A well bore passes down, through the geologic strata, which includes potable water bearing aquifers. There are two types of wells; vertical (conventional) and horizontal, which include a vertical bore section, and one or more horizontal, or lateral legs.
The potable aquifers tend to be nearer the surface, and they must be protected by the casing, and cement in the regions where the bore passes through the aquifer.
Laterals contain geologic risks where the perforations in the tubing, and fractured producing layers encounter faults that may extend into other strata, allowing frack fluid to migrate during completion (sometimes called a frack-out), or later, when the well is producing, allowing the remaining completion water, brine, and other well bore flow components to leak out, potentially resulting in potable water aquifer contamination.
This why the Railroad Commission requires a special UIC for diesel in frack fluid, and this is why virtually no operator uses diesel in the fracking process - there is zero market for MMEX's "diesel" in fracking - zero.
The HOBM issue is similar - and it is far less expensive to use soy-based oil for the drilling fluid make-up. MMEX has nearly zero opportunity here, as the use of diesel in HOBM is declining rapidly - you can look at Blue Dolphin as a demonstrative example. Even if MMEX were really building a topping unit, the market opportunity would be long-gone by the time anything got built.
As has been repeatedly mentioned, there is an even larger problem. Straight-run diesel, even that produced from light or ultra-light sweet crude still has a sulphur content that exceeds USEPA's 3ppm limit for transportation fuels.
As such, anyone hauling MMEX's intermediate, straight-run diesel would have to acquire a separate tanker fleet, segregated storage, and segregated load/off-load racking because of the sulphur contamination problem - straight-run diesel can't be mixed with refined, de-sulpured ULSD.
MMEX advocates have zero market or technical knowledge, and are easily duped by Mad J., the mediocre con-man, because they know so little. With no market, no transportation or distribution infrastructure, even if MMEX was a legit company, they would be completely and totally screwed.
They're using it to extract crude oil, diesel is a product produced from it, how is it any sort of an environmental hazard? It then would just mix with the natural resource it's used to extract. FYI The water it comes up with is not used for drinking water or anything like that nor is it from a source of drinking water.