4.3. SR 02-12-2001City of
River
M£MORANDUM
Item #4.3.
TO:
FROM:
DATE:
Mayor & City Counci~
/ /
Pat Klaers, City Adm~trator
February 12, 2001
SUBJECT: Consider Ventilation Proposal for WWTP Digester
and Grit Removal Buildings
BACKGROUND
Wastewater Chief Operator Gary Leirmoe has been working with our city
engineering firm, Howard R. Green Company, and Safety Coordinator Bruce
West, to evaluate safety issues in the WWTP Digester Building, Grit Room,
and Screen Room. The concern in these areas is the ventilation system.
Attached for your information is a memo from the City Engineer to Gary
regarding an outline of the work that needs to be accomplished and the
estimate for necessary improvements. This type of expense is significant but
the ramification for doing the work far outweighs any cost that may be
incurred. This type of facility improvements is why the city has plant
replacement and expansion expenditures built into the annual WWTP
operating budget. Accordingly, funds are available for this expenditure.
Staff requests Council approval to move forward with bidding out this
project. The City Engineer will be in attendance at the Council meeting on
February 12, 2001, to answer questions on this proposal.
13065 Orono Parkway · P.O. Box 490 · Elk River, MN 55330 · TDD &Phonc (763) 441-7420 · Fax (763) 441-7425
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
Mr. Gary Leirmoe
January 22, 2001
Page Two
The upper level of the digester building will be physically separated from the gas-handlir~g equipment
as defined by NFPA 820. Therefore, it will require only 6 ac/hr of continuous ventilatior) to become
unclassified per the NEC,
Based on these recommendations, additional work will be required. The additional work is summarized as
follows:
1. Physical separation of the upper and lower level;
This wilt require excavation for a new entry into the lower level, as well as removing the existing
stairway and closing off the stairway floor opening. The grate between the upper and lower level must
be removed. If an.opening is required for removal of pumps, the grate should be replaced with a
gasketed, gas-tight cover. All remaining penetrations should be sealed to be gas-tight.
2. Lower Level:
This will require a new heated make-up air unit and exhaust fan to provide 12 ac/hr c.f continuous
ventilation. In addition, electrical wiring and devices will have to be changed to bring the area into
compliance with Class 1, Division 2 per the NEC.
3. Upper Leveh
This will requi~e a new heated make-up air unit and exhaust fan to provide 6 ac/hr of continuous
ventilation. This room will be unclassified per the NEC, so the electrical wiring and devices in the area
are currently in compliance.
If the City would prefer to phase in the improvements over the next two years and the City's building official
agrees, we recommend one of the following options:
1. Make ail improvements in the digester building this year, then make the improvements in the grit and
screen room next year; or
2. Make the improvements in the screen and grit room and part of the digester building improvements
this year and make the remaining digester building improvements next year.
will call you to discuss and address any of your comments or questions regarding this matter,
Sincerely,
Howard P,. Green Company
Kevin F. Newman, P.E.
attachment
c: Terry Maurer - Howard R. Green Company
Ltr-011701-Leirmoe.doc
Howard R, Green Company
CONSULTING ENGINEERS
PROJECT:
DATE:
ELK RIVER WASTEWATER TREATMENT PLANT
12/19100
PRELIMINARY BUDGET
ITEM
SCREEN ROOM
DEMO
MAKEUP UNIT
EXHAUST FAN
SS DUCTWORK
CONTROLS
ELECTRICAL
GAS PIPING
ROOFING
CRANE
MISC LABOR
SUBTOTAL
ENGINEERING
TOTAL
GRIT ROOM
DEMO
MAKEUP FAN
EXHAUST FAN
SS DUCTWORK
CONTROLS
ELECTRICAL
GAS PIPING
ROOFING
CP~NE
MISC LABOR
SUBTOTAL
ENGINEERING
TOTAL
DIGESTOR BLDG
DEMO
MAJ(EUP FAN
EXHAUST FAN
SS DUCTWORK
CONTROLS
ELECTRICAL
GAS PIPING
ROOFING
CRANE
MISC LABOR
SUBTOTAL
ENGINEERING
TOTAL
VENTILATION IMPROVEMENTS
UNIT TOTAL
COST QUANTITY COST
700.00 I $ 700,00
9,600,00 1 $ 9,600.00
2,100.00 I $ 2,100.00
3,000.00 1 $ 3,000.00
1,400.00 1 $ 1,400.00
6,300,00 1 $ 6,300,00
2,100,00 I $ 2,100.00
2,100.00 1 $ 2,100,00
400,00 1 $ 400.00
800.00 1 $ 800.00
$ 28,500.00
25% $ 7,125.00
$ 35,625.00
700,00 1 $ 700.00
9,600.00 1 $ 9,600.00
2,100.00 1 $ 2,100,00
7,500.00 1 $ 7,500.00
1,400.00 1 $ 1,400.00
7,000.00 1 $ 7,000.00
2,100.00 1 $ 2,100,00
2,100.00 I $ 2,100,00
400.00 I $ 400.00
800.00 1 $ 800.00
$ 33,700.00
25% $ a,425.00
$ 42,125.00
700.00 1 $ 700.00
7,000.00 2 $ 14,000.00
1,750.00 2 $ 3,500.00
7,700,00 I $ 7,700.00
1,400.00 1 $ 1,400,00
12,600,00 1 $ 12,600.00
2,100,00 I $ 2,100.00
2,100.00 I $ 2,100.00
400.00 I $ 400.00
4,200.00 I $ 4,200,00
$ 48,700,00
$ 12,175.00
$ 60,875.00
STRUCTURAL
ENGINEERING
TOTAL
TOTAL
TOTAL
25%
10% CONTINGENCY
$ 29,000.00
$ 7,500.00
$ 36,500.00
175,125.00
17,512.50
192.637.50
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