Las Vegas is the most populous city in the USA state of Nevada. The Las Vegas Valley, a 600 square mile (1600 km²) basin and surrounding area, is part of Clark County in southern Nevada.

Mr Scott says the Las Vegas Valley Water District (LVVWD) is responsible for over 4,500 miles of pipe in Las Vegas and unincorporated Clark County. Mr Scott says “We also manage over 100 miles of pipe in separate small water systems in the communities of Jean, Searchlight, Blue Diamond, Laughlin, and Kyle canyon.”

The breakdown of total miles of pipe by material is shown below.

The largest steel pipe, including mortar lined steel pipe, bar wrapped steel pipe and pre-tensioned wire wrapped pipe is 102 inches in diameter. Most pipe in this class ranges from 24-48 inches in diameter. PVC pipe ranges from 4 inches up to 42 inches and ACP from 4 inches to 60 inches. Most PVC and ACP pipe are from 6 – 8 inches.

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Mr Scott says that because of Las Vegas’ phenomenal population growth over the past ten years, the average age of all pipes in the distribution system is only about 18 years. The average age for PVC pipe is eight years compared to ACP, which has an average age of between 29 and 34 years.

ACP has the highest break rate per mile compared with all other pipe materials.

When asked what portion of assets the LVVWD inspects every year, Mr Scott says they are currently focusing assessment activities on ACP and steel pipe. “For ACP, our assessments are prioritised based on our CARE-W [computer aided rehabilitation of water networks] model that ranks pipe in terms of risk of failure – based on statistical failure modelling and hydraulic criticality – based on hydraulic modelling tool re-net.

“Other criteria such as impact to customers, potential damage to rods and types of customer served are also important considerations,” says Mr Scott.

For steel, the LVVWD assessments are prioritised based on corrosion potential information collected from the Cathodic Protection system, as well as the potential consequences of failure, impact to customers and break history.

“We have just this year implemented our CARE-W model, and have started a full-blown assessment program,” says Mr Scott. “This year we will assess approximately 10 miles of ACP, and from 10 up to 15 miles of steel pipe.”

Mr Scott says that the total amount of ACP to be assessed each year will vary depending on the output of the model. The LVVWD plans on assessing approximately 20 miles of steel pipe annually.

Trenchless International asked if the District has adequate funding to conduct the inspection and repair programs. Mr Scott answered “Funding is a challenge for all utilities, this is why we are careful to assess only those pipes at the most risk.”

The LVVWD is just beginning to investigate the advantages of Trenchless Technology following a successful CIPP project. The District will be evaluating the applicability of Trenchless solutions on a case by case basis.