I usually stay out of discussions here, everyone is much more knowledgeable about matters than I am and I enjoy reading everyone's take on matters, but I am going to weigh in on the culvert discussion. I live in Texas, very near Dallas now, but have lived all over the state. When a new subdivision goes in, the developer has to also design in an area of water retention, when I lived in Webster, it was a hugh deep ditch that ran the length of the subdivision and was maintained by the city. If you lived there, you paid a MUD tax because of it. In La Porte, it was a big square area, covering several acres, that held water almost all the time and was considered a wetland. If these things are on both sides of a road, the culverts connecting them are at ground level and are to equilize the water level in each pond. They have baffles made into them to trap debris and usually above these baffles are grates that can be removed to allow for clean out. In my experience, if it is an evaporation type area, it is very well maintained, mowed and trash removed on a regular basis because to not do so could cause all the homes in the subdivision to flood. Sewer and drains from within the subdivision do not drain into these things, only rainwater run off. If I am remembering correctly, the EPA has something to do with the installment requirements. I will do more research on it.
From what I have seen in the past, when it does rain enough to fill or partially fill these things, because the pipe is at the lowest level, as the water rises, the trash that can float does just that and when the rain stops the water soaks in or evaporates, leaving the once floating trash all around the sloped sides, where it is usually collected pretty quickly by whoever maintains the retention pond. They are also referred to as catch ponds.
Sorry for such a long post.
All of the above rambling is just my experience from what I have seen/observed in the past and all my own opinions.
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