Controlled Blasting Activities
RestoredWaters RI – formally known as the Narragansett Bay Commission’s Combined Sewer Overflow (CSO) Project – is Rhode Island’s largest and most important clean water project and will improve the health of the Seekonk River and Upper Narragansett Bay. The centerpiece, which marks the third and final phase of the RestoredWaters RI project, is a deep-rock tunnel that will capture and store storm-related sewage overflows. This tunnel, called the Pawtucket Tunnel, will be 2.2 miles long and 125-150 feet below ground.
A Tunnel Boring Machine (TBM) will horizontally excavate the tunnel by slowly grinding its way through deep bedrock, but in order to get the TBM below ground and to create the vertical shafts that bring the sewage overflows to the tunnel, the construction team will first need to remove the bedrock by blasting at a few specific locations along the tunnel route.
What is blasting?
Blasting is performed to fracture rock so it can be excavated for construction. The contractor drills holes in the underground rock; each hole is loaded with a carefully-calculated amount of explosives, which are then detonated. A typical blast will last approximately 3-5 seconds. Typically, there are no more than 1-3 blasts per day at each location.
Neighbors may hear a warning horn just prior to the blast, a muffled blast noise, and may feel a slight vibration. The area will be monitored with seismographs to measure levels.
How can I find out when a blast will occur?
You can opt in to email notifications by sending your contact information to firstname.lastname@example.org.
Will I feel the blast?
Most of the energy from a blast is used to break rock, but some energy will travel from the blast site in the form of groundwaves and airwaves. These can cause your house to mildly vibrate or shake. Humans and animals are very sensitive to all vibrations and it is possible that you will feel or hear your house shake from the blasting, even at very low levels. All the blasts related to the RestoredWaters RI project are designed below levels known to cause property damage, but we encourage any interested homeowner within 500 feet of the blasting sites to consider allowing the project team to perform a survey of their property.
Why do some blasts feel stronger than others?
How a blast feels depends on groundwaves or airwaves that reach your house. These are influenced by the type of blast, the distance from the blast, the amount of explosives, whether you are inside or outside your house, and even the weather. Your pets may also sense blast vibrations. Pets, like humans, are sometimes startled by the sound of a blast or warning signals.
Blasting for RestoredWaters RI:
- Blasts can only occur between 7 AM and 5 PM
- Typically, no more than than 1-3 blasts/day in each location
- Ground vibration limits set at 2.0 in/sec and air vibrations limits at 133 dBL
- Each blast monitored at 4 locations
Who sets the guidelines for safe and effective blasting?
In the United States, safe vibration standards are based on scientific studies conducted by the U.S. Bureau of Mines (USBM). In addition, the contractor for RestoredWaters RI follows guidelines established by the International Society of Explosive Engineers (ISEE) for monitoring vibrations and air overpressure.
What is the schedule for blasting?
The following is our current blasting schedule. Please note that these dates are anticipated and are subject to change based on project progress, resource supplies, etc. We will update this schedule as needed.
For more information about RestoredWatersRI’s controlled blasting activities, please contact our project team at email@example.com or call 401-305-2350.