Abstract: A secondary containment system for containing fuel leaks or leaks of other environmentally hazardous fluids includes a containment chamber and a detection system for detecting leaks. The containment system includes a fluid-carrying inner pipe and a containment pipe surrounding the inner pipe with an interstitial space being defined between the two pipes for containment of leaks. The interstitial space is pressurized with an inert fluid at a constant pressure greater than the pressure of the fluid flowing through the inner fluid-carrying pipe. Monitoring of the pressure of the inert fluid in the interstitial space triggers an alarm indicating that a leak has occurred. The location of the leak can be determined by the use of multiple pressure sensors. The containment pipe is reenforced to withstand pressures of at least 75 psi.