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.
When a digger wasp finds a grub, it paralyzes it, digs a chamber in the soil, and lays an egg on the grub. The soil that is dug for the chamber appears on the lawn as a fist-sized mound. There can be a few mounds to hundreds of mounds in a lawn, depending on the severity of the grub problem. Digger wasp flying and hovering on a sandy foot path near a sub-urban street. After landing on different positions, it chose a place and started to dig into the ground. It digging a hole of about 10mm deep.