Next? Dams. There are about 84,000 dams in the USA, and most of them are approaching their projected end-of-life - a hundred years or so (most of them are of t

Next? Dams. There are about 84,000 dams in the USA, and most of them are approaching their projected end-of-life - a hundred years or so (most of them are of the earthen type, not the concrete kind.) And ... civil engineers are going into retirement and their workforce is not getting refilled, about a 20% reduction. The common theme is that this was all done a century ago in a progressive push that was unaware of any environmental consequences or long-term maintenance needs. For example, the Columbia river (NW) was so dammed up for electric generation, it impacted salmon spawning. Today, USACE spends something like $5 million a year to make salmon elevators and in many places, literally truck them upriver so that commercial fishermen can later retrieve about $450k worth of salmon a year downriver. And as it turns out, we didn't need that much electricity to begin with and the demand never materialized in time to capitalize on it (manufacturing). And unlike salmon, we can't truck electricity elsewhere. Edit: since I'm a dam dork, here's a construction type breakdown I did five years ago. Edit 2: dam_type not related to year_built, summaries just placed next to each other. count dam_type year_built count 70,278 Earth <1900 14,623 9,031 (Unknown) 1900-09 2165 1,446 RCC 1910-19 1964 1,215 Gravity 1920-29 2321 724 Concrete 1930-39 3930 455 Other 1940-49 4115 420 Rockfill 1950-59 11,517 201 Masonry 1960-69 18,717 136 Buttress 1970-79 12,910 103 Arch 1980-89 5189 58 Stone 1990-99 4393 51 Timber Crib 2000-09 2290 16 Multi-Arch Only 847 of those dams are tailings dams, used for industrial processing. More than 0, but less than 84,000. Of those, none are listed as concrete (730 Earth, 61 Unknown, 43 Other, 13 Rockfill).