Skyline Sanitary Sewer Project

Project Update: 

11/19/19 project update/ contractors project schedule

As you are aware, the Township is in the process of constructing sanitary sewers to serve the residents in the Skyline Drive area. The Township contractor, PM Construction, has advised that they have encountered a significant amount of rock in some areas of the project. Prior to designing the project we completed soil borings to determine the depth, type and extent of rock along the length of the project. Based upon the initial borings we anticipated that the rock encountered would be rippable, unfortunately the contractor has run into some rock outcroppings between our borings that has proven to be unrippable. This has resulted in significant delays in constructing the sewer main using conventional hydraulic jacking and mechanical breaking of the rock. 

In the interest of expediency, PM construction proposes to complete fracturing of the rock using drilling and micro blasting. This type of fracturing of the rock is similar to what would be used for residents who need to remove rock for installation of a house foundation or pool. The rock fracturing will be completed in only those isolated areas where the depth of the rock is too deep for conventional mechanical breaking. The use of chemical expansion technology to fracture rock was also reviewed and concluded to be not as efficient for this application and type of rock encountered. The micro blasting is being completed J. Fritz Blasting and Excavating,

PM construction is in the process of identifying the extent and limit of those rock excavation areas. Once this has been completed, those resident within 200 feet of the rock excavation will be notified. The contractor will be performing pre-blast surveys of these properties to ensure there are no measurable impacts to residences. The contractor will also be completing seismic monitoring to ensure that all vibrations are well within regulated limits. These measurements are required to be submitted to the State. The pre-blast surveys will be completed by PROTEC. Additional information on what is done as part of the pre-blast surveys can be found on PROTEC’s website, http://www.protecservices.com/Services.php

There are several YouTube videos available that my help residents better understand the type of micro blasting being utilized for this project.

Link https://www.youtube.com/watch?v=Fsttt6Tu1Uk is an example of blasting for a new road where blasting was used after rock fracturing using chemical expansion was insufficient to break the rock. The rock in this example is at the surface of the roadway. The rock that the Township will be blasting is a couple of feet below the surface of the roadway. The blasting methods the Township’s contractor will be using are intended to fracture the rock without any damage to the roadway surface. Fracturing the rock in this manner will allow for the removal of the rock with significantly less construction noise generated by mechanical jacking and hammering of the rock as has been done these past two months. Below are two additional examples of similar types of blasting used for rock removal.

10/21/19 Blasting video on Rolling Hill Dr: https://youtu.be/T6P6ERpoA4U

Blasting for a sewer connection, https://www.youtube.com/watch?v=nf2FxGWIo3k&t=122s

Blasting for a home addition, https://www.youtube.com/watch?v=BwSIoJkKfeI

Blasting adjacent to a school, https://www.youtube.com/watch?v=zXPFwaM_aJA

You may find answers to frequently asked questions about blasting at, https://explosives.org/frequently-asked-questions/. Information about blasting vibrations can be found at, https://vibrationdamage.com/blasting_vibrations.htm.