Facility Expansions and Modifications

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By the early ‘80s, the Joint Use Plant was operating at its design capacity.  Service Area growth at the time was high and the state threatened a tap moratorium in the cities service area.  A moratorium would have halted residential construction.  The cities avoided the moratorium by returning the old Englewood WWTP to service.  A quick rehabilitation of the plant was designed and constructed in 1982.  The project added 5 mgd capacity at a cost of $1,600,000.


The threatened moratorium was caused by a shortfall in plant capacity and the inability of the plant to consistently meet discharge limitations.  The capacity shortfall was created in the planning stages of the original Joint Use Plant.  An early plan identified the need for 35 mgd treatment capacity.  The capacity would be provided by building a new 20 mgd plant and keeping the two old 15mgd treatment plants in service.  Keeping the old plants in service conflicted with the intent of not upgrading the old plants and was deleted from the plan.  The lost capacity was not replaced in the new plant design.


In 1982 the cities entered a contract management arrangement at the plant.  The director and superintendent were contract employees and the remainder of the staff continued as city employees.  The purpose of contract management was to gain technical expertise and improve treatment efficiency and cost control.  Several of the organizational improvements made are still in use today.  Several major projects were also completed.  Contract management was discontinued in 1985.


The solids handling building was modified in 1984.  Solids handling at this location included sludge thickening before the digesters and sludge dewatering before disposal.  Neither of the original systems functioned properly and were replaced with the present system of high-speed centrifuges.  The centrifuges are second-hand equipment that had never been used and were purchased from New York City.  The project cost was $1,515,000.


Additional work was completed at the Englewood WWTP in 1985 to increase treatment capacity.  A secondary process was installed to add 3 mgd.  The cost was $2,166,000 and total Bi-City plant capacity was then 28 mgd.


At the same time as the Englewood expansion, an expansion to the Joint Use Plant was being engineered and constructed.  The project modified and expanded the secondary treatment process, as well as making some other improvements in other process areas.   Seven (7) mgd capacity was added at a project cost of $5,657,000.  Total Bi-City plant capacity was increased to 35 mgd.


Up to this time, the plant could not reliably meet permit effluent limitations.  The facilities work done while under contract management resulted in improvements to the compliance record and no fines were issued; however, permit violations were experienced two to four times per year.  With the completion of the temporary rehabilitation to the Englewood WWTP and other solids handling modifications, the compliance record improved dramatically.  Permit conditions were met consistently until the requirements for ammonia removal were included in 1992.


An addition to the Administration Building was completed in 1985.  The addition contained men’s and women’s locker rooms and an operations center.  The facilities added in this project were improvements to the existing building, but did not meet the needs of the facility.  The addition was subsequently modified to provide more useful space.  The project cost was $450,000.


Each city maintained an Industrial Pretreatment Program to control industrial discharges to the treatment plant.  The EPA was not satisfied with the performance of either program and, in 1986, issued an administrative order of consent to the cities.  The order required the cities to improve the programs or face severe penalties.  The two programs were consolidated at the plant with the creation of the Industrial Pretreatment Division.  Division personnel are responsible for maintaining the program in each city’s service area, while each city retains oversight and enforcement authority.  Since program consolidation at the plant, the program has been recognized as outstanding by the Region VIII EPA office.


The need for ammonia removal from plant effluent was identified by the state in the early ‘80s.  Ammonia is toxic to aquatic life and the plants effluent discharge reportedly caused the water quality standards for ammonia to be exceeded.  The state agreed to provide a temporary modification to the standard in 1982.  The modification allowed the cities time to obtain water quality information on the river and determine an adequate effluent limitation for ammonia.  The temporary modification was extended several times and the ammonia limitations were established in the discharge permit renewal cycle around 1990.


The number of plant expansions, and rehabilitation’s, coupled with the need for additional treatment, were the driving forces behind a long range planning effort that began in 1988.  Requests for proposals and interviews for an engineering consultant led to the selection of Brown & Caldwell Engineering Consultants to perform the plan.  The plan was developed as a 201 Facilities Plan, which takes a long-term look at facility needs in accordance with EPA regulations and guidance.  The plan identified the work needed to meet requirements by the year 2015 and focused on achieving:


1. Permit Compliance

2. Public and Worker Health and Safety

3. Odor Prevention and Control

4. Optimizing Capital and Operating Costs


The work to meet needs was divided into three phases:


Phase I - Facilities needed by 2010

Ia - immediate process and system replacement needs

Ib - process and replacement needs that could be deferred, and

Ic.- future capacity needs

Phase II - Facilities needed by 2040 (more of a guesstimate for this period of time), and

Phase III - The ‘maximum’ treatment capability at the existing site.


The plan was formally approved by the City Councils of Littleton and Englewood in 1989 and the implementation of Phase Ia began.  The major objectives of Phase Ia was to rehabilitate worn out equipment, phase out operation of the Englewood WWTP, convert the secondary treatment process, eliminate or control 95% of the odors generated at the facility and add ammonia removal systems.  The project took over a year to design and almost two years to construct.  It severely impacted over 90% of the processes at the plant and, for a period of several months, involved the entire plant site.  The project was completed in 1991 with a final cost of $26,300,000.  


The Phase Ia construction project was financed through the State Water Pollution Control Revolving Fund.  The revolving fund replaced the EPA Grant Program and is a continuing funding mechanism for wastewater projects in the state.  The loan is at 4.65% interest and as the loan is paid back, the funds will be made available for other projects at other facilities.


During construction of Phase Ia, a floating digester cover required replacement.  The 85-foot diameter ‘boat floating on sludge’ failed in service and sank into the digester.  Replacement of the cover was accomplished during the Ia construction period at a cost of $650,000.


The new ammonia removal process was brought on-line in 1991.  Startup of the new process was generally on track for permit compliance until the summer of 1992.  During the summer, the most stringent ammonia limitations come into effect and start up of the system reached a plateau at an ammonia removal level that did not meet permit limitations.  The staff and Brown & Caldwell worked during this time to improve system performance and in November 1992, system performance achieved design expectations.  The State was notified of the non-compliant operation of the system and staff was led to believe no formal enforcement action was to be taken for the non-compliant operation.  However, in 1993, the State decided to proceed with enforcement action, even though the system start up problems had been corrected and water quality standards in the South Platte River had not been exceeded.