Overview | Ice Jam Event Details | Ice Breaking Demonstration Details | Ice Control Structure

Ice Breaking Demonstration Details

Arconic (formerly Alcoa) conducted a United States Environmental Protection Agency- (EPA) directed Ice Breaking Demonstration Project (Demonstration Project) in March 2007 to evaluate the effectiveness of mechanical ice breaking as an interim measure for mitigating future ice jam related sediment scour in the lower Grasse River.

The Demonstration Project was conducted March 19 through 24, 2007, and involved breaking the intact ice cover in an approximate 7-mile reach of the lower Grasse River (see figure below). A primary goal of the project was to evaluate the feasibility of breaking the intact ice cover from the lower Grasse River in order to allow ice entering from upstream during natural breakup to be transported through the lower Grasse River without causing a significant ice jam and related scour event.

Project Description

Arconic (formerly Alcoa) conducted a United States Environmental Protection Agency- (EPA) directed Ice Breaking Demonstration Project (Demonstration Project) in March 2007 to evaluate the effectiveness of mechanical ice breaking as an interim measure for mitigating future ice-jam related sediment scour in the lower Grasse River. The work was undertaken in response to the spring 2003 ice jam event that caused disturbance of both the cap placed as part of the 2001 Capping Pilot Study and PCB-containing sediments below the cap.

As a result of the 2003 ice jam event, EPA and the company conducted an evaluation of both interim and long-term measures to prevent future ice jam events from occurring in the lower Grasse River. An interim (and potentially longer term) pier-type ice control structure (ICS) was originally proposed as a component of the 2005 Remedial Options Pilot Study; however, this was not pursued due to community concerns related to the placement of the ICS in the Town of Louisville. Therefore, mechanical ice breaking in the lower river was identified as the only potentially feasible non-structural interim measure. Note that the company is continuing to evaluate the potential for long-term structural ice control measures.

A decision process was put in place in advance of the Demonstration Project to evaluate whether ice breaking was warranted in spring 2007 based on both actual and predicted ice and weather conditions. Following a review of available 2007 data on ice coverage, ice thickness and air temperature, a "go" recommendation was made by the company's ice expert group and subsequently agreed with by EPA.

The Demonstration Project was conducted March 19 through 24, 2007. The project involved breaking the intact ice cover in an approximate 7-mile reach of the lower Grasse River, with the goal of opening a channel in the river to allow the ice entering from upstream of Massena during natural breakup to freely flow through the lower Grasse River without significant jamming.

Community Outreach and Notificaion

Safety of the community and personnel involved with the ice breaking and monitoring activities, along with protection of the surrounding environment, were critical considerations during the planning and implementation stages of the Demonstration Project. Arconic (formerly Alcoa) committed significant efforts to ensure that safety was the highest priority prior to, during, and after completion of the ice breaking activities. The company, working in conjunction with EPA, developed and implemented an extensive community notification program and developed emergency planning and response procedures to inform and protect the community.

Community notification efforts included community meetings, announcements in local papers and on local radio and television stations, distribution and posting of community mailers and flyers, announcements at local community group meetings, schools, local businesses, community centers, and door-to-door visits to residents along the lower Grasse River. The company also installed warning signs and lights at 20 river access/egress points and posted banners on bridges over the lower Grasse River and Raquette River.

Concerns were expressed during the community outreach efforts regarding the ability to successfully reach all potentially affected parties (e.g., recreational users of the lower river) irrespective of the level of effort employed in the notification process, particularly in view of the potential consequences of a safety incident involving a recreational river user. This was a major concern both during the conduct of the project and from the conclusion of the project through the natural ice out of the lower Grasse River, which occurred approximately five days later.

Ice Breaking Activities

A tug and barge were mobilized to the Alcoa East Plant on December 21, 2006 to stage equipment prior to river freeze-up. Additional equipment (e.g., excavators, lighting, etc.) was mobilized to the Alcoa East Plant on March 14, 2007 to prepare for ice breaking activities, which began on March 19, 2007.

Ice breaking was performed in an approximate 7-mile reach of the lower Grasse River with two excavators operating from a barge that was moved by a shallow-draft tug. Two crews worked in alternating 12-hour shifts, 24 hours per day to complete the project.

Progress made during each shift was dependent on many conditions including ice thickness, river flows, air temperature, wind speed, and river course. These conditions impacted the ability to clear ice from the channel once it was broken, and backtracking was required during several shifts to clear and widen channels that had become clogged with ice pieces or where ice had reformed. No work was conducted during the day shift of March 21, 2007 due to extremely cold temperatures. Equipment failures also resulted in delays, but downtime associated with this work was limited. Overall, five days of ice breaking was needed to completed the planned work.

Monitoring activities conducted during the course of ice breaking activities included measurement of ice thickness, tracking of ice breaking progress, turbidity monitoring, noise monitoring, warning sign/banner observation and photographic documentation. In addition, due to concerns regarding safety, the captain and crew of the ice breaking operation and shore side support personnel monitored the work area for the presence of individuals on the ice.

Ice breaking operations were completed on March 24, 2007 to a location approximately 2,000 feet downstream of the Alcoa Bridge. The originally proposed upstream extent of ice breaking activities was approximately 500 feet downstream of the Alcoa Bridge, but crew observations of frazil ice (or fine, small, needle-like or thin, flat, circular plates of ice suspended in water) led to the termination of operations short of the planned location. An ice breaking channel width of approximately 200 to 250 feet was achieved throughout the river, with the exception of the final approximately 3,000 feet where the channel was narrower (approximately 130 to 150 feet) and oriented toward the southern shore of the river. Attempts to break a wider channel resulted in visibly turbid water conditions, presumably due to relatively shallow water depths in this area.

There were no community or worker health and safety incidents during ice breaking operations. On four separate occasions individuals were observed on the ice and during one shift headlights were observed near a boat launch in proximity to the ice breaking operation. On these occasions, and in accordance with the established health and safety procedures, operations were stopped until it was confirmed that the river was clear and it was safe to continue operations.

Post-Ice Breaking Community Surveys and Input

Focus group meetings and surveys were conducted after the Demonstration Project to understand community reaction to the project and evaluate the effectiveness of community notification measures employed during the project. In general, survey participants noted a major concern about the potential for a snowmobile accident occurring as a result of the project, and extensive public notification was considered the best way to guard against this possibility. Other major concerns noted by the community included: noise at night; a shortened winter recreational season; environmental disturbance; and worker safety.

The participants indicated that the notifications procedures implemented by Arconic (formerly Alcoa) and EPA were comprehensive and effective, and the average respondent received notification from at least four different sources. Signage was also noted to be situated in the appropriate locations and was effective. However, it was noted that certain community members do not pay attention to what is happening in the community and they are potentially at risk, regardless of the notification system.

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