technologies in wastewater collection systems

Emerging Technologies in Emerging Technologies in Wastewater Collection SystemsWastewater Collection Systems

Douglas McCutchen, CCMDouglas McCutchen, CCMBrian Karmasin, P.E., BCEEBrian Karmasin, P.E., BCEE

CMAA Annual Conference CMAA Annual Conference –– Oct 2008Oct 2008San Francisco, CaliforniaSan Francisco, California

Keville Enterprises

TodayToday’’s Presentation Outline s Presentation Outline

Overview of TechnologiesOverview of TechnologiesDesign considerationsDesign considerationsCost implicationsCost implicationsAdvantages/disadvantagesAdvantages/disadvantages

Case Study: Scott Mill Hill, Case Study: Scott Mill Hill, Jacksonville, FLJacksonville, FL

Engineering Feasibility StudyEngineering Feasibility StudyDesign ImplementationDesign ImplementationProcurementProcurementConstructionConstruction

TodayToday’’s Presentation Outline s Presentation Outline Overview of TechnologiesOverview of Technologies

Design considerationsDesign considerationsCost implicationsCost implicationsAdvantages/disadvantagesAdvantages/disadvantages

Case Study: Scott Mill Hill, Case Study: Scott Mill Hill, Jacksonville, FLJacksonville, FL

Engineering Feasibility StudyEngineering Feasibility StudyDesign ImplementationDesign ImplementationProcurementProcurementConstructionConstruction

Overview of TechnologiesOverview of Technologies

Conventional gravity systemsConventional gravity systemsShallow gravity systemsShallow gravity systemsVacuum sewer systemsVacuum sewer systemsLow pressure systemsLow pressure systemsSmall diameter gravity sewer systemsSmall diameter gravity sewer systems


Conventional gravity systemsConventional gravity systemsShallow gravity systemsShallow gravity systemsVacuum sewer systemsVacuum sewer systemsLow pressure systemsLow pressure systemsSmall diameter gravity systemsSmall diameter gravity systems

The Gravity Sewer System Includes The Gravity Sewer System Includes Trunk Sewers, Manholes, Collection Trunk Sewers, Manholes, Collection Lines, and Private LateralsLines, and Private Laterals

Why consider conventional gravity Why consider conventional gravity sewers?sewers?

Tried and true for decadesTried and true for decadesSystem works passively (except for lift System works passively (except for lift stations)stations)Flexibility to expandFlexibility to expand

Design ConsiderationsDesign Considerations

Size and slope of pipes determined by Size and slope of pipes determined by minimum scouring velocity requirementsminimum scouring velocity requirementsInstallation can require deep excavations Installation can require deep excavations to maintain grade to maintain grade Potential for I/I problems due to leaky Potential for I/I problems due to leaky manholes, pipe jointsmanholes, pipe jointsOperation & maintenance costs and Operation & maintenance costs and requirements are well knownrequirements are well knownRequires lift stations Requires lift stations –– must have available must have available propertiesproperties

Cost ImplicationsCost Implications

Most cost effective for areas with Most cost effective for areas with topographic relieftopographic reliefRoadway rebuild typically required due to Roadway rebuild typically required due to large open cut trencheslarge open cut trenchesMinimal relief = deep sewers = more moneyMinimal relief = deep sewers = more money

Wider open cut trenchesWider open cut trenchesDewateringDewateringImpacts to surrounding areasImpacts to surrounding areas

O&M costs only for pumps at lift stations O&M costs only for pumps at lift stations

AdvantagesAdvantages

Familiarity Familiarity with the operation and maintenance of gravity sewer systems and lift stations.

MaintenanceThere are no mechanical components to gravity connections and therefore no routine maintenance is associated with it.

Operating cost Operational costs for the gravity sewer systems are only for the pumps at the various lift stations.

Storage Gravity sewer systems typically have large amounts of storage volume.

Future Expansion

Conventional gravity sewers are typically oversized in design and are generally accommodating to future flow.

Peak flow shaving

Can use a SCADA system to set lift station cycle times to shave peak flows at their WWTPs.

DisadvantagesDisadvantagesConstruction cost

Depending on the depth of construction, amount of dewatering, and amount of replacement done, cost can run high.

Impact to natural environment

Gravity sewers in flat areas can tend to run deep. Deep installation can lead to wide trenches and impact to natural flora and fauna in the area.

DewateringThis alternative can require extensive dewatering due to high groundwater conditions and deep trenches; therefore the construction cost can be higher.

Multiple site requirements

Typically, several lift stations are required for a sewered area. Ownership of the land and/or easements would be required to facilitate the installation of the stations.

InfiltrationBased on the depth of sewers, the groundwater table and the number of manholes, the groundwater infiltration in the collection system can be high.

Installation of Conventional Gravity Installation of Conventional Gravity Sewer SystemSewer System



What is a Shallow Gravity Sewer?What is a Shallow Gravity Sewer?

Same concept as conventional gravity sewer except:Same concept as conventional gravity sewer except:

Cleanouts instead of manholesCleanouts instead of manholes

Packaged low flow lift stationsPackaged low flow lift stations

Maximum depth of pipe before pumping is 8 to 10 Maximum depth of pipe before pumping is 8 to 10 feetfeet

Why consider shallow gravity sewers?Why consider shallow gravity sewers?

Same technology as the tried and true Same technology as the tried and true gravity systemgravity systemPipes installed at minimal cover means Pipes installed at minimal cover means easier and quicker constructioneasier and quicker constructionDecreased aesthetic impacts during Decreased aesthetic impacts during constructionconstructionUtility can preclude hiring engineer for lift Utility can preclude hiring engineer for lift station design since lift stations are station design since lift stations are packagedpackaged


Size and slope of pipes determined by Size and slope of pipes determined by minimum scouring velocity requirementsminimum scouring velocity requirementsTraffic loading in right of way concernsTraffic loading in right of way concernsDecreased flexibility when line is plugged Decreased flexibility when line is plugged due to lack of manholesdue to lack of manholesRequires additional, but smaller, lift Requires additional, but smaller, lift stations compared to conventional gravitystations compared to conventional gravityAdditional lift stations yields additional Additional lift stations yields additional maintenance requirementsmaintenance requirements


Most cost effective for areas with Most cost effective for areas with topographic relieftopographic reliefRoadway rebuild typically required due to Roadway rebuild typically required due to large open cut trencheslarge open cut trenchesMinimal relief = deep sewers = more moneyMinimal relief = deep sewers = more money

Wider open cut trenchesWider open cut trenchesDewateringDewateringImpacts to surrounding areasImpacts to surrounding areas

O&M costs only for pumps at lift stations O&M costs only for pumps at lift stations


Familiarity Familiarity with the operation and maintenance of gravity sewer systems and lift stations.

MaintenanceThere are no mechanical components to a gravity connection and therefore no routine maintenance associated with it.

Storage Gravity sewer systems typically have large amounts of storage volume.

Peak flow shaving

Utilities can use a SCADA system to set lift station cycle times to shave peak flows at their WWTFs.

Installation cost Minimal excavation and backfill along with dewatering.

Future Expansion Expandable in developments.

Closed system Infiltration from the collection system is minimized.

DisadvantagesDisadvantages

Multiple Site Requirements

Typically, several lift stations are required for a sewered area. Ownership of the land and/or easements is required to facilitate the installation of the stations.

Solids Deposition

Placing pipe in the ground at shallow depths could translate into a minimal slope, causing solids to settle out in the piping.

Traffic Loading Pipes can possibly be damaged by traffic loading.

O&M CostsA large number of pump station systems can increase O&M costs due to the power consumption and maintenance required on the units.



Why consider vacuum sewers?Why consider vacuum sewers?

Poor site conditions (bad soils, high Poor site conditions (bad soils, high groundwater)groundwater)

Neighborhood retrofitNeighborhood retrofit

Site issues for multiple lift stationsSite issues for multiple lift stations

What is a Vacuum Sewer System?What is a Vacuum Sewer System?

Collection chambers Collection chambers Sit in ROW and collect sewage from Sit in ROW and collect sewage from homes/businesseshomes/businesses

Vacuum mainsVacuum mainsConvey sewage from the collection chamber to the Convey sewage from the collection chamber to the vacuum pump stationvacuum pump station

Vacuum pump stationVacuum pump stationVacuum pumps and collection tank provide negative Vacuum pumps and collection tank provide negative pressure on the collection systempressure on the collection systemSewage pumps draw out of collection tank and pump Sewage pumps draw out of collection tank and pump into force main for further conveyanceinto force main for further conveyance

A Vacuum Sewer System Relies on a A Vacuum Sewer System Relies on a Central Vacuum Station to Central Vacuum Station to ““SuckSuck””Wastewater from Each Valve PitWastewater from Each Valve Pit

CollectionCollectionChamberChamber


Collection chamberCollection chamberProvide 1 chamber serves up to 4 householdsProvide 1 chamber serves up to 4 householdsAccommodate HAccommodate H--20 traffic load20 traffic loadSet at elevation to allow gravity flow from the Set at elevation to allow gravity flow from the homehome

PipelinePipelineSDR 21 PVC SDR 21 PVC --Transmission mains and service Transmission mains and service lateralslateralsMinimum slope of 0.2% between liftsMinimum slope of 0.2% between liftsDuctile iron pipe above gradeDuctile iron pipe above gradePipeline installed in a sawtooth profilePipeline installed in a sawtooth profile

Sawtooth ProfileSawtooth Profile


Vacuum StationVacuum StationLocate in low spot in the collection areaLocate in low spot in the collection areaTwo sets of pumps Two sets of pumps –– vacuum and sewagevacuum and sewageOdor control system neededOdor control system neededStandby diesel generator requiredStandby diesel generator requiredCareful selection of sewage pumps is crucial Careful selection of sewage pumps is crucial for proper facility operationfor proper facility operation


Best suited for areas with poor soils and/or Best suited for areas with poor soils and/or high groundwater with some topographic high groundwater with some topographic reliefreliefShallow construction yields reduced Shallow construction yields reduced roadway repair requirementsroadway repair requirementsVacuum station houses two sets of pumps Vacuum station houses two sets of pumps which will increase O&M costswhich will increase O&M costsIncreased field time for operations staff Increased field time for operations staff due to maintenance needs for collection due to maintenance needs for collection chamberschambers


Single site requirement

Typically, only one vacuum and pumping station is required. The station can typically pull vacuum at the vacuum main at a distance of up to 10,000 linear feet.

Pipeline Small pipe diameters are sufficient if station is properly located.

Impacts to surroundingenvironment

Smaller piping and shallow depths tend to lead to smaller impacts to existing flora and fauna, homeowner landscaping, and driveways.

Closed systemInfiltration from the collection system is minimized, therefore reducing the operating and pumping costs at the wastewater treatment facility.

System integrity

The integrity of the system (from collection chambers to the vacuum station) can be monitored by the operators from a control panel located at the vacuum station

DisadvantagesDisadvantagesMaintenance Calls Operators will be required to respond to low

vacuum alarms in a timely fashion.

Spare Parts Inventory Utility will need to purchase and maintain a spare parts inventory for the vacuum system.

Future Expansion Vacuum sewers are not as flexible as conventional gravity sewers if future growth is expected.

Storage Storage in the collection system does not compare to gravity sewer systems.

Peak flows/loadings to WWTFs

Stations typically run in a batch cycle, meaning WWTFs will see unsteady flows if the majority of the service area is on vacuum.

AestheticsVacuum system chambers are located in front yards of each home and can require a 4 to 6 inch vent system in customer’s yards.



What is a Low Pressure Sewer What is a Low Pressure Sewer System?System?

Common force mainCommon force mainIndividual grinder pump stationIndividual grinder pump station

Grinder Pumps May Be Installed at Grinder Pumps May Be Installed at the Rightthe Right--ofof--Way or Near the HomeWay or Near the Home

Right-of-Way

Force Main

Home Sewer

Grinder Pump Unit

Service Lateral

Force Main

Why consider pressure sewers?Why consider pressure sewers?

Difficult site conditionsDifficult site conditionsTopographyTopographyHigh groundwater levelHigh groundwater level

TopographyTopography

EconomicsEconomics

Infiltration / InflowInfiltration / Inflow

Design ConsiderationsDesign ConsiderationsGrinder PumpGrinder Pump

One unit per homeOne unit per homePlastic tank and controlsPlastic tank and controlsPositive Displacement vs. CentrifugalPositive Displacement vs. Centrifugal


Pressure MainsPressure MainsSmall Diameter 1 Small Diameter 1 ½½--in to 4in to 4--ininMaterial PVC or HDPEMaterial PVC or HDPEOperating Pressure < 70 psiOperating Pressure < 70 psi

Service ConnectionService ConnectionService pipe 1 Service pipe 1 ¼¼--in in Shut off / check valve at property lineShut off / check valve at property line


Manholes / AppurtenancesManholes / AppurtenancesUsed for isolation, cleanouts and air releaseUsed for isolation, cleanouts and air release

A STEP System Removes Solids A STEP System Removes Solids with a Septic Tank Prior to Pumpingwith a Septic Tank Prior to Pumping


ConstructabilityTrenching is reduced due to small diameter piping. Installation can also be done utilizing trenchless technologies.

Construction costShallow excavation and backfill, along with small diameter piping reduces construction costs.

Infiltration

The lack of manholes in a pressure system, along with the use of gasketed PVC or butt-welded HDPE, reduces or eliminates infiltration.

SafetyThere are no manholes or wetwells to be entered by the operation and maintenance personnel.

DisadvantagesDisadvantagesO&M Costs The homeowner is required to provide power

and maintain the system.

Maintenance cost Annual maintenance is generally required.

Maintenance knowledge Homeowner will have to learn how to maintain the pumps.

Reliability Power outages can potentially cause overflows into homes.

Storage Storage in the system is only in the gravity line and/or septic tank.

Public perceptionShifting O&M costs to the homeowner may cause customer complaints to the utility provider.



What is a Small Diameter Gravity What is a Small Diameter Gravity Sewer?Sewer?

Building sewer Building sewer

Interception tankInterception tank

Service lateralService lateral

Collection mainCollection main

Lift stationLift station

A Small Diameter Gravity Sewer A Small Diameter Gravity Sewer System Removes Solids to Reduce System Removes Solids to Reduce Required Pipe SizeRequired Pipe Size

Why consider small diameter gravity Why consider small diameter gravity sewers?sewers?

Poor site conditions (bad soils, high Poor site conditions (bad soils, high groundwater)groundwater)

Provides gravity service through the systemProvides gravity service through the system

Use of septic tank provides safeguard for Use of septic tank provides safeguard for sewage storagesewage storage


Hydraulic design should allow for infiltration and Hydraulic design should allow for infiltration and inflow in pipelineinflow in pipeline

Interceptor tanks must be watertightInterceptor tanks must be watertight

Provide means to flush collector mainsProvide means to flush collector mains

Lift station needs to consider wastewater will be Lift station needs to consider wastewater will be septic and corrosiveseptic and corrosive


Reduced capital costsReduced capital costs

Small pipe sizeSmall pipe size

Shallow construction (24 to 30 inches)Shallow construction (24 to 30 inches)

Use of cleanouts minimizes manhole costsUse of cleanouts minimizes manhole costs

Installed in ROW Installed in ROW

AdvantagesAdvantagesFamiliarity O&M staff is familiar with the operation and

maintenance of a gravity sewer system.

Maintenance There are no mechanical components to a gravity connection.

Operating cost Operational costs are only the pumps at the various lift stations.

StorageGravity sewer systems have large amounts of storage volume. The septic tank also has storage volume.

Peak flow shaving Use SCADA system to set lift station cycle times to shave peak flows at their WWTFs.

Construction costLess excavation and backfill than conventional sewers and lack of manholes and smaller pipe sizes decreases capital costs.

Closed system Infiltration from the collection system is minimized.

DisadvantagesDisadvantages

Multiple site Requirements

Typically, several lift stations are required for a sewered area. Ownership of the land and/or easements is required to facilitate the installation of the stations.

Septic Tanks Solids from the septic tanks must be pumped out periodically by the homeowner.

Limited experience SDGS systems are not widespread, however several hundred have been installed in the

Odors Odors may result from sewage going septic in the stations.

TodayToday’’s Presentation Outline s Presentation Outline

Overview of technologiesOverview of technologiesDesign considerationsDesign considerationsCost implicationsCost implicationsAdvantages/disadvantagesAdvantages/disadvantages

Case study: Scott Mill Hill, Case study: Scott Mill Hill, Jacksonville, FLJacksonville, FL

Scott Mill Hill, Jacksonville FLScott Mill Hill, Jacksonville FL

Background InformationBackground Information

Existing neighborhood that includes over Existing neighborhood that includes over 400 homes and small businesses400 homes and small businessesIdentified as part of JEAIdentified as part of JEA’’s Septic Tank Phase s Septic Tank Phase Out programOut programLocated in proximity to the St. Johns RiverLocated in proximity to the St. Johns RiverVery high groundwater levelVery high groundwater levelGeotechnical investigations indicated some Geotechnical investigations indicated some areas had extremely poor soilareas had extremely poor soil

Owner ConcernsOwner Concerns

Difficulty finding three separate sites for Difficulty finding three separate sites for gravity sewer lift stationsgravity sewer lift stationsConstruction impacts to residentsConstruction impacts to residents

Roadway closuresRoadway closuresTree removalTree removal

Construction costsConstruction costsAcquire property or easements for lift Acquire property or easements for lift stationsstationsInstalling gravity sewer in high Installing gravity sewer in high groundwater/flat area near St Johns Rivergroundwater/flat area near St Johns River

Engineering Feasibility StudyEngineering Feasibility Study

Evaluated conventional gravity sewer versus Evaluated conventional gravity sewer versus vacuum sewervacuum sewerOwner did not want low pressure system Owner did not want low pressure system 20 year lifecycle cost indicated vacuum 20 year lifecycle cost indicated vacuum sewer was 18% cheaper than conventional sewer was 18% cheaper than conventional gravity sewer systemgravity sewer systemJEA decided to install vacuum systemJEA decided to install vacuum system

Design ImplementationDesign Implementation

Preliminary Preliminary investigationinvestigation

Soft digsSoft digsGeotechnical boringsGeotechnical boringsSurveySurvey

Routing analysis for Routing analysis for vacuum mainsvacuum mainsHomeowner survey for Homeowner survey for service connectionservice connection

Design ImplementationDesign Implementation

Line sizing and layoutLine sizing and layoutRoadway impactsRoadway impactsTraffic impactsTraffic impactsVacuum station sizingVacuum station sizing

Line layout and designLine layout and design

Vacuum Station Collection TankVacuum Station Collection Tank

Incoming Incoming vacuum mainsvacuum mains

Sewage pumpsSewage pumps

Isolation valvesIsolation valves

Vacuum Station Vacuum PumpsVacuum Station Vacuum Pumps

Suction pipingSuction piping

Discharge pipingDischarge piping

Odor control Odor control requiredrequired

Value Engineering OpportunityValue Engineering Opportunity

Initial bids were highInitial bids were highVE Team VE Team Areas of DiscussionAreas of DiscussionChanges made and savings achievedChanges made and savings achieved

ConstructionConstruction

QA inspection QA inspection oversightoversight

Daily vacuum Daily vacuum TestingTesting

Final 4Final 4--hour Testhour Test

Testing of vacuum Testing of vacuum chamberschambers


Backfill and Backfill and compactioncompaction

Use of Use of dedicated air dedicated air intake linesintake lines


Use of Use of ““liftslifts”” to to avoid utility conflictsavoid utility conflicts

Changes during Changes during constructionconstruction

Questions & AnswersQuestions & Answers

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