Post closure period should be defined in the permit.  When the site is closed, final capped, etc., the post closure period should start.  I have not heard of situation where it is closed for 30 years before the post closure begins.  Unless defined differently, my assumption is the time starts with final capping, and the 30 years monitoring wants to confirm that there are no issues, leakage, groundwater effects, etc.

I would address each landfill separately, unless defined differently in permit.  Your questions are best answered by permit, regulations for your locale.  The permit should comply with all applicable requirements for federal, state, county and local regulations. The land titles should be amended to indicate this activity, so people don't buy the land and build houses, develop, drill wells, or grow food on the area 50 years from now.

I aggree with William. Post closure starts with final capping. And yes the post-closure shuold start independently from the question if a further landfill on the site is still in operation. The reason is that the closed landfill needs monitoring, eg. regarding settlement.

Ayushi

There are two different measuring sticks by which to evaluate a site. One is the scientific, biophysical condition; and the other is the regulatory regime superimposed upon the site.

The biophysical condition is foundational. First questions to ask is, what is the nature of the hazardous waste? Presumably it is industrial and could include heavy metals, acids or alkalis, or pesticides. These are very long-lasting and probably remain toxic far beyond 30 years. (Radioactive waste is in another category altogether). So you would assess the likelihood of contaminating groundwater, the likelihood of flooding, the porosity of the substrate and the capping material, the ability of the cap to shed rainwater away from the dump, the location of drains and the amount of moisture in the dump material that might cause it to leach out through the base.

Superimposed upon the site are regulatory restrictions by either the landholder through lease conditions or other title measures; or a government authority through planning/development conditions, environmental regulation or mining tenures. I agree with William above, that the critical question here is the conditions of the permit. A government authority cannot impose restrictions more powerful than the governing legislation allows. So a permit will specifiy conditions that are as restrictive as the head legislation allows, or less restrictive. The permit is definitive. If the permit specifies 30 years, then that is what should be enforced.

In most cases industrial waste has to be secured forever and does not become harmless after a mere 30 years. However, the 30 years is usually enough to monitor the site and identify any leakage, settlement or failure of the capping material or drainage system, as Harald has explained.

Sorry Geoff. I did not put the question. But I do not feel this really adds to the discussion, What is your point?

Harald

I was trying to make the point that a closed landfill needs monitoring. The 30 year period should be long enough to allow conclusions to be reached about its safety, on the basis of monitoring during that period.

At the time of site closure, or other time as specified by local regulations a post closure maintenance plan will be developed.   

Hello!! Post closure period starts when the environmental authorities approve the final closure works. This means that an administrative document (permit) should be issued. The 30 years responsibility start to be counted exactly from the date when this permit is issued.