Structural Calculation for Precast Septic Tanks

I need a structural engineer to calculate the load-bearing requirements for underground precast concrete septic tanks, specifically those with a capacity of 1,000 to 5,000 gallons.

Requirements:
- Structural calculations for underground concrete structures
- Knowledge of soil and hydrostatic pressure impacts
- Experience with septic tank design and regulations

Ideal Skills and Experience:
- Degree in Civil or Structural Engineering
- Proven experience with underground concrete structures
- Familiarity with septic system requirements and local regulations

Please provide a detailed approach and relevant experience.