The Situation

The Iroquois Falls, Ontario 110 MW cogeneration plant is capable of producing 300,000 lbs/hr of steam for the Abitibi-Consolidated paper mill, in addition to supplying electricity to Ontario Hydro. It is also capable of producing noise levels of 119.5 dBA. Before Northland Power allowed its facility to "hiss" and "spark" into existence, it called on ATCO Noise Management to provide a complete noise management solution.

In order to meet the stringent 35 dBA requirement at the nearest residence, ATCO analyzed the significant noise contributors within the plant, which included: two enclosed General Electric (Model LM6000) aero-derivative gas turbine-driven generators; two combustion air inlet filters; two heat recovery steam generators (HRSGs); and one steam turbine generator. The fact that the facility was built along a riverbank, with the nearest residence located just 750 feet away at an elevation 82 feet higher than the plant floor, was also carefully scrutinized.

The Solution

ATCO Noise Management worked with Northland Power right from the project's inception and participated in drafting the acoustical specifications in the bid documents to EPC contractors. ATCO took full advantage of the "lay of the land" in its design of the acoustical building envelope and acoustical ventilation system. Relying on its comprehensive suite of 25 tested and approved acoustical assemblies, ATCO chose its Type J assembly for the north and west walls directly facing residences where sound attenuation was of paramount importance. Type E was selected for the roof, while the less costly Type A assembly was utilized for the east wall facing the forest, and the south wall facing the river, where noise containment was not as critical. With the high levels of sound absorption afforded by the north and west walls, ATCO was able to locate the steam generators at the northeast corner of the building. This configuration placed the gas turbines furthest away from the residences with the building itself acting as a noise shield for the turbines and their air intake structures. To address the significant potential for noise leakage created by the plant's ventilation system - rated at 20 air changes per hour - ATCO utilized its custom-designed silencers, along with strategic placement of the ventilation equipment. Because a standard roof installation of the exhaust fans would permit their noise to easily carry to nearby homes, the ventilation system was configured to allow their installation on the south wall facing the river. Taking advantage of the topography surrounding the plant, ATCO positioned the air intakes four feet above the ground on the west wall facing the residences, with the knowledge that the intervening hill would provide a natural noise barrier. Optimum cross-ventilation was an additional benefit of this placement.

The end result - the residents of Iroquois Falls can see the plant that lies below their town, but they would have to strain to hear it…

About Us

As a company providing a full turnkey service to its clients, ATCO Noise Management is responsible for all design, material procurement and construction. This has enabled us to accumulate a comprehensive database of material and labour costs which are incorporated into the acoustical design model, resulting in cost effective solutions to noise problems. We also offer ambient noise surveys, regulatory review, preparation of acoustical specifications, budget pricing and post-construction testing.