Manhole beneath raised building structure NFPA

[EngPhenomena]

There is an existing inlet on an aircraft fueling ramp that is in question. The proposed project calls for extending the building to provide additional gates. The inlet happens to be in the main stormwater trunk line and it will now be underneath the proposed building extension.

NFPA 415 has language about drainage inlets being set back a minimum of 50 feet. We plan on changing it to a manhole. The grades also need to meet NFPA requirements which call for minimum 1 percent grade away from all airside structures for the first 50 feet.

The manhole will end up being a high point. The confusion is this paragraph.
5.1.4 "The drainage system of any aircraft fueling ramp shall be so designed that the fuel or its vapor cannot enter into the drainage system of buildings, areas utilized for automobile parking, public or private streets, or the publice side of airport terminal or aircraft hangar structures...."

My interpretation is that as long as the stormwater system is independent of the above statement it would meet code.

Knowing that fuel and vapor can still get into the stormwater system the following options are being evaluated:
1. Move the manhole structure outside the set back. Very expensive.
2. Can a junction structure be installed without access. Least Expensive.

 

[bimr]

You question is difficult to understand without a plan. Is the stormwater trunk line under your building? If so, is it small or large?

Is there a security aspect? Someone could crawl through a stormwater trunk line into the airport.

 

[SteveWag]

Put in the manhole and use a bolted, gasketed lid or inner lid. Check out the NEENAH R-3495.
Steve

 

[EngPhenomena]

bimr - its a main trunk line, 42" RCP. The security part is more of a concern for the Port. Just a point of clarification, the building will be constructed above grade on columns such that there is a 9ft clearance for small vehicles to pass under, i.e. moving luggage.

Stevewag - I will look into this. Thank you.

 

[bimr]

In NFPA 415 Section 3.1.6 "Grates and drain covers shall be removable to facilitate cleaning and flushing".

My opinion is that you should reroute the fuel drainage system so that the drain line does not go under the building.

NFPA 415 also states that the fuel or its vapor cannot enter into the ...public side of airport terminal.

What do you know about the drainage system? How old is it and what is the condition?

 

[bimr]

The link below is not the current version of the NFPA document

http://www.minhbao.com.vn/userfiles/file/A_NFPA415.pdf

However, if you look at the drainage diagrams in the Appendix, you willnote that the fuel drains are routed around the terminal.

Considering that a significant volume of fuel may be involved, one would doubt that the local fire commissioner would accept fuel drainage under the building.