Note: The following is not a verbatim transcript of the Zoning Hearing Board meeting; it is simply one person’s summary of the major points made by those involved in the hearing process.  For that reason, quotation marks are not used unless a direct quote was recorded.  For information about obtaining an official ZHB transcript, contact the New Hanover Township office.

Note 2: Mr. Walter B. Satterthwaite, principal of Walter B. Satterthwaite Assocs., Inc. was unable to attend this zoning hearing board meeting. Satterthwaite has recently undergone knee surgery. He may or may not attend the next meeting.  

The Zoning Hearing Board accepted Douglas Rudenko, VP and NE Regional Manager and manager of technical services for Vibra Tech Engineering as an expert witness.

Stephen Harris, attorney for Gibraltar Rock began questioning his witness, Douglas Rudenko, VP and NE Regional Manager and manager of technical services for Vibra Tech Engineering.    

Harris asked Rudenko to explain how a blast is set-up and exploded and what vibration is produced.  Rudenko explained that the blast is done in one hole and that pressure causes rock to fracture and continues to fracture out. One by-product of this is vibration, which is wasted energy.  In his attempt to simplify the physical effects of an explosion, Rudenko used a picture of a pebble dropping into water with ripples moving out from the center in a concentric pattern.  

Was this an attempt to simplify a complex event or an attempt to minimize the impact of blasting?

Rudenko spent the next 25 minutes talking about how a seismograph works. Actually he explained what information appears on a seismological report.  Harris asked Rudenko about the Bureau of Mining reports that show which numbers indicate damage and which do not. Rudenko said that the main study was RI8507 “Structural Response and Damage Produced by Ground Vibration from Surface Mine Blasting”.

Note: This study can be found at the International Society of Explosive Engineers web site: http://www.isee.org/tis/Invest/87_79/ri87_79.htm

Rudenko said that this study was founded on 219 blasts to 76 residential structures, plus data from six other studies. The point of all this blasting was to determine the effects of ground vibration on residential structures.  Rudenko said there were three types of damage identified in these studies: threshold damage, minor damage, and major damage.  The PA DEP defines these as follows:

• Threshold Damage - Loosening of paint, small cracks in plaster and drywall at joints between construction elements, lengthening of old cracks.

• Minor Damage - Loosening and falling of plaster, cracks in masonry around openings near partitions, hairline to 3 millimeters thick (0 to 1/8 inch), fall of loose mortar.

• Major Damage - Cracks several millimeters in thickness in walls, structural weakening, broken glass, fall of masonry, e.g., chimneys, and load support ability affected. See http://www.dep.state.pa.us/dep/subject/All_Final_Technical_guidance/bmr/562-2112-504.htm for more information.

Next Harris asked Rudenko for the measurement that the Bureau of Mines considers the best description of ground motion. Rudenko stated that it is “particle velocity”. The Pennsylvania DEP has a maximum allowable peak particle velocity, which is discussed at www.dep.state.pa.us/dep/deputate/minres/bmr/forms/5600-PM-MR0021.pdf 

Rudenko told the ZHB ‘all homes eventually crack because of environmental stresses”. And, that if blasting is kept below the numbers identified in RI8507, then the potential is nil that damage to residences will occur. ---Of course, what would you expect him to say?

Rudenko next talked briefly about RI 8896, “Effects of Repeated Blasting on Wood Frame Homes. He also mentioned that there were studies done about vibration to concrete block and brick structures.  He next talked about a study by Berger from 1980.  The only link I could find on the Internet for this refers to Survey of Blasting Effects on Ground Water Supplies in Appalachia: A Minerals Research Contract Report. Vols. I and II. Warrendale, PA: Philip R. Berger & Associates, Inc. (under contract no. J-0285029 with the United States Bureau of Mines). November 1980.

Harris then asked Rudenko about “air-over pressure” or also known as “airblast overpressure”. Rudenko said that an explosion causes pressure that is released and moves the rock (in the quarry) cause air to be pushed. This causes a fluctuation of air pressure.  This is explained in RI 8485, “Structure Response and Damage Produced by Airblast from Surface Mining”, which can find this study at the International Society of Explosive Engineers web site: http://www.isee.org/tis/Invest/87_79/ri87_79.htm.

Harris next asked him to define a “Preblast Inspection”. A pre-blast inspection looks at existing structures and documents their cracks and flaws.  Outside the residence they take photos and verbally document the flaws. Inside the documentation is generally verbal only.

Harris finished by asking him if with a reasonable degree of geological certainty, will damage be caused if vibrations are kept below Bureau of Mining levels. Rudenko, of course, answered, “There will be no damage”.

Francis Recchuiti, an attorney for a local resident began his cross-examination of Rudenko.

Recchuiti asked Rudenko a series of questions about the materials the he (Rudenko) was to bring to the ZHB meeting. 

During Rudenko’s testimony he used slides with data.  Recchuiti picked on the fact that Rudenko didn’t indicate on any of his slides the authorship of the data. Recchuiti’s point was that, if the data was not referenced no one who reviewed the slides and data will know where it comes from. Rudenko finally admitted that on one slide in particular some of the data was from two different sources (neither of which was indicated) and some of the data was his own (from past experience). Recchuiti continued to ask about sources of information, next asking him about a Canadian study that Rudenko mentioned during his testimony. Recchuiti asked if the Canadian study was government backed. Rudenko said he didn’t know. Recchuiti said that neither did he or the Zoning Hearing Board. Not only didn’t Rudenko know anything about the Canadian study, he seemed to no know it’s name either. Recchuiti then asked him how long he had prepared for tonight’s meeting and Rudenko said two month. Recchuiti next jibed him by asking him why he didn’t expect that he would be asked the name and authorship of the Canadian study. Rudenko said he didn’t know anyone would ask it.

The next meetings will be May 28, 2002.

See Also:
Summary of the previous meeting (March 2002)