(Coordinated Environmental Solutions for Septic Problems Occurring On Long Island)

Municipal Officials Conference: Managing Cesspools and Septic Systems To Protect Long Island’s Waters

A one-day program on the impacts of inadequate onsite wastewater treatment on the quality of our coastal waters.

Friends of the Bay, in collaboration with Manhasset Bay, Hempstead Harbor and Oyster Bay/Cold Spring Harbor Protection Committees and the Town of Oyster Bay, presented a special full-day program for municipal officials on the mechanics of onsite wastewater treatment and its impacts on water quality in our harbors and bays.

Scientific evidence now shows that a large proportion of our region’s in-ground septic systems do not treat sewage adequately before the effluent reaches our groundwater, which then flows into our surface waters laden with bacteria, pathogens and nutrients. The result is closed beaches, closed shellfish beds, and harmful algal blooms which can kill marine life and sicken humans.

To view the PROGRAM PRESENTATIONS from this conference, CLICK HERE.

How a  Septic System Works:

On Long Island’s north shore, a typical septic system is comprised of four main components: a pipe from the home, a septic tank, a leaching pool, and the soil.

The septic tank is an underground water-tight container designed to hold waste-water long enough to allow the solids to settle out (forming sludge) and separate from the liquid and allowing oil and grease (scum) to float to the surface. Partial decomposition of the solid materials takes place in the septic tank. The waste-water is discharged from the septic tank into the leaching pool, where it can be slowly released through percolation and filtered by the surrounding soil. Bacteria in the soil digest the waste-water, removing most harmful organisms, organic matter, and some nutrients before it reaches the groundwater.

A CESSPOOL (as opposed to a septic tank and leaching field) is by definition a “failed system,” because it does not treat effluent adequately. There are many cesspools still in use on Long Island.

cesspool diagram_3

Design Considerations:

The septic tank is an essential component of the system because this is where solids settle out of the effluent, along with the first stage of microbial treatment.

Liquid waste leaving the septic tank must then be disbursed for leaching through the soil. The leaching pit typical on Long Island is far from ideal for this purpose, as it concentrates the effluent many feet below the surface, over a small soil area, reducing the contact time the effluent has with the most effective cleansing soils near the surface. In locations where the groundwater table is high (close to the surface) the net result is untreated sewage going directly into the groundwater. Should such a system be located near surface water (streams, ponds and tidal waters) the sewage is carried by the groundwater to these water bodies in a short time.

Nutrients.  In recent years, scientists have determined that Long Island’s groundwater is especially rich in nitrogen, and that the source of this nitrogen is our septic systems. Even a well-designed and properly functioning traditional septic system does not remove nitrogen from the waste stream.  Nitrogen is the limiting nutrient for marine algae; the more nitrogen in the water, the more algae will grow. Harmful Algal Blooms (such as red tide and brown tide) are increasing in frequency and spreading to more and more of our coastal waters as a result. Health and environmental authorities are looking to newly-developed advanced treatment systems which can be added to septic systems to remove nitrogen.

Un-Sewered Areas in Nassau County (white):

NC Sewered Areas 2014

Depth to Groundwater, Nassau County North Shore:

Those areas shown in red have very short travel times from septic system to surface water.

depth to groundwater

The Importance of Septic System Maintenance:

Effective treatment of sewage helps to prevent the spread of infection and disease and serves to protect water resources. When a septic system fails, it allows untreated human waste and its associated nutrients as well as bacterial and viral pathogens to contaminate the groundwater and surface water.

Unfiltered sewage can cause diseases and infections in both people and animals and is a primary cause of local beach closures. Excess nitrogen and phosphorus can have a serious impact on the Long Island Sound, Manhasset Bay, Hempstead Harbor, Oyster Bay, and Cold Spring Harbor, causing excess aquatic weed growth, hypoxia, fish die-offs, and closure of shell fishing beds.

Protect Your Septic System!

Properly constructed, operated, and maintained systems can have a life expectancy that exceeds twenty-five years. The septic tank should be inspected regularly and accumulated solids pumped out every three to five years. The necessary frequency increases with heavy use, whirlpools, hot tubs, or garbage disposals.

The more water a household conserves, the less water enters the septic system. Efficient use of water can both improve the operation of the septic system and reduce the failure rates.

Failure Symptoms

  • Wastewater backups into the home
  • Offensive odors and sluggish drains
  • Lush, green, vegetative growth over the system
  • Pooling water around septic system and/or basement
  • Frequent (more than once per year) pump outs needed

Causes of Failure

Destroying beneficial bacteria responsible for digesting solids through disposal of solvents, poisons, and other household chemicals into the system.

Overflowing the system with large quantities of water pumped into the septic system (such as from a hot tub, swimming pool discharge, or excessive wash water) which stir the solids in the tank and pushes them out into the leaching pool causing it to clog and fail.


To learn more about CESSPOOLS CLICK HERE to view presentations from the Municipal Officials Conference.

Any additional questions, feel free to contact us at info@friendsofthebay.org