Mill Pond
Mill Pond in Sullivan County, New Hampshire has a water quality grade of D (Nutrient-rich). Phosphorus: 28.9 µg/L. Chlorophyll-a (algae): 4 µg/L.
- Type
- Mesotrophic
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Mill Pond →
Mill Pond is a mesotrophic lake in Sullivan County, New Hampshire. Water quality is graded D based on 1 sampling years through 2025. Compared to the 23 other monitored lakes in Sullivan County, Mill Pond ranks #22 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-07-27. Grade methodology: LakeGrade methodology.
Watch Mill Pond water quality
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Swimming Safety
Grade onlyBacteria advisory
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
No clarity data. Phosphorus level: 28.9 µg/L. Chlorophyll-a: 4 µg/L. Trophic State Index: 48.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 28.9 µg/L | Poor |
| Chlorophyll-a (Algae) | 4 µg/L | Not graded |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Mill Pond
Compare lakeside cabins, hotels, and vacation rentals near Mill Pond in Sullivan County, New Hampshire — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Mill Pond are listed below.
Top-rated places to stay near Mill Pond
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Fishing Mill Pond
EPA Impairment Status
Mill Pond is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHIMP700030204-05-02 · Official waterbody report · Matched by proximity (0.03 km)
County Ranking
Ranked #22 of 24 lakes in Sullivan County
Nearby Lakes in Sullivan County
Frequently asked questions about Mill Pond
Where is Mill Pond?
- Mill Pond is a lake in Sullivan County, New Hampshire. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Mill Pond?
- Mill Pond in Sullivan County, New Hampshire has a water quality grade of D (Nutrient-rich). Phosphorus: 28.9 µg/L. Chlorophyll-a (algae): 4 µg/L.
Is Mill Pond safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Mill Pond has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 4 µg/L. Always check local health department advisories before swimming.
Explore Mill Pond across LakeGrade
More New Hampshire Lake Rankings
Top 25 by overall water quality score
Top 25 by Secchi water clarity
Grade A/B + low algae filter
Panfish-rich, public access
Full state directory
Other Grade D Lakes in New Hampshire
Hillsborough County · Nutrient-rich
Cheshire County · Nutrient-rich
Cheshire County · Nutrient-rich
Hillsborough County · Nutrient-rich
Hillsborough County · Nutrient-rich
Hillsborough County · Nutrient-rich
Mesotrophic Lakes in New Hampshire
Where this data comes from
14 measurements from 1 monitoring station, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
1111330014 samples · 2021–2025
Analytical methods
- 10-115-01-1 F ~ LACHAT; Total Phosphorus- Manual persulfate digest
- CHLOROPHYLL A-B-C DETERMINATION (MODIFIED)
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database