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Onsite Water Supply and Sewage Disposal: 

Onsite Water Supply and Sewage Disposal Department of Environmental Health Washtenaw County, Michigan

Sewage System Overview: 

Sewage System Overview Septic Tank Separates liquid wastes from solid wastes Anaerobic breakdown of bacteria No additives needed Needs pumping every 3-5 years

Septic Tank Cross-Section: 

Septic Tank Cross-Section

Septic Tank Installation: 

Septic Tank Installation

Sewage System Overview: 

Drainfield Cleans liquid wastes by filtration Aerobic treatment of bacteria Converts ammonia to nitrates 4000 sq. ft. needed for average new home Returns liquids to groundwater aquifer Sewage System Overview

Drainfield Cross-Section: 

Drainfield Cross-Section

Drainfield Installation: 

Drainfield Installation

Onsite Sewage Requirements: 

Onsite Sewage Requirements On-site systems CANNOT be used if municipal sewer is available Soil evaluation is done before issuing any sewage permit Homeowners are required to prepare plot or site plan in order to receive permit

Onsite Sewage Requirements: 

Onsite Sewage Requirements 3 feet of sand A primary and expansion area must be available – typically 4000 sq. ft. Water table can’t be within top 12 inches of the ground surface New home site must meet all site criteria, while replacement systems are installed to make the best of a bad situation

Onsite Sewage Terminology: 

Onsite Sewage Terminology Conventional System: System installed on soils that meet minimum requirements and within established construction guidelines. Engineered System: Commonly misused term. Often used to describe system installed when regular gravity-fed septic tank and drainfield system cannot be installed. Alternative System: System installed on soils that do not meet minimum requirements, but within established construction guidelines. Experimental System: System installed on soils that do not meet minimum criteria and with no established construction guidelines.

Onsite Sewage Terminology: 

Soil Evaluation/Perk Test: Evaluation of raw land to determine if a sewage system can be installed in a given location. Drainfield Clustering: Practice of locating several sewage systems in one area because of soil conditions. Sewage Pretreatment: System that treats sewage after septic tanks and before final disposal. Typically used to compensate for heavy soils or small lot size. Time of Sale (TOS) Inspection: Inspection of well and septic system at time of property transfer. Onsite Sewage Terminology

Soil Evaluations & Sewage Permits: 

Soil Evaluations & Sewage Permits

Aging Sewage Systems: 

Aging Sewage Systems

Water Supply Program: 

Water Supply Program Well regulation in effect since 1983 Well construction regulated by both County regulation and the State of Michigan Well Construction Code Approximately 900 new drinking water wells drilled annually: 40% of new wells are replacement wells 90% of new wells are sand or drift wells

Water Supply Requirements: 

Water Supply Requirements Well permit required for all drinking water wells Drinking water wells required to be at least 50 feet deep Well drillers required to submit well logs Old wells required to be abandoned when replacement wells are drilled All wells sampled for Coliform bacteria, Nitrates, and Arsenic

Well Permits: 

Well Permits

Water Quality Issues: 

Water Quality Issues Bacterial Quality Nitrates Arsenic Industrial/Underground Storage Tanks Salt – Dissolved Solids Well Abandonment

Water Quantity Issues: 

Water Quantity Issues Designated “Well First” areas 7 gallons per minute required for metes and bounds 10 gallons per minute required for subdivisions Hydrogeological reports reviewed for subdivisions Large capacity irrigation wells a concern

Soil Evaluations & Well Permits 2/24/02 - 2/25/03: 

Soil Evaluations & Well Permits 2/24/02 - 2/25/03

Slide21: 

Potential Contaminants in Water

Slide26: 

“Well First” Areas

Slide27: 

Sample Well Record