March 1, 2017
Drilling Services Achieves Sound Abatement with Electric Rotary Rig
Successfully Meeting 65dBA Zoning Code Requirements
A Boart Longyear™ LR™175 electric/hydraulic rotary drill with a quiet genset operating the electric motor and a self-contained electric mud system was utilized in place of the typical diesel/hydraulic rotary drill.
Mountain Regional Water Special Service District is a large government water supplier which serves nearly 5,000 customers in the western region of Summit County, near Park City, Utah. The District covers roughly a 25 square mile territory and has an elevation gain of over 3,000 feet. “Serving customers in this area can be a real trial, not only because of the energy challenges with servicing such a diverse geography, but also the difficulties finding groundwater at high elevations, and in a steep mountainous environment. All groundwater sources in this territory are based on deep bedrock aquifers, with many obstacles. And most of the District’s 15 or so wells produce 200 gallons per minute or less.” says Mountain Regional Water District’s Doug Evans.
In 2015, the District decided to expand its well production and targeted an aquifer that would be highly productive. The Bison Bluff well was proposed to be a 1,000 foot deep well, with a completed depth of 700 feet and fitted with a 16 inch diameter steel louvered casing.
Meeting 65dBA Residential Zoning Code Requirements
The District outlined several criteria that needed to be met to make this a succcessful project. First, the drilling to be performed near Park City was situated within a residential neighborhood. This would require critical noise control, as well as lighting and difficult access considerations. Secondly, the project needed to be completed in the winter, before the Christmas holiday season, when water demands were at a minimum. The timing was important because an existing production well near the project would be precluded from operation during the drilling. This all meant that the project would need to be drilled around the clock and would also be under the microscope of the local home owner’s association and Summit County officials.
Local County ordinances identified noise prohibitions as well as criterion for measuring noise levels when it is anticipated the requirements in the ordinance might be exceeded. The stated noise threshold required that the noise levels not exceed 65 dBA.
Before the project began, noise monitoring was conducted to measure and document the existing ambient conditions adjacent to the project site. The results of the ambient noise levels indicated existing dBA levels between 60.3dBA and 69.3dBA which meant that essentially no recordable increase to the ambient dBA levels could be added by drilling activities. Boart Longyear proactively prepared and delivered a detailed report of the study to both the District and the County.
Used electric/hydraulic rotary drill and sound attentuation measures
As a result, a Boart Longyear™ LR™175 electric/hydraulic rotary drill with a quiet genset operating the electric motor and a self-contained electric mud system was utilized in place of the typical diesel/hydraulic rotary drill. This greatly reduced the typical operating noise level.
Sound attenuation curtains were also constructed on three sides of the project site and air dump mufflers were installed on the drilling rig, to further reduce noise output. In addition, since the drill site could create intermittent noise that could have exceeded the 65dBA threshold, Boart Longyear instituted additional mitigation measures.
- Shift changes were scheduled for 7:00 am and 7:00 pm.
- Truck deliveries were restricted to daytime hours.
- Back-up alarms were disconnected and spotters were used.
- Noise from banging, hitting of down hole tools, hand tools, and other equipment was monitored and reduced to “as absolutely necessary” situations and was restricted to daytime only.
Measured results well below threshold
Using the same methodology used for identifying the existing ambient noise levels, the maximum noise level generated by the Boart Longyear drilling operations was recorded at the same three locations. One additional site (SML 4) was added in order to evaluate how much of the noise energy traveled above the sound attenuation walls and potentially impacted the residences on the bluff overlooking the project site. The average measured and calculated noise levels were well below the threshold.
The project was completed successfully with no disruption to the local community and there was no recordable down-time or violations to the strict noise ordinance.
According to Doug Evans, Chief Technical Officer at Mountain Regional Water, “District management and staff could not say enough about the professionalism and technical expertise exhibited by the Boart Logyear team. The District was included in all phases of the drilling project, from initial safety planning to completion and cleanup. The Boart Longyear team met the challenges head on, and worked with the District on a community education plan, and even went door to door with District personnel as we handed out literature and educated the community, not only on the needs of the project, but how all of their concerns would be mitigated. Boart Longyear also utilized state of the art equipment in this project to minimize drill time and to lessen any impacts. Utilizing their LR175 electric drilling rig, which had an extremely large impact on noise, the entire site was also protected by sound walls, and lighting at night was minimized by using many small shop lights on the site instead of large construction flood lights. The site also abutted up against a very popular community walking trail and the area was kept very safe, clean, and neat.”
“The completed well tested at 1,500 gpm, which was above our expectations. In the end, the project actually came in UNDER budget, primarily because of the fact that any extras which could be needed in the drilling contract, to deal with problems or delays, were for the most part – completely eliminated! Of the many drilling projects I have been involved with over the years, none has turned out to be as successful and trouble free as this one.”
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