Foster Lake
Linn County, Oregon1,220 acresView mapDirections
Nutrients and algae sit mid-range for this region.
↓ down from A at the last regrade
- Mesotrophic
- Impaired · Temperature
- #2 of 2 in the county
- Public access
- Limited data
Foster Lake in Linn County, Oregon has a water quality grade of C (Fair). Chlorophyll-a (algae): 2.4 µg/L. Surface area: 1220 acres.
- Area
- 1,220 acres
- Type
- Mesotrophic
- Chlorophyll-a
- 2.4 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
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Foster Lake is a 1,220-acre mesotrophic lake in Linn County, Oregon. Water quality is graded C based on 1 sampling years through 2025. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 1 other monitored lakes in Linn County, Foster Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Oregon DEQ, last sampled 2025-10-16. Grade methodology: LakeQuality methodology.
What Foster Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Big water1,220 acres
Swimming Safety
Grade onlyLimited data
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.
The C is nutrients and algae, not a swimming clearance. Foster Lake is listed impaired under Clean Water Act §303(d) (IR 5) for temperature. Check local advisories before you swim.
Water Quality Grade: C (Fair)
No clarity data. Chlorophyll-a 2.4 µg/L. TSI 39. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 2.4 µg/L | Fair |
| Trophic State Index (TSI) | 39 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 1,220 acres |
| Public Access | Yes |
No bathymetric survey has been published for Foster Lake, so its depth is not documented here.
Recreation & Access
- Calkins ParkPublic
- Sunnyside ParkPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Foster Lake
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Chlorophyll-a | ↑ Improving | -0.3 µg/L/yr | 2 |
Reservoir Info (USACE NID)
Foster Lake is a man-made reservoir impounded by the Foster Dam (completed 1967), built primarily for flood risk reduction on the South Santiam River; rockfill-type dam, 126 ft tall and 4,800 ft long.
- Surface area
- 1,220 ac
- Normal storage
- 56,000 ac-ft
- Max storage
- 61,000 ac-ft
- Drainage area
- 494 sq mi
- Hazard class
- High
- Owner
- USACE - Portland District
All listed purposes: Flood Risk Reduction;Other;Irrigation;Navigation;Recreation;Hydroelectric.
Source: USACE National Inventory of Dams, NID ID OR00012 · Operator website
EPA Impairment Status
Foster Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit OR_LK_1709000604_02_100772 · Official waterbody report
County Ranking
Ranked #2 of 2 lakes in Linn County
Nearby Lakes in Linn County
Frequently asked questions about Foster Lake
Where is Foster Lake?
- Foster Lake is a lake in Linn County, Oregon. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Foster Lake?
- Foster Lake in Linn County, Oregon has a water quality grade of C (Fair). Chlorophyll-a (algae): 2.4 µg/L. Surface area: 1220 acres.
Is Foster Lake safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Foster Lake is listed impaired under Clean Water Act §303(d) (IR 5) for temperature. Check local advisories before you swim.
Are there boat ramps on Foster Lake?
- Foster Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Calkins Park, Sunnyside Park. Public access is listed as yes.
Explore Foster Lake across LakeQuality
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Other Grade C Lakes in Oregon
Mesotrophic Lakes in Oregon
Where this data comes from
8 measurements from 1 monitoring station, 2024–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Department of Environmental Quality - State of Oregon
OREGONDEQ8 samples · 2024–2025
Analytical methods
- 10200 H ~ Chlorophyll a-b-c Determination
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