Looking for someone to dig out our sewer pit (19.5" x 31")

Our sewer pit is filled with dirt and rocks. Our plumber needs to access the pipes and I’m looking for someone to dig out the pit as far down as it will go and line it with cement. I’ve tried searching online, but I’m unclear what type of vendor this is as I think it’s too small for a contractor and masons deal with brick. Thanks in advance for any recommendations!