President Donald Trump has promised to rebuild America’s airports, bridges, tunnels, roads and other infrastructure, something both Democrats and Republicans agree should be done. The country needs a full $3 trillion in infrastructure over the next decade. The $1 trillion plan revealed by Trump’s economic advisers relies heavily on public-private partnerships, and private equity firms are lining up for these plumbing investments. In the typical private equity water deal, for example, higher user rates help the firms earn annual returns of anywhere from 8 to 18 percent – more even than a regular for-profit water company might expect. But the price tag can come as a rude surprise for local ratepayers.