For much of the way, Imperial Highway is signed as State Route 90. A de facto freeway portion of the route in Yorba Linda is also known as the Richard M. Nixon Parkway. The portion in Los Angeles County is located about one mile north of, and runs parallel to, Rosecrans Avenue.
Are areas of your lawn bumpy and uneven? When you walk across these areas does the soil sink or feel soft? If so, some type of soil dwelling critter is probably the cause. During winter the activity of moles, earthworms, and mole crickets can cause mounds and tunnels in lawns that result in uneven or rough patches. To fix these problem areas you must first diagnose which critter is causing the damage. Earthworms.
The aboveground damage they cause, however, is quite apparent. Entire plants can disappear before your eyes, pulled down by the roots as a gopher snack. Once a gopher infestation begins, the yard becomes riddled with mounds roughly 1 foot in diameter. These are the deposits of soil cleared to expand their tunnel system. They are usually horseshoe shaped with a distinct plug of soil in the middle that caps the hole.