Discussions continue on a proposed excavation site on Brookline Road in Mason, with Wednesday’s meeting centered mainly on traffic, road conditions and dust.

Brookline Road LLC has proposed an excavation site on approximately 67 acres on Brookline Road in Mason. The site is proposed to excavate gravel over the course of several years in three-acre increments and will be operated by Onyx Corporation.

The Mason Planning Board considered the results of a traffic study submitted by Transportation Engineering, Planning and Policy LLC related to potential traffic and road impacts from the project. The report considered the roadways and intersections in Mason and Brookline that will be subject to the majority of truck traffic from the site.

TEPP conducted traffic studies on two occasions — May 28-30 and June 4-6 — on Brookline Road west of Parker’s Maple Barn, near the site, and on Mason Road west of Route 13.

Based on a maximum daily use of 50 trips in and 50 out, TEPP found that the increases “do not change the order of magnitude of traffic volumes on Brookline Road or Mason Road.”

Even at a maximum of 100 trips, TEPP said the increases were not notable for the roads, which had 933 to 3,568 existing vehicle trips daily.

The Nashua Regional Planning Commission also submitted comments on the roads, concluding that proposed truck routes can accommodate the increased traffic volume but noting concerns about road degradation from heavy vehicles and safety during morning and afternoon peak hours.

The board spent significant time Wednesday discussing road and traffic impact.

Allen Rosenberg, co-chair of the Brookline Planning Board, said the town has lingering concerns about the environment, roads and the traffic study. He said the study covered a short period of time and did not account for peak tourist traffic seasons.

Select Board representative Antje Skorupan, who also serves on the Planning Board, said the board had been most interested in the effect of increased heavy vehicle traffic specifically, which she said the study did not adequately address.

Planning Board member Jenny Scholl called the study “incomplete” and “subjective,” citing a need for more specificity in areas such as defining what constitutes a “heavy vehicle” and the impact of adding large numbers of heavy vehicles on road pavement.

The board also discussed whether proposed Saturday trucking hours were acceptable, with members suggesting allowing property maintenance operations on Saturdays but not trucking. Member Chris Jones suggested a schedule that accounts for school bus routes.

The board discussed dust control and Onyx’s commitment to install a dust monitor on the downwind side of the property. Jones said that was significantly better than the state standard of visual monitoring, calling it a “huge step up.”

Proposed conditions

Onyx has submitted proposed findings of fact and conditions it would find acceptable, based on discussions during public hearings.

The conditions are divided into two parts: what Onyx must do before starting excavation and what it must do during excavation.

Proposed pre-excavation conditions include obtaining an Alteration of Terrain permit from the state Department of Environmental Services, providing a $60,000 surety for reclamation of at least three acres and obtaining an excavation permit from the Mason Select Board.

Operational conditions include reapplying for a permit with the Select Board every two years and adjusting the reclamation surety as needed, completing reclamation of each three-acre phase within 12 months, and filing Intent to Cut permits for tree clearing and Intent to Excavate permits.

Onyx has also agreed to install a dust monitoring device on the eastern edge of the property, provide quarterly reports to the Select Board, and submit to annual inspections by a licensed engineer with reports to the Select Board. The company has also agreed to replant the removed tree buffer after completion of the first phase.

Onyx has agreed to abide by stipulations of a draft memorandum of understanding with the town, which includes submitting a road maintenance bond of $50,000 and restricting truck traffic from Gilman Hill Road in Mason and Russell Hill Road and Cleveland Hill Road in Brookline.

Onyx agreed to conduct annual inspections of roads along its hauling routes, with invitations extended to road agents for both Mason and Brookline. Onyx will be allowed to complete any repairs requested by the Mason Select Board at its own expense. If Onyx is unable to complete repairs, the town can draw on the bond to do so.

The bond may only be used for repairs to roads in Mason or Brookline that the Select Board reasonably determines have been degraded by Onyx’s truck traffic.

The board continued the public hearing until July 29 at 7:10 p.m. at Mason Elementary School.