Earth Support Corp

Belknap CountyNew Hampshire

Sanbornton, New Hampshire

Bedrock sits a median 20 ft down across 608 logs, close to the New Hampshire median of 20 ft. 1 of its 13 inventoried bridges is rated poor (8%, against 8% statewide).

Median depth to bedrock

20 ft

middle half 10–45 ft · 608 logs

Bridges rated poor

1

of 13 inventoried

FEMA repair $, Belknap County

$3.3M

federal share since 2010 · county-wide

01 · Ground

Rock turns up a median 20 ft down

From 608 depth-to-rock records inside Sanbornton (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 Sanbornton's logs reach rock between 10 and 45 ft

Depth to bedrock: 10th–90th percentile whisker, middle-half box, median tick; dashed line = New Hampshire median.
median 20 ft
NH 20 ft
0255075 ft
0501001502000–5 ft5–10 ft10–20 ft20–50 ft50–100 ft100+ ft
n = 608 logsSource: NH DES well inventory
▸ Show the numbers
Depth to rock (ft)Logs
0–544
5–1093
10–20147
20–50180
50–100114
100+30

Rock within 10 ft

28%

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. 21% of logs here go past 50 ft.
Bedrock & soils across New England

02 · Bridges

1 of 13 bridges are rated poor — about the same as the New Hampshire rate of 8%

Every highway bridge and large culvert in the 2025 National Bridge Inventory that stands inside Sanbornton. Median age 64 years.

62% good, 8% poor

FHWA good / fair / poor rating — the lowest of deck, superstructure, substructure or culvert.
  • Good8 · 62%
  • Fair4 · 31%
  • Poor1 · 8%
n = 13 structuresSource: FHWA National Bridge Inventory 2025
▸ Show the numbers
BuiltStructures
pre-19102
1960s8
2010s3

The poor-rated bridges

Bridges rated poor in Sanbornton
CarriesOverBuiltDaily traffic
BROOK ROADSALMON BROOK190096
Every poor bridge in New England

03 · Dams & disasters

Belknap County has drawn $3.3M in federal disaster repair since 2010

FEMA Public Assistance is reported by county, so the figure below is Belknap County-wide context, not a Sanbornton number.

FEMA Public Assistance, Belknap County

$3.3M

Federal share obligated across 118 projects in 9 declared disasters since 2010. The largest category is roads & bridges (51%); roads & bridges took $1.7M.
Dams, disasters & moving ground

04 · Next door

Sanbornton and the 7 towns that border it

A dash means no data for that layer, not zero.
Sanbornton compared with neighbouring towns
TownPoor bridgesRock depth
Sanbornton, NH1 / 1320 ft
Laconia, NH1 / 1718 ft
New Hampton, NH0 / 1330 ft
Tilton, NH0 / 1060 ft
Belmont, NH0 / 722 ft
Franklin, NH0 / 630 ft
Hill, NH1 / 647 ft
Meredith, NH0 / 412 ft

Where these numbers come from

Method, sources & caveats

Sanbornton is the Census county subdivision 3300167300 (Belknap 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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