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About Horizontal Directional Drilling

Massachusetts Water Resources Authority - March 2004

What are the Fore River Siphons?

The Fore River Siphons are two 36-inch sewer pipes that will be constructed under the Fore River as part of the Braintree-Weymouth Relief Facilities Project utilizing a technology called horizontal directional drilling or HDD. When they are complete they will connect to the already constructed North Weymouth Relief Interceptor (NWRI) and Intermediate Pump Station (IPS).

How does Horizontal Directional Drilling (HHD) work?

Horizontal Directional Drilling: how it works

Two siphons will be constructed under the Fore River utilizing a technology called horizontal directional drilling or HDD. Work will occur from two locations: a drill rig location which is in Idlewell at the end of Arlington Street and a pipe assembly location which is at the Exelon property in North Weymouth. From the drill rig location, a a drill rig will drill a pilot hole under Fore River to the Exelon property in North Weymouth. The hole will then be enlarged through successive reams until it is large enough to fit the pipe. Since the end of February the contractor has been welding the pipe at the Exelon property that will be pulled by the directional driller back through the hole.

How long will HDD construction take?

Completion of each siphon will take approximately 4-6 weeks. This includes about 3-4 weeks of drilling and 1-2 weeks to pull the pipe back.

What are the allowable hours of operation?

The contractor is allowed to work Monday - Friday from 7a.m. to 7p.m. except during pipe pullback which is allowed 24-hours-a-day, seven-days-a-week. Work beyond this time frame can be requested by the contractor and authorized by the MWRA.

Why is it necessary to work 24-hours-a-day, seven-days-a-week during pipe pullback?

Once pipe pullback begins, the operation must be continuous until it is complete in order to avoid a potential collapse in the previously reamed hole. A collapse would require the contractor to excavate at the point of collapse and would likely result in significant delays.

What will be done to make sure the night work is not too disruptive?

Typically, the biggest issues that arise for neighbors during night work are related to noise and light. To make sure these do not become a problem on this project, we have included many noise and light requirements in the contract. The contract includes stringent noise limits and HDD will be closely monitored by MWRA staff and consultants for compliance with these limits. The contractor is required to use proper mufflers and self-adjusting back-up alarms on all equipment and shields and enclosures around stationary equipment. The contract also includes many requirements to protect nearby residents from the glare and illumination of temporary lighting, including aiming lighting away from nearby homes and equipping lighting with shielding, reflecting or visors. Adherence to the established noise and light requirements will be strictly enforced.

What should I do if a problem arises during the night?

Please call 1-888-Tunnel2 should a problem occur between 5p.m. and 8:30a.m. Monday to Friday and on Saturdays and Sundays. All other calls should be directed to Michele Gillen at (617) 788-1191 during regular work hours - 8:30a.m. to 5p.m.

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