What’s Up With Innovative Alternative Septic Systems?

We live on Shoestring Bay, a beautiful estuary of Popponesset Bay. Unfortunately, the water quality fails every Massachusetts standard for clean water. Why? Too much nitrogen and phosphorous leaching into the water—80% of which can be attributed to our Title-5 septic systems. The current clamor for replacing septic systems with new sewers is growing, and sewering projects are already underway in Chatham and Harwich.

There’s been a lot of talk about Innovative Alternative (IA) septic systems as a potentially cheaper alternative to sewering to help mitigate the causes for the Cape’s failing waterways. Following is a Q+A to answer some of the questions we’ve been asked about IA systems.

Why Are the State-Approved Title-5 Systems Failing?

Typical Septic
Typical Title 5 Septic System Design

Title-5 was originally adopted in Massachusetts in 1978 and was updated in 1995. The problem with the basic design of Title 5 systems is that they work best in heavy loamy/clay soils where effluent has time to dissipate the nitrogen and phosphates, assisted by microorganisms in the soil.
The Cape’s sandy soil is a different story. The leach-field effluent moves faster through sandy soil into the groundwater. The faster “percolation rate,” as noted below, adds more nitrogen than the bodies of water can handle.

Here are the dirt-y facts on soil percolation rates:

  • In clay/loam soils, effluent can travel at as much as 5 millimeters/day (MM/D).
  • In loam-rich soils, effluent travels at up to 6 MM/D
  • In sandy soils, this increases to 20 MM/D

What Can Be Done Besides Spending Billions on Sewering the Cape?
In areas where sewering is cost-and-space-prohibitive, Title-5 septic systems might be retrofitted with Innovative Alternative (IA) Septic components. One “first generation” IA design includes an additional tank filled with wood chips where specialized bacteria remove some of the nitrogen before depositing the effluent to the leaching field; this system retrofit reduces N (nitrogen) content from (average of Title-5 systems) 26 MG/L (milligrams per liter) down to 19 MG/L. But this can’t compete with sewering (with secondary water treatment), which reduces the nitrogen content of effluent down to 3-5 MG/L.

NitROE Tank Addition System

A newer IA system design, NitROE from CES-Clean Water, might compete with sewering. The NitROE adds an aeration (with an air pump) limestone-filled chamber to the wood chip tank, helping to off-gas much of the nitrogen from the effluent prior its release to the leach-field/drain-field. While the results are impressive—N content down to < 10 MG/L—some professionals we interviewed indicated that these types of systems alone may not be sufficient to stem the tide of Nitrogen’s impact on water quality.

So, What’s Next?

Screen Shot 2019-10-10 at 3.43.42 PM
Towns participating in Barnstable County’s I/A Database

CES-Clean Water’s NitROE®, HOOT and Blackwater all make systems that have achieved low-nitrogen effluent (< 10 MG/L) in recent tests. Towns up and down the Cape and Islands, including our own town of Barnstable, are testing a variety of IA systems.  The number of homes in these tests vary, from 19 in P’Town to 93 in Barnstable and 340 in Mashpee.

If the tests continue to show promise, some or all of these IA systems might qualify (within years) for certification by the State and Local Health Departments. This could open the door for revised Title-5 rules for new septic systems and could allow proactive homeowners an opportunity to cut their nitrogen output through retrofit installations.

IA systems alone are not the answer. It will take a multi-pronged approach (sewering and IA systems) to solve our Nitrogen problem.

What’s It Going to Cost?
Here are the facts as we know them:

  • Choosing 100 percent sewering is preferable but likely cost-prohibitive; costs can run from $800 to $900 per kilogram of Nitrogen removal.
  • IA systems are predicted to average $55 to $144 per kilogram of Nitrogen removal.
  • An IA system retrofit will cost the average 3-bedroom homeowner $10,500 to $15,000 depending on the location of the septic system and the amount of restorative landscaping construction required.
  • There may be some grants (available through public and private agencies) and funding sources (including zero-interest loans for income-qualified households).

Stay tuned for more information on consistent test results and maintenance operation costs. To learn more about Barnstable County’s (basically the whole Cape and Islands) IA Septic System Tracking program contact Brian Baumgaertel, Program Administrator, 508-375-6888 or Emily Michele Olmsted, Program Assistant, 508-375-6901


  1. https://www.researchgate.net/figure/Potential-percolation-rates-as-a-function-of-soil-texture_fig13_287804711

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