Siting of petroleum storage tanks – underground vs. aboveground At petrol pumps and similar facilities, storage tanks are normally installed underground when the required capacity is less than how many kilolitres (kL)?

Introduction / Context:
Storage tank siting considers safety, footprint, environmental risk, and economics. Filling stations typically use underground storage tanks (USTs) for moderate capacities to minimize fire risk and save space, whereas very large capacities trend toward aboveground tanks in dedicated terminals.

Given Data / Assumptions:

• Retail-scale petrol/diesel storage rather than refinery terminals.
• Common regulatory and industry practice thresholds.
• Focus on nominal capacity breakpoints used in design guides.

Concept / Approach:
Conventional practice places fuel tanks underground at smaller to moderate capacities, with a common guideline break near 45 kL for single-tank installations at retail sites. Below this, USTs are economical and safer for public settings; above this, multi-tank configurations or terminal-style aboveground tanks may be considered with additional safety spacing and bunding.

Step-by-Step Solution:

Verification / Alternative check:
Fuel station designs frequently adopt multiple underground tanks of 10–45 kL per grade, reflecting this order of magnitude.

Why Other Options Are Wrong:

• 20 or 30 kL: Below common single-tank maxima; too conservative for a general rule.
• 85 kL: Typically exceeds single UST sizes for retail and implies terminal-scale storage.

Common Pitfalls:
Confusing regulatory limits (which can vary) with industry practice; the question asks for the typical design cutoff used in petrol pump layouts.

Final Answer:
45