Earth Support Corp

Hillsborough CountyNew Hampshire

Antrim, New Hampshire

1 high-hazard dam is rated in poor or unsatisfactory condition. Bedrock sits a median 55 ft down across 339 logs, deeper than the New Hampshire median of 20 ft.

Median depth to bedrock

55 ft

middle half 19–96 ft · 339 logs

Bridges rated poor

1

of 10 inventoried

Poor high-hazard dams

1

National Inventory of Dams

FEMA repair $, Hillsborough County

$39.7M

federal share since 2010 · county-wide

01 · Dams & disasters

1 high-hazard dam needs work

FEMA Public Assistance is reported by county, so the figure below is Hillsborough County-wide context, not a Antrim number.
High-hazard dams in poor condition in Antrim
DamConditionBuilt
Gregg Lake DamGreat BrookPoor1908

High hazard potential means failure would probably cost lives — it rates the consequences, not the dam’s condition.

FEMA Public Assistance, Hillsborough County

$39.7M

Federal share obligated across 415 projects in 10 declared disasters since 2010. The largest category is emergency protective measures (90%); roads & bridges took $1.8M.
Dams, disasters & moving ground

02 · Ground

Deep ground: 51% of logs go past 50 ft before rock

From 339 depth-to-rock records inside Antrim (NH DES well inventory). Logs cluster where people drill wells and bore for roads, so treat this as the town’s pattern, not a site answer.

Half of Antrim's logs reach rock between 19 and 96 ft

Depth to bedrock: 10th–90th percentile whisker, middle-half box, median tick; dashed line = New Hampshire median.
median 55 ft
NH 20 ft
050100150 ft
0204060801000–5 ft5–10 ft10–20 ft20–50 ft50–100 ft100+ ft
n = 339 logsSource: NH DES well inventory
▸ Show the numbers
Depth to rock (ft)Logs
0–521
5–1022
10–2043
20–5080
50–10093
100+80

Rock within 10 ft

15%

of logs (31% across New Hampshire). Shallow rock means ledge in excavations, refusal for driven piles and rock anchors rather than soil nails; deep ground means taller shoring and more groundwater. 51% of logs here go past 50 ft.
Bedrock & soils across New England

03 · Bridges

1 of 10 bridges are rated poor — above the New Hampshire rate of 8%

Every highway bridge and large culvert in the 2025 National Bridge Inventory that stands inside Antrim. Median age 32 years.

70% good, 10% poor

FHWA good / fair / poor rating — the lowest of deck, superstructure, substructure or culvert.
  • Good7 · 70%
  • Fair2 · 20%
  • Poor1 · 10%
n = 10 structuresSource: FHWA National Bridge Inventory 2025
▸ Show the numbers
BuiltStructures
1910s1
1950s1
1980s1
1990s3
2010s4

The poor-rated bridges

Bridges rated poor in Antrim
CarriesOverBuiltDaily traffic
LIBERTY FARM ROADNORTH BRANCH RIVER199196
Every poor bridge in New England

04 · Next door

Antrim and the 7 towns that border it

A dash means no data for that layer, not zero.
Antrim compared with neighbouring towns
TownPoor bridgesRock depth
Antrim, NH1 / 1055 ft
Hillsborough, NH3 / 2681 ft
Hancock, NH1 / 1262 ft
Nelson, NH0 / 618 ft
Bennington, NH1 / 546 ft
Stoddard, NH0 / 517 ft
Deering, NH0 / 430 ft
Windsor, NH—23 ft

Where these numbers come from

Method, sources & caveats

Antrim is the Census county subdivision 3301101700 (Hillsborough County). Every record is placed here by its coordinates, not by the place name the source uses.

  • Towns are Census county subdivisions: cities, towns, plantations, and Maine/New Hampshire unorganized territories and townships. Every record is placed in a town by its coordinates (point-in-polygon), not by the source's own place label — so a bridge in Roxbury counts for Boston and a well in 'North Waltham' counts for Waltham.
  • Bridges: FHWA NBI 2025, highway structures ≥ 20 ft including large culverts. 'Poor' is FHWA's good/fair/poor rating (lowest of deck, superstructure, substructure or culvert ≤ 4). Percent-poor is shown only for towns with at least 5 structures.
  • Depth to bedrock is the median of driller- and boring-reported depths in the town, shown only where at least 10 logs exist. Water-well logs over-sample rural lots and hilltops; one town median never describes a particular site.
  • Bedrock depths use the same state databases and filters as the Bedrock & soils module (bedrock wells and borings that reached rock, 0 < depth ≤ 400 ft, exact re-filings dropped), but every log is placed in a town by its coordinates rather than the driller's town field, so town counts can differ slightly between the two pages. Connecticut and Rhode Island have no statewide public well-log database with depths.
  • Dams: only high-hazard-potential dams whose latest condition assessment is Poor or Unsatisfactory are counted (live NID). Connecticut and Rhode Island assessments may lag.
  • FEMA Public Assistance dollars are federal share obligated for disasters declared since 2010, reported by county — they are county context, not a town figure.
  • Grant awards are Massachusetts only (EEA Dam & Seawall program, MVP Action grants, CZM Coastal Resilience). Other states' programs are not yet included.
  • Ground-related permit counts cover only the municipal portals the pipeline reads (Boston, Cambridge, Somerville, Worcester, Framingham, Providence, Portsmouth, Hartford and a few others) — an absent count means 'not covered', not zero.
Data as of
Sep 11, 2026
Generated
Sep 11, 2026
Records
367,748
Refresh
Live pull · weekly

Published by Earth Support Corp as a public resource. Regional statistics for planning and curiosity. They are not an engineering report, a bid recommendation or a statement about any particular site, firm or project. Spot an error? Tell us and we will correct it. Full method: methodology.

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