Soil Erosion caused by sewer?

In 2002 we had our foundation leveled. 20+ piers. During that time, a cement patch was placed at the base of the garage. 8 1/2 years later, the cement patch has sunk over four inches and is now at about a 30 degree angle below level and our driveway has sunk below the home foundation preventing us from driving our small car into the garage. The cause is certainly soil erosion, it's evident throughout the yard, the neighbors and his other neighbor. Is there someone I can call to come out and check the status of the sewer line that passes in front of our homes? I suspect the soil erosion is caused by a leak or 'sink hole' under the sidewalk and street. Thanks in advance!
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