How to build a self-service (coin-operated) car wash without concrete - cheapest technically viable foundation?

I’m planning a small self-service (coin-operated) car wash and want to avoid pouring a traditional concrete slab to reduce costs.

Constraints:

• Area: ~20–40 m²
• Load: passenger cars (1.5–2.5 tons), occasional SUVs
• Climate: freeze–thaw cycles (winter temperatures below 0°C)
• Water usage: high (constant drainage required)
• Goal: lowest-cost solution that is still structurally and operationally viable
• No heavy construction equipment preferred

I’m considering alternatives to concrete, such as:

• Compacted crushed stone + geotextile + paving slabs
• Plastic or composite modular grids
• Metal grating over a drainage trench
• Interlocking pavers on sand/gravel base

Questions:

1. What foundation / surface structure is technically suitable for a car wash without concrete?
2. How should drainage be designed in such a setup to handle large volumes of water?
3. What layer structure (geotextile, gravel thickness, compaction) is required to safely handle vehicle loads?
4. Are there proven low-cost designs used in real-world car wash installations?
5. What are the main failure points of non-concrete solutions (subsidence, water damage, frost heave)?

I’m not looking for a “perfect” solution - just the cheapest design that is still structurally sound and maintainable.

If possible, I’d appreciate diagrams or references to similar implementations.