Fluid level monitoring system and method incorporating pressure sensor system having inflatable/collapsible bag

A fluid level sensing system for sensing a fluid level in a landfill well, the system comprising:

• a first housing having a first bore and a second bore extending therethrough, wherein:
• the first housing is configured to be inserted into a landfill wellbore for exposure to landfill fluid in the landfill well and such that the first bore is in communication with the landfill fluid in the well;
• and
• the second bore is configured to communicate with an ambient environment in the well to enable a controlled vacuum from an external vacuum source to be applied to the ambient environment within the well;
• a sealing plate adapted to be secured to the first housing, the sealing plate including first and second bores in communication with the first and second bores, respectively, of the first housing, when the sealing plate and the first housing are secured together;
• a second housing secured to the first housing;
• a dual flexible assembly positioned within the second housing, the dual flexible assembly including first and second enclosures, with the first enclosure being housed within the second enclosure such that only a single opening is formed in the second enclosure;
• the first enclosure including an opening and being in communication with the first bore in the first housing, and isolated from the second bore in the first housing, and configured to expand and contract in response to a change in pressure in the first bore of the first housing caused by a changing fluid level in the well;
• the second enclosure including an opening coaxially arranged with the opening in the first enclosure, and being in communication with the second bore of the first housing, and isolated from the first bore of the first housing, and configured to expand and contract in response to the controlled vacuum to cause the second enclosure to act on the first enclosure and to exert a compressive reference pressure on the first enclosure as the first enclosure expands and contracts in response to the changing fluid level in the well;
• a movable element housed in the second housing and movable in response to expanding and contracting movement of the first and second enclosures in response to the changing fluid level in the well;
• and
• a sensor responsive to movement of the movable element for providing a signal indicative of movement of the movable element, the signal being indicative of a fluid level within the well at a given time.