AN ECONOMICAL AN ECONOMICAL RIVER INTAKE PUMP RIVER INTAKE PUMP

STATIONSTATION

By: Walter T. Winn, Jr., P.E., DWRE, BCEE, F.ASCEBy: Walter T. Winn, Jr., P.E., DWRE, BCEE, F.ASCEGina R. Bolton, P.E., M.ASCEGina R. Bolton, P.E., M.ASCE

Northeast Texas Section WEAT Biennial SeminarNortheast Texas Section WEAT Biennial SeminarLongview, TexasLongview, Texas

OverviewOverview

IntroductionIntroduction Water SupplyWater Supply Intake ConstraintsIntake Constraints Unconventional Intake DesignUnconventional Intake Design Modifications to Design after Construction Modifications to Design after Construction

SubmittalsSubmittals Resolution of Operational IssuesResolution of Operational Issues ConclusionsConclusions

Trinity Rural Water Supply Trinity Rural Water Supply CorporationCorporation

Located in Trinity, Polk, and Walker CountiesLocated in Trinity, Polk, and Walker Counties Serves approximately 1,400 customersServes approximately 1,400 customers System previously served by ground water and System previously served by ground water and

purchased water from Trinity River Authority purchased water from Trinity River Authority (TRA) Trinity Co. Regional System and the City (TRA) Trinity Co. Regional System and the City of Trinityof Trinity

Additional water not available from TRA Additional water not available from TRA Regional System & Trinity. No groundwater of Regional System & Trinity. No groundwater of acceptable quality and quantity.acceptable quality and quantity.

New Source of SupplyNew Source of Supply

Water rights from Lake Livingston owned by Water rights from Lake Livingston owned by TRA and reserved for local useTRA and reserved for local use

Raw water from Trinity River at headwaters of Raw water from Trinity River at headwaters of Lake LivingstonLake Livingston

Plant site located 1Plant site located 1--½½ mile north of SH 19 mile north of SH 19 crossing of the Trinity River, west of SH 19crossing of the Trinity River, west of SH 19

Intake ConstraintsIntake Constraints

Poor soil conditionsPoor soil conditions High groundwater tableHigh groundwater table Financial limitationsFinancial limitations Decided to try unconventional floating pump Decided to try unconventional floating pump

station designstation design

Plant Flow DiagramPlant Flow Diagram

Soil ProfileSoil Profile

Unconventional Intake DesignUnconventional Intake Design

Submerged intake pipe and intake screenSubmerged intake pipe and intake screen SelfSelf--priming centrifugal pumps priming centrifugal pumps Above ground floating platform systemAbove ground floating platform system

Intake Pump DetailsIntake Pump Details

Lowest available pump setting is 135 ft mslLowest available pump setting is 135 ft msl Can retain prime to a river level of 106 ft mslCan retain prime to a river level of 106 ft msl 100 year flood elevation is 141 ft msl100 year flood elevation is 141 ft msl Pumps can operate over a 36 ft of variation in Pumps can operate over a 36 ft of variation in

river levelriver level

Modifications to Design After Modifications to Design After Construction SubmittalsConstruction Submittals

The pumps selected by Contractor were The pumps selected by Contractor were significantly heavier than the originally specified significantly heavier than the originally specified pumpspumps

Concrete slab on platform was modified to use Concrete slab on platform was modified to use light weight concrete and reduce slab thickness light weight concrete and reduce slab thickness from 6from 6”” to 5to 5””..

Float Test of PlatformFloat Test of Platform

Problems Discovered in TestingProblems Discovered in Testing

Platform twisting, putting torque on the posts Platform twisting, putting torque on the posts and pipe rollers holding it in place.and pipe rollers holding it in place.

Platform was not level as it was tilting towards Platform was not level as it was tilting towards the corner where the pumps were placed. the corner where the pumps were placed.

Therefore, the weight was not evenly distributed Therefore, the weight was not evenly distributed across the platform.across the platform.

Back to the drawing board.Back to the drawing board.

Initial ConfigurationInitial Configuration

Revised ConfigurationRevised Configuration

Buoyancy CalculationsBuoyancy Calculations

Concrete Ballast

Issues in OperationIssues in Operation

Pumps kept losing prime Pumps kept losing prime Operation at design flow rate of 700 gpm was Operation at design flow rate of 700 gpm was

fine, but unable to reduce the flow rate below fine, but unable to reduce the flow rate below 300 gpm300 gpm

Chlorine Dioxide SystemChlorine Dioxide System

Air Release Valve

Electric Solution Valve

FIGURE 1 INTAKE PUMP CURVES

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

55.00

60.00

0 100 200 300 400 500 600 700 800

Flow (gpm)

Hea

d (ft

)

SystemCurve at131

680 rpm

780 rpm

880 rpm

980 rpm

1080rpm

Resolution of Operation IssuesResolution of Operation Issues

Pumps kept losing prime Pumps kept losing prime –– Found that chlorine Found that chlorine dioxide injection into pump suction was dioxide injection into pump suction was introducing air. Added electric solution valve introducing air. Added electric solution valve and air release valve.and air release valve.

Operation at design flow rate of 700 gpm was Operation at design flow rate of 700 gpm was fine, but unable to reduce the flow rate below fine, but unable to reduce the flow rate below 300 gpm 300 gpm –– Found that flat pump curves caused Found that flat pump curves caused VFDs to VFDs to ““searchsearch”” for flow set point. Controls for flow set point. Controls changed to set pump speed instead of flow rate.changed to set pump speed instead of flow rate.

ConclusionsConclusions

Worked through issues to develop Worked through issues to develop unconventional river intake pump station.unconventional river intake pump station.

Saved Trinity Rural WSC an estimated $650,000, Saved Trinity Rural WSC an estimated $650,000, about 65% of the original estimated intake about 65% of the original estimated intake pump station cost.pump station cost.

Questions?Questions?