Squamscott River Siphon Improvement Project regularly updated

Project Updates

4/19/24 - The contractor will perform an exploratory drill from the Swasey Parkway side of the river starting around Monday, April 29. This drilling activity would be limited to a few days.  The heater is no longer necessary, but the reclaimer machine will need to be operated.  The results of this drilling effort will enable the contractor to decide on the construction means for the next bore hole. 

4/12/24 - All efforts to remove the 18-inch reamer proved unsuccessful.  The reamer will need to be abandoned in-place.  A new drill attempt will be required.  The contractor and engineer are developing plans and schedules for this next attempt.  There will be no work over the weekend. 

4/5/24 - While some progress is being made with the extraction effort to remove the 18" reamer, the operation is still unsuccessful.  Crews will work on Saturday, April 6 to continue this task.  The air hammer on the Mill side of the river will be utilized to assist in the extraction of the reamer which could still be a noisy activity. There are no additional costs to the Town relating to this circumstance.

3/29/24 - The 8" steel casing was installed to the 18" reamer on Wednesday, March 27.  The reamer was pushed an additional 7 feet back toward the parkway.  A new rod-capturing tool was constructed that will attempt to connect with the broken drill rod end.  Insertion of the rod capturing tool is advancing from the parkway, toward the broken drill rod.  If successful, the broken shaft will be escorted out of the drilled shaft with this tool toward the parkway. The air hammer on the Mill side of the river will continue to be used to assist in the extraction of the reamer which could still be a noisy activity. There are no additional costs to the Town relating to this circumstance.

3/22/24 - The initial attempt of using a recoupler to connect the separated drill rods was unsuccessful.  Eight-inch steel casing will be delivered to the Mill side of the site on Monday, March 25.  These casings will be welded together over the drill rods and used to push the reamer toward the parkway extraction area.  Crews will be working over the weekend preparing for the casing assembly.  On Monday, the drill rig will begin to push the casing toward the reamer.  If necessary, an air hammer may be used to assist in the pushing process.  An air hammer was used last year on Swasey Parkway for a portion of the work.  The air hammer contemplated for use on this effort will be a smaller unit, however it would still be noisy activity. There are no additional costs to the Town relating to this circumstance.

3/21/24 - On March 19th the drilling rod on the Swasey Parkway side disconnected from the 18-inch reamer. The drilling activity was in the process of a second reaming pass which was enlarging the current bore hole to 18 inches in diameter. At the time of the disconnection, the reamer was approximately 500 ft from the parkway heading toward the Mill side of the river. It was later determined that the cause of the disconnection was a weld failure in the drill rod approximately 160 ft from the drill rig. The contractor is currently developing plans and will attempt to reconnect the drill rods.  There are no additional costs to the Town relating to this circumstance.

3/01/24 - On February 28th, the 12-inch reaming drill successfully made it from Swasey Parkway side to the Mill side of the river. Construction is continuing with the 18-inch reamer.   Exeter TV did a short video update in their March 1st edition of The Exeter Biweekly Report which can be watched on their YouTube page. 

2/12/24 - Due to the mild winter weather, crews have been able to make great progress with the second sewer siphon pipe as part of the Squamscott River Sewer Siphons Project. On Thursday, February 8th the most difficult part of drilling was completed successfully with the drilling of the pilot hole from the Swasey Parkway side to the mill side of the river. Crews have now been able to shift to using a new 12-inch reaming drill head to begin widening the hole in preparation for pulling the pipe through. As took place with the first pipe, following the 12-inch reamer, an 18-inch reamer will be used to widen the hole once more. After the second ream, the contractor will assess the borehole condition and determine if another ream is required. Once drilling is complete, the siphon pipe will be pulled through the borehole. The reaming process is expected to take place over the next six weeks. Upon completion of the reaming process, it is anticipated the infrastructure will be operational within six to eight weeks. Exeter TV stopped by the construction site to see the pilot hole being completed, watch their video update on their YouTube page. 

1/8/24 - Drilling of the pilot hole through the ledge of the Squamscott River will begin tomorrow, January 9th. Drilling for the 12-inch siphon pipe will require several stages. The first is the pilot hole, followed by two reaming operations that increase the hole diameter. Lastly, a pipe will be pulled through. It is anticipated that this operation will take approximately three months to complete. Construction schedules and information are subject to change with weather and other factors.

Updates 2020 - December 2023

PLEASE TAKE NOTE:

· Appropriate traffic control measures will be in place.  
· All driveways will remain accessible.
· Soil borings will cause some noise and disruption.
· Fieldwork will occur between 7:00 AM and 5:00 PM

If you have any questions regarding any of this work, please do not hesitate to contact Paul Vlasich, P.E. at pvlasich@exeternh.gov or by phone at (603) 773-6160.  

Project Background

There are two parallel 8 inch inverted sewer siphon pipes under the Squamscott River that transport sewage from approximately half of Portsmouth Avenue and surrounding neighborhoods via the Webster Pump Station. These siphons were installed in 1965. Engineering analysis has determined the siphons are at capacity during normal dry weather flows and undersized for any further additional new connections or during extreme wet weather events. Sanitary sewer overflows (SSOs) have occurred immediately upstream of the two siphons at Duck Point at the bottom of Jady Hill Avenue.

The original scope of this project was to continue use of the existing siphons and to add another siphon pipe to increase the current capacity. This increased capacity would in turn allow improvements to the Webster Avenue sewage lift station, thereby increasing its pumping capacity as well. This project would provide capacity for future sewer uses such as sewer extension to Holland Way, Hospital expansion, or development along Portsmouth Avenue. This project will also reduce the probability of sanitary sewer overflows (SSOs)

This project is eligible for financing through the Clean Water State Revolving Loan Fund (SRF) including 10% loan principal forgiveness.

Note that this project description was updated 4/15/2021 to reflect the findings of the siphon inspections and the resulting change in project scope.

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