Millen Pond-Deep Spot
Millen Pond-Deep Spot in Sullivan County, New Hampshire has a water quality grade of A (Excellent). Phosphorus: 8.1 µg/L. Chlorophyll-a (algae): 3.1 µg/L.
- Type
- Mesotrophic
- Public access
- Yes
Millen Pond-Deep Spot is a mesotrophic lake in Sullivan County, New Hampshire. Water quality is graded A based on 2 sampling years through 2025. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 23 other monitored lakes in Sullivan County, Millen Pond-Deep Spot ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2025-08-25. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
No clarity data. Phosphorus level: 8.1 µg/L. Chlorophyll-a: 3.1 µg/L. Trophic State Index: 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 8.1 µg/L | Good |
| Chlorophyll-a (Algae) | 3.1 µg/L | Good |
| Trophic State Index (TSI) | 38 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Millen Pond-Deep Spot
Compare lakeside cabins, hotels, and vacation rentals near Millen Pond-Deep Spot 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.
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Recreation & Access
- Millen Lake AccessPublic
Named access points from the USGS National Boat Ramps inventory, snapped within 5 km. More lakes with boat ramps
Fishing Millen Pond-Deep Spot
EPA Impairment Status
Millen Pond-Deep Spot is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NHLAK802010101-06-01 · Official waterbody report · Matched by proximity (0.26 km)
County Ranking
Ranked #2 of 24 lakes in Sullivan County
Nearby Lakes in Sullivan County
Frequently asked questions about Millen Pond-Deep Spot
Where is Millen Pond-Deep Spot?
- Millen Pond-Deep Spot is a lake in Sullivan County, New Hampshire. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Millen Pond-Deep Spot?
- Millen Pond-Deep Spot in Sullivan County, New Hampshire has a water quality grade of A (Excellent). Phosphorus: 8.1 µg/L. Chlorophyll-a (algae): 3.1 µg/L.
Is Millen Pond-Deep Spot safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Millen Pond-Deep Spot has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 3.1 µg/L. Always check local health department advisories before swimming.
Are there boat ramps on Millen Pond-Deep Spot?
- Millen Pond-Deep Spot has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Millen Lake Access. Public access is listed as yes.
Explore Millen Pond-Deep Spot 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 A Lakes in New Hampshire
Hillsborough County · Excellent
Hillsborough County · Excellent
Cheshire County · Excellent
Merrimack County · Excellent
Cheshire County · Excellent
Merrimack County · Excellent
Mesotrophic Lakes in New Hampshire
Where this data comes from
35 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- New Hampshire Department Of Environmental Services (BEACH)
1111330035 samples · 2020–2025
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
Named boat-access points from the USGS National Boat Ramps inventory