HomeMy WebLinkAbout2008-07-22 BRAA Memo Re Sanitary Sewer Options `
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Memorandum Bonest -m�~
233 Highway soW
To: [ennisPostler Project: Xcel Energy Fly Ash Site ` ^ Date: 0'22'2008 St. 55113
From: Kim Hay Client: City of Oak pork Heights Tel 651-636-*600
Fax 651-636-1311
Re: Sanitary Sewer Options File No: 000055'08000-1 www.uonestroo.com
We have rev several options for the existing trunk sanitary sewer under the Xcel Energy
Fly Ash Site. This memo provides details on the various options and their related costs.
Option includes the installation of gravity sanitary sewer around the north side of the existing
fly ash pit and force main from the south. Construction would include o75hplift station to
pump flows from the south half of the City. Existing sanitary sewer and structures in the fly ash
pit would be abandoned. This option would provide the City with e new, reliable trunk sewer
line, but mmuN also add the maintenance of a lift station. Preliminary layout of this option can
be seen in Figure 1 (attached).
Option 2 is for tunneling o new sewer line through the Uv ash pit parallel to the existing pipe.
The advantage would be that a casing pipe would be installed around the carrier pipe, allowing
for easier repairs in the future iy need be. The disadvantages are that'aoking pits would be
installed at each end of the tunneling, and possibly interim manhole locations, which would
disturb a large area of the existing fill and lining of the fly ash pit. Also, means and methods of
tunneling through the sodimented fly ash would need tobe explored further.
Option 3 includes costs for installation of a cured-in-place pipe lining in the existing trunk
sewer lines. C|PP lining is designed to act as stand-alone pipe. Lining the sewer does not
necessarily provide additional strength but if the existing RCP sewer were to fail, the pipe
would gain the strength of the underlying C|PP. Pipe lining also slightly decreases the capacity
of the pipe, but C|PP [ining would provide for o smoother Uovv than the existing RCP. Because
C|PP lining is typically used for pipe repair and rehabilitation, more research would be necessary
to determine the exact effect o[ lining a pipe that is currently in good condition if this option
was chosen.
A summary oy construction costs for review isasfollows:
Sewer O ptions
CONSTRUCTION COST + 25% ENGINEERING & PLANNING
Option 1 $333t2OO.00 $416,500-00
Part 1 — Gravi Sewer $153,100.00
Part 2 — Force Main/Lift Station $180,100.00
Option 2 $594,500.00 $743,125.00
Option 3 $255,000.00 $318,750.00
Option 4 $8,445.00 $10,556.00
The City also has the option of doing nothing at this point. Some of the existing pipe has had
40 to 70 feet of fill on it for almost twenty years. From soil borings taken by Braun Intertec in
1984, the fly ash pit has limestone bedrock under the fill so long term settlement is not likely to
occur. If the City chooses not to proceed with an alternate sewer plan at this time, televising
and inspection of the existing sanitary and storm sewer should be completed to document the
existing conditions. Costs for this are shown above under Option 4. Additionally, escrow
money should be provided to the City by Xcel to cover the cost of the potential future sewer
installation.
Existing trunk storm sewer also runs under the existing fly ash fill site, and under or adjacent to
the proposed additional fill area. Although relocating the storm sewer is not being analyzed or
recommended at this time, the City should have an agreement with Xcel Energy whereby they
would be responsible for any future pipe failure attributable to the additional fill loading.
Attachments:
Cost Estimates
Figure 1 -- Gravity Sewer, Lift Station and Force Main
Page 2 of 2
XCEL FLY ASH SITE - COST ESTIMATE
No. Item Units Qty EE Unit Price EE Total Price
OPTION 1
PART 1 - GRAVITY SANITARY SEWER:
1 MOBILIZATION LS 1 $12,000.00 $12,000.00
2 CONNECT TO EXISTING MANHOLE EA 2 $1,000.00 $2,000,00
3 CONSTRUCT MANHOLE OVER EXISTING PIPE EA 1 $3,500.00 $3,500,00
4 24" PVC SANITARY SEWER, SDR 26 LF 1,800 $50.00 $90,000.00
5 4' DIAMETER SANITARY MH, 8' DEEP, INCL R-1 642-B FA 3 $1,800.00 $5,400,00
CSTG AND CONC ADJ RINGS
6 4' DIAMETER SANITARY MANHOLE OVERDEPTH LF 100 $100.00 $10,000.00
7 IMPROVED PIPE FOUNDATION, PER 6" INCREMENT LF 1,800 $2.00 $3,600.00
8 ABANDON SANITARY SEWER PIPE LF 2,700 $8.00 $21,600,00
9 SEEDING, INCL SEED, FERTILIZER, MULCH AND DISK AC 2,5 $2,000.00 $5,000.00
ANCHOR
TOTAL PART 1 $153,100.00
PART 2 - FORCE MAIN AND LIFT STATION:
10 LIFT STATION STRUCTURE LS 1 $150,000,00 $150,000,00
11 6" DIP FORCEMAIN LF 1,100 $25.00 $27,500.00
12 CONNECT TO EXISTING MANHOLE EA 1 $1,000,00 $1,000.00
13 SEEDING, INCL SEED, FERTILIZER, MULCH AND DISK AC 0.8 $2,000,00 $1,600,00
ANCHOR
TOTAL PART 2 $180,100.00
TOTAL OPTION 1 $333,200.00
OPTION 2 PIPE TUNNELING;
14 MOBILIZATION LS 1 $20,000,00 $20,000.00
15 CONSTRUCT AND REMOVE JACKING PITS EA 2 $30,000,00 $60,000.00
16 24" PVC SANITARY SEWER PIPE, IN CASING LF 1,250 $60.00 $75,000.00
17 40" STEEL CASING PIPE, JACKED LF 1,250 $350,00 $437,500.00
18 SEEDING, INCL SEED, FERTILIZER, MULCH AND DISK AC 1.0 $2,000.00 $2,000.00
ANCHOR
No. Item Units Qty EE Unit Price EE Total Price
TOTAL OPTION 2 $594,500.00
OPTION 3 PIPE LINING:
19 CITY SEWER CLEANING LF 2,500 $2.00 $5,000.00
20 SANITARY SEWER, CURED -IN -PLACE LINING LF 2,500 $100,00 $250,000.00
TOTAL OPTION 3 $255,000.00
OPTION 4 ANALYSIS OF EXISTING CONDITIONS:
21 CLOSED CIRCUIT TV INSPECTION - SANITARY SEWER LF 2,830 $1.50 $4,245.00
22 CLOSED CIRCUIT TV INSPECTION - STORM SEWER LF 1,000 $2.00 $2,000.00
23 VISUAL INSPECTION OF STORM SEWER LF 1,100 $2.00 $2,200.00
TOTAL OPTION 4 $8,445.00
TOTAL OPTION 1 - GRAVITY AND FORCE MAIN $333,200.00
TOTAL OPTION 2 - TUNNELING $594,500.00
TOTAL OPTION 3 - LINING $255,000.00
TOTAL OPTION 4 - ANALYSIS OF EXISTING CONDITIONS $8,445.00
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