HomeMy WebLinkAboutCommittee of the Whole Minutes 12.16.1997 MINUTES
CITY COUNCIL COMMITTEE OF THE WHOLE
December 16~ 1997 6:30 p.m.
Council Chambers
MEMBERS PRESENT:
OTHERS PRESENT:
Chairman Chuck Rodgers
Gary Temple Gay Easton
Dirk Kroll Donna Kilpatrick
Bud Johnson Norman Orr
Miles Walton William Staudinger
V. Joe Leckie
Don Hackmann
Andy Loebe
Mike Zuhoski
Ken Olson
Cal Cumin
Terry Ruff
Larry McCann
Dave Mosser
Donna mentioned ~hat she has enjoyed her 12 years
the city council. She has mixed feelings about leaving
is ready to step down and turn it over to Ken Olson.
on
but
Mike reported that Alan Hovious is in Helena and
Police Reserve recorded 330 hours of service last month.
the
Bud mentioned that there has been some discussion and
he feels it is time to review the master plan for zoning.
The budget process is in the near future and the project
should be looked at during the coming budget year. Also,
there was discussion at the joint meeting with the Billings
City Council and the County Commissioners regarding the
unified zoning regulations. Bud was wondering if Laurel
should consider joining or aligning our regulations in the
same fashion.
Bud wants the council to consider the number of staff
members that are asked to attend the regular council
meetings. He feels that there may be other effective ways
to accomplish the things we need to do aside from requiring
their attendance at these meetings.
Cal mentioned that he thought it was a good idea to
look at the unified City-County code that Billings and
Yellowstone County have and see if there is room for Laurel
to fit into that, with our particular environment.
Cal said that he will look into the cost of reviewing
and updating the zoning master plan.
Discussion regarding the way votes are recorded when
motions are passed. If there is a roll call vote taken, it
will be stated as such in the minutes.
Dirk complimented Patrick Kennedy and the police
reserves for their professionalism at the basketball game
the other night.
It was mentioned that a letter was sent to Terry Fink
the other day.
Donna thanked everybody who participated in the
Christmas to Remember.
Gay complimented Donna for all the work she has done in
the parks and hated to see her leave.
Bill reported that "Bright and Beautiful" needs a lot
more work.
Larry gave a public works update.
Dave Mosser, Morrison-Maierle, Inc., gave a report on
the City of Laurel raw water intake system.
Meeting adjourned at 6:57 p.m.
Respectfully Submitted,
Don Hackmann~ City Clerk
CITY OF LAUREL RAW WATER INTAKE SYSTEM
WATER TREATMENT PLANT
12/16/97
Basis of Summary
1. Financing Future Water System Taps & Extensions; Sept. 1997 report by Morrison
Maierle.
2. Water Treatment and Distribution Master Plan; 1994 report by HKM Associates.,
Existiu Conditions
1. Capacity of Plant following improvements:
filters & treatment facility 10 million gallons per day / (7,000 gpm)
raw water intake system
summer
winter
high service pumps
total
firm capacity
2. Water Demands
maximum day for City
: present
future
winter average day
industrial / large commercial fire
7 mgd - city / 3 mgd - Cenex raw water
3.6 mgd total (18" perforated line)
12.0 mgd / (8,500 gpm)
8.8 mgd / (6,100 gpm)
4.6 mad / (3,200 gpm)
6.2 mgd / (4,200 gpm)
1.2 mgd / (1,000 gpm)
(4,500 gpm)
3. Distribution System Pressures
- max. day demands w/ 7.0 mgd plant and 4,500 gpm fire flow.
pressures in Cherry Hill & Murray Park drop to 0 to 5 psi.
flow out of storage = 3,900 -pm.
- max. day demand w/ 10.0 mgd plant and 4,500 gpm fire flow.
pressures in Cherry Hill & Murray Park drop to 28 to 33 psi.
flow out of storage = 1,700 gpm.
Raw Water Intake System- Existing Conditions
r
1. River Intake Structure Problems - (see attached figure)
a. Air enters the intake system when the river is low & demands high. Air can air-lock raw water
pumps stopping their production.
b. Slushy ice buildup on intake screens during winter. Prevented by single perforated 18" line.
C. June 1997 during high river flow - sand buildup and large branches trapped in structure.
d. Wooden gate too small for opening - can't close during high flows.
e. 3/8" x 2" bars at 3" centers across 36" openings were never installed. (Would have helped with
large branches in item c.
f. '/z" screens on 20" lines incur velocities across screen openings (at 10 mgd) of a ft/sec. 0.5 ft/sec
recommended. Accelerates plugging.
.-.'I 51ORRISON-MAJERLE,luc,
0 Page 2
2. Intake System Lines
a. 20" lines in river sized OK for up to 15 mad average day flow.
b. The 10" and 12" yard piping is at maximum recommended capacity.
Raw Water Pumps
A. Consists on two 2,000 gpm pumps and one 1,400 gpm pump.
b. Total capacity = 7 mgd. Firm capacity = 4.9 mgd.
Raw Water Intake Alternatives for Laurel
1. Install 4 submersible pumps in river structure, place bar screens in river structure, and
install new 30" yard piping.
Cost = $500,000
2. Install 3 new raw water pumps in raw water pump building, refurbish the two 2,000 gpm
existing pumps, bar and intake screens in river structure, and install new 30" yard piping.
Cost = $450,000
'). Install') new raw water pumps in raw water pump building, refurbish the two 2,000 gpm
existing pumps, construct large concrete wetwell and connect 20" lines to wetwell,
modify raw water pump suction to pull from wetwell, and install new 30" yard, piping.
Cost = $400,000
4. Construct earth holding pond and pipe from holding pond to raw water pumps, install 3
new raw water pumps in raw water pump building, refurbish the two 2,000 gpm existing
pumps, remove river structure, and install new 30" yard piping.
Cost = $2,300,000
5. Construct new river intake structure upstream of 8th Avenue drainage ditch, install 6500
feet of piping, install 3 new raw water pumps in raw water pump building, refurbish the
two 2,000 gpm existing pumps, remove river structure, and install new 30" yard piping.
Cost = $2,500,000
6. Do Nothing and continue to experience above problems, and problems will increase as
the City grows.
Cost = $0.00
Cec n'cal Considerations & Recommended Alternative
SEE ATTACHED PAGES 19 thru 21 FROM REPORT.
Z1 MORRISON-MAIERLE.ivc.
LOCATION OF
WINTER 18"
PERFORATED PIPE r
I
21' MAIN
GATE
20"D.I.
PIPING
(2)45'
BENDS
20"D.I.
PIPING
SUCTION CHAMBER I
SLUCE
GATE /
a '36" S0. PENING
\-20" SCREENED OUTLET
WITH 90' ELBOW RISER
SUCTION CHAMBER
SLUCE
GATE -
/
(2) 90' BENDS
(VERTICAL)
36" SQ. PENING 35'
4'W x 6'L
WOODEN GATE
IN 4' x 10'
OPENING
NOTE: WATER LEVEL THROUGH 4'
OPENING HAS DROPPED TO APPROXIMATE
3' OF WATER DURING LOW FLOW CONDITIONS
4't
FLOW
BRIDGE PIER
EXISTING LAUREL INTAKE STRUCTURE I FIGURE 2-1
F-_ 1
61
2.2.4 Technical Considerations
Technical issues and-concerns that are inherent with the proposed alternatives are reviewed as
follows:
Alternative No. I - The submersible pumping system will allow the direct pumping of water from
the intake structure to the water plant. Direct pumping will eliminate the potential for air
trapping and accumulation in the raw water piping, and will eliminate one of the possible air
intake areas. During the winter months when the Yellowstone River is carrying151ush and ice,
precautions will need be carried out and design features incorporated into the modifications to
the existing intake structure in order to minimize possible ice and slush problems with the
pumps. Submersible pumps are designed to deal with solids such as the ice and slush. The
temporary suction line which is now installed each winter would not be necessary in the future.
The bar screens will protect the submersible pumps from large debris.
Alternative No. 2 - Continuing with vertical turbine and trash pumps in the existing pump
building will offer some significant improvements over what currently exists. The piping from
the intake manifold through to the water treatment plant will all be replaced. This will eliminate
one of the possible air intake conditions. In addition, air release mitigation measures could be
designed into the pumping system to minimize future air locks. The intake structure
modifications would result in increased screen area and other measures to prevent possible
vortexing conditions. River icing and slush problems would be minimized and the temporary
suction line which is installed each winter would not be necessary.
Alternative No. 3 - Construction of a wetwell between the intake structure and the existing pump
building offers the same technical merit as Alternative No. 2. The primary difference is this
alternative will incorporate a new structure which will require additional maintenance.
0703.006.07.010-0211
W:\0703\OOaO7WPOKT. WPD
Revised: September 11. 1997 19
Alternative No. 4 - Issues for consideration with the construction of an earth holding pond are
numerous and will require careful consideration. An earth holding pond improves and makes
quality of the water entering the plant much more consistent by allowing the removal of larger
matter and grit. Screening also accomplishes this, but screens require frequent cleaning. Ponds
require considerable area, which the City currently does not have on the plant site. With a
refinery directly to the north and a slough to the west, the possibility of outside contamination to
the water in the holding pond also exists. Depending upon what additional contaminants might
enter the water as it is stored in the holding pond, the conditions of treatment required by the
plant could change.
Alternative No. 5 - The City has indicated that if a new intake structure was to be constructed,
the structure should be located upstream of the storm and area drainage ditch which enters the
Yellowstone River in the 8th Ave. area. This will require approximately 6,500 feet of large size
pipe line to be run from the new intake to the plant. Easements, pipeline distance, and
maintenance are major issues with this alternative.
Alternative No. 6 - The primary justification for doing nothing to the current raw water intake
would be that a new water treatment plant at a new location will be built in the near future. With
the City now investing $2.5 million into the existing treatment plant for modifications, a new
plant is not projected for the immediate future.
2.3 RECOMMENDED ALTERNATIVE AND IMPROVEMENTS
Of the six alternatives, Alternatives 1. and 2 have the most merit. As it is not the intention of this
report to establish the preliminary design criteria for each of these alternatives,, these two will be
treated equally and it is recommended that the City carefully consider both alternatives in the
future.
A summary of the major issues which are believed that will be required for each of the two
alternatives include: .-
Alternate No.1
• install one 2,000 gpm submersible pump in the existing intake structure.
• install three 3,000 gpm submersible pumps in the existing intake structure.
• install 120 if of 30" yard piping with necessary valves and fittings. Abandon the existing
yard piping.
• install stationary bar screens over the two 36" square openings to the pump suction
chambers.
• modify the 4 ft wide gate on the upstream side of the intake structure.
AhemAte No. 2
• modify the suction and discharge piping to the existing 2,000 gpm raw water pump.
• add three new 3,000 gpm raw water pumps.
0703.006.07-010-0211
W:10703\006\07\REP0KT. WPD
Revised: Saptembvc 11, 1997 20
• install 24 lineal feet Of) of 24" diameter circular intake screen, inside the existing intake
structure, to the pump suction lines.
• install 100 if of 30" yard piping with the necessary valves and fittings. Abandon the
existing yard piping.
• install stationary bar screens over the two 36" square openings to the pump suction
chambers.
• modify the 4 ft wide gate on the upstream side of the intake structure.
0703.006.07.010.0211
W :\0703\006\07REPO RT. W PO
Revixd: September 11, 1997
21