hobas for penstocks

Newsletter | No. 60 | January 08

ò Meandering through the WhiteMountains, a large wooden penstockserved as the main water supply for alocal hydro facility. Jackman Station, asthe facility is referred to, is fed by theFranklin Pierce Reservoir, which was cre-ated by the hydro’s dam and surroundingearthen dikes. The water elevation in thereservoir is managed according to springrun-off.

Public Service of New Hampshire(PSNH), the Granite State’s largest elec-tric utility, serves more than 475,000homes and businesses. PSNH’s powergeneration facilities consist of nine hydro-electric plants, including the JackmanHydro station, which was built in 1926.This facility, located in Hillsborough, hasbeen serving the area for years, but thepenstock was approaching the end of itsservice life.

HOBAS for Penstocks

Reliable CCFRPM

Prior to the recent improvements, 5,000feet of wood stave penstock extendedfrom the Franklin Pierce reservoir to asurge tank upstream of the powerhouse.This 7.5-foot diameter penstock wasmade up of vintage wood stave sections,circa 1926. Repairs were undertaken in1954 and in the 1970’s, yet the down-stream sections of the wood penstockstill leaked badly. This leakage causedicing problems during winter months andrequired constant maintenance. In 2003,the penstock had a significant rupturethat impacted abutting properties. Toprevent future failures and ensure reliableoperations of the hydro facility, repairs tothe existing penstock were necessary. In

CO N T E N T S

3 | Product ProfileThe PerformanceAdvantage

4 | HOBAS Used on PeaceProject

6 | High Point Picks HOBAS

CONTACT HOBAS PIPE [email protected].: (281) 821-2200

Continued on page 2

THE HIGH STRENGTH AND CORROSION RESISTANT HOBAS PIPE HAS MANYADVANTAGES IN PENSTOCKS.

2 | HOBAS PIPELINE 1/08

a series of contracts, PSNH decided toreplace the remaining wood stave pen-stock with a new pipeline.

Kleinschmidt, headquartered in Pittsfield,Maine, that specializes in energy andwater resource projects, was retained todevelop a feasibility study and engineer areplacement pipeline. Kleinschmidt ini-tially evaluated five pipe material optionsfor the penstock replacement: woodstave, concrete, HDPE plastic, steel andfiber reinforced polymer (FRP). Factorsthat led to the final determination includ-ed the structural reliability, corrosionresistance, hydraulic capacity, ease ofinstallation (pipe weight) and perform-ance history of the pipe material.Kleinschmidt provided their evaluationand recommendations to PSNH, whichchose the fiberglass pipe option and pur-chased CCFRPM pipe manufactured byHOBAS PIPE USA of Houston, Texas.

Design Considerations

“The corrosion resistance and relativestiffness of FRP pipe meant it could besupported on the existing grade and halfburied, rather than placed on saddles orcompletely covered in a buried trench.This design flexibility, combined with alonger projected service life lead to a com-petitive total construction cost for the FRPalternative,” stated Keith Martin, a projectengineer and civil/structural engineer withKleinschmidt’s Pittsfield, Maine, office.

“The lower frictional resistance of HOBAScompared to other materials allowed thereplacement pipe to be reduced to a 7-foot diameter without additional headloss,” stated Martin.

The pipe was half buried in the shallowtrench of the existing penstock, requiringminimal excavation costs and low environ-mental disturbance. Approximately 300feet of the new penstock were supportedabove ground on steel saddles to accom-modate the topography as well as mini-mizing the impact to the wetlands that thepenstock crossed.

HOBAS REPLACES WOOD STAVE PENSTOCK Continued from page 1

SOME OF THE PIPE WAS INSTALLEDON CRADLES TO MINIMIZE THEENVIRONMENTAL IMPACT. HIGHSTRENGTH HOBAS PIPES ARE IDE-ALLY SUITED TO ABOVE GROUNDAPPLICATIONS.

“HOBAS CCFRPM is manufactured by aunique computer controlled centrifugalcasting process. To achieve the higheraxial strength necessary for the above-ground installation, additional reinforce-ment is placed in the longitudinal directionduring the manufacturing process,”explained Rene Garcia, Sr. engineeringassociate with HOBAS Pipe’s Houstonmanufacturing facility. The design flexibil-

THE LIGHTWEIGHT HOBAS FIBER-GLASS PIPE SECTIONS WERE CAR-RIED TO THE POINT OF INSTALLA-TION AND ASSEMBLED USING THESINGLE EXCAVATOR VISIBLE IN THEBACKGROUND.

Continued on page 8

HOBAS PIPELINE 1/08 | 3

Consistent Quality and Performance

ò Most U.S. municipalities have HOBASpipe in their systems and the use ofHOBAS pipe in the USA is expandingfaster than ever after more than 20 yearsof reliable performance. More than 40,000miles of HOBAS pipe has been installedaround the world.

Versatile

HOBAS pipes can be economicallydesigned for non-pressure and pressureservice by varying the quantity, placementand orientation of the glass-fiber rein-forcements.

Smoother Surfaces, High Flow Capacity

HOBAS Pipe is manufactured with aunique, precise, computer-controlled,centrifugal casting process that no othermethod can deliver. This produces veryconsistent, high-density pipe with a mold-smooth exterior surface and a glass-smooth nonporous liner that is resilientand abrasion resistant. In addition tosuperior hydraulics, thin-wall constructionproduces an oversized I.D. for the highestflow capacity available.

The Performance Advantage

Leak-Free Joints

Another HOBAS advantage is push-together joints for a 100 percent leak-freepipeline that preserves the streets aboveand reduces treatment costs.

Straightforward Installation

Installation is quick and easy with pre-dictable, reliable pipe performance byevery method. Push-together joints aresimple and fast to assemble. Lightweightpipes are safe and easy to handle, oftenwith the smaller equipment typically onthe site.


Continued on page 5

ò In 1986, the United States Congressestablished The United States Institute ofPeace (USIP) and has provided $100 mil-lion for construction of a permanent head-quarters facility in Washington D.C. It willbe located at the northwest corner of theNational Mall, facing the Lincoln Memorialand adjacent to the Korean War andVietnam Veterans memorials.

Construction of the facility is scheduledfor completion by the first quarter of 2010.However, there is a great deal of work tobe done prior to groundbreaking. Thisincludes shoring the existing infrastruc-ture. The “United States Institute of PeaceSewer Rehabilitation Project” will ensurestructural integrity to the existing bricksewer that is located under the proposedbuilding site.

HOBAS USED ON PEACEPROJECT

Structural Requirements

The District of Columbia’s water andsewer authority, DCWASA, operates1,800 miles of sewers and provides retailwater and wastewater services to its cus-tomers in the district. DCWASA ischarged with ensuring reliability of thearea’s infrastructure. A brick sewer thatwas reportedly built in 1896 has beenserving the area. Although it was in faircondition, with only a few repairs requiredin recent years along its entire length,planners decided that it needed perma-nent preservation to support future con-struction.

They also decided that slipline rehabilita-tion was necessary to ensure the sewer

would not interfere with the future USIPfacility. HOBAS centrifugally cast, fiber-glass reinforced, polymer mortar(CCFRPM) pipe was the only product thatmet all of the project requirements. Thenew CCFRPM sewer is structurallysound, leak free and provides adequatecapacity.

Randolph Rostas, senior project managerwith the engineering firm of Metcalf &Eddy (M&E), Washington, D.C., wasdesign engineer for the project. Projectmanager was Naveen Krishnamurthy fromtheir office in Baltimore, Md. Their engi-neers evaluated the existing site condi-tions as well as the building proposals.The approximate ground profile nowexists 40 feet above the top of the exist-ing sewer. Depending on which of the finaldesigns for the USIP building is adopted,the proposed lowest level of the slabcould be just five feet above the existingsewer. Regardless of the final design, thepipe to be installed had to be structurallysound, grouted in place and capable ofhandling the final loads.

Preserving Capacity

The existing brick sewer was sliplinedwith 360 linear feet of 69-inch diameterHOBAS CCFRPM pipe. The actual insidediameter of the original brick sewer variedfrom location to location but was general-ly 73 to 75 inches. M&E thoroughly evalu-ated the host pipe conditions in order tomaximize the diameter of the slipliningpipe. The radial clearance calculatedbetween the HOBAS pipe OD and thebrick host pipe ID ranged between 0.25and 1.25 inches.

HOBAS CCFRPM’s efficient cross-sec-tion provides high strength with a thinwall. HOBAS also offers many pipe diam-

THE HOBAS PIPE IS LOWERED INTO THE EXCAVATION DURING THE SLIPLININGPROJECT OF THE CIRCA 1896 BRICK SEWER DURING UNITED STATESINSTITUTE OF PEACE SEWER REHABILITATION PROJECT IN WASHINGTON, D.C.

THE USIP HAS PROVIDED THIS ARCHI-TECT’S RENDERING OF ITS PERMANENTHEADQUARTERS BUILDING PROJECT.

(PHOTO COURTESY OF UNITED STATES INSTITUTE OF PEACE, WASHINGTON, D.C.)


eter choices for this type of application.Some pipe manufacturers offer only“standard” diameters while HOBAS hasmany “in between” sizes, such as the 69-inch nominal diameter utilized in this proj-ect. The very tight fit possible with theflush bell spigot pipe connectors alsocontributed to maximum flow recovery.

General contractor for the USIP project,Clark Construction Group, LLC,Bethesda, Md., brought Hall Contracting,Charlotte, N.C., onboard as the installa-tion sub-contractor for the sliplining oper-ation. Hall had utilized HOBAS on morethan 10 past projects dating back to 1997.K. Michael Hall, CEO, noted “Hall tacklestough large diameter slipline projects andhas used HOBAS pipe almost exclusivelydue to its toughness and ease of installa-tion. This job was no exception.”

The capacity of the existing sewer in thearea that was relined ranged from 103 to119 million gallons per day (MGD) whilethe capacity after rehabilitation was calcu-lated to be 101 MGD. Flow monitoringafter rehabilitation on previously installedHOBAS projects showed a Manning’svalue of .009 to about .011. Manning’s val-

ues in this range are commonly utilized topredict capacity after sliplining. “On thisparticular project, we designed the sewerutilizing a predicted Manning’s value of0.011 for the HOBAS pipe,” statedRostas.

THE BRICK CONSTRUCTION OF EXISTING 19TH CENTURY SEWER IS VISIBLEDURING THE SLIPLINING REHABILITATION PROJECT FOR THE PROPOSEDUSIP BUILDING IN WASHINGTON, D.C.

Ease of Installation

K. Michael Hall commented on the instal-lation, “It appeared from our ‘post TV run’that the flow depths had indeed been low-ered by some 10 to 20 percent.”

“The sliplining went very well,” said Hall,“and after the pipe insertion, we groutedthe annular space ourselves with a light-weight grout and this also went very well.The inspection ports revealed that thegrouting filled the annulus completely.Three ports were installed at the 12o’clock position spaced evenly along the330-foot run. Upon inspection, the portswere solid with grout. We removed thevalves and replaced the tapped holes with1-inch PVC plugs.” The plugs were provid-ed by HOBAS.

With sewer work complete, the engineerand installer both said they were pleasedwith the performance of the pipe and thelevel of service provided by HOBAS.Speaking for engineering firm M&E,Rostas echoed Hall’s satisfaction with theproject, saying, “I had used HOBAS pipein the past and I felt very comfortable withthe product. In this case, I recommendedits use and we are again pleased with theoutcome.”

AS A 20-FOOT SECTION OF HOBAS PIPE IS LOWERED INTO THE EXCAVATION,THE LINCOLN MEMORIAL CAN BE SEEN IN THE BACKGROUND.


ò In 1859, when High Point was namedafter the “highest point” on the NorthCarolina Railroad between Goldsboro andCharlotte, city founders knew that its cen-tral location would attract industry andcommerce. Today, High Point draws visi-tors from 50 states and more than 100countries for the biannual InternationalHome Furnishings Market, the largestevent of its kind in the world.

In 1989 the City of High Point determinedit had to replace a major sanitary sewer.The existing sewer was concrete, so theydecided to replace it with a pipe thatwould provide a longer service life. Two ofthe major factors affecting projected serv-ice life are an inherently corrosion resist-ant pipe and a leak free system. Both ofthese requirements were included in thespecifications.

Thalle Construction Co., Inc. ofHillsborough, N.C., was named as thecontractor and Davis-Martin-Powell &Associates, Inc. of High Point was theconsulting engineer for the project namedDeep River Outfall Segment 2.

HIGH POINT PICKS HOBAS

Long Term Solution

Ben Palmer of Davis-Martin-Powell &Associates, Inc., said, “Basically, the linethat was replaced was 40 years old, con-structed of concrete pipe. It had reachedits life, undersized, deteriorating. It hadseveral point failures in the line just fromthe degradation of the concrete. That wasreally the driving force behind replacingthe whole line. And they were looking for areplacement material that was going to beresistant to the hydrogen sulfide gassesthat were present in the line. And, that ledthem to the HOBAS pipe.”

Ed Powell, president of Davis-Martin-Powell & Associates, echoed Palmer’scomments, saying, “We wanted a pipethat would be inert to the hydrogen sulfideand HOBAS fit the bill.”

Palmer continued, “The city had installeda short segment of 66-inch HOBAS pipeinto a new wastewater pumping stationthat they had built in the early 90’s, whichactually was the starting point for thismajor outfall replacement. They had alsoused some 36-inch HOBAS for a sectionof the force main coming out of the sta-tion. That was really their first experiencewith HOBAS, they liked what they sawand that was what led to the selection ofHOBAS for the remainder of the outfallline.”

Deep Direct Bury

Commenting on the depth of the project,Palmer said, “There were a number of dis-cussions between the city and HOBASregarding the depth it was going to haveto be installed at and HOBAS assured usthat with proper installation, it could with-

stand those burial depths. During andafter the installation, there was no notice-able deflection of the pipe. So, we feltpretty comfortable based on the informa-tion that HOBAS had provided.

“The segment 2 project is completed andperforming as promised. The main trunkline for segment 3 is nearing completion.”

Since HOBAS centrifugally cast, fiber-glass reinforced polymer mortar pipe wasthe only product that inherently fits thecity’s requirements without any add oncoatings or linings, it was the only pipenamed in the specs. Powell explained,“HOBAS CCFRPM pipe can be fabricatedinto a variety of fittings such as elbows,wyes and tee-base manhole risers, so thecity could have the required qualitiesthroughout. The FWC couplings on themain line could also connect to the fittingsmaintaining the leak free quality.”

The City of High Point began specifyingHOBAS pipe for a variety of applicationsin the early 1990’s, and has used morethan 10 miles of this pipe in a variety ofapplications for corrosive environmentsincluding sanitary sewers and foul air. Ofthe many jobs, Deep River OutfallSegment 2 and Segment 3 are the mostrecent. Powell said, “When the entireDeep River outfall replacement is com-plete, including all of the jobs since westarted using HOBAS, more than 40 milesof HOBAS pipe will have been used,”

Thalle Construction installed 13,700 feetof HOBAS 54- to 66-inch sewer pipe atdepths of 35 to 60 feet. The deep sewerconstruction included more than 200,000cubic yards of pre-cut benching andrestoration, 74,000 cubic yards of rockexcavation, 1,427 feet of 96 and 90-inchdiameter tunnels and the removal of 4,500feet of the existing aerial sewer crossings.

AN EXCAVATOR IS USED TO LOWERA SECTION OF HOBAS PIPE IN THETRENCH DURING THE CONSTRUC-TION OF DEEP RIVER OUTFALLSEGMENT 2 IN HIGH POINT, N.C.

Continued on page 7

THE CRUSHED GRANITE USED FORBACKFILL WAS PLACED UP TO 70 PER-CENT OF THE O.D. ON THE SHALLOW-ER DEPTHS. FOR THE DEEPER COVERSOF MORE THAN 15 FEET, THEY PLACEDTHE SAME MATERIAL 12 INCHES OVERTHE TOP OF THE HOBAS PIPE.


Much of the line was installed throughgranite in a rock quarry and requiredblasting. Ed Kuehnel, project managerfor Thalle, was involved in every aspect.He said, “It was definitely a tough job, upto 60 feet in the ground with an averagedepth of about 40 feet. We had one 800-foot run that was 60 feet deep from endto end.

“There was a tremendous amount ofearthwork involved just to get to the pointwhere you could install the pipe. We hadto excavate and build ourselves a benchat 20 feet. We had to get the earth downto a 20-foot cut. The biggest challengeswere the depth and the rock. We had todrill and blast to get the mass rock andtrench rock out.

Bedding was six to 12 inches deep,depending on the depth of the excava-tion, using crushed granite ?-inches indiameter. After the installation crew putthe bedding down, they laid the pipe onthe bedding and adjusted the final lineand grade. The same material was usedfor backfill. On the shallower depths, itwas placed up to 70 percent of the O.D.For the deeper covers of more than 15feet, they placed the same material 12inches over the top of the pipe. The pipeembedment material was available fromthe rock quarry that the pipeline traverses.

Usually when pipeline construction goesthis deep, the engineers strongly consid-er tunneling. In High Point, the mixed faceconditions and hilly terrain were negativefactors for tunneling. The wide-open areaof the project allowed for the deep directbury with the benched construction andonly a minimum of tunneling. Powell said,“The HOBAS was ideal. It was easy tohandle for direct bury and worked just aswell in the tunnels.”

The extreme depth extending to about60-feet in much of the line eliminated theneed for several lift stations that wouldhave been needed in a shallower instal-lation. Choosing a deeper installationand a pipe system with an extended,maintenance free life, the City of HighPoint demonstrated that it recognizesthe long-term benefits of investing ininfrastructure.

Performance Confidence

“The job turned out really well. We werevery pleased with the pipe. It was the firsttime that I personally had worked with thatpipe. It’s easy to install. It’s lighter so yourrigging and equipment can be lighter.”

Because of the depth, the engineersspecified a pipe stiffness of 72 psi for all ofthe installation and had full confidence inthe structural characteristics of theHOBAS pipe, so there was no questionabout its strength.

Greg Hall, High Point project engineer,commented on the city’s acceptance ofthe new line. He said, “We air test eachjoint independently. On pipes of 30-inchand larger, a test pressure of 3.5 psi wouldapply. We’ve had less than six joints failand every one of those would be classifiedas an installation problem. Minimal effortwas required to correct all six prior to jobcompletion.This project was one of many phases thatHigh Point is undertaking to replace theinterceptor system on the east side oftown. As it neared completion, the citycontinued its reliance on HOBAS, startinga new job using 54-inch pipe.

“Overall, counting this job and two previ-ous jobs, we’ve put in 10 miles of HOBASpipe. We have not used any RCP in a longtime but we do know from surroundingcommunities that they have had consider-able problems with it.

“We’ve been more than pleased with theperformance of the HOBAS pipe and theinstallation has gone smoothly. “The pre-cautions in handling the pipe are nogreater than with any other material..”

Superior Technical Service

The sections that were replaced had somesignificant infiltration problems. Hall said,“It’s hard for us to put a figure on infiltra-tion because that segment is only phasefour out of six, so it’s hard to get a number

A SURVEYOR’S STATION IS USEDTO DIRECT THE LOCATION OFHOBAS PIPE IN THE TRENCH DUR-ING THE CONSTRUCTION.

till the whole project is built. I can’t giveany numbers but I know that infiltrationhas definitely decreased..”

Hall also addressed future plans, “HOBASwill continue to be allowed for use on anyproject we have. The company is great towork with. In fact that is something wewere talking about last week in the publicservices department. Their technical sup-port and their technical people areJohnny-on-the-spot. If we’ve got anyquestions – they’re right on top of it.”


HOBAS PIPE USA

1413 E. Richey RoadHouston, Texas 77073

Tel: (281) 821-2200

ADDRESS SERVICE REQUESTED

ity is just one of the benefits provided bythis product.

“PSNH bought the HOBAS pipe directlyand CCB, Inc. of Westbrook, Maine (CCB)was contracted to install it,” stated Mr.Newell Porter, project manager with CCB.“Prior to this project, I had heard ofHOBAS pipe but had never installed it.”

The job site posed some challenges asthe pipe was installed in a remote area.“The pipe arrived as scheduled andunloaded near the roadside. This phaseof the job was 1,020 feet of 84-inch diam-eter HOBAS pipe. The individual jointswere then carried to the point of installa-tion with an excavator. We had no truckaccess to the installation point. A HOBASfield rep was onsite pretty much from dayone. The first part of the installation wasthrough a curve where 10-foot joint sec-tions were connected and then deflectedto make up the curve,” stated Porter.

The HOBAS FWC coupling joint utilizedon this project is a pressure joint. It iscommonly used in direct bury applicationand also for above ground installations

HOBAS FIELD SERVICE CREW ASSISTEDTHE INSTALLATION CONTRACTOR

such as penstocks. It is a structural fila-ment wound sleeve over wrapped andmechanically locked to an internal full-faced elastomeric membrane. The sealingdesign includes both lip and compressionelements so the joint is suitable for bothnon-pressure and pressure service up to250 psi. “In our case, we air tested eachjoint after assembly with a 10 psi air test.None of the joints leaked. Once the linewas in operation, we were required tovisually inspect each and every joint for asign of leakage and there was none,”stated Porter.

Tight Sealing Joints

JML Trucking and Excavating of Errol,N.H., was the installation sub-contractorfor CCB. Mr. Butch Lane echoed the gen-eral contractor’s sentiments, “It really is agood pipe. The joints are really tight. Iknow that we’ve had people come by andlook at the project, and they are all happy.We were able to put PSNH online twoweeks ahead of schedule and that makesthem happy.”

“At the end of the project, it was found tobe approximately seven times cheaperper foot to utilize the fiberglass pipeoption partially backfilling the penstockthan to support it above ground,” summa-rized Martin. Hydraulic advantages andlongevity of the line will also provide lifelong savings.

HOBAS pipes have been utilized in aboveground applications in the USA since1989 and worldwide for penstock applica-tions for over 20 years.

HOBAS REPLACES WOOD STAVE PENSTOCK Continued from page 2

hobas for penstocks

Documents