A panel of engineers and Massachusetts Office of Dam Safety officials told Newton’s Public Facilities Committee that Bullis Pond Dam cannot safely pass the design storm under current conditions and needs repairs that will remove vegetation from large portions of the upstream and downstream slopes.

The presentation, led by former city engineer Lou Taverna and consultant Lee Wooten of GEI, and followed by comments from Bill Salome, director of the state Office of Dam Safety, laid out three feasible approaches and the committee’s preferred option: an erosion‑protection solution using articulated concrete block mats covered with topsoil and grass. The designers said that under the modeled 100‑year (1% annual chance) event the dam would be overtopped by about 2 feet and that overtopping of that depth has a high likelihood of causing a breach unless erosion is arrested.

Why this matters: committee members and state staff said a breach could send floodwaters into neighborhoods, Newton North High School and toward the Mass Pike. The city has a dam‑safety order and must bring the structure into compliance with state regulations issued after inspections found multiple deficiencies, including vegetation intrusion, slope erosion and masonry deterioration.

Engineers’ findings and the chosen design

Lee Wooten of GEI described the dam’s principal deficiency as insufficient spillway capacity for the design storm and showed inundation maps that extend downstream into residential areas and the high school campus. He said the chosen fix would place articulated concrete blocks on the downstream slope, burying and covering them with topsoil so the final surface is grassed. He said the block mat option (the selected design) is less disruptive to the road and utilities than two alternatives — installing a sheet‑pile cutoff wall or raising an existing core wall — and is $1 million to $2 million cheaper than those other schemes.

Wooten said the block‑mat option still requires tree and brush clearing in the areas of the mats and a grading/compaction operation so the mats lie evenly. He described the block mattress installation steps: tree and brush removal, stripping to about a foot depth where required, placement of bedding layers and mats, and final seeding. He estimated the area of the block mattress at about 8,200 square feet as shown on the consultants’ slides.

State Office of Dam Safety policy and tree removal

Bill Salome, director of the Office of Dam Safety at the Department of Conservation and Recreation, told the committee that “trees don’t belong on dams,” a longstanding theme in dam safety training because large roots and uprooted trees can create seepage paths and sudden erosion during overtopping. Salome said his office treats significant vegetation and large trees on embankments as a factor in classifying a dam’s condition and that the office expects dam owners to remove trees where they threaten embankment integrity.

The consultant’s tree inventory identified roughly 199 total trees in the broader area affected by some designs, with about 6 trees greater than 6 inches in diameter in the immediate mattress area and the remainder smaller. Depending on the option, total tree removal estimates discussed in the meeting ranged from about 72 trees (for some options) up to roughly 200 trees for the most extensive layouts shown. The design team said most affected trees are on public land; consultants said no private trees were expected to be cut in the proposed limits of disturbance shown in the presentation.

Flood modeling detail and committee requests

Wooten and state staff described modeled inundation depths that vary as floodwater moves downstream: near the dam the model shows up to about 3 feet of depth at the nearest road, 2.4 feet at Gay Street and about 1 foot near the Mass Pike. The consultants said their hydraulic model predicts roughly 2 feet of water flowing over the dam crest in the selected design storm scenario, and that the block mats are designed to prevent the downstream slope from eroding and progressing to a breach.

Committee members pressed the team for additional, incremental modeling. Councilors asked for: (1) maps showing the difference between baseline (overtopping without breach) flooding and a catastrophic breach; (2) more detail on how the downstream culvert/grate at Hull Street would be affected if vegetation or sod were washed into it; and (3) clear documentation of how the nine early alternatives were winnowed to three and which stakeholders were consulted in each step. Several councilors requested a more detailed timeline and documentation of meetings with the Bullis Pond neighborhood group.

Permitting, next steps and funding

Wooten listed permits expected for the project, including dam safety approvals, environmental permits and historic‑notification filings. He said the project remains in conceptual design and that the city is pursuing grant opportunities administered by the state; final design and contractor procurement would follow Office of Dam Safety review and sign‑off. The state director confirmed the city received a dam safety order (certificate of non‑compliance) in July 2018 and that the office has asked the city for a timeline and community input on a path to compliance.

Council action and committee disposition

After questions and discussion, the committee voted by voice to hold the item for further analysis and follow‑up. Councilors said they wanted additional modeling and written documentation of the alternatives analysis and stakeholder consultations before selecting a final design and approving funding or construction steps.

What to watch next: the city plans further community outreach, a follow‑up working‑group meeting and additional hydraulic modeling that committee members requested. The city is also exploring state grant funding for final design and construction; Office of Dam Safety review and permit issuance will be required before construction can begin.