GrokSurf's San Diego

A few monsoonal clouds helped only slightly with 105 degree temperatures

They don’t make a big public fuss about it and they don’t usually refer to it as such but for Las Vegans, Indirect Potable Reuse (IPR) plays a big role in helping to cope with difficult water supply issues. After drawing most of its water from Lake Mead, Las Vegas produces an average of 193 million gallons (mgd) of wastewater per day. The wastewater is treated to an advanced purification and disinfection process and is returned to Lake Mead via the Las Vegas Wash. The water is then reused by the city (and by downstream users like San Diego).

The returned water gets credited to Las Vegas as part of the calculation specifying how much water the city can draw from Lake Mead, so IPR is integral to keeping those showers and faucets running. Because of that allowance, the IPR operation in Las Vegas is commonly referred to as “Return-Flow Credits.”

Since San Diego is only now preparing to undertake a study of a small-scale IPR operation for itself while Las Vegas is already doing it full-scale, I decided to see if I could visit the Las Vegas facilities and get a feel for how IPR has worked out for them. Not only were they willing to allow me to visit, the Southern Nevada Water Authority graciously scheduled a whole series of tours for me over a three-day period. That was a special treat after a disappointment I had when I asked to visit the Alvarado Water Treatment Plant a short distance from my home in San Diego and the reply was “The Federal government made us stop the tours following 9/11 and they haven’t allowed us to start them again.”

My visit last week included visits to the two existing water pumping and transmission facilities at Lake Mead as well as the third intake under construction, the Alfred Merritt Smith Water Treatment Plant, the River Mountains Water Treatment Plant, the Water Quality Laboratory and Applied Research & Development Center, the Clark County Water Reclamation District, the Las Vegas Wash, and Lake Mead & Hoover Dam.

I’ll need to digest everything I learned and intend to write about it in the future, but for now I’d like to share some photos from the visit. You can click them for enlargements.

Pumping water from Lake Mead

Two bunker-like intake pump stations are located at the base of Saddle Island near what used to be the shoreline of Lake Mead.

Pump undergoing repair

	Surge control tank

Near the intake pump stations is the Alfred Merritt Smith Water Treatment Plant which can treat up to 600 mgd. Water from the lake can go directly to ozonation without pretreatment.

Ozone Contactor basin

Floc (flocculation) basins

The plant also has a large machine shop where many in-house repairs can be done. It has one of the largest lathes in the U.S.

In addition to supplying water to the Smith treatment plant, the water transmission pump stations push water up and west towards the River Mountains Water Treatment Plant and to numerous laterals serving other areas. Several booster pump stations are needed to get the water to the top and beyond.

In this overview taken from on high looking east toward the lake, you can see IPS-1 and IPS-2 pump stations at the base of Saddle Island (and the waterline where Lake Mead used to make it an island), then up the mountain towards us are the booster pump stations for the underground pipelines.

This is the other side of Saddle Island, taken from Lake Mead. The actual intakes are farther out under deeper water; that structure serves a different purpose

Booster pump station looking up at air vent towers. Those towers are where I stood to take the overview picture above

Bighorn sheep near air vent towers

The River Mountains Water Treatment Plant currently produces about 300 mgd but will eventually produce up to 600 mgd. It also uses ozonation for water purification. The entire grounds are meticulously maintained and were originally designed for self-guided tours, although now only guided tours are permitted.

The control room can also run operations at other plants	Flow splitter
Part of the ozone facility	Another section of the ozone facility

Next to the River Mountains treatment plant is the Water Quality Laboratory and Applied Research & Development Center. This facility does all the real-time water quality testing for the entire Las Vegas region with teams of staff in the field obtaining samples and scientists and technicians in the building analyzing the data. Additionally, the R&D center performs research on emerging water quality issues including the presence of endocrine disruptors and other pharmaceuticals in the nation’s municipal water supplies. They have some of the most advanced scientific equipment in the nation. If you’re a bio or chem lab techie, you’ll probably salivate at some of these pictures.

The Clark County Water Reclamation District facility at the far eastern end of Flamingo Road performs the advanced IPR treatment and purification allowing the water to be returned to Lake Mead through the outflow into the Las Vegas Wash. One notable feature is that they just completed a full-scale pilot membrane/ozonation project and approved $50 million for permanent membrane/ozonation of the wastewater. San Diego, are you paying attention?

	Ozone generators
UV treatment	Purified outfall enters the Las Vegas Wash

After leaving the reclamation plant, the water heads down the Las Vegas Wash and into Lake Mead.

Gauge measures flow through the wash to determine return-flow credit	Natural-looking flow control weirs help prevent erosion
View of the Wash where it enters Lake Mead	View from Lake Mead where the Las Vegas Wash enters

With water levels at Lake Mead dropping to dangerously low levels that threaten the ability of at least one of the existing intakes to get water, Las Vegas is constructing a third intake that will draw water from deeper in the lake.

Here's where the downshaft is being dug to enable the tunnel boring machine to drill under the lake. The entire construction area used to be under water

Tunnel construction site seen from Lake Mead

Barge and crane at location of new water intake

The final highlight of my visit was a boat ride on Lake Mead. Daniel Luong, Senior Water Quality Laboratory Technician showed me locations on the lake where water samples are taken weekly for laboratory analysis. We visited the location of the two existing water intakes, the place where the third intake is being constructed, the mouth of the Las Vegas Wash, and just upstream of Hoover Dam.

The water authority's boat can carry 5-6 lab technicians performing various tasks	Boulder City spilling over the hilltop towards Lake Mead
Hoover Dam with new bypass bridge in background nearly completed	Daniel pulling water sample for the lab with the dam in the background

So Las Vegas returns a good amount of water to Lake Mead, and that's good, but if downstream users don't reduce their take from the Colorado River, who knows if Hoover Dam's spillways will ever flow again?

I would like to thank everyone who met with me and made my visit possible: Ron Zegers, SNWA Director; Scott Huntley, SNWA Public Information Manager; Roger Buehrer, LVVWD Public Information Officer; Doug Drury and Linda Grossman, Clark County Water Reclamation District; Dave Johnson, River Mountains Water Treatment Plant; Mark Walters, SNWA Production and Distribution Manager; Daniel Luong, Senior WQ Lab Technician, and Willie Frehner, Principal Laboratory Scientist, SNWA Laboratory.