A shut off pipeline lowered Lake Miramar's water levels about 20 feet below normal in the past few weeks for a long-term project, said city officials.
The water level was also lowered because the treatment plant was drafting water from the reservoir to service city water customers, according to the City of San Diego.
The maintenance is part of the Miramar Clearwell Improvements project, confirmed the city. It's located at the 10700 block of Scripps Lake Drive.
Any dangerous areas where extra shoreline was exposed is roped off. City officials say parts of the shore are too soft for the public to safely access.
A worker at the nearby concession stand told NBC 7 about a mud mound and a mysterious structure across the lake.
"Everyone always asks about what the orange mound of mud is. That’s just a sentiment deposit from what the waters brought into the lake," said Jason Noeldechen, who works at the concession stand nearby.
"There's some structure across the lake that has revealed itself and we have no idea what it is. Probably go take a look later," said Noeldechen.
The boat ramp was closed leaving a lot of fishermen unhappy, said Noeldechen.
Some of the project's goals are to demolish the existing clearwells, associated piping and facilities, as well as construct two new clearwells, associated piping and facilities that will increase the combined storage capacity to about 58 million gallons.
Besides that, the project will construct a new Chlorine Contact Chamber with an adjoining lift station, a new maintenance building and install miscellaneous site improvements and a new guard shack.
The project is expected to be completed by 2020.