B2_DRAFT_03.4_Section_C_AppendixC_SLAC_Design_Procedures_Sewer_Services.pdf

DESIGN PROCEDURES - NEW SEWER SYSTEMS

February 24, 2025

DESIGN PROCEDURES FOR NEW SEWER PIPING AND SERVICES

The following criteria have been established by SLAC Civil Engineering (SLAC CE) to guide consulting engineers in preparing studies, reports, and design documents for capital improvement and maintenance projects. Conformance to these guidelines is required, and these criteria should be considered as minimum design requirements. The DESIGN ENGINEER shall strive to identify potential problems at the earliest stage and meet with SLAC CE to develop or present alternative solutions during the project’s preliminary engineering phase. The planning and design of sewer facilities shall conform to the California Plumbing Code and to SLAC Technical Standards.

These standards apply to the design and construction of the sewer system only.

SLAC discharges on average approximately 43,000 gpd of wastewater via approximately 10-miles of sewer line (including 1-mile of force main). Wastewater must follow volume and water quality requirements set by West Bay Sanitation District, Silicon Valley Clean Water, and the California State Waste Discharge Requirements, administered by the San Fracisco Regional Water Quality Control Board. To date, we operate approximately sanitary 16 lift stations on the SLAC campus.

General Requirements and Process

1. SLAC’s Project Manager shall schedule an initial meeting with SLAC CE to review project sewer utility requirements and design guidelines prior to preparing and submitting plans for cost estimating or outside regulatory review.

2. Designs shall comply with current California Regional Water Quality Control Board, California Plumbing Code (CPC), California Code of Regulations (CCR), San Mateo County Health Department, and SLAC Facility Design Standards.

3. The sewer system layout shall be approved by SLAC CE.

4. Minimum size gravity main shall be 6-inches in diameter and sized for the design flow.

5. Size and slope sewer services according to CPC requirements and will be shown in both plan and profile on the design plans. A hydraulic profile will also be provided in the plans.

6. Do not run a 4-inch service line more than 100 feet from a manhole.

7. Maintain a minimum cover of 4-feet wherever vehicle traffic crosses the proposed alignment.

8. Separate sanitary sewer service lines per California Code of Regulations (CCR) Title

22, division 4, chapter 16.

9. Calculations or computer modeling may be required for sizing more complicated sewer systems and for evaluating the impact on the existing systems, as determined by SLAC

CE.

DRAFT

10. SLAC sewer mains will remain accessible for maintenance and repairs, as well as protected in delineated paved roadbeds for identification, monitoring, and future accessibility.

11. Under no circumstances will sewer mains or service laterals be conveyed under building foundations or permanent structures.

12. Sanitary sewer main and service line 4-inch through 8-inch shall be polyvinyl chloride (PVC) SDR 26 Geen sewer pipe and shall conform to ASTM D 3034-73 with bell and spigot connections. Elbows, 22.5 degree and 45 degree are allowed and 90 degree and tee’s are prohibited.

13. Cleanouts will be placed within 10-feet of a building connection and at every directional turn.

Sewer Demand Projection and Design Calculations (Pipe and Lift Stations)

Design calculations submitted for SLAC CE review shall be in a neat, acceptable form, and shall indicate the date, signature of the supervising engineer, and their State of California Engineering Registration Number and expiration date.

Prepare calculations of estimated wastewater demands for review and approval by SLAC CE.

Calculations should include estimates for:

a. Infiltration: The infiltration allowance for areas to be served shall be 600 gallons per acre per day or 500 gallons per inch diameter per mile per day whichever is larger.

b. Inflow Sources: No inflow sources which include rainwater, stormwater, groundwater, street drainage, subsurface drainage, roof drainage, yard drainage, and water from yard fountains, ponds, lawn sprays or any other uncontaminated water shall be discharged into the public sewer. Design will provide SLAC with a hydraulic loading calculation for all new facilities to demonstrate downstream manhole surcharges are prevented. If a risk of surcharge exists, the designer will include solutions, such as upsizing downstream collection system or the installation of an equalization basin for cooling tower discharge management, etc.

1) The Average Day, contact the SLAC CE for typical water usage for type of facility under consideration.

2) Maximum Day Demand is equal to twice the Average Day Demand.

3) Peak Hour Demand is equal to four times the Average Day Demand (twice the Maximum Day Demand).

Gravity Pipeline

Design calculations for sewers and pipelines shall be presented in tabular form and shall include the following information for each section of sewer: 1) terminal manhole designation,

2) ground elevations at the rim for the terminal manholes, 3) incremental and cumulative tributary areas, 4) incremental and cumulative tributary occupied services, 5) incremental average and maximum domestic sewage flow, 6) incremental infiltration allowance, 7) cumulative design flow, 8) invert elevations for terminal manholes, 9) length of sewer run, and

10) sewer diameter, pipe material, slope, capacity, and velocity.

Gravity sewers shall be designed for obtaining reaeration velocities and to prevent sulfide buildup by maintaining a self-oxidizing condition. No surcharging of gravity sewers shall be allowed. Inverted siphons shall be avoided.

1. Minimum Size Main Sewer: The minimum diameter for main sewers shall be 6-inches.

The use of 4-inch pipe may only be allowed for the following conditions, and if approved in writing and in advance by SLAC CE:

a) Little or no possibility of future extension.

b) Minimum slope of 1 percent on dead-end runs less than 200 feet.

2. Gravity Sanitary Sewer Lateral Connections: The minimum diameter for gravity sewer laterals shall be 4-inches. For gravity sewer laterals serving commercial or industrial buildings the minimum diameter shall be 6-inches.

The SLAC CE may grant a variance for commercial or industrial buildings, with only restroom facilities, to allow the use of a 4-inch side sewer. Such use must be guaranteed for future use of the facilities and no additional change will be allowed.

3. Minimum Slopes: The minimum slope of gravity sewer laterals shall be 2 percent for 4-inch sewers and 1 percent for 6-inch sewers. The minimum slope for main sewers shall be that required to obtain a velocity of 2 feet per second when the sewer is flowing full or one-half full. For the purpose of computing velocity, the Manning's coefficient of roughness "n" shall be 0.015 for sewers 8-inches in diameter and smaller, and 0.013 for sewers larger than 8-inches in diameter.

4. Steep Slopes: Special design features may be required for main sewers installed on steep slopes. Depending upon conditions of the specific installation, such items as underdrains, check dams, special anchorage, or special pipe material may be required. Based upon data supplied, SLAC CE will assess each case and recommend certain special requirements.

5. Minimum Depth: The minimum depth of cover for any SLAC sewer mains shall be 3 feet. If it is impossible to obtain the specified minimum depth, the sewer shall be either PVC-C900 DR 26 or ductile iron pipe for the entire length from manhole to manhole.

For gravity sewer laterals, minimum depths of cover shall be 3 feet, from property line to connection to sewer main. Where the minimum depths of cover are impossible to obtain, the use of GREEN PVC-C900 DR 26, or polyethylene encased ductile iron pipe will be required.

The use of public or gravity sewer laterals with less than 2 feet of cover will require advance, special approval from SLAC CE. Concrete Caps will not be permitted except where specifically approved by SLAC CE.

Lift Stations Design calculations for lift stations shall include the following information: 1) pad elevation at lift station surface, 2) invert elevation of wet and dry well, 3) invert elevation of incoming and outgoing piping, 4) headloss calculations, 5) anticipated incoming and discharge flow calculations, 6) pump run time calculations, including lead and lag, 7) wet well storage calculations, 8) peak flows, 9) system curve/pump curve overlay, and 10) velocity through force main.

1. Forcemains shall be designed using a Hazen and Williams coefficient for roughness "C" of 100 for non-plastic pipe, and 130 for plastic pipe.

2. Minimum Size Forcemain: The minimum diameter forcemain shall be 2-inch for grinder pump systems, and 4-inches for raw wastewater pump stations. Forcemains shall be sized for a maximum fluid velocity of 8 feet per second and of a pressure not to exceed half the pressure rating of the pipe, unless approved by the SLAC CE.

3. Slope and Termination: Forcemains shall have a uniform slope preventing high spots forming possible air pocket traps. Where high spots cannot be prevented, suitable air and/or vacuum release valve shall be installed at the high points. Each forcemain shall terminate in a vented transition structure designed to provide hydraulic characteristics compatible with the pump performance curve.

4. Maximum Size Forcemain: Forcemains shall be sized to carry grit and settleable solids expected in sewage tributary to the pump station. Minimum velocities of 2 feet per second should be maintained. Long forcemains and transition structures shall be designed resistant to corrosion resulting from sulfide generation.

5. Thrust Blocks: Concrete thrust blocks must be provided at all bends of the forcemain with angles 11 degrees or more. Thrust block must be sized based on soil conditions and maximum force exerted.

Pump Design Grinder pump system shall be a complete unit, including grinder pump, check valve, tank basin, electrical quick disconnect (National Electric Manufacturers Association -NEMA 4X), pump removal system, shut-off valve, anti-siphon valve, internal wiring and controls.

NEMA4x will include a gasketed door enclosure intended for indoor or outdoor use primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, and hose directed water; undamaged by ice which forms on the enclosure.

1. Concrete anchor shall be poured-in-place.

2. The pump shall be an integral, vertical rotor, motor driven, solids handling pump of the progressing cavity type with mechanical seal.

3. The pump shall be capable of delivering 15 gpm against a rated total dynamic head of 0 feet and 9 gpm against a rated total dynamic head of 138 feet. The pump must also be capable of operating at negative total dynamic head without overloading the motor.

Under no conditions shall in-line piping or valving be allowed to create a false apparent head.

4. The grinder shall be placed immediately below the pumping elements and shall be direct– driven by a single, one-piece stainless steel motor shaft. The grinder impeller assembly shall be securely fastened to the pump motor shaft.

5. Cleanout Stations will be two-way and shall be installed along the small diameter gravity or forcemain. The location of the cleanout station shall be submitted to SLAC CE for pre-approval.

6. The lateral discharge line shall be no smaller than 2”.

7. For each Grinder pump system, a 2- inch maximum lateral check valve shall be installed along the lateral discharge line. The location of the lateral check valve shall be submitted to SLAC CE for pre-approval.

8. A Control unit shall be installed for the grinder pump(s). The location of the Control unit shall be submitted to SLAC CE for pre-approval.

9. A potable Hose Bib (labeled potable) to support localized maintenance shall be installed within 4-feet from the grinder pump(s). The location of the Hose Bib shall be submitted to the SLAC CE for pre-approval.

10. Design plans and specifications shall direct the contractor to provide one spare pump to SLAC CE, subject to final approval by SLAC CE.

11. In the event that an on-site ejector pump is required to convey wastewater from a building to a grinder pump, the on-site ejector pump shall be sized to discharge at a rate no more than the grinder pump discharge rate.

Location

1. The grinder pump system shall be located so as to provide vehicle access for maintenance unless otherwise approved by the SLAC CE. The SLAC CE shall pre-approve the location.

2. The tank shall be installed outside of vehicular access areas, including but not limited to below a driveway or parking area.

Manholes and Cleanouts

1. Manholes shall be provided at every change of size, alignment, direction, grade, or elevation.

2. The distance between manholes shall not exceed 300-feet.

3. Manholes may be provided in lieu of cleanouts in underground building sewers, building drains, and branches thereof 8-inches and larger.

4. Locate manholes at junction points, changes in gradient, and changes in conduit size.

5. A cleanout may be used at the end of a line 6-inches or greater in diameter and less than

200-feet in length if there are no definite plans for its extension.

6. Sanitary Sewer Drop Connection. Use a drop connection whenever the elevation difference between the invert of the entering pipe and the crown of the existing pipe exceeds 2-feet.

7. Manhole Steps: Design and construct steps in accordance with 29 CFR 1910.24, Step bolts and manhole steps. Steps must conform to the requirements of ASTM C 478.

8. Sewer laterals require a cleanout at the Lot Line (also referred to as Lease Line) or point of termination noted on the Drawings, per latest technical standards.

9. Cleanouts shall match the size of the sewer main.

Alignment

1. New water mains and new supply lines shall not be installed in the same trench as, and shall be at least 10 feet horizontally from and one foot vertically above, any parallel pipeline conveying:

a. Untreated sewage,

b. Primary or secondary treated sewage,

c. Disinfected secondary-2.2 recycled water (defined in section 60301.220),

d. Disinfected secondary-23 recycled water (defined in section 60301.225), and

e. Hazardous fluids such as fuels, industrial wastes, and wastewater sludge.

2. New water mains and new supply lines shall be installed at least 4 feet horizontally from, and one foot vertically above, any parallel pipeline conveying:

a. Disinfected tertiary recycled water (defined in section 60301.230), and

b. Storm drainage.

3. Approval is required by SLAC CE, of any new potable water mains and new potable supply lines installed closer than 4-feet horizontally from, and one foot vertically above, any pipeline conveying:

4. If crossing a pipeline conveying a fluid listed above in subsection 1 or 2, a new water main shall be constructed no less than 45-degress to and at least one foot above that pipeline. No connection joints shall be made in the domestic water main within 8-feet horizontal separation from the fluid pipeline.

5. Horizontal and vertical clearance from other pipelines shall be measured from inside edge of pipe to inside edge of pipe to result in the maximum separation. Where these minimum separations are not feasible, consult with the SLAC Civil Engineer.

6. If a 10-foot horizontal separation is not practical, a separation of at least 4-feet may be allowed subject to special construction conditions. In no case is horizontal separation of less than 4-feet or construction in the same trench as potable pipes and appurtenances allowed. Where these minimum separations are not feasible, consult with the SLAC Civil Engineer for guidance, including the use of a pipe sleeve which extends a minimum of 10-feet on either side of the potable water piping crossing.

7. Domestic water main separation from other underground pipelines shall comply with the California Code of Regulations Title 22, Division 4, Chapter 16, Article 4, Section 64572 Water Main Separation.

8. In paved areas, minimum cover shall be 42-inches from finished grade to top of pipe, or 2-feet below subgrade, whichever is greater. If approved by SLAC CE, water supply lines placed in unpaved areas shall require a minimum cover of 36-inches from finished grade to top of pipe. If these minimum covers are not feasible, consult with the SLAC CE for pipe material alternatives and requirements.

9. Gate valves shall be installed to isolate each branch run from the water supply main. Valves shall be Mueller Resilient wedge gate valves, unless approved by SLAC CE.

10. Tapping sleeve branch connections from existing mains shall be used only by prior approval by SLAC CE. No same line size tapping sleeves will be allowed.

11. Air release/vacuum relief valves will be installed at high points and at significant changes in grade in the water system profile. SLAC CE shall review proposed sizes and locations of air release/vacuum relief valves during design and during construction if field conditions require changes in grade in the water system profile.

12. No potholing and excavation shall be allowed with vacuum trucks unless a SLAC Excavation Permit has been obtained by the SLAC Project Manager and work approved by

SLAC CE.

13. Under no circumstances will potable water or sewer mains or service laterals be conveyed under building foundations or permanent structures.

Closed-Circuit Television (CCTV)

1. Phase 1: Inspection.

Sewer sections shall be inspected by means of remote CCTV. If a blockage hampers the inspection of the sewer in one direction, then the Contractor shall attempt to complete the section by televising from the other manhole to complete the section.

The Contractor must immediately report the obstruction to the Owner or his representative (hereinafter referred to as “Owner”). All CCTV work shall conform to current National Association of Sanitary Sewer Companies (NASSCO) Pipe Assessment Certification Program (PACP).

CCTV inspections will be delivered entirely in electronic format.

1. All PACP Header information shall be completed in accordance with PACP

Guidelines. In addition to mandatory Header fields, additional fields are required as noted on the attached Header Field Matrix.

2. The documentation of the work shall consist of PACP CCTV Reports, PACP database, logs, electronic reports, etc. noting important features encountered during the inspection. The speed of travel shall be slow enough to inspect each pipe joint, tee connection, structural deterioration, infiltration and inflow sources, and deposits, but should not, at any time, be faster than 30 feet per minute, except as noted otherwise in this document.

3. The camera must be centered in the pipe to provide accurate distance measurements to provide locations of features in the sewer and these footage measurements shall be displayed and documented on the video. All PACP Observations shall be identified by audio and on PACP log. All video must be continuously metered from manhole. The pipe should be clean enough to ensure all defects, features and observations are seen and logged. If cleaning is required, see NASSCO Performance Specification Guideline for Sewer Pipe Cleaning.

2. Phase 2: Sewer Pipe Cleaning.

Based on the Owner’s review, he or she will determine if additional work will be required.

The Owner, at his sole discretion, will either declare the work on the particular sewer section complete or notify the Contractor of additional work (i.e. Phase 3: Light Sewer Cleaning, Heavy Cleaning, Deposit Cut, Root Cut Medium, Root Cut Ball, or Lateral Cut).

See NASSCO Performance Specification Guideline for Sewer Pipe Cleaning.

3. Phase 3: Additional Sewer Pipe Cleaning.

The Contractor shall perform the assigned additional work, which may be any one of the following items: Light Sewer Cleaning, Heavy Cleaning, Deposit Cut, Root Cut Medium, Root Cut Ball, or Lateral Cut.

4. Phase 4: Post Cleaning Inspection.

Final televising of the sewer section to evaluate the condition of the sewer section after all cleaning has been performed in phase 3. Phase 4 will be required to be performed and will be reimbursed at the bid unit price.

a The recorded video must show the entire circumference of the sewer. Any flow control to remove standing water and debris shall be incidental to the contract. It is not the intent of this specification to require bypass pumping to control heavy flow; however, the Contractor must, at a minimum, make reasonable effort to control the flow. The Contractor must also consider weather conditions to obtain the best video image of the sewer. This may require the Contractor to delay any video work after major rain events until the system can return to lower dry weather flow. The Contractor shall submit PACP data to include the electronic video reports, logs, etc. for the Owner’s review as required in Part 1 Section 6.

b The sections of sewer to be cleaned and televised through this contract will be located primarily within the paved areas of the public right-of-way; however, there may be some sewer sections that are located within public easements on private property. The successful bidder will be responsible to coordinate and gain access to any and all sewer sections and will be responsible for any restoration in accordance with Part 3 Section

3.7. This will include written authorization between Contractor and landowner. Costs associated with access will be included with other items bid in this contract.

Materials Forced mains will be High Density Polyethylene (HDPE) SDR11.

Gravity mains will be C900 Polyvinyl Chloride (PVC) SDR26 or thicker.

Sewer Pipe Requirements

1. T’d or saddled connections from forced mains to gravity mains are not allowed, force main discharges must go to manholes, no exceptions.

2. Carbon steel/galvanized/cast iron building services are prohibited. Metallic building services entering the building/structure shall be copper or ductile iron.

3. Minimum water service size shall be one inch.

4. Services larger than 2-inches must be.

5. Tapping sleeve connections shall be used only by prior approval of SLAC CE. No same line size tapping sleeves will be allowed.

6. Repair of breaks in pipelines shall be made by making clean cuts on either side of the breaks, inserting new straight sections of pipe with plain ends in line, and connecting the ends with flexible couplings similar and equal to the couplings manufactured by Calder.

Clamp screws shall be retightened after a lapse of at least five minutes. Maximum trench width limitations at top of pipe must be observed during repairs as well as original construction. Meter boxes shall be located where they are easily accessible to the meter reader, in the sidewalk or 18-inches behind and set parallel with the curb. Meters may not be closer than 3-feet to a driveway or parking spaces, in order to avoid being obscured by parked vehicles.

7. Water services shall not be located closer than 5-feet from a sewer lateral, with a minimum of 30-inches of cover.

8. All meters, detector meters and radio read assemblies are to be supplied and installed by the Project.

9. Sewer meter shall be of Parshal Flume design.

10. Debris caps shall be installed in all valve boxes and conform to SLAC’s Technical

Specifications.

References

A. American Society for Testing and Materials (ASTM)

1. ASTM D 2122: Determining Dimensions of Thermal Plastic Pipe and Fittings.

2. ASTM D 2321: Underground Installation of Thermoplastic Pipe for Sewers and

Other Gravity Flow Applications

3. ASTM D 2837: Hydrostatic Design Basis for Thermal Plastic Pipe Materials

4. ASTM D 3350: Polyethylene Plastics Pipe and Fittings Material

5. ASTM C478: Precast Reinforced Concrete Manhole Sections.

6. ASTM D3034: Type PSM Polyvinyl Chloride (PVC) Sewer Pipe and Fittings

7. ASTM F 714: Polyethylene Plastic Pipe Based on Outside Diameter

8. ASTM F794: Standard Specification for Poly Vinyl Chloride (PVC) Ribbed Gravity

Sewer Pipe and Fittings Based on Controlled Inside Diameter.

9. ASTM F1667 – Guide for Construction Procedures for Buried Plastic Pipe

10. ASTM F477: Specification for Elastomeric Seals (Gaskets) for Joining Plastic Pipe.

11. ASTM C478

B. American Water Works Association (AWWA) C. California Department of Transportation (CDT): Standard Specifications: Sections 55, 65, 70, 71, 75 and 90.

D. California Division of Drinking Water, California Code of Regulations – Title 17, Public

Health, and Title 22, Social Security a 22 CCR §64572 Water Main Separation

E. California Plumbing Code, latest edition F. 29 CFR 1910.24, Step bolts and manhole steps.