In recent years, there has been an increase in the number of property damage complaints against excavation contractors working for construction companies. A primary reason for most of the blasting related litigation and claims occur because the principal contractor (i.e. construction companies) don’t exercise enough caution and fail to take the neighbourhood in confidence. Another reason is the human tendency to gather the information suiting the already made decision. In this case, due to combined lack of knowledge of explosives and blasting as well as previous conditions of structures, when people find the fractures and cracks, they claim them as blasting damages. Escalation of such issue takes the shape of political and social problems, thus making it complicated which often leads to a project halt. For instance, in the last year Park Hyatt, Hyderabad knocked court doors to stop the blasting work carried out a builder adjacent to the hotel.

Why Pre-Blast Survey?

A major blasting claim results in the delay of a project and the project proponents may be forced to redesign the project and lose some valuable space to avoid nuisance and the delay. Bad publicity from a lawsuit can negatively impact a company’s reputation. Also, employees of project proponents often have to invest a substantial amount of time participating in defence of the claim. Taking into account the above considerations, it is clear that claims for blasting damages, with or without merit, incur substantial costs for the entities involved.

What is Pre-Blast Survey?

Pre-Blast survey creates a record on paper and video of the pre-existing condition of all buildings, improvements and surface utilities and subsurface (if needed) utilities located within a reasonable radius of all locations where blasting may occur. It provides the security of an independent study of properties near the blasting area. These records may then be referenced to determine if the blasting activities had any effects on these structures

How Is Survey Done?

The company conducting a pre-blast survey notifies the neighbours to permit to walk around the house/ property.  If the neighbours agree to have a survey, an appointment is scheduled. On the scheduled day, the technical person walks around the interior & exterior of property- house, the doors, walls, windows and foundation (base). They record and photograph any cracks or damage they see. They also record the type and quality of construction, maintenance and design standards adopted.

What happens after the Survey?

A report containing data sheets and the photographs taken around the property is compiled. This record then serves as a baseline study of the condition of any property that can be referenced to determine if any changes have occurred.

If the neighbours refuse to allow the survey of the property, then they will be informed by post. If the refusal continues, it will be recorded through postal acknowledgement and record of the same is communicated to the concerned authorities and the people.

What if there is Blasting Damage?

The pre-blast survey reports may then be referenced to determine if the blasting activities had any effects on these structures.

Uttam Blastech is a leading company offering solutions to the construction, mining and excavation. Our experts are adept at conducting a comprehensive pre-blast survey which results in meticulously curated reports and protection against any potential litigation hassles.

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Whenever ground vibrations are measured at a particular location, the blast frequency also needs to be considered for damage assessment. From the data obtained, it can be seen, that blasts with a higher frequency and higher vibrations are less damageable than the blasts with lower blast frequency and higher vibration readings or blasts with lower blast frequency and lower vibration readings. Apart from vibrations and blast frequency intensity, factors like the nature of structures (likely to be affected by the blasting), need to be understood for assessing damage. A concrete structure can withstand more vibrations than mudwalls.

Blasting is not the sole source of ground vibrations. Heavy duty truck movements, railway rake movements, aircraft landings, oscillating water in dam structures also generate a significant amount of vibrations which can prove to be devastating at times. On several occasions, vibrations from these sources that frequently occur are commonly ignored, can cause major damages to structures. Continuous vibrations as a result of these, also need to be considered for damage assessment and analysis. This highlights the need for the establishment of a system that takes into account all the vibrations occurring continuously.

We need systems which measure all vibrations constantly and continuously irrespective of its source, time of occurrence and intention to monitor. Only continuous monitoring of vibrations enables the project authority to contest or defend the blasting activities and provide sufficient proof that the damages resulted are due to these other sources of vibrations and not blasting damages indeed. 

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While the Project Management Team is responsible for recording data and taking measurements, the residents of the neighborhood are at the receiving end of these ground vibrations and air blasts. A dispute always seems to exist between the Generator (Project Management Team) and the Receiver (neighborhood).

On one hand, the Project Team claims to be carrying out the blasting under strict regulatory conditions and efficient control, while on the other, the neighbors tend to feel that their structures are being affected as a result of these ground vibrations, often citing out damages.  Regulatory authorities like the local administration & DGMS go with the neighbors in the absence of reliable and accurate data. Even in the presence of recorded, reliable data, the Receiver has disbelief in the measured readings.

A number of parameters play a significant role here. Like the measuring device, weather, periodicity of measurement, actual time of the blast, actual time of recorded data , calibration of the instrument, methodology of instrument setting, etc. On several occasions there are errors, incorrect methods or fudging found in the data measurements. In most cases, the measurement systems are Discrete and not Continuous.

To minimize the disputes and the differences between Generators and Receivers , the Project Team needs to be build the confidence  and instill trust in the minds of the Receivers by adopting transparent measuring systems and data documentation. Continuous monitoring of ground vibrations may also help in gaining their confidence and prevent small conflicts from blowing out of proportions.

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