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D
Decentralized Wastewater Management - Active oversight of multiple on-site or
cluster wastewater treatment systems in a state or local area through regulatory
control, licensing, financing assistance and other means, with the intention of
protecting the environment and public health, and achieving water quality goals.
Deep Observation Hole - Open pit dug to permit examination of the soils and to
obtain data relative to the mean annual high groundwater elevation and depth to
impervious materials.
Design Flow - Quantity of sanitary sewage in gallons per day (gpd) for which a
system must be designed in accordance with 310 CMR 15.203.
Design Life - Estimated length of time before a system will have to be replaced or
rehabilitated. Septic systems have a design life of 20-30 years, given proper
siting, construction, and maintenance.
Disposal System Construction Permit - Written approval by local Board of Health
authorizing the construction, upgrade, or expansion of an on-site system.
Distribution Box - Level, watertight structure which receives septic tank effluent
and distributes it in substantially equal portions to two or more lines leading to a
leaching area.
Distribution Line - Pipe used for dispersion of septic tank effluent into leaching
trenches or leaching fields.
Dosing Tank - Watertight structure placed between a septic tank and either a
distribution box or a soil absorption system, equipped with a pump designed to
discharge septic tank effluent to the soil absorption system and to provide a rest
period between such discharges.
Drainfield - See Soil Absorption System.
Drywell - Pit with open-jointed lining or holes through which stormwater drainage
from roofs, basement floors, foundations, or other areas seeps into the
surrounding soil.
