You're right to be curious – the foundation size does sound large for a 20-foot light pole with LED heads, but there are several reasons why they might be that size. Let's break it down

Is the foundation size normal? Probably Overkill, but Not Necessarily Wrong

In general, for a 20-foot pole with LED heads (which are significantly lighter than older light fixtures), a 6-7 foot deep, 24" diameter foundation is likely overkill, especially if the soil is compacted. However, here's why it might be justified: Soil Conditions

This is the most crucial factor. If the soil is very loose, sandy, or silty, or if the water table is high, a larger foundation is needed to provide adequate stability. Poor soil significantly reduces the holding power of the concrete.

Wind Load

Pickleball courts are typically outdoors and exposed to wind. The design must account for the worst-case wind conditions in your area. The larger foundation helps resist overturning forces from the wind. While a 20-foot pole isn't that tall, wind load increases significantly with height.

Local Building Codes

Building codes often dictate minimum foundation requirements based on pole height, wind zone, soil type, and other factors. The community center may be adhering to strict code requirements.

Safety Factor

Engineers often incorporate a safety factor into their designs. A larger foundation provides a greater margin of safety, particularly in areas with potentially extreme weather.

Frost Depth

If you live in an area with significant frost, the foundation needs to extend below the frost line to prevent heaving due to freezing and thawing.

Future Proofing

The community center might be anticipating future needs. Perhaps they are planning to add larger light fixtures later, or they are using a standard foundation design that can be used for taller poles at other locations.

Simple/Standard Design

Sometimes it's just simpler and cheaper to use a standard foundation design rather than calculating a custom foundation for each individual pole.

Ease of Construction

A larger diameter hole is easier to dig and work in, especially if they don't have specialized equipment. This can translate to lower labor costs, which can offset the extra material costs of the larger foundation.

Liability

Over-engineering is better than under-engineering, from a liability perspective.

Regarding the Corrugated Plastic Tubing (Instead of Sonotube)

Yes, using black corrugated plastic tubing instead of traditional sonotubes is perfectly acceptable and I have seen it used increasingly. Here's why:

Cost

Corrugated plastic tubing is often cheaper than sonotubes, especially for larger diameters.

Durability

It's highly durable, weather-resistant, and won't degrade in wet soil conditions.

Ease of Handling

It's lightweight and easier to transport and maneuver than heavy cardboard sonotubes.

Stripping

In some cases, corrugated tubes can be left in place permanently.

Environmental Considerations

Some corrugated plastic tubes are made from recycled materials.

Smooth Interior

As you mentioned, the internally smooth surface is important. This ensures a clean, uniform concrete pour and prevents voids from forming in the foundation. The external corrugations don't affect the integrity of the concrete.

In Summary:

While the foundation size sounds* large for your specific situation, it's impossible to say for sure without knowing the soil conditions, wind load requirements, local building codes, and other design considerations. It's possible it's overkill, but it's also possible there are legitimate reasons for the size.The use of corrugated plastic tubing is perfectly acceptable and a common practice.If you're truly curious, you could politely ask the project manager or engineer responsible for the installation about the rationale behind the foundation size. They should be able to provide a reasonable explanation. However, keep in mind they may not be at liberty to share all details. Flag for review