2015.11.10 CC and WS Combined - Laserfiche WebLink

Home Browse Search

Water Treatment Plant 4's filter treatment residuals are discharged after 24 hours detention in an open holding tank. The top clean water is currently discharged to Jones Lake. WTP 4 and 5 have recently been refurbished with improvements including; new filter under drain, new filter media, baffle walls to increase detention time and paint coatings. Discharging water to the environment rather than recycling the water results in additional cost to the City in several forms including higher labor costs, associated permitting fees, lab testing fees, and additional energy consumption. With City Project 15-13, Staff recommends preparing plans and specifications to recycle/reclaim the backwash water at WTP 3 and 4. Staff will return to the City Council when plans are complete to authorize bids in 2016. Vessel 3A Rehabilitation In 2004, the Minnesota Department of Health (MDH) notified the City that four of our deep drinking water wells were found to exceed the regulatory level of 5.4 PicoCuries per liter for radium. In 2005, City water department personnel installed new special chemical feed equipment at City Water Treatment Plants 3, 3A, 4 and 5 in hopes of reducing the radium to below the regulatory level. The chemical feed equipment was a minimal cost solution but unfortunately did not correct the radium problem. In August of 2005, the City received a Notice of Violation from MHD ordering the City to develop a plan to reduce the radium to acceptable levels. In conjunction with the MDH, the City signed a Bilateral Compliance Agreement with the Minnesota Department of Health (MDH). Essentially, the agreement stated the City must return Water Treatment Plants 3 & 3A to compliance in 2006, Water Treatment Plant 4 in 2007, and Water Treatment Plant 5 in 2008. In 2006, the City removed the filter media in the two filters at Water Treatment Plants 3 and 3A and replaced it with a finer filter material, inspected the filter interiors for corrosion, and made coating repairs as necessary. At the same time a different complex chemical feed system was installed. The work was completed and has reduced the radium levels below 5.4 picocuries per liter for radium as required by the MDH. In 2007 at Water Treatment 4, and in 2008 at Water Treatment 5, the City installed new finer filter media while reusing the existing chemical feed system, sandblasted and painted the entire filter interior to remove the existing corrosion and installed an airwash system to assist with the backwash process. The work was completed has reduced the radium levels below 5.4 picocuries per liter for radium as required by the MDH. With City Project 15-13, Staff recommends preparing plans and specifications for Vessel 3A Rehabilitation: including removal of the existing media, blasting of the entire vessel interior (and disturbed portion of the exterior), new filter under drain, new filter media, installation of welded baffle walls, and new paint coatings. This work may be delayed until after improvements are made to WTP 1 (2018) to avoid the possibility of limiting the volume of water available at a given time.