There is grass growing on the roof, total spending is more than $70 million, and the project necessitated digging a nearly 50-foot hole. And at the end of the day, most people still don’t know what they’re looking at. No, this isn’t another apology about a failed do-it-yourself swimming pool project. Instead, I’m trying to answer a question readers keep asking: What the heck is that odd-looking structure at 31st and Louisiana streets.

As we have reported several times before, it is not as exciting as you may hope: It is a city-owned sewage pump station. Well, maybe it is exciting. It certainly is one of the more unique projects in town. I spent some time recently getting briefed by city utilities engineer Melinda Harger on the project. So, knowing that you all are looking for interesting small-talk to make at upcoming holiday parties, here are some fun facts about the funny-looking building.

First, you should know that the pump station is part of the largest project in town that most people have forgotten about. As we’ve reported, the city is building a $74 million sewage treatment plant south of the Wakarusa River. But for city residents, most of that construction has been out of sight, out of mind. The sewer plant is in a remote area — if you drove south of O’Connell Road until you hit the Wakarusa River, you would find the plant site. (You’d also be wet. There’s no bridge there.)

But crews are now in the final stages of the multiyear project. Harger told me current plans call for the plant to begin operations in February. She also told me that it looks like the project is going to come in under budget. Tentatively, spending is tracking closer to $72 million. There is an asterisk, though. For much of 2015 when the city was bidding the project, officials thought it would be about a $70 million project. Bids, though, came in high. But now, actual costs are coming in a bit lower.

Yes, I know. As you are standing around the punch bowl, people are going to want to hear more details about this pump station. Well, tell them it is kind of like an air-traffic control tower — except for sewage. (Then, just for kicks, offer to refill their punch glass.) But the pump station, once it becomes operational, will be a key piece of city infrastructure. Lawrence sewage takes a very winding path to get to the city’s current treatment plant in eastern Lawrence. Think of sewage being generated near Sixth and Wakarusa, for instance. It doesn’t travel through downtown Lawrence to get to the sewer plant just east of Eighth and Delaware. Instead it goes south, all the way toward 31st Street, before it then starts to turn east. Near Louisiana Street it starts to turn back to the north toward the sewer plant in eastern Lawrence. This new pump station will have a feature that will allow the sewage to keep on flowing to the existing plant in eastern Lawrence, or it can go into another pipe and be pumped to the new treatment plant south of the Wakarusa River.

In case you are confused, the new treatment plant isn’t going to replace the existing plant. Lawrence is going to be a two-sewer plant town. Yeah, it is a big deal. I probably should have led with that.

The thing you have noticed about the pump station building is its funny shape. Most of that is related to the city’s decision to build a green roof for the building. That simply means there is soil atop the roof. It currently has some grass on it, but Harger told me the site eventually will be full of native grasses.

The roof, however, is not the most interesting part of the building. That designation is reserved for the part of the building you can’t see. While the building looks small, it actually stretches 45 feet below ground. That’s comparable to a multistory building on Massachusetts Street, except it is all underground. The city had a webcam on the construction site. You can view a time-lapse of the webcam here. If you like construction projects, it is pretty cool. All the underground work does help explain the price tag for the pump station. It cost about $7 million, Harger said. The $7 million price tag is part of the estimated $72 million cost for the entire Wakarusa plant, which includes all the piping, pump stations and other equipment needed to make the plant functional.

As for what is in the building, Harger said it is basically just an electrical room, with a hoist that reaches down to the bottom of the pit so that the pump can be removed if it ever has to be replaced. So, there is not a version of an air-traffic controller deciding whether sewage is cleared for landing at the south Wakarusa plant or the eastern Lawrence plant. That’s all done via computer.

If there were such a job, it would be a thankless one. But that describes many of the jobs in the city’s department of utilities. Even though they oversee two critical functions — water and sewer service — they don’t get much recognition for the important work they do. They are not as visible as police, fire or even the trash truck crews. When they do their jobs well, they don’t give you much to talk about. Be thankful for that because as people keep reminding me, there really aren’t many good reasons to talk about sewage at a holiday party.

In other news and notes from around town:

While we are talking about construction, the Kansas Department of Transportation announced today that the South Lawrence Trafficway won a national award. It was for timely completion. Actually, anybody who followed the project knows I’m kidding. (For those of you not in the know, half of the project was completed in the 1990s, while eastern half got stalled with legal, environmental and funding problems until it opened late last year.)

Instead, the project won a gold medal award from the American Concrete Pavement Association. The six-mile, $183 million project did use a lot of concrete. The project also won a Sustainable Practices Recognition Award from the association for its efforts to protect plants and animals in the adjacent Baker Wetlands.

That award won’t be universally touted in Lawrence. The project’s impacts on the Baker and Haskell wetlands were major causes behind the lawsuits and delays. However, the project did end up getting built with several features designed to alleviate those impacts, including large sound walls that separate the wetlands from the road.