Category: Recycled water

Purple Pipe Doesn’t Live Up to Hype

Published / by dcoffin / Leave a Comment

LADWP water plans are generally more about perception than results and 'Purple Pipe' is certainly the poster child proving that.

Purple pipe is used to distribute non-potable recycled water and is often presented as one of the departments cornerstone resources to meeting the city's water supply demand since it frees up potable water that would have been used for irrigation or industrial use. Thumb through many of the DWP’s presentations and you'll find impressive glossy photos of purple pipe that suggest that it's been making big contributions to increasing the City of Los Angeles water supply. Even the Mayor and the city’s neighborhood councils are lulled into this group think.  

purple pipeHowever when perception meets gritty reality, purple pipes contribution to the city's water supply is simply underwhelming and not deserving of so much attention. Past LADWP water plans told us recycled water was supposed to deliver be delivering ~30,000 Af/y to the city by 2015. But instead the city's been getting an average of only 7,600 Af/y.

There are several reasons for this shortfall, the biggest being the same reason the city isn’t able to effectively replace its aging water mains. The immense cost of such an effort and the disruptive nature of digging up thousands of miles of city streets in a city that is already built out and paved over is prohibitive. The department says it would take 300 years to replace its crumbling water mains. Building a distribution network of purple pipe runs into the same problems of cost and disruption.

This leaves the department to choose routes where it can get the most bang for its buck. Generally this means it has to be a customer who can use lots of recycled water and is relatively near by the filtering plant. In the city's west side for example, only a few customers like LAX, Westchester Golf Course, Loyola Marymount and Playa Vista fall into that category.

Sure it would be nice to have purple pipe running alongside the city's water mains that finally connects up to every large commercial and residential complex but that's not going to happen.
recycle

The other reason for the lack of progress is that recycled water is primarily for irrigation and industrial use. In the 1980's the city's industrial use was ~30,000 Af/y but overtime this has fallen to an average of just 19,000 Af/y. The rest would go to city parks, golf courses and new commercial/residential developments that are close enough to filtering plants that makes it economically viable to tear out a few streets and lay new purple pipe.

This is not a growing customer segment that justifies the departments claim that it will increase recycled water to 42,000 Af/y by 2025 and 59,000 Af/y by 2035.

Dissecting L.A’s Paper Water – Recycled

Published / by dcoffin / 1 Comment on Dissecting L.A’s Paper Water – Recycled
One prominent member of the City of Los Angeles's 'paper water' portfolio is recycled water. Like L.A.'s groundwater supply, its Urban Water Management Plans between 1990 and 2005 had projected rapidly growing recycled water supplies that would never be realized.
Recycle Water Projections versus Actual Supply
Recycle Water Projections v. Actual Supply
The chart at the right plots the huge gap between the actual recycled water supply the city had access to and the anticipated supplies that each UWMP projected. The gap between the two is the paper water that would be used to as evidence that medium and high density projects going through the planning process would have sufficient water when in fact they didn't. For example when we look at the 1990 UWMP projections, the city expected that its program for recycle water supply would triple within 5 years and eventually provide the city with over 30,000 af/y in 2000. This never happened. When the following 1995 UWMP came out it didn't begin where the 1990 plan left off. If fact it would cite less water in 2000 than the '90 plan which suggests that the effort to increase recycled water was making no progress. Of course paper water being what it is, that plan would still suggest (with no factual basis) that recycled water would still triple, this time within 10 years and then more than quadruple to 38,000 af/y within 15 years. The next 2000 UWMP was no different, it would also start off with less water than the preceding plans had projected and then nearly quadruple within 15 years with supplies approaching 30,000 af/y.
Recycled water supply versus total supply
Recycled water supply v. total supply
Little progress meeting past targets The actual supply between 1985 and 2010 hasn't been nearly so grand as the city's expectations and glossy presentations that suggested that recycled water would help the city meet its needs. The actual recycle water supply between 1995 and 2005 was so tiny at just 1,748 af/y and was barely perceptible on a chart. Between 2006 and 2014 the city's recycle supply would grow to just 6,410 af/y which is far below any of the past UWMP projections that ranged from 19,950 af/y to 38,000 af/y and light years behind the projected 850% increase now cited in the 2010 UWMP to 59,000 af/y by 2035. This huge gap between 'projected or anticipated supply' and 'actual supply' is an unfortunate characteristic of the city's water supply we would call paper water. It's a promise spanning 5 water plans and 25 years that was used to mischaracterize the city's supply to approve high density development. The gap has only widen between 1990 and 2015 and given the city's history of meeting its projections, I don't have much faith that it will meet the 59,000 af/y target it has set for 2035. If it could have met the much lower targets it had set in earlier plans, it would have done so by now. However the obstacles such as trying to roll out a citywide network of purple pipe were just to huge to overcome.
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