Memorandum
City
of
City
Manager’s Office
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TO: |
Mayor and City Commissioners |
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FROM: |
David L. Corliss, City Manager |
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CC: |
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Date: |
February 25, 2008 |
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RE: |
Wastewater Utility Improvements and plans for the future |
The purpose of this memorandum is to discuss a proposed 2008 Wastewater
Facilities Master Plan, the initial capacity and timing of the Wakarusa Water
Reclamation Facility (WWRF), and improvements at the Four Seasons Pump Station. The memorandum also discusses delivery method
(design-bid-build, design-build, construction management, etc.).
Based on the recommendations of the 2003-2008 Wastewater Master Plan,
the City has made a significant investment in our water and wastewater
infrastructure. This Master Plan has served its useful life and been the basis
for the City’s Capital Improvement Program for over four years but is based on
a limited amount of technical data that is now over six years old. In addition
to completion of numerous construction projects, actual population growth rates
have fallen below the assumptions used in the Master Plan. Rather than just
studying the initial capacity and timing of the WWRF, a new Facilities Plan should
be prepared to quickly answer the question of WWRF capacity/timing and provide
a new Capital Improvement Program based on a new system model.
Infrastructure Investment
Beginning with the adoption of the 2003 Wastewater Master Plan the
Department implemented a schedule of Capital Improvement Projects (CIP)
designed to replace and rehabilitate aged infrastructure, and increase the
capacities of existing facilities to accommodate growth. The Department has
also taken the lead, or participated in, constructing facilities designed to
extend the sanitary sewer system to areas of growth; most notably to the
northwest and southeast of the City.
With the implementation of the CIP schedule, the Department has
completed over $11 million dollars worth of projects including; the
reconstruction and expansion of three (3) North Lawrence Pump Stations, the
expansion and rehabilitation of Pump Station 16 (6th and Kentucky)
from 8.0MGD to 18.0MGD, the installation of approximately 6,000 linear feet of
gravity relief interceptor in the Yankee Tank Creek Basin, the installation and
rehabilitation of over 4,000 linear feet of gravity sewer in the Alvamar Area,
the replacement of aged sanitary sewers in the 6th & Indiana, 17th
& Massachusetts and 14th & New Hampshire areas, and the
abandonment of Pump Stations 26 and 33 and the redirection of their flows to
nearby gravity sewers. The Department has also completed approximately $3.5
million dollars worth of in situ rehabilitation of over 1,500 manholes and
68,000 linear feet of gravity sewer pipe. Department Staff have also
implemented measures to increase the reliability and efficiency of existing
infrastructure. For example, staff constructed and installed new PLC
(Programmable Logic Controller) control systems at all sanitary sewer pump
stations.
The Department of Utilities, in response to the Northwest Area Update,
accelerated the construction of Pump Station PS48 along with its forcemain and
gravity interceptor. This $12 million dollar facility was designed and
constructed to alleviate current sanitary sewer capacity issues in the Northwest
area of the City, as well as provide for the future development of the area. In
response to this same study the Department also implemented the installation of
larger capacity pumps in Pump Station PS44. The Department is currently
participating in the Douglas County Southeast Area Sanitary Sewer Benefit
District. These facilities, including a new regional Pump Station PS49, will
provide sanitary sewer capacity to the area southeast of
The Department continues to implement needed projects including the
expansion of Pump Station PS25 in the
Technical Data Comparison
The proposed 2008 Wastewater Facilities Master Plan will be based on
improved and more detailed system and flow information than any previous system
evaluation. Over the last several years, the department initiated efforts using
the latest technologies to enhance critical system data acquisition and
information accuracy specifically for this purpose.
In October of 2006, twenty-seven permanent flow meters, four portable
flow meters, and thirteen rain gauges were installed through the collection
system. These devices are providing remote, continuous data collection of
system flows and rainfall. These meters and gauges are distributed throughout
the system and provide for complete and comprehensive information about system
capacity and performance, not just system wide, but for each basin. See the attached
maps for a visual comparison of the location, and numbers, of meters
between the 2003 evaluation and the proposed 2008 evaluation. The data used in
2003 was collected over the spring of 2000 and represented a sampling of only a
few areas. The areas sampled and the resulting analysis assumed the worst-case
infrastructure condition. The resulting flow parameters were then applied
system wide.
Using the latest global positioning systems (GPS) and equipment staff
have acquired extremely accurate information about the collection system
configuration, including determining actual installed slopes of gravity sewers.
The system information includes the entirety of the public system. The system
evaluation effort performed in 2000 (that was the basis of the 2003 plan)
evaluated only the major lines accounting for about 24% of the system. The
currently proposed study will evaluate all of the system. See the attached
chart of pipe sizes.
A summary table representing those differences follows:
Data for Current and Future Master Plans |
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Data Collected in 2000 |
Data currently available -2008 |
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RAIN AND FLOW DATA |
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Number of meters |
7 |
32 |
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Number of rain gauges |
4 |
13 |
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Total days monitored |
70 |
> 510 |
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Period evaluated |
April-June 2000 |
Oct 06 - Current |
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Number of data points |
45,000 |
>2,000,000 |
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Basins evaluated independently |
4 |
25 (all) |
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COLLECTION SYSTEM DATA |
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Collection system liner feet |
1,886,000 |
2,097,000 |
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Collection system liner feet modeled |
464,000 |
2,089,000 |
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% of system to evaluate |
25% |
100% |
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System configuration assumptions made |
Yes |
No |
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These flow metering and GPS efforts in combination provide a level of
detailed information far beyond what was used in the 2003 Master Plan. This
level of information will allow for a more efficient and accurate determination
of system capacity and maintenance problems. This data will also be an asset in
the development of a very accurate capital improvement program now and in the
future.
Population Growth Rates
The Master Plan used population growths rates that ranged from 2.0% to
2.7% to predict the population from 2000 to 2050. The average population growth rate from 2000
to 2007 has been 1.66% compared to the Master Plan estimate of 2.2% for the
same period. However, since 2005, the average growth rate has been less than
1.0%. As indicated in previous memos, with an average population growth rate of
1% the City’s population will not exceed 100,000 until 2017 as opposed to 2010
as projected by the Master Plan. The
growth rates for the proposed Facilities Plan will have to factor in the recent
economic slow down in order to provide an accurate forecast of future utility
needs for the city.
Wakarusa Water Reclamation
Facility
The Master Plan demonstrated the need for the WWRF. However, the
difference in growth rates noted above may have an impact on the initial size
and timing of construction of the WWRF. With the flow data and system asset
information that is available, once a model is completed and growth projections
set, it will be relatively easy to look at initial capacity and timing of the improvements
for the WWRF. If the recommendation is either to begin construction immediately
or to delay construction to a future date, the City is well positioned for the
construction of the WWRF, with land acquisition, land use approvals and
regulatory approvals in place. We have the ability to proceed to final
design and construction for this facility at the appropriate time.
Four Seasons Pump Station
While a new Master Plan is being prepared, there are immediate
improvements needed at the Four Seasons Pump Station facility, generally
located west of Kasold near
Delivery Methods: Design/Build
and Design-Bid-Build
City Commission direction on the delivery method for these important
projects is desired. The selection of a delivery method for public
infrastructure involves a number of important public policy issues and
priorities. Typically, the City has followed the Design-Bid-Build system,
whereby the City selects a design engineer to provide a full design of the
project, the project is publicly bid, and the bid is awarded to the lowest
responsible bidder. This system places a
high value on the competitive bidding process to provide evidence that public
funds are appropriately spent and allocated.
The separation of responsibilities between the design consultant and the
contractor is also viewed as a positive check on roles, although advocates for
design-build point out that it can create unnecessary and costly situations in
the execution of a quality and timely project. Advocates of design-build
highlight the value of timely production of the public infrastructure because
certain phases of a project can be initiated without the necessity of complete
construction documents. In fact, the
cooperation between the design consultant and the contractor is viewed as a
positive factor in reducing both time and cost in a public project. Design-build typically includes portions of a
project which are not competitively bid but instead self-performed by the
design-build contractor. The
Design-Build team presents a guaranteed maximum price (GPM) which includes both
bid and non-bid items. A difficulty with
a GPM from the Design-Build team can occur if the proposed price is not
acceptable to the owner, or if there is a concern in publicly justifying
non-bid portions of a GPM.
We have successfully used Design-Build when the importance of producing
a timely infrastructure improvement was a significant factor and plan to
recommend this method in the future in appropriate situations. We further
recommend that our purchasing policy and ordinances be amended to better
reflect this delivery method for construction projects.
Commission discussion and direction on this issue is desired. To some
extent, the selection of a delivery method is based on the weighing of the
importance of competitively bidding all portions of a project versus the
potential for value savings and time savings with a combination of the design
consultant and the contractor. Either
method can be effectively used by the community and will be efficiently and
effectively implemented by City staff.
Recommendations
With changes in community growth patterns and projections, the
completion of construction projects identified above and with new and more
comprehensive technical system data, staff recommends preparing a new 2008
Wastewater Facilities Master Plan. The new Facilities Plan will review the
timing and scope of the WWRF; provide a model of the entire wastewater system
using the enhanced system data and update of the Capital Improvement Program
based on the new model information. Staff also recommends proceeding with the
improvements to the storage capacity at Four Seasons Pump Station.