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August 2017
ES-11
City of Morgan Hill
Sewer System Master Plan
peak dry weather flow, 2) peak wet weather flows from storm rainfall Event No. 1, and 3) peak wet
weather flows from storm rainfall Event No. 2
The calibrated hydraulic model was used as an established benchmark in the capacity evaluation
of the existing sanitary sewer system. The model was also used to identify improvements
necessary for mitigating existing system deficiencies and for accommodating future growth.
The hydraulic model is a valuable investment that will continue to prove its worth to the City as
future planning issues or other operational conditions surface. It is recommended that the model
be maintained and updated with new construction projects to preserve its integrity.
ES.8 CAPACITY EVALUATION
The calibrated hydraulic model was used for evaluating the sanitary sewer system for capacity
deficiencies during max day dry weather flows (MDDWF) and max day wet weather flows
(MDWWF). The system performance and design criterion was used as a basis to judge the
adequacy of capacity for the existing sanitary sewer system. The design flows simulated in the
hydraulic model for existing conditions and the general plan buildout include:
x
Existing MDDWF = 2.8 mgd
x
Existing MDWWF = 3.7 mgd
x
Buildout MDDWF = 4.7 mgd
x
Buildout MDWWF = 6.0 mgd
In general, the hydraulic model indicated that the sanitary sewer system exhibited acceptable
performance to service the existing customers during both peak dry weather and peak wet
weather flows. Future flows were then added to the hydraulic model and the existing system was
expanded in order to serve these future customers. The proposed improvements for the future
system are shown with pipe sizes on an overall exhibit on
Figure ES.3
. This master plan also
included a capacity assessment of the Morgan Hill-Gilroy Joint Sewer Trunk.
ES.9 CAPITAL IMPROVEMENT PROGRAM
The Capital Improvement Program includes pipeline, lift station, and pipe rehabilitation projects
recommended in this master plan (
Table ES.5
). Each improvement was assigned a uniquely
coded identifier associated with its basin, and which is used for locating it on
Figure ES.3
.
The estimated construction costs include the baseline costs plus
30 percent
contingency
allowance to account for unforeseen events and unknown field conditions. Capital improvement
costs include the estimated construction costs plus
30 percent
project-related costs (engineering
design, project administration, construction management and inspection, and legal costs).