City of Morgan Hill Sewer System Master Plan 2017

August 2017

4-8

City of Morgan Hill

Sewer System Master Plan

The trunk then turns south on Monterey Road as a parallel 21-inch and 30-inch to California

Avenue, where it consolidates into the Joint Trunk sewer.

4.3 JOINT MORGAN HILL – GILROY SEWER TRUNK

The C

ity of Morgan Hill’s sewer flows

are collected via the major trunk systems described in the

previous sections, and ultimately flow is conveyed to the intersection of California Avenue and

Monterey Road. At this point, flows enter the Joint Morgan Hill-Gilroy Sewer Trunk, and proceed

west on California Avenue to Harding Avenue. From this intersection, flow continues south on

Harding Avenue, jogging along Highland Avenue and easements in agricultural lands to the city of

Gilroy at Day Road. Flow then jogs through the city of Gilroy and is ultimately discharged to the

SCRWA WWTP.

The Joint Trunk is maintained by a Joint Exercise of Powers Agreement between the City of Gilroy

and the City of Morgan Hill (Appendix A) and dated May 19

, 1992. This agreement establishes

the formation of the South County Regional Wastewater Authority (SCRWA), and includes an

exhibit that documents the pipeline capacities and the capacity allocation for each segment of the

Joint Trunk. The agreement dictates that a 4.0 MGD capacity allocation exist in the Joint Trunk

and a 7.5 MGD capacity reservation in the City of Gilroy trunk system to accommodate Morgan

Hill’s flows.

There have been several studies since the 2002 Sewer System Master Plan that evaluated the

capacity adequacy of the existing Joint Trunk, and the need for construction of the Relief Trunk.

The City of Morgan Hill has initiated construction of the Relief Trunk, and is currently in the

design-build process to connect the Relief Trunk to the trunk system in the City of Gilroy.

4.4 LIFT STATIONS

When routing flows by gravity is not possible due to adverse grades, lift stations are used to pump

flows. The City currently maintains fourteen lift stations in the sewer collection system, as

summarized on

Table 4.2

and shown on

Figure 4.5

Table 4.2

also includes wet well dimensions,

capacity, and holding time of each lift station. Only four of the fourteen lift stations were included

in the hydraulic modeling effort, and due to their location on major trunk systems. The modeled lift

stations are listed as follows:

Lift Station G:

This lift station services the area located along Old Monterey and along

Sanchez Drive to the west. The lift station is located at 8615 Monterey Road. This lift

station includes a duty pump that is rated at 800 gallons per minute (gpm). The pump

discharges into an 8-inch force main that heads south along Butterfield Boulevard.

Lift Station H.

This lift station services the area that is along Llagas Road, east of

Enderson Court, and west of Sanchez Drive. The lift station is located at 320 Llagas Road.

The lift station includes a duty pump that is rated at 500 gpm. The pump discharges into a

4-inch force main that heads southeast along Hale Avenue.