Developers in the city of San Diego are facing tougher government enforcement at construction sites that have the potential to pollute rivers and streams — including fines and even stop-work orders. That’s the result of a settlement San Diego officials entered into with water quality regulators that will require the city to pay $3.2 million and step up policing of development. The agreement was reached after the San Diego Regional Water Quality Control Board brought a civil liability complaint against the city for alleged violations of its stormwater permit last year.