Merrimack CountyNew Hampshire
Andover, New Hampshire
6 of its 20 inventoried bridges are rated poor (30%, against 8% statewide). Bedrock sits a median 50 ft down across 342 logs, deeper than the New Hampshire median of 20 ft.
- Live · as of Sep 11, 2026
- 9 public sources · method
- ← All towns
Median depth to bedrock
50 ft
middle half 20–102 ft · 342 logs
Bridges rated poor
6
of 20 inventoried
FEMA repair $, Merrimack County
$238M
federal share since 2010 · county-wide
01 · Bridges
6 of 20 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 Andover. Median age 92 years; 2 posted for weight.
35% good, 30% poor
FHWA good / fair / poor rating — the lowest of deck, superstructure, substructure or culvert.
- Good7 · 35%
- Fair7 · 35%
- Poor6 · 30%
Structures by decade built
n = 20 structuresSource: FHWA National Bridge Inventory 2025
▸ Show the numbers▾ Hide the numbers
| Built | Structures |
|---|---|
| pre-1910 | 1 |
| 1920s | 3 |
| 1930s | 8 |
| 1950s | 4 |
| 1960s | 1 |
| 2000s | 1 |
| 2010s | 2 |
The poor-rated bridges
| Carries | Over | Built | Daily traffic |
|---|---|---|---|
| NH 11 | NHRR(ABD) | 1929 | 2,674 |
| NH 11 | SUCKER BROOK | 1929 | 2,674 |
| NH 11 | SUCKER BROOK | 1929 | 2,674 |
| US 4 | BLACKWATER RIVER | 1933 | 2,652 |
| BRIDGE ROAD | BLACKWATER RIVER | 1882 | 96 |
| LAST STREET | SUCKER BROOK | 1936 | 96 |
02 · Ground
Rock turns up a median 50 ft down
From 342 depth-to-rock records inside Andover (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 Andover's logs reach rock between 20 and 102 ft
Depth to bedrock: 10th–90th percentile whisker, middle-half box, median tick; dashed line = New Hampshire median.
median 50 ftNH 20 ft
050100150 ft
n = 342 logsSource: NH DES well inventory
▸ Show the numbers▾ Hide the numbers
| Depth to rock (ft) | Logs |
|---|---|
| 0–5 | 8 |
| 5–10 | 24 |
| 10–20 | 53 |
| 20–50 | 86 |
| 50–100 | 77 |
| 100+ | 94 |
Rock within 10 ft
12%
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. 49% of logs here go past 50 ft.
03 · Dams & disasters
Merrimack County has drawn $238M in federal disaster repair since 2010
FEMA Public Assistance is reported by county, so the figure below is Merrimack County-wide context, not a Andover number.
FEMA Public Assistance, Merrimack County
$238M
Federal share obligated across 470 projects in 25 declared disasters since 2010. The largest category is emergency protective measures (86%); roads & bridges took $10.9M.
04 · Next door
Andover and the 6 towns that border it
A dash means no data for that layer, not zero.
| Town | Poor bridges | Rock depth |
|---|---|---|
| Andover, NH | 6 / 20 | 50 ft |
| Warner, NH | 2 / 29 | 28 ft |
| Danbury, NH | 5 / 18 | 29 ft |
| Wilmot, NH | 0 / 14 | 26 ft |
| Franklin, NH | 0 / 6 | 30 ft |
| Hill, NH | 1 / 6 | 47 ft |
| Salisbury, NH | 0 / 3 | 28 ft |
Where these numbers come from
Method, sources & caveats
Andover is the Census county subdivision 3301301460 (Merrimack 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
- U.S. Census Bureau cartographic boundary files — county subdivisions (2024, 1:500k)Public domain
- FHWA National Bridge Inventory (2025 delimited files)Public domain
- USACE National Inventory of DamsPublic domainHigh-hazard dams rated Poor or Unsatisfactory (live NID).
- USGS U.S. Landslide InventoryPublic domain
- MassGIS / Massachusetts Geological Survey — Bedrock Data PointsPublic recordBorings and well logs that reached rock (MassDEP well drillers, USGS, MWRA, MassDOT…); seismic/HVSR and map-derived shallow-bedrock/outcrop points excluded.
- NH DES Water Well Inventory, Maine Geological Survey Wells Database, Vermont DEC well recordsPublic recordBedrock wells only; driller-reported depth to bedrock / overburden thickness.
- OpenFEMA Public Assistance Funded Projects Details (v2)Public domain
- MA EEA / CZM grant awards — Dam & Seawall, MVP Action, CZM Coastal ResiliencePublic record
- Municipal open-data permit portals (Boston, Cambridge, Somerville, Providence, Portsmouth, others)Public recordOnly permits flagged as ground-related (retaining walls, excavation, foundations) are counted.
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.