Sewer root control in Los Angeles

Since digging up countless miles of the 6,500 mile system to clean out the pipes is not a cost-effective solution, the program hinges on the combination of a strict cleaning schedule and chemical applications.

A new three-year contract begins with city crews cleaning the pipes using mechanical rodding machines and high-velocity sewer cleaners. Then, the pipes are chemically treated with the active ingredients metam-sodium and dichlobenil, which have been used in sewer maintenance for more than 30 years.

Once the chemical has been applied, the pipes are cleaned again six months later to prevent the collection of dead roots and other debris that could possibly cause blockages.

“Common blockages are caused by either fats, oils or greases, which can be fought by developing ordinances and scheduling routine cleanings; or root intrusion – and this requires a different solution, as regular cleaning does not prevent root regrowth,” said Barry Berggren, division manager for the City of Los Angeles wastewater collection system. “It’s a lot like pruning a tree, you cut roots from a sewer, but they will just grow back thicker and stronger.”

The chemical effectiveness is twofold. First, the metam-sodium breaks down into a gas that kills roots on contact, while the dichlobenil inhibits root growth and prevents the root from growing back. However, when the metam-sodium breaks down, it targets only the roots – it does not move through the root system to kill the plant. Thus far, the city’s root control program is said to have a 99.6 per cent success rate – or, in other terms, about 0.4 per cent of the pipes treated will experience an overflow within two years.

While the metam-sodium is a somewhat restricted chemical, it has been used for years in the agriculture industry and has no effect on the downstream 80 to 400 million gallon treatment plants.

Although the program has been successful and pipe maintenance remains on a 20 to 24 month cycle, it seems that the root problem is not easily remedied.

“More than 50 per cent of the root problem stems from private house laterals – the pipes between the house and the connection to the city’s mainline sewer,” said Mr Berggren. “Most of the time, roots grow from the private laterals and move into the city system.”

Often private homeowners do not realise that the roots have infiltrated their systems and although there are private sewer cleaners that will come out and clean your pipes, the roots that are cleared from the homeowner’s pipes are often pushed into the city’s pipes, causing
blockages.

Throwing another wrench into the program, each pipe segment must be analysed to ensure that it is given the correct treatment. The dose of the chemicals and cleaning depends on the type of tree, the size of the root, the severity of intrusion, and the slope and movement of water through the pipe.

Generally two types of roots are found in sewer lines – veils and tails. Veil roots penetrate the top or sides and hang from the pipe’s upper surface and skim the steady flow. Tail roots, however, grow into the pipe from any direction and continue to grow downstream. Eventually, the tail root fills the pipe and causes major damage. Tail roots upward of 40 feet long have been removed from sewers.

Root growth is usually less prevalent in late spring and summer when the tree’s canopy is growing. Once fall and winter blow in, the lack of rainfall and colder temperatures cause the roots to go in search of a suitable source of nutrients. A microscopic opening would allow roots to infiltrate the pipe’s integrity.

In addition to overflows and blockage, roots also cause a reduction in hydraulic capacity and loss of self-cleaning velocities as it solidifies its home in the pipe.

The program in LA

With its humble beginnings in a pilot program covering only 150 miles of sewer pipe, root control in Los Angeles has long since been a priority. In the early 1990s, a chemical treatment program began but the end of the decade brought a change in which pesticides were restricted and the program was dissolved.

The Bureau of Sanitation spent approximately $US750,000 by the end of the fiscal year in 2002 on the pilot program. That price tag has since increased to $US2 million per year.

Nevertheless, the benefit of the program clearly outweighs any monetary sum, saves money in the long run and is a step toward addressing the Environmental Protection Agency’s (EPA) sanitary sewer overflows concern. The EPA estimates that 43 per cent of overflows are caused by pipe blockages and approximately half of those are caused by roots.

The program in Los Angeles seeks to take on this problem and is so large that it takes two separate contractors to do the job. Both Pacific Sewer Maintenance and Dukes Root Control will receive $US1 million a year for three years, beginning in May 2006, and the root control program is just one of many efforts in sewer line maintenance. Crews work seven days a week to ensure that the system remains free flowing.

“The root control program is reaching maturity and will, most likely, continue for the foreseeable future,” says Mr Berggren. “There is little that can be done to prevent roots from entering an established sewer, especially in an arid region such as Los Angeles.”

SewerData puts project information online

Gone are the days of having to trawl through mountains of paperwork to find test results or other project information. SewerData is an internet-based solution that enables engineers, contractors and their clients to record, track and analyse wastewater projects through a secure website.

“Even a relatively small wastewater investigation and rehabilitation project can produce several thousand records,” said Steve Apeldoorn, a Director of ProjectMax. “The management of the data collected is often underestimated. When traditional paper-field records and basic spreadsheets are used, records are frequently lost or are incorrectly recorded; valuable time is wasted locating and retrieving data.

“With SewerData, all of the information needed to manage a contract is available at your fingertips, providing a clear picture of what is happening on the project and where problem areas may exist,” said Steve.

SewerData provides an interactive display of the works by integrating geospatial information and database records. Pipes, manholes and properties are colour coded to show the status of various tests and rehabilitation activities that need to be completed.

In SewerData issues like property owner concerns or rework requirements are displayed in dialogue boxes that pop up when the computer mouse hovers over the affected asset. SewerData also links rehabilitation instructions, log-sheets, drawings and reports to individual assets, which are displayed by double clicking on the asset. This information provides a real understanding of the project status and what needs prioritising.

Further efficiencies can be gained by integrating SewerData with the client’s existing asset management software.

SewerData developers ProjectMax provide consulting services to local authorities and utility operators. One of the company’s specialities is the project management and design of wastewater investigation and rehabilitation contracts.

Steve Apeldoorn says the team at ProjectMax are always trying to improve the way they do things. “We often find the answer can be achieved by harnessing new technology to improve how projects are managed. SewerData is an example of ProjectMax’s way of working.”

For further information on how SewerData can improve the management of wastewater investigation and rehabilitation projects call 00 64 9 963 2700 or visit
www.projectmax.co.nz

Sewer and drain cleaning using recycled water: a win-win situation

Why use quality drinking water for sewer and drain cleaning when there are highly efficient and productive alternatives? Organisations such as Brisbane Water and Newcastle City Council who recognised the enormous potential of recyclers to save water and increase productivity have achieved substantial savings.

The latest high efficiency, low maintenance recyclers offer massive benefits to their owners. Water recycling allows continuous cleaning operation and eliminates the need to stop for water. Conventional machines stop production to refill several times a day, while recyclers can simply work on until the debris section of the unit is full.

A recycler can thus achieve substantially greater productivity over conventional machines which have limited water storage and hence pumping capacity. A conventional machine runs out of water in approximately 15 minutes and ceases to be productive until water has been replenished. Under certain circumstances cleaning production with conventional machines is limited to less than 2 hours per day.

A recycler on the other hand may be working a full shift without having to stop for more water. Comparing a recycler’s production potential of 8 hours against 2 hours for a conventional machine, it can be seen that a recycled water unit works smarter, not harder. The value of the additional productivity over the lifetime of a unit can be up to twice the purchase cost of a water recycle machine.

The design and componentry of modern recyclers is aimed at achieving a high recycle rate at low cost and with minimum maintenance requirements. A recycling machine delivering 100 per cent production is infinitely more beneficial to its owners/operators than conventional machinery that manages only 20 per cent production and saves no water at all.

Instead of using conventional, dirt sensitive triplex pumps, the heart of the latest recycle machine consists of a slow stroking, high pressure transformer pump that can handle contaminated water with particles sizes up to 0.5 mm. At approximately 23 strokes per minute, this pump produces 340 litres per minute at 2,900 psi. The pressure transformer is preceded by a maintenance free, self cleaning recycle strainer which removes particles in excess of 0.5 mm Ì÷ and thus eliminates the fine particle filtration process which is costly, complex and maintenance intensive.

With millions of dollars being spent by governments and utilities alike to “÷save every drop’, the new recycling sewer and drain cleaners also make your water conservation support a very profitable venture. Let’s save our drinking water and not pour it down sewers and drains.

HDD beneficial for water and sewer construction: BTB

The advantages offered by directional drilling can be just as beneficial for water and sewer construction as they are for communications, electrical power and natural gas projects.

While HDD does, indeed, have much to offer builders of segments of the underground public works infrastructure, demand for drilling services for water and sewer projects has lagged far behind that for the “dry” utilities.

The amount of water pipe installed by HDD increases each year, but even though some directional drilling contractors have been making on-grade installations for several years, the trenchless procedure has not made a major impact in the sanitary sewer market.

There are two primary reasons why:

* The majority of those who operate and plan the construction of sanitary sewer systems are not aware that HDD is suitable for many of their projects; and
* Many sewer system professionals who are aware of directional drilling do not believe HDD machines are capable of installing pipe at the critical grades essential for gravity-flow sewer systems; therefore they do not consider HDD a viable option.

Both viewpoints are based on either a lack of understanding or outdated information, as the technology to make on-grade bores is available now.

Directional drilling equipment today is capable of handling pipe in sizes that make up much of our sanitary sewer infrastructure. Similarly, guidance electronics designed to facilitate grade control – when properly used – help drillers achieve consistent results that make HDD on-grade installations cost effective for project owners and profitable for contractors.

These facts remain unknown to public works professionals largely because the HDD industry has not promoted the proven technology directional drilling offers the civil engineers, public works engineers and managers who plan sanitary sewer projects.

On jobs appropriate for HDD, significant savings in restoration costs can be realised.

BTB Australia has recently worked on a number of projects involving sewer installations, including pressure sewer installations, gravity sewers and sewer to grade.

At Mernda, BTB has installed 180 m of 150 mm sewer pipe on a grade of 1:158 in solid bluestone rock formation, and is continuing with a number of other similar bores on the same project for MFJ Constructions. The installations are generally through existing properties with limited access, and the time and environmental benefits were a determining factor given the rock conditions.

BTB has also completed two large diameter bores on the Mernda project for Tenix and Yarra Valley Water, also in extreme rock conditions. A third bore crossing under the Plenty Gorge and installation of a 400 mm pressure sewer pipeline are almost complete.

BTB is currently completing work in Flinders, installing a complete pressure sewer system as the primary contractor for Utility Services. Over 13 km of pressure pipeline, fittings and valves have been installed.

These pressure sewer systems are becoming more popular with the utility companies and they offer a great deal of cost and environmental savings as compared to traditional open cut sewer constructions.

Pipe Jacking enables sewer upgrade to cross major highway

In order to successfully complete this project the sewer had to cross a major state highway.

Due to expansion of Johnsonville the main trunk sewer serving the suburb has become undersized leading to surcharging of wastewater back into local properties under certain conditions.

Maunsell was asked to carry out an investigation and design a sewer upgrade to remedy this issue.

The design consisted of laying a new sewer along Johnsonville Road, under State Highway 1 and alongside the highway to connect to the existing trunk sewer.

Open trenching across the highway was not an option due to the need to maintain full use of Wellington’s major arterial route in and out of the city.

Directional drilling was initially considered but the existence of possible culverts, the current trunk sewer line, the former centennial highway and uncertain backfill materials under the existing highway in the proposed alignment meant this option was abandoned.

An initial geotechnical investigation identified engineered fill, moderately to highly weathered greywacke and silt deposits and this together with the known obstacles that could be encountered meant that pipe jacking was chosen as the best methodology to insert the new sewer under State Highway 1.

In order to ensure the pipe jacking was not affected by any obstacles and to allow a person to work at the jacking face as necessary, an oversized 1,350 mm internal diameter pipe was designed to be thrust with the new sewer line inserted into this at the completion of the works.

The contract was tendered as a complete package including both trenched portions and the pipe jacking works. The successful tenderer, HEB Smithbridge engaged D Paku Ltd to undertake the pipe jacking portion of the works. D Paku is a specialist pipe jacking company that works throughout New Zealand.

Pipe jacking launch and receiving pits were installed using sheet piling and pipe jacking was undertaken conventionally using a hydraulic jacking rig. Due to the expectation of meeting the existing trunk sewer, the excavation was carried out using a hand driven technique rather than a mechanical borer.

During the pipe jacking operation a number of obstacles were encountered both running across and following the direction of jacking, including the current trunk sewer (flow was diverted through a pumped bypass), steel telecom cable ducts, mass concrete culverts, engineered fill and hard rock. These were all expertly managed by D Paku who maintained the design grade throughout the 65 m length of the pipe jacking works.

Maunsell had worked with HEB Smithbridge on a previous project in the Wellington region, but had no previous experience with D Paku. A strong working relationship was swiftly built up between the parties involved leading to successful delivery of the project.

Tenders let for Timaru sewer pipe tunnels

Three separate tunnels will be constructed, two metres in diameter, bored at depths of between four and 19 m and each about 400 m long. The first tunnel will run from Washdyke Lagoon to the Alliance Smithfield access road. A second tunnel will run directly underneath Westcott and Richmond Streets, and the third from Ashbury Park to Virtue Avenue. All sections of pipe will then be linked, and joined to pipes already installed across Caroline Bay and around the Washdyke Lagoon.

The successful tenderer for the tunnel drilling is Auckland-based Harker Underground Construction Ltd, while the pipe linking contract went to Works Infrastructure Ltd. The contracted completion date for the project is mid 2009.

Harker said that it is delighted to have been awarded the Timaru contract, which was won by combining a back-hoe TBM erecting ring beam and lagging sections inside an erecting can. A tried and true method of installation in the USA, Harker believes this a first for New Zealand.

The company said that although other methods were considered, it was felt that this was the most cost effective method that guaranteed line installation within the client’s tight construction tolerances and at a grade of only 0.06 per cent. Mixed ground conditions ranging from alluviums (which will suit the TBM) to basalt rock which will be excavated using a drill and blast technique.

Timaru Council District Services Manager Ashley Harper said the tunnelling was a specialist operation with only a few firms in the country capable of undertaking the project. Test bores at the site of the tunnels were conducted this month and were required by the tenderers prior to their formalising the tender process. He said Harker Construction would relocate to Timaru for almost two years while carrying out the work.

“While connections with treatment stations have yet to be completed, large diameter sewer pipes have been laid from Station Street across Caroline Bay and the tunnelling will be completed prior to upgrading work at the northern end of Caroline Bay.

“This is part of our co-ordinated approach to both projects,” Mr Harper said.

The tunnelling program will have a minimal effect on residents, Mr Harper said.

“While on the surface there will be no lasting changes to the landscape, the tunnelling process and the installation of pipe connection stations will see increased activity by workmen and machines with some minor short-term access disruption to a few Richmond Street properties.

“But that’s about all,” he said.

The Timaru District Council is almost half way through its multi- million dollar sewer replacement program. The work is being done in a manner that is timed to avoid unnecessary disruption to the public, and as part of an upgrade that must be done before the town’s right to discharge sewage into the sea expires in 2010.

At the time of going to print, a crew was establishing the first compound area ready for tunnelling early in the new year.

Sewer relining works at Cockatoo Island

The island has been expanded over the years from 12.9 hectares to 17.9 hectares. The sandstone knoll that is Cockatoo Island has undergone extensive cutting and filling to create distinct upper and lower levels.

Prior to 1788, Cockatoo Island was heavily timbered with red gums and was a home to thousands of sulphur crested Cockatoos. Indigenous people would have used the island during this period although no record has been found. The island was used as a prison during 1830s and 1840s.

The conditions for convicts on Cockatoo Island were harsh and the work was tough. From 1839-40 convict labour was used to cut deep into the rock and construct silos for storing the colony’s grain supply.

Cockatoo Island became the Commonwealth Naval Dockyard in 1913. By 1918 a new power house was built, and is powerful enough to allow the de-watering of the Sutherland Dock in around three-and-a-half hours.

It is close to ten years since Cockatoo Island was last used. The Harbour Trust has been decontaminating the island and rehabilitating many of the buildings and structures on the island.

The vision for Cockatoo Island is to revitalise this unique place as a landmark harbour attraction that has the potential to become a great cultural centre.

Electricity, water and sewerage have been reinstated on the island. Four new electrical substations have been installed to handle all future power requirements of the island.

The Sydney Harbour Federation Trust is spending millions of dollars on decontaminating and rehabilitating the island.

Cockatoo Island contains important evidence of the history and development of Australia. Located at the meeting of two rivers, it has magnificent harbour views and is a visual landmark with its distinctive silhouette.

In July 2007, Veolia Water Network Services was engaged to rehabilitate approximately 1 km of deteriorated sewer pipes scattered all over the Island. This total length comprised of 150 mm, 225mm and 300 mm diameter pipes. The pipes were rehabilitated using CIPP, UV curing system.

The Veolia Water Network Services crew was able to maintain high quality standards as always despite the intricate access conditions and high rates of water and sand infiltration. This project was completed on time and within the established budget without compromising any safety.

To accomplish the mission successfully, Veolia Water Network Services employed the use of its latest state-of-the-art combination units and vacuum suckers.

New Interflow development seals gap in sewer renewal technology

Lateral connections to lined sewers have always presented problems for water authorities.

While there are several technologies that can structurally line a deteriorated sewer main, none can reliably provide a seal when cut to make a lateral connection. This means roots and groundwater can infiltrate the sewer, while sewage can leak into the water table.

Attempts to provide seals by trenchless methods have been regularly thwarted because of the conditions of the junctions. Poorly made original connections, ground movement, junction cracking, and shrinkage of the liner all challenge any “÷no dig’ attempts to apply a long term seal.

The project in Geelong for Barwon Water aimed to install “÷short form liners’ at six lateral connections that had previously been abandoned as too difficult. Previously it was considered that the only sealing option was to excavate and install new junctions.

For Interflow, the success of the project was the culmination of an extensive research and development program.

The need for sealing lateral connections to lined sewers, whatever the type of liner, has been recognised worldwide for some years. Whether cured-in-place, fold and form or wound-in-place, no type of liner is water tight at lateral connections unless a seal is applied. European Standards, ASTMs and Australian Water Authority Specifications all specify separate seals at these locations.

Polyurethane grout installed either by flooding or by using a specially developed inflatable lateral sleeve grouting packer was common practice until a few years ago. The seal could easily be hydrostatically tested immediately after installation. While it became the industry standard, experience showed it could not maintain an effective seal for a sufficient length of time to justify its expense.

When water authorities demanded a better solution, the Trenchless Technology industry responded. Various types of cured-in-place “÷short form liners’ with a tee or “÷top hat’ configuration were developed that could be installed without digging. Made from materials known to be suitable for use in sewer conditions, they had the advantage of providing not just a seal, but a positive barrier against infiltration from water or roots.

Interflow’s junction seal, called the LCR (Lateral Connection Repair) was developed by the company’s Sydney-based Research and Development team.

The installation procedure involved impregnating silicate resin onto a polyurethane coated, polyester felt tee, mounting it on an inflatable tee-shaped packer and installing it from the manhole nearest to the lateral connection. The packer was pushed up the pipeline until CCTV monitoring showed it had reached the lateral connection The packer was then inflated to hold the resin impregnated tee tightly against the pipe (or liner) and the junction of the house service line up to past the first joint. The inflated packer would be left in position until the resin had cured then deflated and removed.

The result was a cured silicate resin fitting strongly bonded to both the liner in the sewer main and the house service line up to past the first joint.

The use of this and similar technology was limited by the high proportion of non-standard junctions. Many house service lines connected after construction of the main presented obstructions which prevented trenchless installation of a seal. Disruptive excavation to construct a new connection to the lined sewer main was still frequently required.

In mid-2006 Interflow received an AusIndustry Grant to further develop this technology. The aim was to develop an improved solution that offered better sealing properties and which could be installed in a wider range of “÷non-standard’ junctions.

The result has been a new product to be called Interfit. As demonstrated at Geelong, it is an important advance in lateral connection repair technology.

Interfit uses a proprietary silicate resin blended by Interflow to suit this application. When installed in sewer conditions, curing time at ambient temperatures is typically reduced from 2 hours to 45 minutes. This means the sewer is obstructed for less time, and more seals can be installed in a working day.

The tee, which is impregnated with the resin, is of PVC-coated glass fibre felt. Together with the resin, it offers increased strength, toughness and impermeability.

The two part resin is pre-packaged in the correct quantities for the size of Interfit to be installed and is mixed and applied with a specially developed “÷gun’. The gun ensures complete mixing, essential to the fitting developing the correct properties, and offers greater quality assurance.

The packer is smaller and lighter for easier handling. Its patented design offers the ability to install Interfit in a wider range of non-standard junctions. The packer has a hollow core and so allows flow to continue in the pipeline during installation.

The project at Geelong involved installing fittings at six “÷cut in’ junctions. These were junctions that had been installed by cutting into the existing pipelines some time after they were installed – using varying degrees of care. On most of the junctions the first joint was displaced, whether by original installation or subsequent ground movement. Four of the six junctions had 45 or 60 degree bends coming straight off the connection. The original pipelines and all of the house service lines were of vitrified clay.

Sealing of these junctions had been specified as part of a previous sewer lining contract, but was not possible with the available technology. As excavation to install new connections was considered too inconvenient, they were left unsealed.

Interflow’s crew was able to demonstrate that the Interfit could be successfully installed in all of these junctions. With the light weight and smaller size of the packer meaning less force needed to move it, greater care was possible to manoeuvre the lateral sealing bulb past the potential obstructions at the entrance to the house service line.

Further installations are planned on similar projects.

The development of the Interfit is another example of Australian ingenuity advancing the Trenchless Technology industry and has potential application worldwide.