HomeMy WebLinkAbout3.0 PC Staff Report 08.12.1998REQUEST:
PC 8/12/98
PROJECT INFORMATION AND STAFF COMMENTS
Site Application for Approval for
Expansion of Domestic Wastewater
Treatment Works
APPLICANT: West Glenwood Sanitation District
ENGINEERS• Schmueser Gordon Meyer, Inc.
LOCATION: A site located in the SE1/4NW1/4
Section 6, T6S, R89W; located
adjacent to the west side of
Glenwood Springs, near the West
Glenwood I-70 Interchange.
I. RELATIONSHIP TO THE COMPREHENSIVE PLAN
The Garfield County Comprehensive Plan of 1995 identifies this area of the
treatment facility as a Low Density Residential - 10 ac. or more per d.u., due
primarily to the floodplain area.
II. DESCRIPTION OF THE PROPOSAL
It is proposed to expand the West Glenwood Sanitation District wastewater
treatment facility approved flow capacity of 0.375 MGD to 0.750 MGD. The
existing facility is treating effluent for 706 EQR, which includes both resinti
commercial users in the West Glenwood area. (See application pgs. �° )
The District is proposing to expand the treatment facility to deal with the growth
in the area and the transient population of the area resulting from the motels and
hotels. The proposed expansion will essentially duplicate the existing facilities,
part of which are in the City Limits of Glenwood Springs and part are in the
unincorporated area of the County. The District has purchased or acquired
additional property to the east of the existing facility, but within the City. They
acknowledge that it would be more appropriate to create a regional facility for the
District and the City, but have found that it is fiscally premature for the
development of such a facility at this time.
III. MAJOR ISSUES AND CONCERNS
A. State Statutes: C.R.S. 25-8-702, 1981, defines the parameters by which
the Colorado Department of Health, Water Quality Control Division can
review and approve or deny a site application for sewage treatment works
(See application form included in overall application). The applicant is
required to obtain a recommendation of approval, denial or no comment
from the County Planning Commission, County Board of Health, County
Board of County Commissioners and various other local and regional
agencies.
Garfield County's involvement in the process is to determine whether or
not the proposed wastewater treatment works are consistent with "the
long-range comprehensive plan for the area as it affects water quality and
any approved regional wastewater management plan for the area". The
Comprehensive Plan identifies the as an urban area, with the exception of
the areas along the Colorado River floodplain, which are Low Density
Residential. This designation is due primarily to the floodplain issues.
The West Glenwood Sanitation District has considered the consolidation
of their facilities with the City of Glenwood Springs, but determined that it
is not economically feasible at this time to consolidate.
Ultimately, the Colorado Department of Health and Water Quality Control
Commission will determine whether or not the proposed wastewater treatment
facility and site are appropriate as proposed. The Garfield County
Comprehensive Plan provides some guidance in terms of developers connecting
into existing systems "when economically feasible". It would appear that it is
economically infeasible to construct a regional facility at this time and meet the
needs of the district . So, in terms of the Comprehensive Plan policy, the
proposed site meets the intent. In terms of the Plan objective to "discourage the
proliferation of private water and sewer systems and special districts", the
proposed facility was an existing site at the time the Comprehensive Plan was
developed.
VI. RECOMMENDATION
That the Planning Commission recommend approval of the site application with
no additional comment.
DESIGN MEMO FOR WEST GLENWOOD SANITATION DISTRICT
BACKGROUND
The West Glenwood Wastewater Treatment Facility, (WWTF), has been in existence since
1963. The existing WWTF is an extended aeration activated sludge process. The plant was
constructed in two major phases. Phase 1, completed in 1963, included the aeration basin,
secondary clarifier, aerobic digester and chlorine contact structure. Phase 2, completed in
1983, added the pretreatment facilities, grit removal, sludge handling and diffused aeration
equipment. The sludge dewatering facilities were added in 1991 and 1997.
The service area is shown on the attached map. The area encompasses the residential
sections just north west of the plant continuing up the Mitchell Creek area then going east to
include the Sunny Acres Development then south to the intersection of Hwy. 6 & 24 and
Donegan Road. The Oasis Creek Development is excluded but the Oasis Creek Commercial
Core is included in the West Glenwood Sanitation District Service Area. An additional service
area is located south of the Colorado River that encompasses all of the businesses located on
Devereux Road, west of the City of Glenwood Springs substation. The community north of
the river is approximately 70 percent developed with primarily single family residential
housing. There is a commercial area which includes restaurants, retail and automobile
dealerships along the north side of Hwy. 6 & 24. The areas south of the new Midland Avenue
bypass are included in the service area. It is initially assumed that this area will remain
commercial but the possibility does exist that there will be mixed zoning. Strong interest is
already being shown for the property to the south of the Colorado which will have an
immediate impact on the West Glenwood Sanitation District plant as this is the facility most
likely to serve the area.
Currently the residential population of the service area is approximately 1223. The residential
population along with the commercial development results in an average total of 706 EQR.
The commercial sector has a number of motels and hotels. This transient population causes
a fluctuation in the number of EQRs that the District plant services. Please see the attached
flow/loading table for the monthly figures for the past four years. The existing facility
currently has a design capacity of 375,000 g.p.d. This expansion will increase plant capacity
to 750,000 g.p.d.
This expansion will increase plant flexibility for operations and maintenance by having a
secondary system whereby one aeration basin or one clarifier can come off line for repairs and
maintenance without shutting down the entire plant.
SCOPE
The scope of this expansion is to design a facility that will accommodate a flow rate of
750,000 g.p.d. The anticipated design will in essence duplicate existing processes. All
equipment will be doubled with the exception of the sludge handling system. A new vacuum
filter and sludge dryer have recently been installed. The plan is also to convert from a chlorine
disinfection system to a U.V. system. Extensive electrical upgrades for controls are included
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in the expansion design with an entire room devoted to operational controls for all aeration
equipment.
It is anticipated that construction can start as early as this Summer with a duration of twelve
months. With this schedule the plant will be able to handle the growth that has begun on
Devereux Road and the Gilstrap parcel, immediately adjacent to the plant. Development in the
area has traditionally followed a pattern of rapid acceleration once one or two developments
have begun. There is also strong interest in the Wulfsohn property south of the Midland
Avenue Bypass that is anticipated to be served by the West Glenwood Sanitation District.
Also with this schedule the District is allowed the luxury of a well planned and executed
project rather than a rush crisis project in order to meet immediate demand. A better project
will be the result.
In 1996 the electorate of West Glenwood voted to approve a bond issuance of $2,100,000.
This bond money has been used to upgrade the plant, purchasing the upgraded vacuum filter
and dryer units. There is currently $1,500,000 allocated for the construction of this requested
expansion. With the district serving as General Contractor for this project the costs associated
with this expansion have been greatly reduced.
APPLICABLE CODES AND REGULATIONS
The project will be subject to the following codes and regulations:
1. 1988 Uniform Building Code (UBC)
2. 1988 Uniform Mechanical Code (UMC)
3. 1988 Uniform Plumbing Code (UPC)
4. 1988 Uniform Fire Code (UFC)
5. 1993 National Electric Code (NEC)
SITE DATA
The site is located on the northern bank of the Colorado River approximately 3 miles west of
downtown Glenwood Springs. Currently the FEMA mapping falls short by approximately 1000
feet. As a part of the Gilstrap Enterprises Subdivision, floodplain mapping was done to the
current site. As the site is situated 20' above the high water mark of the Colorado River, we
do not anticipate any floodplain issues. Access to the site will remain as is, a service road.
Property is currently being obtained in order to allow the expansion of the plant to go in an
easterly direction as there is no room for expansion both at the existing site or to the west of
it. Only commercial development is proposed for the property east of the planned plant
expansion. That development was completed this Spring.
The District is currently pursuing a purchase agreement with Lot 12 of the Gilstrap Subdivision
and the Department of Transportation in order to obtain the property immediately east of the
current site.
There are no other natural or geological hazards in the area.
The West Glenwood Sanitation District currently owns the site the existing plant sits on.
Please find attached a copy of the deed. There are currently two separate parcels that West
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SCHMUESER GORDON MEYER INC
Glenwood Sanitation District (WGSD) is acquiring. The first is Lot 12, Gilstrap Enterprises
Subdivision, and the second is a parcel directly north of Lot 12. This second parcel originally
belonged to the Colorado Department of Transportation (CDOT). CDOT deeded this parcel to
the City of Glenwood Springs (GWS) for use as a public Right of Way for access to the
Gilstrap Subdivision. Before it may be purchased by West Glenwood Sanitation District, the
parcel must be deeded back to CDOT from GWS. The parcel will then be appraised, and then
sold to WGSD. Both of these parcels are in the process of being acquired, and there is no
problem anticipated at this time.
PROCESS DESIGN CRITERIA
Influent BODS = 250 mg/I = 1561 lbs. per day
Influent Suspended Solids = 250 mg/I = 1851 lbs. per day
pH = 6-9 (The yearly average is 7.2)
Wastewater Temperature (Effluent)
Summer 60 degrees F
Winter 50 degrees F
Facility Capacity
The facility shall be designed to treat a flow of 750,000 g.p.d. This is based on projected
flows from anticipated growth in the current service area. This has been arrived at using
demographic studies from the City of Glenwood Springs. Attached please find a table that
indicates growth and associated EQR and flow levels.
Water Quality Discharge Parameters
The proposed facility expansion will continue to discharge to the Colorado River. This portion
of the Colorado River is classified for Aquatic Life Class 1 (Cold), Recreation Class 2, Water
Supply and Agricultural. It is expected that the discharge parameters will remain the same as
in previous discharge permits. The existing discharge limitations are as follows:
Maximum Maximum Maximum
Monthly Avg. Weekly Avg. Daily Avg.
Flow-mgd 0.375
BOD5-mg/I 30 45
TSS-mg/I 30 45
F. Coliform- #/100 ml 6,000 12,000
Total Chlorine- mg/I 0.5
pH - s.u.
SCHMUESER GORDON MEYER INC.
6.0-9.0
DESIGN CRITERIA FOR UNIT PROCESSES
Headworks
1. Bar screen: The existing bar screen is adequate to .75MGD. However, an automatic
bar screen with a screenings press is being considered for installation to supplement
the existing bar screen. The screenings press is required in order to meet federal
landfill regulations that requires that the waste be 25% solids. Also, only with a
screenings press can the waste pass the paint filter test initiated at the dump.
2. Grit System: The existing grit classifier is adequate to .75MGD. It is not recommended
that it be changed at this time.
3. Grit Pump: The Wemco Model C torque pump is adequate to .75MGD. It is not
recommended to be changed at this time. However, a second pump will be considered
for redundancy purposes.
4. Grit Chamber: The current size is 2000 gallons. The dimensions are 8"x10"x4". An
additional grit chamber is needed for .75MGD. It is recommended that the grit chamber
be mirrored with the addition of the second grit pump.
Aeration Process
5. The existing plant currently has (3) 40 HP blowers carrying the load of the aeration
basin and the digester. With the addition of the second aeration basin we would add
(2) 50 HP Huffmans in addition to the existing blowers. This should be sufficient to run
the entire plant. If more air was necessary there could be a 30 HP blower available.
6. Aeration Basin: In order to bring the plant capacity up to .75MGD an additional aeration
basin is needed. The design calls for duplication of the exiting basin. Again a second
aeration basin would enable the operator to take one off line while maintaining
processes. The diffusers would be replaced in the existing basin to optimize this
process. The existing aeration is a circular tank of 60' diameter. It has a depth of 15'
with a 2' freeboard with a volume of 295,000 gallons. This allows a detention time
of 18 hrs. There are also plans to extend the center wall to facilitate detention which
would extend the detention time to 24 hours. The new Aeration Basin will be
rectangular, 40' wide X 63' long X 15' deep. The Basin will be rectangular instead of
circular in order to minimize impact to the river bank.
Clarification
7. Clarifier: The existing clarifier is 25 years old. It is recommended that the drive
mechanism be replaced as well as sandblasting and painting all submerged and
nonsubmerged equipment. It is also recommended that an improved oil and grease
skimming device be installed accompanied with installation of a progressive cavity
pump for pumping scum from the scum pit to the digester. This should be installed in
the pump room. A new clarifier is a minimum requirement for redundancy reasons
alone in order to facilitate repair and maintenance of the old clarifier. It would be a
duplicate of the existing unit. The current configuration is a 40' diameter tank with a
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12' depth and a 2' freeboard. The surface area is 1257 sf with an overflow rate of
196 gal/sf/day. The weir is an exterior outside weir with a length of 126' and an
overflow rate of 1964 gal/ft/day. The new clarifier configuration will use a design
overflow rate of 298 gal/sf/day for the surface and for the weir it will use a 952
gal/ft/day rate. This unit would also be equipped with stanford, density current baffles
with a full trough around the perimeter.
Disinfection Eauioment
8. Due to the inadequacies of the present chlorine system to accommodate expansion and
the problems in general with a gas chlorination system the design calls for a conversion
to a Ultraviolet disinfection system. It will be a vertical tube system with two modules.
The existing chlorine contact chamber will be modified to contain the UV system. The
two UV modules will be placed in a series within one portion of the chamber. In the
channel immediately adjacent to the channel where the units are placed there will be
a place for the cleaning and maintenance of each unit. There will be a hoist located on
the concrete wall for lifting and placing the units either in their assigned place or in the
cleaning channel.
Effluent Measurement
9. The existing effluent flume an measuring devices are adequate for .75MGD. However,
the device needs to be adjusted as to bring it out of its currently submerged state. This
may be partially due to the 8" pipe located at the outlet. It is recommended that this
configuration be changed in order to facilitate flow away from the device. It is
suggested that there be a simple open channel to replace the closed pipe or placing a
manhole immediately after the parshall flume. If a conversion to UV disinfection takes
place then the floor of the UV chamber will be raised two feet to allow for head loss
through the UV system.
Solids Handling
10. The current digester is adequate for the processes of the plant. The Wyss fine bubble
diffusers in the digester have all been replaced as of December 1996.
11. A new ALAR Auto Vac dewatering and thermal dryer unit have just been installed in
the plant. These new units are sized to accommodate the .75MGD requirements. This
upgrades the plants technology to produce up to a 95% solids ash compound. This ash
is virtually free of pathogens and can be used in a Class A disposal program.
The throughput control consists of measurement of the effluent via a parshall flume with an
ultrasonic level detector and a chart recorder and measurement of the return sludge and waste
activated sludge. Currently this system is used as there is no satisfactory way to measure the
influent. All of the effluent recorded measurements are summarized in the Districts Monthly
Reports to the Department of Public Health and Environment.
SCHMUESER GO ON MEYER, INC
ANALYSIS OF TREATMENT ALTERNATIVES CONSIDERED
On a regional basis, two distinct alternatives were considered. Those included expansion to
the existing facility and, secondly, the construction of the regional facility serving West
Glenwood and the City of Glenwood Springs Service Area. Currently, the City of Glenwood
Springs wastewater treatment facility (WWTF) has a design capacity of 2.3 MGD. Current
flows average approximately 1.0 MGD. The City of Glenwood Springs original 201 Facility
Plan, a subsequent 201 amendment and, finally, a report prepared by SGM on the southern
service area conclude that a service area for Glenwood Springs will require a 2.3 MGD facility.
The flows to the Glenwood facility have essentially leveled off between 0.8 and 1 MGD for
the last five to ten years. The plant has experienced only minor flow increases. Given the
historical growth rate and the proposed growth rate as suggested by the Southern Service
Area Master Plan, a plant size of 2.3 MGD is still more than adequate for a 20 -year projection.
It is not economically feasible at the present time for the City of Glenwood Springs to consider
consolidation. The cost of a new treatment facility, associated interceptor sewers and
pumping station would cost in excess of $10 million. The City of Glenwood Springs citizens
have invested in an existing facility which has adequate capacity at the present time and will
so for the foreseeable future. Nonetheless, the City of Glenwood Springs has proceeded with
the purchase of the Chatfield Ranch property, one of the uses of which would be a regional
WWTF in the future.
The need for the expansion to the West Glenwood facility, however, is immediate. Flows at
times in the last two to three years have reached the plant capacity. The District is
experiencing growth and will continue to experience growth in the future. The West Glenwood
plant presently does not have redundancy in the major processes. There is only one aeration
basin and one clarifier which does not allow the operator to take the existing basins off line
for proper maintenance. The expanded facilities will allow the plant operator to repair the
existing facilities now and into the future. For these reasons, this plant expansion is being
proposed at this time. The expansion at the present site is the most economically feasible at
the present time.
The existing processes within the West Glenwood plant have served the District well. The
plant has consistently met the discharge limitations set forth for discharge to the Colorado
River. The aerated grit chamber, extended aeration activated sludge process and secondary
clarifier are all conventional processes for a small WWTF (i.e., below 1 MGD). Therefore, the
proposed expansion will include the addition of processes similar to the existing conditions
with the addition of one new aeration basin and one new secondary clarifier. In addition,
aerated grit chamber facilities will be expanded and a mechanical bar screen will be added.
The one change, however, to the existing process is in the disinfection process. Currently,
disinfection is through gas chlorination and conventional chlorine contact structure. For capital
cost and long term 0 & M cost reasons, the District has opted to include ultraviolet
disinfection. It is believed that this process will allow the District to meet discharge limitations
for fecal coliform and, at the same time, limit chlorine discharge.
Other processes, i.e., oxidation, ditches, aerated lagoons, etc., were not considered viable
because of the lack of available space and high initial up front capital costs. Conventional
activated sludge was not considered because the present operations staff is comfortable with
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the extended aeration process in that it is more forgiving to fluctuating flows, is less
susceptible to upset conditions and is easier to operate. This is very typical for small facilities
less than 1 MGD.
FINANCIAL AND OPERATIONAL ARRANGEMENTS
The West Glenwood Sanitation District is a quasi municipal entity that was incorporated under
the Special District Act of Colorado. It has a Board of Directors, a District Manager, and two
operators. Additional labor is hired on a part time basis as required.
With this expanded plant the operational needs do not increase. Only two operators will
continue to be needed to run the plant. This is as a result of the update to the sludge
processing operation. It is less operator intensive than the existing system. Therefore, the
additional time saved can be applied to the running of the plant. Also, the addition of the room
that contains complete operating controls substantially cuts down on operating time due to
the fact all of the controls are located in one place and can be manipulated without extra time
spent going from one area of the plant to another.
As the plant is self contained, the only outside contracts required are the agreements that deal
with sludge acceptance. Again, with the placement of the sludge handling upgrade these
contracts will be expanded and changed according to the quality of sludge produced. There
are no pretreatment requirements therefore, no pretreatment contracts are required. These
rules and regulation were adopted effective June, 1997.
The financial system and budget is already in place to operate a larger facility. Income is
derived through tap fees, user fees and mill levies. Tap fees from the new growth stimulated
by the opening of the Midland Avenue Bypass will accommodate any increase in operational
costs over the life of the plant. Attached please find a copy of the Districts budget for 1997.
CONCLUSION
The District feels that this is an opportune time to proceed with a plant expansion. It allows
incorporation into a regional plant at a later date and it allows the steady growth experienced
by The City of Glenwood'Springs, in particular the West Glenwood area, to continue without
moratoriums on building permits due to the inability of the Sanitation District to serve the
populace.
The District asks that this application be approved. •
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