Where is Boulder Lake?

Boulder Lake is a lake in Perry County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.

How deep is Boulder Lake?

Boulder Lake has a maximum depth of 47 feet and an average depth of 18 feet. The lake covers 28 acres.

Are there boat ramps on Boulder Lake?

Boulder Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Pyramid State Park. Public access is listed as yes.

Can I fish at Boulder Lake?

Boulder Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Illinois's fish and wildlife agency, so check its current regulations before you go.

Boulder Lake

Perry County, Illinois28 acresView map Directions

No nutrient or algae sampling on record from Illinois EPA for this lake.

Max depth

47 ft

Bathymetric survey

Area

28 acres

Surface area

Shoreline

3.4 mi

Measured length

Impaired · Mercury
47 ft max depth
Public access

See the measurements Directions Where to stay

Boulder Lake in Perry County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 47 ft. Surface area: 28 acres.

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Boulder Lake is a 28-acre lake in Perry County, Illinois with a maximum depth of 47 feet (18-foot average). Limited fish-species data available. Public access is available with 1 public boat landing.

Source: EPA Water Quality Portal sampling records, Illinois EPA. Methodology: how these readings are compared.

What Boulder Lake is good for

From access and monitoring records, not editorial picks.

Boat launch1 documented ramp
Deep water47 ft surveyed max depth

Swimming conditions

No reading

Not rated

Nutrient and algae readings are not a swimming clearance. Boulder Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.

Whether Boulder Lake is safe to swim in today is a call for the Illinois Environmental Protection Agency and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.

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Water quality measurements for Boulder Lake

These are the measurements Illinois EPA publishes for Boulder Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.

No clarity data. TSI undefined.

Ask about Boulder Lake

Answers come straight from the public measurements and survey records on this page.

Lake Details

Max depth

47 ft

Average depth

18 ft

Surface area

28 acres

Shoreline

3.4 mi

Public access

Yes

Listed by Illinois EPA

Recreation & Access

Boat Landings

Yes

Public Access

Pyramid State ParkPublic

Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps

Stays via Stay22

Stays near Boulder Lake

Compare lakeside cabins, hotels, and vacation rentals near Boulder Lake in Perry County, Illinois — 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.

Top-rated places to stay near Boulder Lake

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Follow Boulder Lake’s readings

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Fishing Boulder Lake

→ Boulder Lake fishing regulations (limits, seasons, special rules)

EPA Impairment Status

Boulder Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

Mercury

Designated uses not supporting: Fish consumption.

Source: EPA ATTAINS assessment unit IL_RNZK · Official waterbody report

Nearby Lakes in Perry County

Boulder South Lake8.8 ft clear · Eutrophic0.2 miView →Wesseln Cut0.9 miView →Wesslyn Cut Lake4.5 ft clear · Eutrophic1.2 miView →Pinckneyville Reservoir6.1 miView →East C Streamline Lake7.3 miView →Du Quoin Lake12.3 miView →

Frequently asked questions about Boulder Lake

Where is Boulder Lake?: Boulder Lake is a lake in Perry County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Boulder Lake?: Boulder Lake in Perry County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 47 ft. Surface area: 28 acres.
Is Boulder Lake safe to swim in?: Nutrient and algae readings are not a swimming clearance. Boulder Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
How deep is Boulder Lake?: Boulder Lake has a maximum depth of 47 feet and an average depth of 18 feet. The lake covers 28 acres.
Are there boat ramps on Boulder Lake?: Boulder Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Pyramid State Park. Public access is listed as yes.
Can I fish at Boulder Lake?: Boulder Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Illinois's fish and wildlife agency, so check its current regulations before you go.