It depends on what you are testing for and the action levels associated with your needs. Drinking Water analysis is different than waters under the Clean Water Act, which is different than requirements under SW-846 program. So you need to determine what action level you need to be above or below.
For Drinking Water you can visit: www.epa.gov/dwstandardsregulations
For NPDES under the Clean Water Act it is a little more involved you will have to work in conjunction with your regulatory permit writer to know where your action levels are. The following document is a good start: www3.epa.gov/npdes/pubs/final_local_limits_guidance.pdf
For solid waste under The Resource Conservation and Recovery Act there are no set levels other than hazardous waste determinations. Determinations are used to assign where waste will go (landfill or repository). The hazardous waste program is complicated to navigate. Start at the EPA’s Hazardous Waste home page: www.epa.gov/hw. Most of this program is based upon guidelines, the department issuing a permit will assign your action level.