Conculding something subsurface is not leaking because it currently holding liquids is bad science.  The water table could be high and cracks or holes in the bottom let the water table in.  This may make the vessel look 1/2 or 3/4 full but does not mean it is tight.  Further more you do not know when the last discharge occured to the drains.  If it was a couple hours or a day with small leaks it could take a while to drain.

Another dangerous conclusion is "in my experience contamination is usually not associated with traps (I have drilled near three in last 7 years and all three were “clean”.  Your own statistics based upon your limited experience (3 in 7 years is a small subset) does not rule out a concern.  I have drilled many of these and found impact.  Would you make the same judgement of you drill 3 USTs sites and they were all clean that USTs sites are not a concern because your last three were not ?

In the case for my client, dependent on the business transaction, sometimes we pump out the wastewater collection devices and inspect them.  If we see no evidence of compromise, you could possibly make the determination that it is not a REC.  For hoists, if there is pressure testing data on active lifts (<3 months old) or "recent" subsurface data in the vicinity of the hoists.  But still, if it is active, you have 40-50 gallons of hydraulic oil under pressure...they typically leak, in my experience.  I have reviewed reports by other consultants that did not make the presence of the hoists a REC at all....I disagreed with that but I guess that is the decision of the EP. 

I know this thread is a bit old, but clarifiers and hydraulic lifts are such common issues, that I think this thread is worth revitalizing.

First, as has been said above, I have never heard the term "flammable waste trap." It's what caught my eye on this thread... I thought maybe there was some device I'd never heard of that I should learn more about!

As also has been said by the others, this structure sounds like a standard clarifier. Using proper terminology in Phase Is is important, to prevent ambiguity. I see consultants use all sorts of odd terms for common items, and it frequently leads to confusion.

In general, I don't consider hydraulic lifts and clarifiers at auto repair facilities to be RECs (Note: I said "in general"... there are always exceptions, and each site has to be evaluated on its own merits).

Heather is 100% correct... SBA is extremely conservative when it comes to features such as clarifiers and hoists. But, in my opinion, they are sometimes TOO conservative, which can kill a deal over a non-issue item.

Here's some canned language I like to use for clarifiers and hoists (I posted part of this in another thread that was similar). Feel free to use it, but modify it for the specifics of your site and send me a nickel each time you use it. I should have enough for a cup of coffee by the end of the year.

Clarifiers:

A three-stage clarifier is present outside of the west side of the building. This is essentially a  concrete vault, through which water passes prior to sewer discharge. The pipe on the inlet side is at a higher elevation than the discharge pipe. Therefore, floating oil tends to remain in the vault rather than discharging to the sewer. The only source of discharge to the clarifier at this site is general floor washdown, which generates minimal amounts of water.  Because oil entering this type of clarifier system (sometimes also called an oil/water separator) floats on the water, it typically does not come into contact with the base of the clarifier, which further minimizes leak potential. Motor oil does not tend to migrate in soil, and therefore when releases are found, they are typically very localized. Clarifiers can be of concern at industrial sites where solvents are discharged. They become increasing concerns at older industrial facilities, where their integrity may be compromised by age (ex: cracks, holes). At typical auto repair facilities such as the subject site, clarifiers pose little concern.   When contamination is detected, it is a generally a de minimis condition (i.e. below that requiring regulatory agency involvement).

Hydraulic Lifts:

One 'in-ground" vehicle lift is present in one of the service bays. In-ground lifts have most of their components below grade, as opposed to surface-mount lift systems. Lifts operate by transferring hydraulic fluid, under pressure, among the components. Therefore, there is a reservoir of fluid within the system. Typical automotive lifts contain about 30 to 50 gallons of fluid (some high pressure systems use as few as 5 to 10 gallons). Typically, the fluid is within a piston chamber, which is within a steel housing. Therefore, the basic design provides secondary spill containment. Please note that the reservoirs are not regulated as USTs. Removal of inactive lifts is typically regulated by local municipalities. Some require their removal and some do not. In some instances, the oversight agency may require soil sampling in the vicinity of a lift at the time of removal. It is our experience that when leaks are discovered, the area of impacted soil is highly localized, and is simply over-excavated during lift removal. Hydraulic fluid is quite immobile in soil. It does not contain volatile organic compounds, solvents, or other chemicals that tend to migrate in soil/groundwater. For lifts older than 1979, there is a possibility that the hydraulic fluid may contain PCBs, which could result in a higher soil disposal cost. However, because of the small volume typically involved, such costs are not prohibitive. The subject building was constructed in approximately 1989, and therefore there is no PCB concern.  As such, vehicle lifts represent minimal environmental risk. When contamination is detected, it is a generally a de minimis condition (i.e. below that requiring regulatory agency involvement).