Gasoline Followup

Here is the message I received back from the Minnesota Pollution Control Agency:

The tank inspector for the Metro went out to the site you sent in a
citizen complaint about, and here is her response:
Jxx Mxxxx, Sxxxx, and I went to the neighborhood today. We walked
along 16th Ave NE between Buchanan and Lincoln and looked into all the
storm drains. There were no petroleum odors and we did not observe any
petroleum sheen in any of the drains. The closest gas USTs are at 1847
Johnson St NE and we felt they were too far away from the site. The gas
station at 1847 Johnson St NE was inspected in August 2003 (by me). The
other closest gas station is on the east side of 35W and again, we felt
too far away. We drove up the alley between Buchanan and Lincoln and
observed a garage (at 16h and Lincoln) that has a 55 gallon drum with
small diameter piping going from the drum into the garage. We did not
observe any leakage from the drum. To summarize, we didn’t smell any
petroleum odors, so I am considering this incident closed.

(I changed the names, as I feel these people are doing a good job and I don’t see the need to plaster their names all over the internet.)
On the one hand, I guess I am glad that whatever the problem is it is small enough that they couldn’t detect it.
On the other hand, what exactly did I observe that they couldn’t?
If I smell it again, I will try to take more notes, possibly a sample (?)….

Smell the Gasoline

Today’s experiment is of an environmental nature. It has to do with the gasoline smell that wafts out of the sewer grates on NE 16th Ave and NE Buchannan St in Minneapolis. I often walk my dog near there, as it borders on the Northeast Athletic Fields, a nice open park.
So far I have observed:
The smell is a gasoline or diesel fuel smell.
The smell is strongest when it is coldest out. The smell is strongest at NE 16th Ave and NE Buchannan, but also it is detectable at 16th and Lincoln and at 17th and Pierce. I couldn’t smell anything at 18th and Buchannan, but that is on a busier intersection and I felt a little weird kneeling down to smell the gutter.
On cold days, there is more steam coming out of the grate at 16th and Buchannan than anywhere else in the neighborhood.
There is an old elementary school at the corner of 16th and Buchannan.
The old school is heated by natural gas. I walked around the building and could hear the natural gas meter’s familiar whine.
What I have done :
Last December: I called a Hennepin county (or was it the city of Minneapolis?) agency for environmental protection. Gasoline in the sewer wasn’t their juristdiction but they seemed concerned and recommended that I call 911.
I called 911 and they said call the city Sewer department and even gave me the phone number.
The sewer department said “They’d look into it”. Unfortunately, they never asked for my name so they’re not going to tell me what they discover (if anything).
Today : I got online and emailed the Minnesota Pollution Control Agency. They emailed back and seemed concerned and suggested I call the fire dept. I related the story about calling 911 already and haven’t yet heard from them again.
My Hypotheses
The school is gas heated but still uses radiators. For some reason, they waste some of the hot water into the storm sewer system. That explains why the grates at 16th and Buchannan steam so much more than other grates.
Gasoline is volatile at warmer temperatures. The hot waste water from the school causes the gasoline in the sewer to warm up making it easier to smell at that intersection.
The smell is stronger on cold days because the temperature inversion — the cold air makes the hot air in the sewer rise faster. That brings the smell out into the air more readily.
There is a gas station only four blocks away, up hill from 16th and Buchannan.
If my hypothesis about the warming of the storm sewer at 16th and Buchannan is correct, then the fact that the smell is strongest there does NOT indicate that the source of the pollution is there. The cold gasoline could be running down the storm sewer for many blocks and isn’t detectable by my nose because it isn’t getting warmed up.
There are some sources of error in this experiment. I already cited the socially induced error to my sampling method (being embarrased to sniff the gutter in front of traffic on 18th). Other factors include: My nose got stuffed up after too much sniffing, so I might not have been able to smell as well by the end of the walk. I don’t know how the storm sewers are connected together; I might be sniffing the wrong grates as I migrate away from 16th and Buchannan.
I’ll let you know if I find out any more about this study.

What is Cement?

This weekend I was tiling a bathroom. The stuff you stick the tiles to the floor is a mixture of cement, sand and a few other things. That kind of mixture is similar to what is in concrete concrete, which is a remarkable material used in all kinds of construction. The mystery to me was, “Why does cement harden when the water dries?” And also, “Why do they warn not to let touch the wet mixture?” The answers, it turns out, involves the chemistry of Calcium and Silicon — the same element that is used to make computer chips.
Cement is made from powdered di- and tri- calcium silicates. These chemicals react with water to form Calcium Silicate Hydrate. Calcium Silcate Hydrate is insoluable, so it will form solid crystals that glue the cement together. The reaction is remarkable in a number of ways. First, it is slow — as the reaction proceeds, the growing crystals get in the way of the water molecules that are trying to get to the calcium silicates. That slows down how quickly reaction goes. This slowing process allows concrete to be mixed and kept liquid for about three hours as it is shipped to where it is needed.
Another fascinating feature of cement is that it is made from extremely common materials: limestone and sand. At a cement plant, limestone (Calcium Carbonate) and sand (Silicon Dioxide) are ground into a very fine powder. Then they are heated. As the mixture reaches 800°C water boils away from the raw materials. At about 1200°C the limestone breaks down into Calcium Hydroxide, releasing carbon dioxide into the air. At 1400°C the sand reacts with the Calcium Hydroxide to produce molton cement. The cement hardens to form small pebbles called clinker that are then ground up to produce regular cement.
The calcium hydroxide that is produced as an intermediate ingredient is the reason that it’s not good to leave the cement mixture on your skin. More calcium hydroxide is released as the cement is reacting with the water. Calcium hydroxide is a very caustic base, and can cause burns on your skin.
The carbon dioxide that is released is significant: The manufacture of cement in the United States releases about 40 million metric tons of carbon dioxide into the atmosphere each year. Carbon dioxide is suspected to cause Global Warming.
There are a lot of other subtleties in the use of cement. Compounds of aluminum and polymer additives can change the properties of the final product. The diverse properties, inexpensive starting materials and ease of use make cement one of the best building materials in the world.