Soil Stabilization Work Begins at Wallace Elementary School - May 31, 2019

The contractor building two new schools for Kelso School District, FORMA Construction, is starting construction of the new Wallace Elementary, which requires installing aggregate piers into the ground up to 40 feet deep. FORMA will bring in heavy equipment and loads of aggregate around the second week of June.

The aggregate pier installation is scheduled to start on June 10th and be complete by August 9th. The working hours for pier installation are 7:00 AM to 5:00 PM.

During this operation, the level of construction noise may increase and the levels could reach higher than normal construction noise. This method is much quieter than a typical steel pile driving method, but, similar vibrations might be felt in the vicinity of Wallace Elementary.

Vibro-Replacement Aggregate Pier FACT SHEET

What is an aggregate pier and why is it necessary? Aggregate piers are a common method of stabilizing building foundations in poor soil conditions. To support the building foundation, an aggregate is compacted into the ground beneath the foundation until it reaches a specified level of resistance. For this project, aggregate piers will be installed on a grid pattern just slightly larger than the building footprint, each extending roughly 40 feet below foundation.

How are piers installed? The aggregate piers are installed by heavy equipment and a special drilling and compacting head that allows pre-drilling and forcing aggregate material into the ground and compacted as the drilling head works its way back to the surface.  Watch this animation for a visual:

How long will pier installation take? The aggregate pier installation will start on June 10th. It is anticipated that the pier installation will take 60 days or through August 9th.  The number of piers installed per day will vary based on the soil condition. For aggregate piers, typically 20 piers per day can be installed on average.

What are the contractor’s working days and hours for the aggregate pier work? Aggregate pier installation will take place Monday through Friday, 7:00 AM to 5:00 PM.  Typically the crews work 10 hour days to be able to make up for any equipment failures etc., as performing this work is very hard on even the heaviest of equipment and can cause breakdowns along the way. 

Where will aggregate piers be installed? Aggregate piers will be installed at Wallace Elementary School, 410 Elm St, Kelso. 

What is unique about this project that requires aggregate piers? The poor soil conditions at this site require that the building foundation be supported with this type of soil stabilization support system.

How noisy will the aggregate pier work be? There will be heavy equipment noise while in operation.  From 50 feet away, the noise level can range from 90 to 100 decibels, equivalent to a typical piece of excavation equipment/backhoe noise.

Is the pier installation noise in compliance with the city ordinance? The aggregate pier activities have been limited to hours that will have the least impact to residents. Noise generated from other construction activities are allowed as long as the hours of operation occur from 7:00 AM to 6:00 PM.

Will there be vibration from the aggregate pier installation? The compaction process of the aggregate pier installation may cause the ground to vibrate near the construction zone. Ground vibrations are monitored to ensure no damage will occur. Vibration monitors will be installed outside the working and monitored by a licensed survey team to keep a close watch on any ground movement outside of the working zone. The equipment used will provide real time information regarding vibration levels. If the operation is approaching the thresholds, it will stop and appropriate adjustments will be made. A baseline survey will be completed prior to construction to establish key monitoring points, prior, during, and after the aggregate pier work.

Who should I contact if I have questions? FORMA Construction – Project Manager – Kody Helms –