I think oil relates to Saturn. It's in the 10th house, 29 degrees Virgo. Virgo relates to structure and details. So Jupiter and Uranus are in Pisces, 4th house. I think that sums up "explosive, expansive oil leak in ocean". Mars in Leo, 9th house, it's an issue that's been in the spotlight, action that ties into other, greater issues.
Pluto, north node in the 2nd. This is materials and possessions, it relates to the 8th house of resources. The 2nd house is more connected to the physical side of business(such as real estate), while the 8th house is more transactions(such as business deals). Having a Cancer moon in the 8th, very watery, moody, fluctuating. Pluto, and the north node involves transformation and purpose.
Taurus sun in the 5th. The 5th house could be competition, this is another theme of material energy (now in Taurus) and spotlight (now from the sun), has brought about this issue.
Mercury was in Taurus retrograde at the time. For this situation, it's in the 6th house, along with Venus. I remember the news was concerned about the Volcano incident, but this chart shows another environmental disaster. I think Venus, being a ruler of Taurus, amplifies the Earth, material, solid nature of the Taurus effect of what happened. Mercury brought it to mind.
Neptune in Aquarius, conjunct Chiron 0 degrees Pisces. This emphasizes what happened. The 3rd house involves communication. It's an issue that has been strongly discussed.
Saturn was in 29 degrees Virgo, and Chiron 0 degrees Pisces. Chiron relates to Sagittarius, which is the Ascendant. A healing centaur, hopefully this situation will be properly resolved.
I like your analysis here. I have to say though, that I am also thinking it could be that Pluto represents the oil. The pressures placed on Saturn from the Square of Pluto creating a tense, potentially irreparable destructive dynamic. I'm thinking about how Pluto destroys and resurrects, and Saturn builds slowly. If these two can't work in harmony, there is an issue.
With Uranus there, involved in the T-square, as you pointed out is in Pisces, thus involving the water. It sort of seems though, that while it could have simply been a routine/system malfunction (Virgo) it could also have been something quite out of the blue (and into it) as would be the case with Uranus there.
Jupiter's involvement could go either way. It could mean that the damage will be huge, long-lasting, and pervasive. But Jupiter is well-placed in Pisces, so hope can't totally be abandoned. It could mean, as is the case with natural disasters, an opportunity for the world to unite around a universal mission- the environment.
Neptune in Aquarius is an interesting point. Aquarius is the water bearer, and also humanitarian ideals/attitude, so I think it's sort of echoing the sentiment about what I made with Jupiter and uniting people around an issue with the Water. I'm concerned with Neptune's involvement. It muddies things (just as the oil did) but it might also make the objective with the clean-up unclear. Already we are seeing issues with "who is responsible" and "how to take care of this" and "who should pay."
Taurus Sun is interesting to point out. Oil is a luxury item. It is expensive, and it goes towards what has become more evidence of gluttony, as we use it to literally fuel (especially in the US, Europe, and Asia) the items we depend on to make our lives easier, and in some cases exceptionally more enjoyable. It being in the 5th house only makes me think of how Neptune is in Aquarius, blurring the issues of the "larger humanity" and the Earth, for the sake of more self-centered pleasures, very Leo/5th house. It is about indulgence, joy, and Human Ego and it's need for gratification and consumption, which then could easily fuel competition situations that wear and tear on the environment.
Mercury in Taurus- slow reaction time. Maybe it could have been prevented, but also, the clean up process has been slow. The ability to act is lessened. With Venus there, in the 6th house, the love of service is at the for-front. It's maybe not that people don't care, but now we are seeing that simply caring about the Earth needs to be coupled with thinking about how to care for the Earth. This is just another example of how we need to be more proactive in the environmental measures we take. Mercury in Taurus indicates our slowness to act or to know how to act, and Venus indicates our desire to help the Earth, to cleanse it and serve it, as Venus is dignified in Taurus. The desire is there, but without the know-how, it appears this is the issue.
Chiron I always use to talk about the Human Condition. With Chiron in Pisces, I might say that it is our own damage to ourselves as Human Beings and our lack of being able to see how we relate to the Earth and the Ocean, and how it relates to us, which is the problem. We are behaving disconnected, only highlighting how don't proactively deal with these situations.
(ruler of 
) rules oil and 
now rules 
as the ruler of oil (since it is an "underground" thing).
