MONROE - Monroe's wastewater treatment plant is still bringing home an excellent report card, despite operating more than 15 years beyond its intended life span.

The facility received a 3.46 grade point average, out of a possible 4, on its 2010 Compliance Maintenance Annual Report (CMAR), an annual self-evaluation report required by the Department of Natural Resources since 1984.

The only area of concern in the report - as in at least three previous annual reports - is a grade F in biosolids management, caused mostly by the lack of space to store leftover solid waste, according to George Thompson, the city's wastewater treatment plant superintendent.

Monroe has a biosolid waste storage capacity of about 90 days, which met DNR compliance when the facility was upgraded in 1984. The DNR now requires a storage capacity of 180 days. Biosolid wastes are by-products, such as grit, sand and ash, that can not be digested by micro-organisms in the cleaning treatment process.

"That is just one of the driving forces for the upgrade plans," Thompson said. "It is one of the things we will be addressing as we go through the planning (of new upgrades to the facility)."

The age and capacity design of the facility - last updated in 1984 to handle growth needs of the city for 10 years - has pressed the city to eye an upgrade that could cost about $20 million. Surveys to determine future of the plant are underway. A five-year capital plan, which has helped accumulate about $6 million, will be used to finance, or to secure low interest loans for the new upgrades, said Thompson.

Thompson said employees at the facility are currently working around the problem of biosolid storage by making as many land applications as possible, before crop planting and after harvest. Field applications can't be made on frozen ground.

When applications cannot be made, biosolid waste, which has the consistency of thick, oozing mud rather than a dry solid, has to be dammed by concrete blocks to prevent it from sliding out of the building.

Other aspects of biosolids management, such as the digester and sludge press, are working "mostly in compliance," with DNR requirements, Thompson said.

The problems with those processes also are related to the age and size facility, he added.

Monroe's CMAR report, submitted Monday to the Board of Public Works, shows the plant is maintaining a grade of A in each of its water outflow measurements of ammonia, phosphates, suspended solids and dissolved oxygen or biochemical oxygen demand (BOD).

But some of those grades may be slipping in the near future.

The aging facility is challenged to maintain its original design capacity of 14,000 pounds of BOD per day, Thompson said. The DNR has already changed its ammonia limits and biosolid storage since 1984, and Thompson expects phosphorus limits will become more strict in the next two years.

The facility upgrade plans will take into consideration new, anticipated DNR requirements.

The plant also received A grades in the employee and financial sections of the report. The plant is up to par in its preventative maintenance staffing and exceeds DNR requirements for all of its employees being certified in wastewater operations.

The Monroe Common Council approved the report Tuesday for its submission to the DNR.