New figures show that it could cost the council over 20 million euro to bring sewage treatment and water supplies on Donegal's unfinished housing estates up to an acceptable standard.
The estimates do not include other work such as roads, footpaths and lighting.
The 20.4 million euro figure from the county manager relates to 283 developments made up of around 5,600 units.
The figure comes from a review to determine the current and potential future cost implications for water services.
To worst case scenario cost to bring on site sewage treatement systems up to an acceptable standard is 15.6 million euro - a further 4.1 million euro would be required to upgrade sewage pump systems.
As much as 695 thousand euro needs to be spent on pumping stations.
Because of financial constraints the council is dealing with the matter on a case by case basis with priority being given to cases where there are implications for public health or public safety.
The process involves engagements with developers, financial institutions and residents.
County Manager Seamus Neely says there is an increased impetus in addressing te problems and efforts are being made to find potential funding from national schemes suchn as the Public Safety Initiative.