HomeMy WebLinkAbout2007-03-14 STEARNS AND WHELER REPORTEXECUTIVE SUMMARY
As part of a facility-wide improvements project at the Ithaca Area Wastewater Treatment Plant
(IAWWTP), Stearns & Wheler has been retained by the City of Ithaca, the Town of Ithaca, and
the Town of Dryden to perform a study and cost analysis for miscellaneous plant improvements.
A description of areas investigated, conclusions, and recommendations is presented below.
Detailed discussions will follow in the complete report.
DISINFECTION OF TREATED EFFLUENT
Disinfection of the IAWWTP effluent is provided by adding sodium hypochlorite solution to the
treated plant effluent at the location of the new phosphorus removal system. The effluent is
required to be dechlorinated prior to discharging into Cayuga Lake. Sulfur dioxide gas is
solubilized and injected into the effluent at a remote location in the outfall pipe.
In an effort to reduce chemical cost, usage, and storage of hazardous chemicals, it is desired by
IAWWTP to evaluate alternatives for UV disinfection. Two alternatives were investigated.
Alternative 1 included upgrading the existing system with new dechlorination equipment and a
relocated sulfur dioxide injection point to achieve adequate mixing and detention time for
chlorination. Alternative 2 included replacing the chlorination/dechlorination system with
ultraviolet disinfection.
The estimated construction cost for upgrading the existing disinfection system is $800,000.
However, due to the environmental and safety benefits associated with using UV disinfection in
lieu of chemical disinfection, it is recommended that a UV system be constructed. The estimated
construction cost for a UV disinfection system is $1,600,000.
SEPTAGE RECEIVING STATION
The existing septage receiving station at the IAWWTP utilizes a separate building that houses
two septage unloading stations – one is used for grease-containing loads, and one is for non-
grease deliveries. Each of these stations includes a bar screen and is connected to its own
underground rectangular storage tank. The receiving station for the grease-containing material is
currently equipped with a Lakeside Rotomat grit system for the removal of solids present in the
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grease-containing shipments. The system is frequently jammed by large rocks that are pumped
out of septage tanks, either as contaminants or as debris from tank deterioration. In addition, the
grit that is inherent to septage has caused extensive damage to pipes and fittings due to erosion.
Options for additional storage, improved unloading, and odor control were investigated. To gain
additional septage storage capacity, it is recommended that a third storage tank be added. A new
structure should be built around new unloading pads and grit removal equipment. The new
septage facility will have a datalogger to monitor and record septage deliveries. The structure
should be ventilated and have an odor control system.
The estimated construction cost for a new septage receiving area and holding tank is $1,500,000.
LEACHATE RECEIVING OPERATIONS
The leachate receiving operations at the IAWWTP currently take place at the headworks of the
facility (Influent Building). Tanker trucks which transport leachate from the various landfill
sources discharge leachate directly into the influent stream. This mode of operation can create a
shock load to the facility if a high-strength leachate is delivered. The current required location of
the tanker does not provide spill containment during leachate unloading operations.
Alternatives to avoid possible process upsets from these high-strength loads and provide spill
containment have been investigated. The “Pho-Strip” tanks located at the rear of the facility
which were part of the original phosphorus removal process and are no longer used could
provide storage capacity. Stearns & Wheler has worked with the operating personnel to develop
a leachate storage strategy that will provide flexibility and desired containment.
The recommended leachate handling improvements include adding a contained leachate
unloading pad and converting one “Pho-Strip” tank to a leachate storage tank. The proposed
system will have a datalogger to monitor and record leachate deliveries. The leachate storage
tank will be mixed with air and the exhaust air will be passed through an odor control system.
Attached Figure 5-2 shows the proposed unloading pad and storage tank.
The estimated construction cost for a new leachate handling facility is $530,000.
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MISCELLANEOUS STRUCTURAL/ARCHITECTURAL IMPROVEMENTS
Several technical memoranda have been prepared that evaluated existing structural/architectural
issues through the IAWWTP. These memos provide the background of each issue, evaluation of
alternatives, cost analysis, and recommendations for repair. The content of the technical memos
is included in this report. Following is a summary of each memo.
Roof Leaks at Skylights and Other Locations
To address the several roof leaks throughout the plant, a complete roof replacement is
recommended. The estimated cost of complete roof replacement is $400,000.
Digester Brick Repairs
Areas of the brick face on the digester are cracked, spalling, and out of plumb from the tank wall.
Some sections of brick have been removed. Four alternatives to address the brick face failure at
the digesters have been investigated and evaluated. Each is a viable alternative and, depending
on the desired end product and appearance, any alternative can be recommended.
Alternative A is entire brick removal and replacement with an exterior insulated stucco-like
finish. Estimated project cost is $260,000.
Alternative B is removal of brick face, including insulation, and reconstruction with a new brick
veneer with more expansion joints, closer spaced veneer ties, additional weeps, and a soft joint at
the top of the wall. Estimated project cost is $340,000.
Alternative C is manipulation of the existing brick back into proper alignment, installation of
new and closer spaced anchors into the tank wall, saw cut expansion joints, addition of weeps
and saw cutting of a soft joint at the top of the wall. Estimated project cost is $190,000.
Alternative D is removal of brick face, not including insulation, and installing prefinished ribbed
aluminum panels on the tank exterior. Estimated project cost is $130,000.
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Concrete Deterioration - Alkali-Silica Reaction (ASR)
In order to mitigate ASR and prevent concrete damage, it is recommended that the walls be
treated with lithium nitrate. The estimated project cost to treat approximately 40,000 square feet
of concrete surface is about $155,000.
Concrete Deterioration - Cracks and Leaks
There are several cracks which resulted from cold joints, drying shrinkage cracks, or poor
consolidation. Some cracks have sealed and others continue to leak. It is recommended that the
cracks be repaired from the tank exterior. Following repairs, walls can be rubbed to remove
stains and calcium deposits. The estimated cost to repair approximately 2,000 linear feet of
exterior cracks is $240,000.
Miscellaneous Structural Repairs
Areas requiring structural repair include Entrance Structure No. 2 and areas of damaged or
spalled concrete throughout the plant. After evaluation alternatives to repair Entrance Structure
No. 2, it is recommended the structure be anchored back to the main structure. The estimated
cost for this alternative is $13,000. The estimated cost to repair 100 square feet of damaged or
spalled concrete is $5,000.
Administration Building Space Needs
Additional space in the Administration Building for required laboratory activities, meetings,
briefing of tours/visitors, GIS workstation, and records storage. To create additional space, a
building addition is required. It is recommended that a two-story, 24-foot by 61-foot addition be
added to the Control Building. Estimated total project cost for a building addition is $1,100,000.
Figures 6-1 and 6-2 show the proposed Administration Building addition first and second floor
plans.
Concrete Deck Waterproofing
The existing waterproof coating on walkways and gallery roofs has failed. To limit water
penetration into the galleries and provide a non-slip walking surface, a new coating is required to
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be installed. It is recommended that the surfaces be prepared and applied with a non-slip coating.
The estimated cost to install the waterproof non-slip coating is $6 per square foot. Total estimate
for approximately 20,000 square feet is $120,000.
Digester Cover Guide Rail
The floating digester cover has experienced binding and braking of the guides used to keep the
cover plumb during travel. It is recommended that the guide rails be redesigned and
reconstructed with thicker, more robust materials. The guide slide blocks should be replaced with
rollers to minimize friction and binding. The estimated cost to install roller guides and supports
is $25,000.
COST SUMMARY TABLE
ITEM COST
UV disinfection $1,600,000
Septage handling facility 1,500,000
Leachate handling/storage 530,000
Roof leaks at skylights and other locations 400,000
Digester brick repair 130,000 - 340,000
Concrete deterioration (ASR) 155,000
Concrete deterioration - cracks and leaks 240,000
Miscellaneous structural repairs 18,000
Administration Building space 1,100,000
Concrete deck waterproofing 120,000
Digester cover guide rail 25,000
TOTAL
Use
$6,028,000
$6,100,000
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