Deep Injection Well - Sanibel's Environmental Insurance

Recently, much attention has been given to the possible environmental effects of deep injection wells, and, especially, to the well which is being drilled on Sanibel. Unfortunately, misinformation heard often enough begins to sound like the truth.

The Sanibel City Council has considered all aspects of the sewer system over a number of years and has come to the conclusion that the current and projected wastewater treatment system, of which the well is only one component is the best environmental solution for itself as a city and as a barrier island. As the Sanibel City Council liaison to the Wastewater Research Committee which has just reviewed the system and made its report to the City Council. I concur.

First, a few facts:
Deep injection wells are not a means of disposing of raw sewage. Only water (known as effluent or reclaimed water) which has been treated to be clean enough to use as irrigation water on golf courses or residential lawns will be put into the well when the ground has become so saturated with rain water that there is no other place to put it. Why? Because this water is a valuable ecological resource. By using effluent water to irrigate, we can avoid using expensive water, which has been treated by reverse osmosis to water our lawns, keep the dust down on roads, etc. We value this treated effluent so much that Sanibel, along with many other communities, is building a distribution system to get this water to its citizens. The Wastewater Research Committee is concerned that once the system is complete, people will want more effluent water than is available.

The deep injection well deposits the treated water about 3,000 feet into the earth into a thick boulder zone which is separated from our drinking water aquifer by many layers of impervious clay and rock. It is built using multiple steel casings, set in concrete, to avoid any possibility of the treated water escaping underground. In Sanibel's case, there will be a minimum of three concentric steel casings each set in concrete with a combined wall thickness of 1 3/8 inches of steel plus 8 inches of concrete. The actual injection occurs over 2,000 feet below IWA's deepest production well which feeds its drinking water plant. There are monitors built into the steel/concrete walls to detect leaks and there are two monitoring wells nearby.

On the issue of seepage, the Department of Environmental Protection (DEP) has such strict codes on seepage, that even if you poured water directly from your kitchen faucet into the well and it seeped into the aquifer, it could be considered a violation and the well could be shut down. The DEP demands no seepage - period - and will not issue a final use permit until they are sure all conditions are met.

In some states water can be taken directly from the ground and used for drinking water, but the water from all aquifers in Florida must be treated. Our drinking water on Sanibel is treated by reverse osmosis. If you've ever talked to someone about a water filter system for your home, you'll know that this is the most effective and expensive method used to filter water available. If you listen to the critics who believe that, in spite of every precaution, there may be seepage into the aquifer, any contamination would be removed by the reserve osmosis process. The Island Water Association will also use the well in inject brine taken from the treated drinking water into the well and the brine will mix with the effluent water, weighting it down, further preventing it from seeping upward.

Some people have objected to a deep injection well on a barrier island and would prefer to ship our raw sewage to the Ft. Myers Beach plant to be treated there and then put in its well. The Ft. Myers Beach well is built in exactly the same way as the Sanibel well and puts the effluent water in the exact same geological zone as Sanibel plans to. Our Wastewater Committee, which had three civil engineers with wastewater-related experience on board, studied this option along with many others and determined that there were nor real financial advantages, much more of an environmental risk and much more difficulty in ever getting such a plan approved by the DEP. Some of us had visions of the infamous garbage barge in New York looking for someone else's backyard to dump its load. After six months of investigation, the Committee suggested in its report to the City Council that the biggest reason for Sanibel to treat its own waste is because it's the responsible thing for us to do, rather than to shift the burden to our neighbors. This is an affirmation of previous decisions made by Councils over the years.

As a barrier island which is subject to sea surges and tropical storms, we need a place to put excess water in emergencies. In cases of extreme stress on the environment, such as what Sanibel suffered during the recent El Nino event, we need a place to put excess water where it will do no damage. As Margaret Highsmith, DEP's Director of District Management and a resident of Sanibel said in a letter dated July 8, 1999, "While the injection of wastewater underground may not be the most ideal solution, the other possible options are even less attractive. Of course, the best way to manage wastewater is to use it again, to water lawns and golf courses."

After years of planning and public hearings, the Sanibel Wastewater Facilities Plan was formulated in full knowledge of the points made in Ms. Highsmith's letter. The Plan requires that all wastewater be treated at the high standards now available to make it suitable for irrigation. In cases of an extreme wet weather emergency only, the deep injection well will be used to dispose of excess water in an environmentally safe, monitored and DEP approved way.

The deep injection well is a very important back-up component to our system. It will be another three to five years before Sanibel's complete collection and distribution system is in place, but the well will be operation in a few months, in case we need it. Most of us will not be thinking of where excess water goes during and after a hurricane or tropical storm, but we'll all be glad someone did.

For more technical information on deep injection wells, check the IWA web page: www.islandwater.com

Back to Citizenship