonight's hearing, which does not include residents' questions for Spencer following his testimony and Wiley's cross-examination, nor the testimony of a second acoustics expert called on behalf of PNK Group, Alex Hornecker at Salas O'Brien — the same company the first PNK Group expert witness hailed from.

Another story coming at a later time will cover the third continuance comprehensively.