4.3. SR 02-12-2001 - Laserfiche WebLink

Home Browse Search

Howard R, Green Company CONSULTING ENGINEERS January 22, 2001 File: 811270J-0060 Mr. Gary Leirmoe, Wastewater Chief Operator City of Elk River 13065 Orono Parkway Elk River, MN 56560 RE: VENTILATION SYSTEM IMPROVEMENTS, WASTEWATER TREATMENT PLANT ELK RIVER, MINNESOTA Dear Gary: Attached are preliminary Electrical and Mechanical drawings showing proposed ventilation system improvements in the grit room, screen room, and digester building at the wastewater treatment plant. Also attached is an updated cost estimate for the proposed improvements. As shown in our updated estimate, the cost to bring the electrical and mechanical systems in the grit room, screen room, and digester building up to code standards is expected to be approximately $193,000. As you know, our preliminary cost estimate was approximately $116,000. This difference is a result of additional work needed in the digester building to bring it into compliance with the National Fire Protection Association (NFPA) standard that addresses wastewater treatment facilities, During our site visit on November 28~, we reviewed the existing Elk River Wastewater Treatment Ptant screening, grit, and digester facilities with respect to our preliminary code review and recommendations. E~ased on our site observations, we would reiterate our preliminary recommendations for the screen room and grit room. Consequently, our updated cost estimate for the ventilation system improvements in the screen 'and grit rooms is consistent with our prelim[nary estimate, and in fact is slightly lower. However, with regard to .the digester control building, we have revised our recommendations based on our site .observations. This is due to the type of equipment installed in the lower level of the digester building. We betieve the upper and lower level of the building must be physically separated to bring it into compliance with NFPA 820, "Standard for Fire Protection in Wastewater Treatment and Collection Facilities". To be physically separated and in conformance with the standard requires "a gas-tight partition between two adjacent spaces, or two nonadjacent spaces, with no means of gas communication between the spaces. Personnel entry to the separate spaces is by individual, grade level exterior ports with no physical connection between the two." Following are the criteria required to meet the requirements of NFPA 820: I. The lower level of the digester building contains gas-handling equipment as defined by NFPA 820. The gas handling equipment includes sediment traps, drip traps, and control valves used in the removal of gas from the digesters. Based on NFPA 820, this room will require 12 air changes per hour (ac/hr) of continuous ventilation. The room will be classified perthe National Electric Code (NEC) as Class 1, Division I within 5 feet of the gas handling equipment with the remainder of the room classified as Class 1, Division 2. Ltr-011701 -Leirmoe,do¢ 1326 Ener.,gy Pa~k Drive · St. Paul, MN 55108 · 651/644-4389 fax 651/644-9446 toll free 8881388-4389 ~O/EO'd 9~6 ~'~9 I~9 N~N9 '~ (I~MOH ~':II I00E-60-,q~-4