City of Morgan Hill Sewer System Master Plan 2017

August 2017

4-1

City of Morgan Hill

Sewer System Master Plan

2017

City of Morgan Hill

4.0

CHAPTER 4 - EXISTING SEWER COLLECTION FACILITIES

This chapter provides a description of the City’s existing

sewer system facilities including gravity

trunks, force mains, lift stations, and sewer collection basins. The chapter also includes a brief

description of the SCRWA Wastewater Treatment Plant.

4.1 SEWER COLLECTION SYSTEM OVERVIEW

The City provides sewer collection services to approximately 10,000 residential, commercial,

industrial, and institutional accounts.

The City’s

modeled collection system consists of

approximately 160 miles of up to 30-inch gravity sewer pipes that convey flows, via the Morgan

Hill-Gilroy Joint Trunk, towards the South County Regional Water Authority WWTP, on Southside

Drive in the City of Gilroy, as shown on

Figure 4.1

A system-wide pipe inventory, listing the total length by pipe diameter, is shown on

Table 4.1

This table is based

on information extracted from the City’s GIS. The 8

-inch to 15-inch diameter

pipes account for 55 percent of the total sewer pipe lengths.

4.2 SEWER COLLECTION BASINS AND TRUNKS

Due to topography, the sanitary sewer system is divided into five separate dendritic sewer

collection basins, each defining the boundaries of a sewer collection trunk system. The following

6 major sewer collection basins were created and shown on

Figure 4.2

: the Butterfield Trunk, the

East Dunne Trunk, the Hale-Llagas Trunk, the Hale-Monterey Trunk, the Hill

—

Barrett Trunk, the

Llagas Trunk and the Railroad-Monterey Trunk. The sewer trunk system for each collection basin

is shown on

Figure 4.3

, and a schematic diagram intended to simplify the connectivity between

the basins and trunks is shown on

Figure 4.4

4.2.1

Butterfield Trunk

This trunk starts at the intersection of Cochrane Road and Butterfield Boulevard as a 20-inch

gravity main in a southbound direction. The main then follows Butterfield Boulevard before

increasing to a 24-inch diameter main just south of the intersection of Jarvis Drive and Butterfield

Boulevard, and continues south along Butterfield Boulevard. The Butterfield Trunk ends at the

intersection of San Pedro Avenue where it turns west and discharges into the Railroad-Monterey

Trunk.

4.2.2

Llagas Trunk

This trunk starts west of the intersection of Sanchez Drive and Monterey Road as 15-inch gravity

main. The main continues westerly before reaching Del Monte Avenue where it turns south