Quarry Index:

About the Quarry

Meeting Agendas

Past Meeting Minutess

Definitions

Facts & Questions

Maps & Graphs

About the Reports

Links:
Austin Powder
Hanson Aggregates Servtex
USBM
USBM Criteria (“z” curve chart)
Vibra-Tech

TIMELINE

When did the quarry begin operations?
Servtex Materials, the original owner of the Quarry, began operations in 1937. The current owner of the quarry is Hanson Aggregates Servtex.

When did the City of Garden Ridge incorporate?
1972

When was the Trophy Oaks subdivision developed?
1998

RESIDENT ISSUES

Can I stop the Quarry from blasting?
See legal rights of the quarry

Why was I not informed about the Quarry?
Under property law, the buyer is assumed to have “constructive notice” of all surrounding areas and situations. It is a matter of public record and public knowledge that the Quarry exists.

What if I think I have damage to my home?
There are many factors that can cause structural damage. The only way to determine the cause is to hire an engineering firm that has experience in these matters.

Can I tour the Quarry?
The Quarry Commission periodically coordinates tours and encourages citizens to join these tours.

QUARRY OPERATIONS
Hanson Aggregates Servtex Quarry

• Comprises approximately 3,000 acres
• Produces approximately 25,000 ton of crushed stone daily
• Blasts an average of 2 to 3 times per week
• Blasts are generally near midday
• Blasts are below federal standards
• Currently mining behind Trophy Oaks subdivision

Next phase will probably shift direction to a northwesterly direction towards city hall, Georg Ranch and Old Schoenthal Road

What are the legal rights of the Quarry?

• Blast at highest level allowed by federal guidelines, established by U.S. Bureau of Mines
• Blast as frequently as daily
• Mine the rock on all its property, including all the way to fence line which is the boundary to Trophy Oaks Subdivision

How much longer will the Quarry be in operation?

The current projection is that it will take up to 25 more years to mine its holdings.

What happens when they stop mining behind the Trophy Oaks Subdivision?

The next phase of operations will probably shift direction to a northwesterly direction towards City Hall, Georg Ranch and Old Schoenthal Road.

QUARRY EFFORTS

What steps has the quarry taken to lessen their operational impact on the residents?

• At additional costs to operations, the Quarry has done the following
• Blasts are below federal guidelines
• Blasts an average of 2-3 times per week as opposed to 5 days per week\ Changed the face of the quarry and utilizes benching in order to better direct ground vibrations away from the majority of the City (created additional work and decreased efficiency for quarry)
• Purchased and uses a blast face profiler to reduce air blast during quarry detonations. Generally, it is the air blasts not the noise or the ground vibrations that are most perceptible.
• Changed from using standard blasting caps to electronic blasting caps. Modified detonation delays in order to lessen the perceived impact of blasts. Cost –Additional $3,000 per blast.
• Finishing construction of large earthen berm between the western most limits of the quarry face and the Trophy Oaks subdivision. The berm provides visual screening, helps deflect quarry noise and acts as a physical barrier.
• Provides employees and/or contractors to work with the Commission
• Monitors blast measurements at specific locations upon request
• Pays for independent monitoring of their blasting operations
• Regularly try new methods to lessen the impact of the blasts
• Negotiating a 1,000 foot set back from the nearest residence
• In process of changing back-up alarms of heavy equipment in an effort to reduce noise during night time operations
• Watering of blast sites to reduce the dust levels

QUARRY COMMISSION

Steps the City of Garden Ridge has taken to address the issues between residents and the Quarry:
Established a set back of 2500 feet from FM 3009
Established the Quarry Commission in 2000, with its first meeting August 14, 2000

Why can’t the City of Garden Ridge pass ordinances governing the operations of the quarry?

The City of Garden Ridge is a “general law” city because the population is under 5,000. It can only regulate conduct that the Texas Legislature has given us specific authority to regulate. The Texas Legislature has not given us the specific authority to act in this manner. Once the City reaches a population of 5,000, it will become a “home rule” city and have a “charter” form of government. Under this form of government, the City can regulate conduct such as this, as long as there is no stature/law that says that it cannot.

What is the role of the Quarry Commission?

• Serve as an educational resource to citizens
• Advise about the quarry and its impact
• Function as a point of contact with the management of Hanson Aggregates Servtex to

o Enhance relations
o Work on issues in the best interests of citizens

• Monitor quarry operations for compliance with City Ordinances
• Recommend needed changes to City Ordinances
• Develop a quarry grievance process in order to protect the natural and economic environment and the quality of life in the City of Garden Ridge

Limitations of authority

• The Quarry Commission has no authority over quarry operations
• It cannot close down the operations of the quarry

Who attends and presents at the Quarry Commission meetings?
· City of Garden Ridge Quarry Commissioners
· Representative of Hanson Aggregates Servtex
· Representative of Austin Powder who makes presentation on blasting operations
· Representative of Vibra-Tech who makes presentation on blasting reports
· City of Garden Ridge citizens

What information is regularly presented?
· Blast reports from previous month
· Citizen concerns during Citizens To Be Heard portions of meeting
· On-going efforts of Commission
· Selection of monitoring sites
· Educational information about the Quarry and its operations

RESIDENTS' ROLE
What can residents do to improve the situation?

What can I do to improve the situation
· Attend and participate in Quarry Commission meetings
· Provide feedback concerning blasting levels
· Present recommendations for improvement
· Tour the Quarry

Would legislative action improve the situation?
· There are no state, county or local laws governing mining operations as long as they comply with federal guidelines and meet environmental standards
· If you feel the state legislation is needed, contact your Legislative Representatives

ANATOMY OF A BLAST

What are the federal guidelines?
· The guidelines are affected by several variables as reflected in the “z” curve chart. More information can be learned at Quarry Commission meetings.

Does the Quarry operate within the federal guidelines for blasting and environmental regulations?
· Blasts are below federal guidelines

How often does the Quarry blast?
· An average of 2 to 3 times per week

Why do some people feel the impact of the blasts more than others?
· Many factors affect the perception of the blasts, such as,

o Proximity of the blast
o Geological factors, such as, fault lines
o Individual sensitivities

What factors cause differences between blasts; why can’t all the blasts be the same?
· Geology such as fault lines, weather, direction of blasting, depth of the charge

Peak Particle Velocity – PPV
· This is the measurement of the vibrations that move through the ground and may be felt as they move below foundations. Federal guidelines indicate that damage can occur at 2.00. To err on the side of safety, federal guidelines have been set at 0.50 which may lengthen existing cracks in plaster and at 0.75 which may lengthen existing cracks in sheetrock. In reference to the latter, damage thresholds may be increased as frequency moves above 11 hertz (Hz).

Frequency
· Frequency refers to how many waves occur within a second, which is measured in hertz. High frequency waves occur so quickly that a structure does not have time to respond. Above 11 is better. At lower frequencies, the structure does have time to respond so that the impact is felt. Frequency is also impacted by distance and geology.

Air Overpressure
· Air overpressure is generally the most noticeable impact on structures. As this air wave (measured in decibels (dB)) contacts structures, it causes walls to vibrate. Up to 128 dB is the federal guidelines safe level. Glass may break between 150-170 dB and structural damage may occur at 180 dB.

Weather factors
· On cloudy days the intensity of blasts may be more noticeable. This can result when air blasts are reflected off the clouds and directed downward rather than radiating in all directions. The downward reflection can increase noise and overpressure readings.
· Generally blasting occurs on good weather days

GARDEN RIDGE QUARRY COMMISSION
DEFINITIONS

These definitions only give an overview and are not designed to make you an expert. Links to informational sites are provided.

Aggregates – Engineering term for crushed rock.

Air Overpressure – Air overpressure is generally the most noticeable impact on structures. As this air wave (measured in decibels (dB)) contacts structures, it causes walls to vibrate. Up to 128 dB is the federal guidelines safe level. Glass may break between 150-170 dB and structural damage may occur at 180 dB.

Austin Powder – The current blasting contractor for Hanson.

Bench – The current bench cuts the face into two levels, each with a 50’ face. A blast on a 50’ face generally has less impact than one for a 100’ face.

Damage Threshold – Defined by the USBM as the loosening of paint, small plaster cracks at joints between construction elements or the lengthening of old plaster cracks.

Decking – Small charge or portion of a blast hole loaded with explosives, which is separated from other charges by stemming.

Delay – The time by which detonations are separated, measured in milliseconds.

Face – The wall of rock that is being blasted to produce rock for the crusher.

Frequency – Frequency refers to how many waves occur within a second, which is measured in hertz. High frequency waves occur so quickly that a structure does not have time to respond. Above 11 is better. At lower frequencies, the structure does have time to respond so that the impact is felt. Frequency is also impacted by distance and geology.

Hanson Berm – The mound of dirt that acts as a visual screen and helps to deflect noise. It is 30-40’ tall and up to several hundred feet wide. It serves as a buffer between the quarry and the Trophy Oaks property line.

Hertz – The term used to express the frequency of ground vibrations and air blast; one hertz is one cycle per second.

Inch/Second – The measure of distance and time used to record ground vibrations.

Max Pounds per Delay – The amount of explosives per detonation. Each blast is comprised of multiple separate detonations each of which are separated by milliseconds (delay). While these blasts are perceived as a single blast, they are actually a series on small blasts. Without these minute separations, a single blast would have an extremely high impact.

No Trigger – ground vibration resulting from the blast was less than the seismographs pre-set level of vibration, above which is necessary for the instrument to record an event.

Peak Particle Velocity (PPV) – This is the measurement of the vibrations that move through the ground and may be felt as they move below foundations. Federal guidelines indicate that damage can occur at 2.00. To err on the side of safety, federal guidelines have been set at 0.50 which may lengthen existing cracks in plaster and at 0.75 which may lengthen existing cracks in sheetrock. In reference to the latter, damage thresholds may be increased as frequency moves above 11 hertz (Hz).

Ramp – The sloping surface used to connect the floor of the quarry with the upper bench for transporting the rock from the blasts.

Rows – Line of blast holes to be loaded and detonated.

Seismograph – An instrument that measures and may supply a permanent record of earth borne vibrations induced by earthquakes or blasting.

Set Back – The distance from the current property line to the quarry face.

South Texas Aggregate – Another aggregate producer located on Hanson property.

Stemming – Inert material, such as drill cuttings or gravel, used in the collar portion (or elsewhere) of a blast hole to confine the gaseous products of detonation.

USBM – United States Bureau of Mines

Vibra-Tech Engineers – Engineering firm selected by City of Garden Ridge that monitors each blast.

Whorley Property – A track of land purchased by Hanson, located between Trophy Oaks and the quarry face. A portion is being mined and the remainder, which includes the berm, serves as a buffer.

Hard Rock Quarries in Texas

On February 21, 2007 the City of Garden Ridge as a part of the Northeast Partnership went to Austin to visit with Texas Legislators at which time they were presented with the following document:
Hard Rock Quarries in Texas