California has faced droughts the last three years and there are many possibilities we could continue facing some more in the future. Combined with the potential impacts of climate change and a growing population, it makes sense then to balance our water supply with a source of water that doesn’t rely on rain.
Water desalination is the process of taking salt and other minerals out of seawater to make freshwater. Municipalities, water districts, and private companies in California and other parts of the U.S. are primarily considering using reverse osmosis (RO) technology to develop new seawater desalination.
Reverse osmosis and other membrane technologies force liquid at high pressure through a membrane with pores that block the passage of larger salt and mineral molecules.
The membranes used formed a dense barrier layer designed to allow only water to pass while preventing the passage of salt ions. Reverse osmosis is the final category of membrane filtration “Hyperfiltration” capable of removing particles larger than 0.1 nanometers.
Despite the promise of desalination technology to help rid the world of water scarcity, significant challenges exist including high energy consumption making it an expensive option, impact in marine life at water intakes and outfalls, operational issues, and social and political considerations.
*Water Intake
One of the main environmental concerns associated with seawater desalination is the feedwater intake which may affect the biota of marine life surrounding the system. Impingement and entrainment of fish and other aquatic life may occur when aquatic organisms are trapped against intake screens by the velocity and force of flowing water.
Seawater wells are a viable option to minimize ecological impacts and provide more reliable intake water due to natural filtration suspended solids, organics, reduce turbidity, and lower salt density but intakes depends on the hydrogeology and substrates characteristics associated with the subsurface system and may not be practical for large desalination plants.
Determining the appropriate location and type of intake should include a thorough site assessment and evaluation that will help implementing mitigating measures and reduce environmental impact.
*Energy use
Desalination plants are expensive to construct and operate. The process requires that high pressure be exerted on the high concentration side of the membrane, usually 600-1000 (psi) for seawater, requiring a substantial amount of energy and making the technology more costly than other treatment processes. For example, State Water Project requires an intensive 6.75 kwh per1000gal to transport water more than 3,000 vertical ft from the Delta (Sacramento – San Joaquin River). A typical reverse osmosis plant uses 22kwh per 1000 gal.
Another concern about the high rate of energy which desalination consumes is that plants could lead to increased carbon emissions and contribute to global climate, depending on the energy source used to operate. Renewable energy, such as wind and solar, provides an opportunity for desalination plants to be carbon neutral by reducing fossil fuel use and associated greenhouse gas emissions.
Regardless of the high energy costs, California governments are under pressure to look for new water sources including desalination. The state’s long-standing water supply problems have continued to worsen in recent years due to drought, contamination of groundwater, increasing requirements to maintain water instream for endangered species protection, and population growth.
*Brine (Concentrate) disposal
Among the more challenging issues with respect to desalination processes is disposing of the waste concentrates. Desalination concentrate have higher salinity than seawater, and is denser sinking to the seabed and negatively impacting the environment surrounding the outfall. Several considerations may help facilities develop environmental disposal such as co-discharge with other wastewater effluent that is currently discharging to the ocean; locate concentrate outfalls in a tidal zone; and/or add diffusers to improve mixing.
Regulatory and permitting process
The most significant hurdles to implement desalination technologies come from the complexity of regulations, and local/state/federal agencies limited permitting experience. Agencies involve in the permitting process are the California Regional Water Quality Control Board, the City, the California Department of Health Services, the California Coastal Commission, the State Lands Commission, and EPA.
Multiple agency involvement may contribute to unproductive project time and costs.
California has over a dozen desalination plants and plans for at least four new ones. The Carlsbad Plant is scheduled to begin operating in 2012 with a capacity of 50 MGD ($300M); Huntington Beach Desalination Plant starts this year with a capacity of 50 MGD ($250M); Camp Pendleton with a capacity of 100 MGD ($1.9 Billion); and the Marin Municipal Water District approved construction of what would be the first desalination plant in the San Francisco Bay area, is expected to open in 2014 ($105M).
Friday, March 19, 2010
Saturday, March 13, 2010
Wastewater Lift Station Design Guidelines
Wastewater lift station structures, equipment, piping, controls, and accessories must be engineered according to City requirements, standard guidelines, and in conjunction with the Public Works Design Manual.
General Requirements:
*Lift stations will not be allowed where an acceptable alternative gravity route exists.
*All wastewater lift stations shall have multiple pumps and shall be capable of delivering the design flow rate with the largest pump out of service.
*Pumps and related equipment must be designed so that it can be removed from the wet well with a vehicle mounted crane or other lifting device.
*Lift stations may be submersible pumping stations, package wet well / dry well stations or site designed vertical, dry pit, non-clogging, centrifugal pumping stations, depending on station size, head requirements and motor horse power. All pumps must be capable of passing a minimum three (3”) inch diameter sphere and shall be single speed. They must be designed specifically for handling raw, unscreened domestic sanitary wastewater.
*Above grade stations are preferred. They shall have a finished concrete floor with floor drains and be housed in an easily removable, pre fabricated fiberglass enclosure unless otherwise specified by the City. Below grade pump stations shall be reinforced concrete and shall extend at least 6 inches above finish grade.
**Adequate access, lighting, ventilation (minimum 10 air changes per hour), heating, Net Positive Suction Head (NPSHA), and potable water supply shall be provided to all wastewater lift stations.
Wet Well Design
*Wet wells shall be considered a hazardous environment. Whenever practical wastewater lift station wet wells shall be constructed of pre-cast reinforced concrete and shall be circular to a minimum of seventy two (72”) in diameter with 4-hour capacity or as necessary to accommodate the influent sewer, provide for adequate pump suction pipe or pump submergence as recommended by the pump manufacturer and to provide adequate volume to prevent the excessive cycling of pumps.
*Every effort will be made to prevent wastewater in the wet well from becoming septic. The wet well shall contain adequate vertical room for level sensing adjustments above and below the design levels.
*Primary high water alarm shall be set to wet well influent invert.
*Wet well interior walls and ceiling shall be lined with a material that is resistant to hydrogen sulfide and sulfuric acid. (i.e. fiberglass) and shall have a water proof system if anticipated to be below the water table. Regardless of the elevation of the water table, all joints in the concrete and all penetrations through the concrete shall be grouted with non-shrink grout on both sides of the joint or penetration.
*Access to well shall be through a top slab opening with aluminum hatch cover and frame. It shall allow for the removal of all equipment from the wet well, in no case smaller than 36 by 36 inches.
*Each wet well shall contain a sump (2 feet wide and 12 inches deep minimum) immediately underneath the inlet pipe to help assist in trapping large items to prevent them from entering the pumps.
*A sixty (60”) inch diameter approach manhole shall be constructed upstream of all wet wells, serving as a common point of connection for all sanitary sewer pipes tributary to the pump station. A single pipe shall extend from the approach manhole to the wet well. The approach manhole shall be located within the site fencing of the lift station.
*Provide restrained flexible couplings on all outlet piping within two (2’) feet of the station wall and a resilient-seat gate valve on the line into the wet well.
*Provide a bypass and a magnetic flow meter on the discharge of the pump station within a vault.
Pump Selection and Design Criteria (Consult Local Requirements)
Station Type / Influent Flow Range (gpm) / Maximum TDH / Maximum Motor HP
**Packaged wet well/ dry well; Up to 3,000 gpm (influent); Up to 45 feet (TDH); 100HP@1450 rpm
**Vertical centrifugal; no restrictions for influent flow; no restrictions for TDH; No restrictions for Max. HP
**Submersible Pump; Up to 2,000gmp (influent); Up to 160 feet (TDH); 100 HP @ 1800 rpm
TDH = Total Dynamic Head (estatical lift+ minor losses (i.e. valves) + mayor losses (i.e. pipe friction).
HP = Horse Power = {(Flow (Q gpm) x TDH)/ (3956 x Efficiency of the Pump -ηp)}
1. Submersible Pumps
The lift station will consist of a minimum of two submersible centrifugal sewage pumps, guide rails, wet well access, discharge seal and elbow, motor control center (MCC), starters, liquid level control system and all hardware necessary to make a complete working system.
Pump volute, impeller and motor housing shall be of cast iron construction. Submersible wastewater pumps shall be fitted with leakage sensors for detecting the presence of water in the oil and/or stator housing. (Consult pump manufacturers such as ITT Flygt, Gorman Rupp, Goulds pumps, Peerless Pumps).
Each pump will be furnished with a discharge connection system, which will permit removal and installation of pump without the need for the operator to enter the wet well.
2. Self Priming Centrifugal Pump
The lift station will employ vertical, dry pit, single stage non-clogging centrifugal sewage pumps with motors totally enclosed, fan cooled, and premium efficiency.
The pumps shall be of standard cast iron construction with ductile iron impeller, oil lubricated mechanical seal, and shall include casing wear rings to maintain sealing efficiency between the wear ring and impeller faces.
Design of lift station enclosure for vertical centrifugal stations will be coordinated with the City and Fire Departments with respect to occupancy class and electrical and HVAC system design.
Emergency Station Operation
To ensure that utility power or equipment failures do not cause sewer system overflows, provisions to maintain wastewater pump station including standby power and emergency storage shall be made.
*A diesel engine emergency electric generator shall be provided for all wastewater lift stations. An automatic transfer switch shall be provided to switch to emergency power on a power failure or a drop in any phase voltage to 70 percent of line voltage.
*Emergency storage capacity shall be provided to hold a minimum of 1 hour of peak hour design flow. The wet well, collection system and emergency storage containment can all serve as the emergency storage provided that the 1 hour requirement is met without a spill occurring. The emergency storage must be available above the high water alarm elevation in the wet well and must be continuously available without the need for an operator to switch valves or diversions.
General Requirements:
*Lift stations will not be allowed where an acceptable alternative gravity route exists.
*All wastewater lift stations shall have multiple pumps and shall be capable of delivering the design flow rate with the largest pump out of service.
*Pumps and related equipment must be designed so that it can be removed from the wet well with a vehicle mounted crane or other lifting device.
*Lift stations may be submersible pumping stations, package wet well / dry well stations or site designed vertical, dry pit, non-clogging, centrifugal pumping stations, depending on station size, head requirements and motor horse power. All pumps must be capable of passing a minimum three (3”) inch diameter sphere and shall be single speed. They must be designed specifically for handling raw, unscreened domestic sanitary wastewater.
*Above grade stations are preferred. They shall have a finished concrete floor with floor drains and be housed in an easily removable, pre fabricated fiberglass enclosure unless otherwise specified by the City. Below grade pump stations shall be reinforced concrete and shall extend at least 6 inches above finish grade.
**Adequate access, lighting, ventilation (minimum 10 air changes per hour), heating, Net Positive Suction Head (NPSHA), and potable water supply shall be provided to all wastewater lift stations.
Wet Well Design
*Wet wells shall be considered a hazardous environment. Whenever practical wastewater lift station wet wells shall be constructed of pre-cast reinforced concrete and shall be circular to a minimum of seventy two (72”) in diameter with 4-hour capacity or as necessary to accommodate the influent sewer, provide for adequate pump suction pipe or pump submergence as recommended by the pump manufacturer and to provide adequate volume to prevent the excessive cycling of pumps.
*Every effort will be made to prevent wastewater in the wet well from becoming septic. The wet well shall contain adequate vertical room for level sensing adjustments above and below the design levels.
*Primary high water alarm shall be set to wet well influent invert.
*Wet well interior walls and ceiling shall be lined with a material that is resistant to hydrogen sulfide and sulfuric acid. (i.e. fiberglass) and shall have a water proof system if anticipated to be below the water table. Regardless of the elevation of the water table, all joints in the concrete and all penetrations through the concrete shall be grouted with non-shrink grout on both sides of the joint or penetration.
*Access to well shall be through a top slab opening with aluminum hatch cover and frame. It shall allow for the removal of all equipment from the wet well, in no case smaller than 36 by 36 inches.
*Each wet well shall contain a sump (2 feet wide and 12 inches deep minimum) immediately underneath the inlet pipe to help assist in trapping large items to prevent them from entering the pumps.
*A sixty (60”) inch diameter approach manhole shall be constructed upstream of all wet wells, serving as a common point of connection for all sanitary sewer pipes tributary to the pump station. A single pipe shall extend from the approach manhole to the wet well. The approach manhole shall be located within the site fencing of the lift station.
*Provide restrained flexible couplings on all outlet piping within two (2’) feet of the station wall and a resilient-seat gate valve on the line into the wet well.
*Provide a bypass and a magnetic flow meter on the discharge of the pump station within a vault.
Pump Selection and Design Criteria (Consult Local Requirements)
Station Type / Influent Flow Range (gpm) / Maximum TDH / Maximum Motor HP
**Packaged wet well/ dry well; Up to 3,000 gpm (influent); Up to 45 feet (TDH); 100HP@1450 rpm
**Vertical centrifugal; no restrictions for influent flow; no restrictions for TDH; No restrictions for Max. HP
**Submersible Pump; Up to 2,000gmp (influent); Up to 160 feet (TDH); 100 HP @ 1800 rpm
TDH = Total Dynamic Head (estatical lift+ minor losses (i.e. valves) + mayor losses (i.e. pipe friction).
HP = Horse Power = {(Flow (Q gpm) x TDH)/ (3956 x Efficiency of the Pump -ηp)}
1. Submersible Pumps
The lift station will consist of a minimum of two submersible centrifugal sewage pumps, guide rails, wet well access, discharge seal and elbow, motor control center (MCC), starters, liquid level control system and all hardware necessary to make a complete working system.
Pump volute, impeller and motor housing shall be of cast iron construction. Submersible wastewater pumps shall be fitted with leakage sensors for detecting the presence of water in the oil and/or stator housing. (Consult pump manufacturers such as ITT Flygt, Gorman Rupp, Goulds pumps, Peerless Pumps).
Each pump will be furnished with a discharge connection system, which will permit removal and installation of pump without the need for the operator to enter the wet well.
2. Self Priming Centrifugal Pump
The lift station will employ vertical, dry pit, single stage non-clogging centrifugal sewage pumps with motors totally enclosed, fan cooled, and premium efficiency.
The pumps shall be of standard cast iron construction with ductile iron impeller, oil lubricated mechanical seal, and shall include casing wear rings to maintain sealing efficiency between the wear ring and impeller faces.
Design of lift station enclosure for vertical centrifugal stations will be coordinated with the City and Fire Departments with respect to occupancy class and electrical and HVAC system design.
Emergency Station Operation
To ensure that utility power or equipment failures do not cause sewer system overflows, provisions to maintain wastewater pump station including standby power and emergency storage shall be made.
*A diesel engine emergency electric generator shall be provided for all wastewater lift stations. An automatic transfer switch shall be provided to switch to emergency power on a power failure or a drop in any phase voltage to 70 percent of line voltage.
*Emergency storage capacity shall be provided to hold a minimum of 1 hour of peak hour design flow. The wet well, collection system and emergency storage containment can all serve as the emergency storage provided that the 1 hour requirement is met without a spill occurring. The emergency storage must be available above the high water alarm elevation in the wet well and must be continuously available without the need for an operator to switch valves or diversions.
Wednesday, March 3, 2010
Water Distribution System Design
A water system must safely convey the required amount of high quality water throughout a sound distribution system at the least cost. Therefore, the Engineer must consult pertinent and current requirements from federal, State, and regional agencies to ensure the system complies with all standards and regulations.
Drinking Water System Regulators
*Environmental Protection Agency (EPA)
*California Department of Public Health
*California Public Utilities Commission
*County/City Department of Public of Works
*California Administrative Code, regarding cross-connections and backflow prevention.
*Uniform Fire Code
Improvement Plans Requirements
Provide a detailed utility plan showing onsite and offsite public and private water and fire protection systems, including appurtenances and connections. Show location, pipe material, diameters, fire hydrants, valves, backflow protection, horizontal and vertical separations, slopes, cover, inverts, laterals, right-of-way, crossings, and any other necessary facility to demonstrate compliance with engineering principles and agencies regulators.
Materials
Public water mains may be constructed of PVC (http://www.plasticpipe.org/), Ductile Iron (http://www.dipra.org/), ReinforcedConcrete Pipe, RCP (http://www.concrete-pipe.org/), or Wrapped Steel Pipe. Asbestos cement pipe are not allowed under any circumstances.
*Mains eight (8) to twelve (12) inches in diameter will be PVC, pressure class 150, DR 18, AWWA Standard C900 or Ductile Iron, pressure class 350 per AWWA Standard C151. Where the normal mainline static pressure exceeds 100 psi, DI or PVC Pressure Class 200, DR14 must be used.
*Mains sixteen (16) inches in diameter will be PVC, pressure rating 165psi, AWWA C905, DR25 or Ductile Iron (DI) per AWWA Standard C151. Where the normal mainline static pressure exceeds 100 psi, AWWA Standard C905, DR18 with a pressure rating of 235 psi or Ductile Iron (DI) Pipe must be used.
*Mains twenty (20) inches in diameter and larger water mains will be concrete cylinder pipe, wrapped steel pipe, or Ductile Iron.
*Service laterals will be copper, PVC, or DIP per applicable City Standards.
Alignment
Public water mains shall be designed inside the street right-of-way. In general, public water systems shall be designed only where they serve multiple lots and where appropriate access for maintenance can be provided.
Horizontal Alignment
*Conform to the State of California Department of Health Services “Criteria for the separation water Main and Sanitary sewers”, appendix A. In general, ten (10) feet wall to wall separation.
*Conform to manufacturer requirements for minimum allowable radius curvatures. In situations such as streets with smaller radius curves, the water system will be designed in straight segments parallel to the sewer or storm drain system.
*Minimum separation from storm drains is five (5) feet and from monuments, gas, electrical, phone, cable and other dry utility shall be four (4) feet clear.
*All public water mains must be designed a minimum of five (5) feet from all structures such as manholes or drop inlets. A minimum of three (3) feet from the lip of gutter shall be provided.
* Five (5) feet separation from the edge of easements shall be provided for public water mains.
*Dual water mains shall have a minimum five (5) feet clear horizontal separation.
*Crossings shall be designed close as 90 degrees to that facility. Crossing less than 45 degrees will only be approved when no other design is possible.
*Minimum separation between water and sewer lateral services shall be five (5) feet clearance.
Vertical Alignment
*Provide a minimum of six (6”) inches of vertical separation from storm drains and “dry” utilities.
*Conform to State of California Department of Health Services “Criteria for the Separation of Water Main and Sanitary Sewers”, Appendix “A”. In general, one (1) foot wall to wall separation.
*When the minimum cannot be maintained, concrete encasement or ductile iron pipe may be submitted for approval.
Main Sizing Criteria
*Allowable nominal sizes for public water mains are 8”, 12”, and 16”. The minimum new public main size for residential developments is 8" inches and when serving industrial/commercial and/or multi-family residential developments greater than two units, must be a minimum of 12" inches.
*Public water mains must be sized to meet minimum Fire Code requirement in addition to domestic and irrigation demands.
Cover
*Cover is the distance from the top of the pipe to final finished grade. Typically the minimum standard depths of cover for 4” to 8” inches water mains is 3”-0” feet; for mains 10” to 12” shall be 3’-6”; and for mains 16” or greater minimum cover is 4’-0”.
*Where standard cover cannot be maintained, either an under-crossing or over-crossing shall be provided.
Design Criteria
*Operation Conditions
Pressure (psi) and velocity (fps)
Maximum day: 60 psi(max); 40 psi (min); 5 fps (max)
Maximum day and Fire: 80 psi(max); 20 psi(min); 10 fps (max)
Peak hour: 80 psi(max); 30 psi(min); 7 fps (max)
*If pressure measured at any faucet is less than 35 psi, a pressure booster system is required. If pressure at any faucet exceeds 80 psi, a private pressure regulating device is required.
Rate of Domestic use
*Land Use
Average Day Demand (ADD) - Gallons per Acre Day
Fire Flow (FF) - Gallons per minute (gpm)
Fire Duration (FD) - Hour (hr)
Low Density Residential: 2,500(ADD); 1,500(FF); 2(FD)
Medium Density Residential: 3,200(ADD); 1,500(FF); 2(FD)
High Density Residential: 3,600(ADD); 2,500(FF); 3(FD)
Commercial: 2,200(ADD); 3,000(FF); 3(FD)
Schools: 2,200(ADD); 4,000(FF); 4(FD)
*Potable water demand for planning purposes shall be estimated using the water demand factors outlined in the Master Plan.
**Maximum Day Demand (MDD) = 2.0xAverage Day (ADD)
**Peak Hour Demand = 4.0xAverage Day (ADD)
** The Hazen-William formula shall be used in the hydraulic study of the system, using a “C” value of 130 for cement-lined pipe, PVC C900, and ductile iron pipe.
Looping
For system reliability, to minimize pipe size, and to minimize the number of people affected by a system shutdown, either for domestic or fire protection purposes, no more than 100 residential units may be served by a single-feed water system. Where more than 100 units are to be served, a dual-feed (or looping) public water system must be designed.
Valve Placement
*Intersecting mainlines should be equipped with isolation or shut-off valves (usually gate valves) to minimize disruption during repairs. “T” intersections typically require three valves and cross intersection typical require four valves.
*Valves within 250' feet of an intersection may be considered as part of the intersection.
*All hydrants must be on separately valved sections of the public main.
*Valves shall be designed to maximum interval of 1,000 feet.
Air release and Vacuum relief valves (ARV)
*Air release and vacuum relief valves are required at substantial high points in the system that are one pipe diameter or higher than the remainder system, such as over a hilltop or at the upper end of a dead end main.
Pressure reducing valves (PRV)
*Design pressure reducing valves to maintain overall system balance and to maintain service pressure levels within the parameters established within the system design standards.
Backflow Prevention Devices
These devices are a reasonable and effective mean of protecting water system from backflow.
Backflow prevention devices or air-gaps of a type shall be located as close as possible to the service connection and shall be installed as follow:
*Premises within which any substance is handled under pressure that could potentially permit backflow or back-siphonage into the potable water system.
*Premises which have more than one service connection and which may contain cross-connections that may result in the pollution of the potable water system.
*Premises having gray and/or recycled water use systems.
*Examples of premises which require the installation of a backflow prevention device are: Auto repair/painting, car wash, chemical or processing facilities, fire systems, gas stations, hospital and medical facilities, irrigation systems, restaurants, schools, laundry facility, swimming pool.
**All backflow devices must be listed on the latest revision of the approved USC Foundation for Cross-Connection Connection and Hydraulic Research list. List includes (manufacturer’s name, model, size, etc).
**In General City standards provide a list of premises requiring backflow prevention devices along with the type needing to be installed (Air gap, double check, reduced pressure, double check with detector).
Fire Hydrants
*Design of hydrant locations must meet the Fire Code requirements and be approved by the Fire Department for logistics and by the Utilities Department for maintainability. In general, hydrants shall have 500’ feet maximum spacing or 300’ feet in high fire severity zones.
*Locate hydrants at intersections. If not possible locate them near a property line, and/or five (5’) feet from residential driveways.
Joint Restraint
Thrust blocking or restraints should be provided where changes in water direction occur and where reductions in pipe diameter are made and dead ends. A concrete mass or a mechanical joint restraint device may provide thrust restraints. Water mains installed at a slope of fifteen (15) percent or greater will be designed with restrained joints.
*Typical standard bend angles (degrees) are: 11 ¼ , 22 ½, 45, 90.
Hot Tap
Hot taps are not allowed within two (2’) feet of a joint, otherwise, a “cut-in-tee” shall be used.
Easements
An easement must be provided over any public water system when it is outside the public right-of-way. The easement must be a minimum of fifteen (15’) feet wide if it only contains a water main or twenty (20’) feet if it contains another facility. Separate access easements may be required depending on site conditions.
No structures may encroach on, above or below the surface of the ground in any public water easement.
Abandonment of water mains and services
*remove the valve and saddle for all water services two (2) inches or less and install a full circle clamp on the main.
*For flanged or mechanical joint tees remove the valve and install a blind flange or mechanical joint plug.
*For push-on tees, the tee, valve and thrust restraint must be removed and the main repaired with approved pipe and suitable couplings.
*Valve boxes for abandoned valves must be removed.
*Pipes twelve (12”) inches and larger to be abandoned need to be removed or broken every fifty (50’) feet and filled with sand slurry. (Check City Standards)
*Where a fire hydrant is to be abandoned, the hydrant barrel, break off riser, and check valve are to be removed. Abandonment of fire hydrants must be approved by the Fire Department.
Connections
*A permit shall be obtained for each connection to the water system.
Drinking Water System Regulators
*Environmental Protection Agency (EPA)
*California Department of Public Health
*California Public Utilities Commission
*County/City Department of Public of Works
*California Administrative Code, regarding cross-connections and backflow prevention.
*Uniform Fire Code
Improvement Plans Requirements
Provide a detailed utility plan showing onsite and offsite public and private water and fire protection systems, including appurtenances and connections. Show location, pipe material, diameters, fire hydrants, valves, backflow protection, horizontal and vertical separations, slopes, cover, inverts, laterals, right-of-way, crossings, and any other necessary facility to demonstrate compliance with engineering principles and agencies regulators.
Materials
Public water mains may be constructed of PVC (http://www.plasticpipe.org/), Ductile Iron (http://www.dipra.org/), ReinforcedConcrete Pipe, RCP (http://www.concrete-pipe.org/), or Wrapped Steel Pipe. Asbestos cement pipe are not allowed under any circumstances.
*Mains eight (8) to twelve (12) inches in diameter will be PVC, pressure class 150, DR 18, AWWA Standard C900 or Ductile Iron, pressure class 350 per AWWA Standard C151. Where the normal mainline static pressure exceeds 100 psi, DI or PVC Pressure Class 200, DR14 must be used.
*Mains sixteen (16) inches in diameter will be PVC, pressure rating 165psi, AWWA C905, DR25 or Ductile Iron (DI) per AWWA Standard C151. Where the normal mainline static pressure exceeds 100 psi, AWWA Standard C905, DR18 with a pressure rating of 235 psi or Ductile Iron (DI) Pipe must be used.
*Mains twenty (20) inches in diameter and larger water mains will be concrete cylinder pipe, wrapped steel pipe, or Ductile Iron.
*Service laterals will be copper, PVC, or DIP per applicable City Standards.
Alignment
Public water mains shall be designed inside the street right-of-way. In general, public water systems shall be designed only where they serve multiple lots and where appropriate access for maintenance can be provided.
Horizontal Alignment
*Conform to the State of California Department of Health Services “Criteria for the separation water Main and Sanitary sewers”, appendix A. In general, ten (10) feet wall to wall separation.
*Conform to manufacturer requirements for minimum allowable radius curvatures. In situations such as streets with smaller radius curves, the water system will be designed in straight segments parallel to the sewer or storm drain system.
*Minimum separation from storm drains is five (5) feet and from monuments, gas, electrical, phone, cable and other dry utility shall be four (4) feet clear.
*All public water mains must be designed a minimum of five (5) feet from all structures such as manholes or drop inlets. A minimum of three (3) feet from the lip of gutter shall be provided.
* Five (5) feet separation from the edge of easements shall be provided for public water mains.
*Dual water mains shall have a minimum five (5) feet clear horizontal separation.
*Crossings shall be designed close as 90 degrees to that facility. Crossing less than 45 degrees will only be approved when no other design is possible.
*Minimum separation between water and sewer lateral services shall be five (5) feet clearance.
Vertical Alignment
*Provide a minimum of six (6”) inches of vertical separation from storm drains and “dry” utilities.
*Conform to State of California Department of Health Services “Criteria for the Separation of Water Main and Sanitary Sewers”, Appendix “A”. In general, one (1) foot wall to wall separation.
*When the minimum cannot be maintained, concrete encasement or ductile iron pipe may be submitted for approval.
Main Sizing Criteria
*Allowable nominal sizes for public water mains are 8”, 12”, and 16”. The minimum new public main size for residential developments is 8" inches and when serving industrial/commercial and/or multi-family residential developments greater than two units, must be a minimum of 12" inches.
*Public water mains must be sized to meet minimum Fire Code requirement in addition to domestic and irrigation demands.
Cover
*Cover is the distance from the top of the pipe to final finished grade. Typically the minimum standard depths of cover for 4” to 8” inches water mains is 3”-0” feet; for mains 10” to 12” shall be 3’-6”; and for mains 16” or greater minimum cover is 4’-0”.
*Where standard cover cannot be maintained, either an under-crossing or over-crossing shall be provided.
Design Criteria
*Operation Conditions
Pressure (psi) and velocity (fps)
Maximum day: 60 psi(max); 40 psi (min); 5 fps (max)
Maximum day and Fire: 80 psi(max); 20 psi(min); 10 fps (max)
Peak hour: 80 psi(max); 30 psi(min); 7 fps (max)
*If pressure measured at any faucet is less than 35 psi, a pressure booster system is required. If pressure at any faucet exceeds 80 psi, a private pressure regulating device is required.
Rate of Domestic use
*Land Use
Average Day Demand (ADD) - Gallons per Acre Day
Fire Flow (FF) - Gallons per minute (gpm)
Fire Duration (FD) - Hour (hr)
Low Density Residential: 2,500(ADD); 1,500(FF); 2(FD)
Medium Density Residential: 3,200(ADD); 1,500(FF); 2(FD)
High Density Residential: 3,600(ADD); 2,500(FF); 3(FD)
Commercial: 2,200(ADD); 3,000(FF); 3(FD)
Schools: 2,200(ADD); 4,000(FF); 4(FD)
*Potable water demand for planning purposes shall be estimated using the water demand factors outlined in the Master Plan.
**Maximum Day Demand (MDD) = 2.0xAverage Day (ADD)
**Peak Hour Demand = 4.0xAverage Day (ADD)
** The Hazen-William formula shall be used in the hydraulic study of the system, using a “C” value of 130 for cement-lined pipe, PVC C900, and ductile iron pipe.
Looping
For system reliability, to minimize pipe size, and to minimize the number of people affected by a system shutdown, either for domestic or fire protection purposes, no more than 100 residential units may be served by a single-feed water system. Where more than 100 units are to be served, a dual-feed (or looping) public water system must be designed.
Valve Placement
*Intersecting mainlines should be equipped with isolation or shut-off valves (usually gate valves) to minimize disruption during repairs. “T” intersections typically require three valves and cross intersection typical require four valves.
*Valves within 250' feet of an intersection may be considered as part of the intersection.
*All hydrants must be on separately valved sections of the public main.
*Valves shall be designed to maximum interval of 1,000 feet.
Air release and Vacuum relief valves (ARV)
*Air release and vacuum relief valves are required at substantial high points in the system that are one pipe diameter or higher than the remainder system, such as over a hilltop or at the upper end of a dead end main.
Pressure reducing valves (PRV)
*Design pressure reducing valves to maintain overall system balance and to maintain service pressure levels within the parameters established within the system design standards.
Backflow Prevention Devices
These devices are a reasonable and effective mean of protecting water system from backflow.
Backflow prevention devices or air-gaps of a type shall be located as close as possible to the service connection and shall be installed as follow:
*Premises within which any substance is handled under pressure that could potentially permit backflow or back-siphonage into the potable water system.
*Premises which have more than one service connection and which may contain cross-connections that may result in the pollution of the potable water system.
*Premises having gray and/or recycled water use systems.
*Examples of premises which require the installation of a backflow prevention device are: Auto repair/painting, car wash, chemical or processing facilities, fire systems, gas stations, hospital and medical facilities, irrigation systems, restaurants, schools, laundry facility, swimming pool.
**All backflow devices must be listed on the latest revision of the approved USC Foundation for Cross-Connection Connection and Hydraulic Research list. List includes (manufacturer’s name, model, size, etc).
**In General City standards provide a list of premises requiring backflow prevention devices along with the type needing to be installed (Air gap, double check, reduced pressure, double check with detector).
Fire Hydrants
*Design of hydrant locations must meet the Fire Code requirements and be approved by the Fire Department for logistics and by the Utilities Department for maintainability. In general, hydrants shall have 500’ feet maximum spacing or 300’ feet in high fire severity zones.
*Locate hydrants at intersections. If not possible locate them near a property line, and/or five (5’) feet from residential driveways.
Joint Restraint
Thrust blocking or restraints should be provided where changes in water direction occur and where reductions in pipe diameter are made and dead ends. A concrete mass or a mechanical joint restraint device may provide thrust restraints. Water mains installed at a slope of fifteen (15) percent or greater will be designed with restrained joints.
*Typical standard bend angles (degrees) are: 11 ¼ , 22 ½, 45, 90.
Hot Tap
Hot taps are not allowed within two (2’) feet of a joint, otherwise, a “cut-in-tee” shall be used.
Easements
An easement must be provided over any public water system when it is outside the public right-of-way. The easement must be a minimum of fifteen (15’) feet wide if it only contains a water main or twenty (20’) feet if it contains another facility. Separate access easements may be required depending on site conditions.
No structures may encroach on, above or below the surface of the ground in any public water easement.
Abandonment of water mains and services
*remove the valve and saddle for all water services two (2) inches or less and install a full circle clamp on the main.
*For flanged or mechanical joint tees remove the valve and install a blind flange or mechanical joint plug.
*For push-on tees, the tee, valve and thrust restraint must be removed and the main repaired with approved pipe and suitable couplings.
*Valve boxes for abandoned valves must be removed.
*Pipes twelve (12”) inches and larger to be abandoned need to be removed or broken every fifty (50’) feet and filled with sand slurry. (Check City Standards)
*Where a fire hydrant is to be abandoned, the hydrant barrel, break off riser, and check valve are to be removed. Abandonment of fire hydrants must be approved by the Fire Department.
Connections
*A permit shall be obtained for each connection to the water system.
Wednesday, February 24, 2010
Cleaning an environmental media here – Contaminating an environmental media there
The cleaning of an environmental media resulting in the pollution of others is the outcome from lack of communication, cooperation, and exercised bureaucracy between environmental protection agencies. For instance, Methyl-tertiary-butyl ether (MTBE), a gasoline additive created to reduce air pollution, resulted in severe water pollution in the Santa Monica, Lake Tahoe, and San Diego Basin.
MTBE became an environmental disaster by the time it was banned in 2004. MTBE leached from fuel storage tanks into the groundwater where it dissolves easily, resulting in faster and further migration, thus contaminating public water systems and private drinking wells. MTBE does not degrade easily and is difficult and costly to remove, it is one of the most persistent pollutants in the environment.
Nowadays, under Mission Valley in San Diego lies the largest pocket of MTBE pollution in the region, location of one of the most precious groundwater sources of the city which has a pumping potential capacity of two (2) million gallons of water a day that could provide water supply for eight thousand family units a day however the major problem is the costly removal of this pollutant.
The California Environmental Protection Agency (Cal-EPA) was created to reorganize and unify all environmental agencies and perform under one integrated protection program and strategy, unfortunately, Cal-EPA continues to operate as a collection of boards and commissions without a coherent environmental protection policy. Each board and commission is responsible for a specific type of pollution. Decision-makers do not focus on how their choices affect other areas of the environment.
EPA shall be more aggressive in the implementation of a successful strategic plan, bringing all agencies together and establishing a clear vision of the problem so as to minimize the transfer of pollutants across all media – air, land, and water. Full commitment from the boards and commissions is necessary to paint a picture of where the pollution prevention shall end up and the expected outcomes. The goal in mind is to provide efficient economical solutions for the integration of a unified EPA to prevent further environment disasters.
MTBE became an environmental disaster by the time it was banned in 2004. MTBE leached from fuel storage tanks into the groundwater where it dissolves easily, resulting in faster and further migration, thus contaminating public water systems and private drinking wells. MTBE does not degrade easily and is difficult and costly to remove, it is one of the most persistent pollutants in the environment.
Nowadays, under Mission Valley in San Diego lies the largest pocket of MTBE pollution in the region, location of one of the most precious groundwater sources of the city which has a pumping potential capacity of two (2) million gallons of water a day that could provide water supply for eight thousand family units a day however the major problem is the costly removal of this pollutant.
The California Environmental Protection Agency (Cal-EPA) was created to reorganize and unify all environmental agencies and perform under one integrated protection program and strategy, unfortunately, Cal-EPA continues to operate as a collection of boards and commissions without a coherent environmental protection policy. Each board and commission is responsible for a specific type of pollution. Decision-makers do not focus on how their choices affect other areas of the environment.
EPA shall be more aggressive in the implementation of a successful strategic plan, bringing all agencies together and establishing a clear vision of the problem so as to minimize the transfer of pollutants across all media – air, land, and water. Full commitment from the boards and commissions is necessary to paint a picture of where the pollution prevention shall end up and the expected outcomes. The goal in mind is to provide efficient economical solutions for the integration of a unified EPA to prevent further environment disasters.
Tuesday, February 23, 2010
Take a tour of a wastewater treatment plant and follow the path of water as it gets treated
The Sanitation Districts of Los Angeles County operate ten water reclamation plants and one ocean design facility (Joint Water Pollution Control Plant). It offers tours to schools, clubs, organizations, and the general public of any of their facilities.
Today, February 23, 2010 I toured the San Jose Creek Water Reclamation Plant located next to the City of Whittier. It is the Sanitation Districts’ largest reclamation plant (100 mgd) serving a population of approximately one million people. Fifty (50) percent of the reclaimed water produced at this plant is reused, mostly for groundwater recharge.
Water recycling significantly reduces the Los Angeles Basin’s dependence on costly imported water and helps to replenish a large percentage of the ground water used by the region. The remainder water treated is put into the San Gabriel River and flows to the ocean.
In densely population areas the sewage is collected by a network of underground pipes that convey raw sewer to a wastewater treatment facility. Once in the treatment plant, wastewater goes through a series of actions which will help to clean the water. A wastewater treatment plant’s basic function is to quicken the natural processes by which water purifies itself.
At present the San Jose Creek Water Reclamation Plant uses a basic three (3) stages in the treatment of wastes: primary, secondary, and tertiary treatment.
Primary Treatment Process
It starts with the screening of the wastewater entering the treatment facilities. Water flows through a screen to remove large objects such as wood, rocks, rags, and even dead animals that may cause problems later in the treatment process clogging pumps and small pipes. After the sewage has been screened it passes into what is called a grit chamber where sand, grit, cinders and small stones are allowed to settle to the bottom to later be disposed. With screening completed and grit removed, the sewage still contains suspended solids which are gradually allowed to settle to the bottom of a long concrete rectangular sedimentation tank. The settled material is called primary sludge and it is mechanically remove from the sedimentation tanks.
Secondary Treatment Process
After the sewage leaves the settling tank in the primary stage, it is pumped to an aeration tank where it is mixed with air and sludge loaded with microorganisms that use oxygen to breathe and break down the organic matter. Sewage at the aeration tank remains for several hours allowing the process to removes up to 90% of the organic matter.
Meanwhile, the sewage flows from the aeration tank to another sedimentation tank to remove the microorganisms were they clump together, settle to the bottom, and are removed and recycled back into the treatment process.
Tertiary Treatment Process
The final step uses filtering and chemical treatment. This allows the water to be in better condition before it is put back into the water cycle system. The San Jose Creek Water Reclamation Plant has installed filters containing layers of anthracite coal, sand, and gravel which remove any remaining suspended materials from the water. The reclaimed water is then disinfected with chlorine.
After completion of all treatment processes, reclaimed water, is now free of harmful bacteria and viruses and is safe for human contact. Recycled water is then discharged to the San Jose creek destined to recharge groundwater supplies.
Any remaining chlorine in the purified water is removed prior discharge to protect aquatic life in the receiving environment. Water quality measurement and analysis are completed at laboratories located at the treatment plant to ensure reclaimed water meets all requirements of the Regional Quality Control Board.
The cleaning process from preliminary treatment to final disinfection prior reuse or discharge takes approximately ten (10) hours.
Information about the Sanitation Districts of Los Angeles County’s tours and facilities can be found at their website:
http://www.lacsd.org/about/wastewater_facilities/default.asp
The California Water Environment Association awards “best treatment plant of the year” to those facilities employing a state-of-the- art cleansing process, green technologies such as solar panels, and effluents meet stringent state quality standards. Check their website to know which wastewater treament plants have been awarded best in California. http://www.cwea.org/
Today, February 23, 2010 I toured the San Jose Creek Water Reclamation Plant located next to the City of Whittier. It is the Sanitation Districts’ largest reclamation plant (100 mgd) serving a population of approximately one million people. Fifty (50) percent of the reclaimed water produced at this plant is reused, mostly for groundwater recharge.
Water recycling significantly reduces the Los Angeles Basin’s dependence on costly imported water and helps to replenish a large percentage of the ground water used by the region. The remainder water treated is put into the San Gabriel River and flows to the ocean.
In densely population areas the sewage is collected by a network of underground pipes that convey raw sewer to a wastewater treatment facility. Once in the treatment plant, wastewater goes through a series of actions which will help to clean the water. A wastewater treatment plant’s basic function is to quicken the natural processes by which water purifies itself.
At present the San Jose Creek Water Reclamation Plant uses a basic three (3) stages in the treatment of wastes: primary, secondary, and tertiary treatment.
Primary Treatment Process
It starts with the screening of the wastewater entering the treatment facilities. Water flows through a screen to remove large objects such as wood, rocks, rags, and even dead animals that may cause problems later in the treatment process clogging pumps and small pipes. After the sewage has been screened it passes into what is called a grit chamber where sand, grit, cinders and small stones are allowed to settle to the bottom to later be disposed. With screening completed and grit removed, the sewage still contains suspended solids which are gradually allowed to settle to the bottom of a long concrete rectangular sedimentation tank. The settled material is called primary sludge and it is mechanically remove from the sedimentation tanks.
Secondary Treatment Process
After the sewage leaves the settling tank in the primary stage, it is pumped to an aeration tank where it is mixed with air and sludge loaded with microorganisms that use oxygen to breathe and break down the organic matter. Sewage at the aeration tank remains for several hours allowing the process to removes up to 90% of the organic matter.
Meanwhile, the sewage flows from the aeration tank to another sedimentation tank to remove the microorganisms were they clump together, settle to the bottom, and are removed and recycled back into the treatment process.
Tertiary Treatment Process
The final step uses filtering and chemical treatment. This allows the water to be in better condition before it is put back into the water cycle system. The San Jose Creek Water Reclamation Plant has installed filters containing layers of anthracite coal, sand, and gravel which remove any remaining suspended materials from the water. The reclaimed water is then disinfected with chlorine.
After completion of all treatment processes, reclaimed water, is now free of harmful bacteria and viruses and is safe for human contact. Recycled water is then discharged to the San Jose creek destined to recharge groundwater supplies.
Any remaining chlorine in the purified water is removed prior discharge to protect aquatic life in the receiving environment. Water quality measurement and analysis are completed at laboratories located at the treatment plant to ensure reclaimed water meets all requirements of the Regional Quality Control Board.
The cleaning process from preliminary treatment to final disinfection prior reuse or discharge takes approximately ten (10) hours.
Information about the Sanitation Districts of Los Angeles County’s tours and facilities can be found at their website:
http://www.lacsd.org/about/wastewater_facilities/default.asp
The California Water Environment Association awards “best treatment plant of the year” to those facilities employing a state-of-the- art cleansing process, green technologies such as solar panels, and effluents meet stringent state quality standards. Check their website to know which wastewater treament plants have been awarded best in California. http://www.cwea.org/
Saturday, February 20, 2010
Sanitary pipe system design guidelines
The information and guidelines contained herein are to be used whenever applicable. All sanitary sewers shall be designed in accordance to City Standards and to accepted engineering principles. Always consult design guidelines with the City Engineer to ensure local regulations applied to the specific project and location.
Design submittals shall show all lines necessary for the development or improvement, including pipe size, material, appurtenant, manholes & laterals locations, all sewer profiles (slopes, invert elevations, and finished surfaced elevations), cleanouts, backflow devices, lots to be serviced, property lines, easements, etc.
Pipe Materials:
*Vitrified Clay Pipe (VCP): shall conform to the materials section of the current Clay Pipe Engineering Manual published by the National Clay Pipe Institute www.ncpi.org and shall conform to ASTM requirements, Designation C700, Class II. VCP shall have a dense wall and shall not leak through the barrel more than the allowable when tested in accordance with “Hydrostatic Pressure Test” as described in “Clay Pipe Engineering Manual”.
*Polyvinil Chloride (PVC) Pipe: shall conform to ASTM D3034 (SDR 35) for pipe diameter four (4) inches through fifteen (15) inches and ASTM F679 for pipe diameters from eighteen (18) inches through twenty-four (24) inches. PVC sewer pipe shall only be allowed for residential sewage flows. PVC standard laying length shall be 20 feet minimum, bell and spigot joints with elastomeric gaskets (watertight). www.plasticpipe.org ; www.uni-bell.org
*Reinforced Concrete Pipe (RCP): shall be Class II and conform to ASTM C76 for sewer pipe and lined with PVC T-lock sheets applied at the top 300 degrees of the pipe. RCP standard laying segments are 6 to 8 feet, bell and spigot with rubber gasket joints. www.concrete-pipe.org
*Ductile Iron Pipe (DIP): for sewers shall conform to ANSI A21.50 (AWWA C150) and shall be pressure class 150 minimum unless otherwise shown on plans. Asphaltic or polyethylene outside coating/film and interior ceramic epoxy or cement liner (40 mils) is required. DIP shall only be allowed from manhole to manhole when outside of roadways or sewer laterals, unless otherwise specified.
DIP and Cast Iron restraints calculations and other engineering information can be found on the DIP Research Association (DIPRA) www.dipra.org
Horizontal Alignment: shall be preferably located at the center of street and never under the storm water system. Otherwise, sewer lines shall be located within the paved area of the road with not less than one (1) foot between the outside surface of the pipe and the nearest lip of the gutter or edge of improved road shoulder.
*In general, design public sewer mains in straight street sections to run parallel to the street centerline.
*In curved streets design them on one side of the center line to allow installation of other facilities such as water, storm drains, etc.
*Criteria for the separation water and sanitary sewer most conform to the State of California Department of Health Services (DOHS). The minimum separation required is ten (10) feet clearance between walls otherwise DOHS guidelines must be followed.
*Separation from other wet utilities (Storm drain, sewer, recycle water) will be a minimum of five feet (5) clear between pipes except at crossings.
*Separation from other dry utilities (Gas, electrical cable, etc) will be a minimum of four feet (4) clear between the pipes except at crossings.
*Separation from structures, building over-hangs, gutters, property lines, or edges of easement must be a minimum of five (5) feet clearance and three (3) feet from all monuments, and/or lips of gutters. The alignment will be designed so that any 48 inch manhole shall be centered a minimum of three (3) feet from the lip of gutter and any sixty (60) inch manhole shall be centered a minimum of four (4) feet from lip of gutter.
*Horizontal curves in gravity sewer mains are not allowed.
Vertical Alignment: shall conform to the State of California Department of Health Services (DOHS) “Criteria for separation of Water and Sanitary Sewer”.
*Generally provide a minimum of a foot (1) vertical separation from wet utilities and six (6) inches from dry utilities. When the minimum cannot be maintained other measures, such as concrete encasement or ductile iron pipe, may be submitted for approval of the Director of Utilities.
*Vertical curves in gravity sewer mains are not allowed.
Main Sizing Criteria: will be sized to serve the entire tributary area at build-out densities. Large developments may be required to provide trunk or collection system calculation or have a wastewater model run performed.
*Design Flow: is the average domestic flow, around 125 gallons per person per day, multiplied by the Peak Load Factor (may vary from 1.8 to 3.5). In addition, public sewers shall be designed to carry infiltrated water at the rate of 7% of the design flow. *Collection System Capacity Requires (Q) = Peak Factor (PF) x Average Daily Flow (QADF) + Rainfall Inflow and Infiltration (I/I) + Groundwater Infiltration (GWI)
* The minimum pipe size for main sanitary sewers is eight (8) inches inside diameter.
Hydraulic Calculations: Pipe size, flow rates, velocities, and depth for sanitary gravity flows are determined by solving the various parameters of Manning’s Equation.
Q= vA =(1.49/n)*A*{R^(2/3)}*{S^(1/2)}
Q = flow (ft3/sec)
n = Manning roughness coefficient (RCP-DIP-ABS-VCP n = 0.013; PVC n = 0.010)
R= Hydraulic radius (ft) = A/P
A= Area (ft2)
P= Wetted perimeter (ft)
S= Slope = {(∆E difference in Elev.) / (Horizontal distance)}
.v = velocity (ft/s)
D = Pipe diameter (ft)
.d= depth of flow (ft)
*Design all gravity sewers to achieve a minimum velocity of 2 fps when the pipe is flowing full (Qfull) and do not exceed a maximum velocity of 10 fps.
*Maximum depth of flow (at peak flow conditions) shall be 2/3 D; d/D=0.67 for pipe size ten (10) inch or smaller and 3/4 D; d/D= 0.75 for pipe size twelve (12) inch or larger.
*The preferred minimum slope (S) for gravity sewer is 0.005 (0.5%). Flatter slope conditions may be approved (City Standards)
*The maximum slope is 0.15 (15%), or 15 feet per 100 ft. Consideration to relevant factors such as steep terrain, steeper sewers may be allowed with the use of restrained joints.
Hydraulic Grade Line: The hydraulic grade line shall be determined from the design flows, based upon 100 percent development of the tributary area. Hydraulic grade line calculations must be submitted for the design of all lines 12 inches in diameter or larger.
Cover (Bedding): Minimum cover for all gravity sewers shall be 48 inch from top of the pipe to finish grade (City Standards). Per public works construction standard specifications (“Green book”), for cover less than four (4) feet or more than fifteen (15) feet special bedding is required.
Manholes:
*A manhole (MH) is required at every horizontal or vertical change in alignment (i.e. mains intersection).
*Spacing between manholes is 300 feet maximum (City Standards).
*A manhole is required at the end of every main in excess of 200 feet in length however a rodding inlet or cleanout may be installed in lieu if the main size is ten (10) inch or less.
*Mains eighteen (18) inch or larger in diameter and/or eight (8) feet in depth or more require sixty (60) inch diameter M.H.
*When a change of alignment is greater than 30 degrees allow a minimum drop of 0.1 foot (1.2 in) to compensate for energy loss caused by the change of alignment.
*When pipe sizes change at structures, design the inlet crown at least as high as the outlet crown.
*The change of direction at the manhole between the downstream and any incoming sewer shall be a minimum of 90 degrees.
*Drop manholes are not encouraged. They are typically required when the difference in elevation between the incoming and outgoing sewer is greater than two (2) feet. Upstream slope changes should be used to avoid the need for a drop manhole. If one (1) drop manhole can not be avoided at a connection, use a sixty (60) inch M.H., if two (2) or more are required, use a seventy two (72) inch diameter M.H.
Future sewer extension: when a sewer main extension ends at a manhole and the sewer will be extended further in the future, include in the design a three (3) feet long stub out of the MH with a plug or cap for future connection.
Sewer laterals: must be provide for each lot. The minimum sewer lateral size is four (4) inch and will be located on the property frontage.
*The minimum slop of sewer laterals is two (2 %) percent or ¼ inch per foot for four (4) inch diameter laterals and one (1%) percent or 1/8” per foot for six (6) inch laterals.
*Locate sewer laterals outside of driveway areas where possible. In general, sewer laterals will be in the center third of lots when driveway locations are unknown and a minimum of 10 feet from trees whenever possible. For hillside development, place sewer laterals on the low side of property frontages when not in proposed driveway.
*Laterals serving plumbing fixtures below the nearest upstream sewer manhole rim require an approved backflow overflow device.
Grease interceptors: shall be required for any business having the potential of producing grease. General commercial/retail buildings shall require dedicated grease line for future use.
Abandonment of sewer mains: Sewer mains that are to be abandoned will be securely closed at all pipe ends with a cap or at manholes with a concrete plug. Further, mains twelve (12) inch and larger must be filled with a sand slurry (City Standards).
Easements: When sewer cannot be located within the street, it shall be located in an approved easement. Sewer easement shall be a minimum 15 ft in width if it only contains a sewer main or 20 feet wide if it contains another facility. For deep pipe the easement shall be ((2 x depth) – OD) to a maximum 25 feet.
*No structures may encroach on, above, or below the surface of the ground in any public easement. This includes footings, eaves, decks, etc.
*No trees may be planted in a public sewer easement without first obtaining approval of the Director of Utilities.
Access roads: Clear access must be provided and maintained to all structures on the sewer system. Access roads must be a minimum of twelve (12) feet wide and its location must be approved by the streets and sanitation division.
Creek crossings: Advance approval of the Environmental Utilities Director, City Engineer, and other appropriate agencies is necessary to initiate design.
*Sanitary sewers crossing creeks shall be class 52 D.I.P. encased in reinforced concrete or 3/8 inch thick steel carrier pipe (Casing). The top of the encasement shall have a minimum four (4) feet of cover at the lowest point of the crossing.
Water well clearance: Sewer lines shall maintain a minimum 100 foot separation from all public or private wells (properly abandoned wells are not included). If a clearance of less than 100 feet is approved the pipe material shall be approved by the environmental Utilities Director. In no case shall a clearance of less than 50 feet be allowed.
Performance and testing: all sanitary sewers including laterals will be visually inspected prior backfill placement. Once backfill is completed all sanitary sewers will be air-tested for leakage using current ASTM standards prior to acceptance.
Pretreatment: Special pre-treatment may be required per City code for discharge of individual or commercial wastewater to the sewer at the Developer’s expense. Inquire with the City Water Pollution Control if an industrial wastewater discharge permit is required.
Permitting: Permits are required for all sewer work, including but not limited to the following – Excavation; Obstruction; Traffic control; other as necessary.
Design submittals shall show all lines necessary for the development or improvement, including pipe size, material, appurtenant, manholes & laterals locations, all sewer profiles (slopes, invert elevations, and finished surfaced elevations), cleanouts, backflow devices, lots to be serviced, property lines, easements, etc.
Pipe Materials:
*Vitrified Clay Pipe (VCP): shall conform to the materials section of the current Clay Pipe Engineering Manual published by the National Clay Pipe Institute www.ncpi.org and shall conform to ASTM requirements, Designation C700, Class II. VCP shall have a dense wall and shall not leak through the barrel more than the allowable when tested in accordance with “Hydrostatic Pressure Test” as described in “Clay Pipe Engineering Manual”.
*Polyvinil Chloride (PVC) Pipe: shall conform to ASTM D3034 (SDR 35) for pipe diameter four (4) inches through fifteen (15) inches and ASTM F679 for pipe diameters from eighteen (18) inches through twenty-four (24) inches. PVC sewer pipe shall only be allowed for residential sewage flows. PVC standard laying length shall be 20 feet minimum, bell and spigot joints with elastomeric gaskets (watertight). www.plasticpipe.org ; www.uni-bell.org
*Reinforced Concrete Pipe (RCP): shall be Class II and conform to ASTM C76 for sewer pipe and lined with PVC T-lock sheets applied at the top 300 degrees of the pipe. RCP standard laying segments are 6 to 8 feet, bell and spigot with rubber gasket joints. www.concrete-pipe.org
*Ductile Iron Pipe (DIP): for sewers shall conform to ANSI A21.50 (AWWA C150) and shall be pressure class 150 minimum unless otherwise shown on plans. Asphaltic or polyethylene outside coating/film and interior ceramic epoxy or cement liner (40 mils) is required. DIP shall only be allowed from manhole to manhole when outside of roadways or sewer laterals, unless otherwise specified.
DIP and Cast Iron restraints calculations and other engineering information can be found on the DIP Research Association (DIPRA) www.dipra.org
Horizontal Alignment: shall be preferably located at the center of street and never under the storm water system. Otherwise, sewer lines shall be located within the paved area of the road with not less than one (1) foot between the outside surface of the pipe and the nearest lip of the gutter or edge of improved road shoulder.
*In general, design public sewer mains in straight street sections to run parallel to the street centerline.
*In curved streets design them on one side of the center line to allow installation of other facilities such as water, storm drains, etc.
*Criteria for the separation water and sanitary sewer most conform to the State of California Department of Health Services (DOHS). The minimum separation required is ten (10) feet clearance between walls otherwise DOHS guidelines must be followed.
*Separation from other wet utilities (Storm drain, sewer, recycle water) will be a minimum of five feet (5) clear between pipes except at crossings.
*Separation from other dry utilities (Gas, electrical cable, etc) will be a minimum of four feet (4) clear between the pipes except at crossings.
*Separation from structures, building over-hangs, gutters, property lines, or edges of easement must be a minimum of five (5) feet clearance and three (3) feet from all monuments, and/or lips of gutters. The alignment will be designed so that any 48 inch manhole shall be centered a minimum of three (3) feet from the lip of gutter and any sixty (60) inch manhole shall be centered a minimum of four (4) feet from lip of gutter.
*Horizontal curves in gravity sewer mains are not allowed.
Vertical Alignment: shall conform to the State of California Department of Health Services (DOHS) “Criteria for separation of Water and Sanitary Sewer”.
*Generally provide a minimum of a foot (1) vertical separation from wet utilities and six (6) inches from dry utilities. When the minimum cannot be maintained other measures, such as concrete encasement or ductile iron pipe, may be submitted for approval of the Director of Utilities.
*Vertical curves in gravity sewer mains are not allowed.
Main Sizing Criteria: will be sized to serve the entire tributary area at build-out densities. Large developments may be required to provide trunk or collection system calculation or have a wastewater model run performed.
*Design Flow: is the average domestic flow, around 125 gallons per person per day, multiplied by the Peak Load Factor (may vary from 1.8 to 3.5). In addition, public sewers shall be designed to carry infiltrated water at the rate of 7% of the design flow. *Collection System Capacity Requires (Q) = Peak Factor (PF) x Average Daily Flow (QADF) + Rainfall Inflow and Infiltration (I/I) + Groundwater Infiltration (GWI)
* The minimum pipe size for main sanitary sewers is eight (8) inches inside diameter.
Hydraulic Calculations: Pipe size, flow rates, velocities, and depth for sanitary gravity flows are determined by solving the various parameters of Manning’s Equation.
Q= vA =(1.49/n)*A*{R^(2/3)}*{S^(1/2)}
Q = flow (ft3/sec)
n = Manning roughness coefficient (RCP-DIP-ABS-VCP n = 0.013; PVC n = 0.010)
R= Hydraulic radius (ft) = A/P
A= Area (ft2)
P= Wetted perimeter (ft)
S= Slope = {(∆E difference in Elev.) / (Horizontal distance)}
.v = velocity (ft/s)
D = Pipe diameter (ft)
.d= depth of flow (ft)
*Design all gravity sewers to achieve a minimum velocity of 2 fps when the pipe is flowing full (Qfull) and do not exceed a maximum velocity of 10 fps.
*Maximum depth of flow (at peak flow conditions) shall be 2/3 D; d/D=0.67 for pipe size ten (10) inch or smaller and 3/4 D; d/D= 0.75 for pipe size twelve (12) inch or larger.
*The preferred minimum slope (S) for gravity sewer is 0.005 (0.5%). Flatter slope conditions may be approved (City Standards)
*The maximum slope is 0.15 (15%), or 15 feet per 100 ft. Consideration to relevant factors such as steep terrain, steeper sewers may be allowed with the use of restrained joints.
Hydraulic Grade Line: The hydraulic grade line shall be determined from the design flows, based upon 100 percent development of the tributary area. Hydraulic grade line calculations must be submitted for the design of all lines 12 inches in diameter or larger.
Cover (Bedding): Minimum cover for all gravity sewers shall be 48 inch from top of the pipe to finish grade (City Standards). Per public works construction standard specifications (“Green book”), for cover less than four (4) feet or more than fifteen (15) feet special bedding is required.
Manholes:
*A manhole (MH) is required at every horizontal or vertical change in alignment (i.e. mains intersection).
*Spacing between manholes is 300 feet maximum (City Standards).
*A manhole is required at the end of every main in excess of 200 feet in length however a rodding inlet or cleanout may be installed in lieu if the main size is ten (10) inch or less.
*Mains eighteen (18) inch or larger in diameter and/or eight (8) feet in depth or more require sixty (60) inch diameter M.H.
*When a change of alignment is greater than 30 degrees allow a minimum drop of 0.1 foot (1.2 in) to compensate for energy loss caused by the change of alignment.
*When pipe sizes change at structures, design the inlet crown at least as high as the outlet crown.
*The change of direction at the manhole between the downstream and any incoming sewer shall be a minimum of 90 degrees.
*Drop manholes are not encouraged. They are typically required when the difference in elevation between the incoming and outgoing sewer is greater than two (2) feet. Upstream slope changes should be used to avoid the need for a drop manhole. If one (1) drop manhole can not be avoided at a connection, use a sixty (60) inch M.H., if two (2) or more are required, use a seventy two (72) inch diameter M.H.
Future sewer extension: when a sewer main extension ends at a manhole and the sewer will be extended further in the future, include in the design a three (3) feet long stub out of the MH with a plug or cap for future connection.
Sewer laterals: must be provide for each lot. The minimum sewer lateral size is four (4) inch and will be located on the property frontage.
*The minimum slop of sewer laterals is two (2 %) percent or ¼ inch per foot for four (4) inch diameter laterals and one (1%) percent or 1/8” per foot for six (6) inch laterals.
*Locate sewer laterals outside of driveway areas where possible. In general, sewer laterals will be in the center third of lots when driveway locations are unknown and a minimum of 10 feet from trees whenever possible. For hillside development, place sewer laterals on the low side of property frontages when not in proposed driveway.
*Laterals serving plumbing fixtures below the nearest upstream sewer manhole rim require an approved backflow overflow device.
Grease interceptors: shall be required for any business having the potential of producing grease. General commercial/retail buildings shall require dedicated grease line for future use.
Abandonment of sewer mains: Sewer mains that are to be abandoned will be securely closed at all pipe ends with a cap or at manholes with a concrete plug. Further, mains twelve (12) inch and larger must be filled with a sand slurry (City Standards).
Easements: When sewer cannot be located within the street, it shall be located in an approved easement. Sewer easement shall be a minimum 15 ft in width if it only contains a sewer main or 20 feet wide if it contains another facility. For deep pipe the easement shall be ((2 x depth) – OD) to a maximum 25 feet.
*No structures may encroach on, above, or below the surface of the ground in any public easement. This includes footings, eaves, decks, etc.
*No trees may be planted in a public sewer easement without first obtaining approval of the Director of Utilities.
Access roads: Clear access must be provided and maintained to all structures on the sewer system. Access roads must be a minimum of twelve (12) feet wide and its location must be approved by the streets and sanitation division.
Creek crossings: Advance approval of the Environmental Utilities Director, City Engineer, and other appropriate agencies is necessary to initiate design.
*Sanitary sewers crossing creeks shall be class 52 D.I.P. encased in reinforced concrete or 3/8 inch thick steel carrier pipe (Casing). The top of the encasement shall have a minimum four (4) feet of cover at the lowest point of the crossing.
Water well clearance: Sewer lines shall maintain a minimum 100 foot separation from all public or private wells (properly abandoned wells are not included). If a clearance of less than 100 feet is approved the pipe material shall be approved by the environmental Utilities Director. In no case shall a clearance of less than 50 feet be allowed.
Performance and testing: all sanitary sewers including laterals will be visually inspected prior backfill placement. Once backfill is completed all sanitary sewers will be air-tested for leakage using current ASTM standards prior to acceptance.
Pretreatment: Special pre-treatment may be required per City code for discharge of individual or commercial wastewater to the sewer at the Developer’s expense. Inquire with the City Water Pollution Control if an industrial wastewater discharge permit is required.
Permitting: Permits are required for all sewer work, including but not limited to the following – Excavation; Obstruction; Traffic control; other as necessary.
Save time and money by implementing Project Quality Management
The quality paradigm has assumed great importance in modern day business scenario. Management of quality in a project entails two different processes, quality assurance, and quality control.
Quality assurance is a dynamic, interactive process that monitors data collected and analyzes it such that meets project requirements. It refers to the overall management system which includes the organization, planning, documentation, evaluation of project activities and design. The purpose of quality assurance is to help producing data of known quality that states certain level of confidences and enhances the credibility a company in reporting monitoring results, ultimately saving time and money.
Quality assurance shall ensure:
*Data meets clients/project needs, goals and objectives.
*Effective presentation of results.
*Well-designed projects that are precise, accurate, represent the true conditions of the project and are complete.
*Projects are designed using standardized and acceptable techniques.
*Implementation of standards and requirements regulated by federal, state, and local laws.
Quality control refers to the routine technical activities whose purpose is, essentially, error control.
Quality assurance is a dynamic, interactive process that monitors data collected and analyzes it such that meets project requirements. It refers to the overall management system which includes the organization, planning, documentation, evaluation of project activities and design. The purpose of quality assurance is to help producing data of known quality that states certain level of confidences and enhances the credibility a company in reporting monitoring results, ultimately saving time and money.
Quality assurance shall ensure:
*Data meets clients/project needs, goals and objectives.
*Effective presentation of results.
*Well-designed projects that are precise, accurate, represent the true conditions of the project and are complete.
*Projects are designed using standardized and acceptable techniques.
*Implementation of standards and requirements regulated by federal, state, and local laws.
Quality control refers to the routine technical activities whose purpose is, essentially, error control.
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