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.
Digging dogs, uneven soil settling, poorly done grading and roots can cause depressions and holes in a lawn. Removing trees or shrubs from the area also will create a hole. The hole requires filling with soil for the area to be level with the remainder of the lawn. Leaving the hole open will not harm the lawn and grass will grow to cover it, but the area can be dangerous. Children or others walking across the area can trip on an uncovered hole and injure themselves.