REVIEW AND ANALYSIS OF THE EXISTING SEWER SYSTEM
AND ESTABLISHMENT OF A REVISED MASTER SEWER PLAN
FOR THE CUPERTINO SANITARY DISTRICT

INTRODUCTION

During the five years since the original District Master Plan was prepared, extensive changes have taken place throughout the area that is served by the Cupertino Sanitary District sewer system. There has been a rapid growth in a number of residential, multiple, and commercial developments. The density in units and population has increased far beyond that anticipated for an area that was formerly thought of as a rural community with a minimum building lot of 10,000 square feet in relative level areas and acre sized lots in hill areas. Triplex construction, apartment construction and the soon-to-be-constructed "high-rise' apartments were not considered for this area, but they are now a fact. The neighborhood commercial centers are being replaced or supplemented by larger developments and the development of industrial parks are in the formative stages.

There are lands outside of the District, but within the future service area of the District where new developments are planned, or where the soil has been overloaded and septic tank failures have occurred.  In these areas and other areas where septic tanks may not function properly, expenditure of funds would be better invested in the construction of permanent sewer systems.

In considering these facts, it is evident that the existing mains may be running full within the next few years. New lines, larger lines and parallel lines will be needed and must be planned for now.

General plans and zoning ordinances of the Cities of Cupertino and Saratoga and the unincorporated areas of the County have been reviewed and considered as a guide as to present and future land usage in order to revise the Master Sewer Plan.

CONTENTS OF THIS REPORT

This report discusses the following subjects that are analyzed and summarized in various tables and exhibits:

ANALYSIS OF THE EXISTING SEWER SYSTEM

An analysis of the existing facilities was made in detail in order to study where extensions, diversions and paralleling of lines are necessary. The various trunks, their velocities and capacities are listed in Table I.

CRITERIA FOR DESIGN OF THE REVISED MASTER SEWER PLAN

The recently adopted General Plans for the Cities of Saratoga and Cupertino and recent County developments, were studied to determine the patterns of land usage and its effect on the sewerage system. Table 2 summarizes these findings and establishes the criteria for design of the Revised Master Sewer Plan.

ANALYSIS OF LAND USE BY TRUNK SERVICE AREAS

Table 3 shows the acreage of various land usage and resulting flows within each Trunk Service Area, and summarizes the same for the entire District.

TABULATION OF THE COMPUTED ULTIMATE SEWER FLOWS

Table 4 integrates the information in Tables 1, 2, and 3, in order to tabulate the ultimate anticipated flows needed to establish the design of the sewerage system and point out where new construction is necessary.

CONSTRUCTION PRIORITY LIST AND RECOMMENDATIONS

The following projects shown on Exhibit "B" are listed in the priority as needed by the District. However because of the timing of particular developments that would aid the financing of certain trunks, the priority order is certainly flexible.

COST STUDY OF THE CONSTRUCTION PROJECTS PLANNED

A study of the costs and methods of financing each project is necessary to establish an orderly plan to extend, divert, and parallel certain District trunks and necessary appurtenances.  Table 5 details the estimated costs of each of the proposed projects. Table 6 summarizes these findings, and also estimates probable financial participation by the District and by others for each project.

SEWAGE OUTFALL AND TREATMENT FACILITIES

Currently, the District has an agreement with the Cities of San Jose and Santa Clara for treatment and disposal of sewage wastes emanating from the District.  The agreement grants the District a 3.4 M.G.D. (average flow) capacity.  Evidence from this report indicates an eventual capacity of 7.9 M.G.D. (average flow) will be needed.

An outfall agreement with the City of Santa Clara is about to be concluded at staff level, and it is anticipated that this agreement between the City and the District will be executed before January, 1965. This will entitle the District to an outfall capacity of 6.8 M.G.D. (peak flow).  Evidence from this report indicates an eventual capacity of 11.8 M.G.D. (peak flow) will be needed.

he current proposed outfall agreement provides that the City of Santa Clara shall install a trunk sewer on Homestead Road from Lawrence Station Road westerly to the District's boundaries that, together with the existing trunk sewer, will provide the District with 6.8 M.G. D. (peak flow).  The District Board should give some thought at this time as to the possibility of increasing the proposed pipe size to handle the ultimate flow of 11 .8 M.G.D. (peak capacity) anticipated. If Santa Clara would agree to this, it would increase the District's outfall participation by about $15,000.

It appears that the District will need additional sewage outfall and treatment facilities sometime between 1970 and 1975. There are certain alternates to consider, but the internal system of the District is so designed that it can conform to various plans that may be investigated. This problem of additional sewage outfall and treatment facilities is of such a nature that it should be considered in a subsequent report.

METHODS OF FINANCING SEWER SYSTEM EXPANSION

In 1962, a District General Obligation Bond Issue for $1,700,000 was approved by the voters. About $833,000 of this amount was paid to the City of San Jose for reserve capacity in the San Jose-Santa Clara Sewage Treatment Plant. At the end of this year about $565,000 will be paid to the City of Santa Clara for reserve capacity in a joint outfalI line to the treatment plant. Other expenses amounted to about $20,000.  The balance of the bond money of $282,000 plus interest earned of $54,000, results in $336,000 available for Capital Improvements on the District's internal system.

Also, the District has been accumulating a surplus in the form of an Unappropri­ated Reserve Account of about $70,000. In addition, this current fiscal year there will be about $60,000 in the Capital Outlay Sewer Construction Account available, and about $40,000 can be set aside in this Annual Budget Account toward construction programs necessary to conform to the Revised Master Sewer Plan.

In summary then, the current funds available and anticipated budget funds total up to the following:

Table 6 summarizes all of the proposed projects and indicates that the probable total cost for the District's share of the additions to the sewer system will be about $568,900.  It, therefore, appears that these projects can be financed on a "pay-as-you-go" basis with current funds available and anticipated annual revenue.

SUMMARY AND RECOMMENDATIONS

The sequence of the suggested priorities is based upon general information available. The timing of Freeway projects, development of certain properties and critical flow information at various points may require adjustment of the sequence of priorities and, therefore, they should be considered as being flexible.

The current trend of land usage results in a higher density and it is important that the District be prepared to supply sanitary sewer service to all properties in the future service area. It is, therefore, recommended that the Board of Directors of the Cupertino Sanitary District adopt this report and time each project to the economic benefit of the whole District.  The District has sufficient bond money and annual construction funds coming in to move forward with the necessary projects. Certain portions of projects may be required in the immediate Future and they can be done at the expense of the District and reimbursed at ordinance rates at time of connection.

It is further recommended that the District Board consider the advantages and disadvantages of increasing the pipe size of the Santa Clara sewer outfall proposed on Homestead to handle the ultimate anticipated peak flows. This plan of action could save future funds, but would limit the choices of alternate plans for ultimate sewage disposal. A subsequent report on additional sewage outfaII and treatment facilities should be considered before 1970.

TABLE 1

ANALYSIS OF THE EXISTING SEWER SYSTEM

(See Exhibits "A" and "B")

*Capacity shown for Force Main was determined from System Curves of the Pump Station and Force Main with both pumps operating.

#Head Loss due to bends, loss of velocity, etc., not calculated arid, therefore, not deducted on Syphons.

TABLE 2
CRITERIA FOR DESIGN OF THE REVISED MASTER SEWER PLAN
(See Exhibit "A")

G. P. D. = Gallons per day
M.G.D. = Million Gallons per day
Peak Flow = Average Flow x 1.50

TABLE 3
ANALYSIS OF LAND USE BY TRUNK SERVICE AREAS
(See Exhibit "B")

LAND USE AND AVERAGE FLOWS IN G. P. D. PER ACRE

TABLE 5

COST STUDY OF THE CONSTRUCTION PROJECTS PLANNED

 DESCRIPTION OF TRUNK                                                                 ESTIMATED COST