Tuesday, June 23, 2015

Competing With San Diego's De$al Plant

Southern California Dreamin'
What a difference a few decades can make...

MeanMesa lived in San Diego before the economy there "gently" created the necessity for an evacuation. The "final straw" came when the one year lease was to be renewed on the little house which had served so humbly as Short Current Essays' Galactic Head Quarters was  suddenly priced out of reach. The old rent was $695. The new rent was $1190. There was more. Gasoline was dancing around the $4/gallon mark, and ENRON had just finished savaging the state's power generation -- not to mention brutally ending the career of the "fairly good" California Governor, Grey Davis.

It was pretty clear that the "EUREKA" State was shedding every resident living on less than six digits of annual income. This meant that it was definitely U-Haul time. Finally, after some packing and planning the long road trip to Albuquerque was made in the absolutely eerie silence of September 11, 2001. MeanMesa had watched the planes hit New York while finishing that last cup of morning "California coffee" before hitting the road.

However, this post is not about "sentimental journeys." Instead, it's all about water.

Back in 2001 southern California was already beginning to feel the "first bite" of the water problem, but then, things were still comfortably theoretical. In those days Galactic Head Quarters was situated in a fairly rough, low income, primarily minority section of the city called "City Heights." One of the "schemes" to solve the water problem was to recycle some of San Diego's treated sewage water into potable water. Naturally, the "success" of the plan would need to be tested by diverting some of this recycled water for actual use by some of the city's residents.

Since it was clearly too risky to pump this stuff into one of the high end gated communities ringing the city, the city water planners settled on "City Heights." It was hideous. Simply running a shower for sixty seconds had already made the bathroom smell like an out house before one had even gotten wet. Once that happened, things got even worse. The plan was ultimately abandoned.

Under the rather ambiguous leadership of the new weight lifting Governor, practically nothing was done about the problem for years. Water bills went up, but San Diego's city edict of "mandatory loveliness" was still very much in force. The golf courses were immaculate, and the lawns in the new, million dollar subdivisions were enjoying very generous doses of irrigation every morning and evening.

The conservative, corporate agricultural magnates in the Central Valley were getting even richer as their vast irrigated farms provided fresh produce for the country, and Sacramento always answered when those boys called.

No one realized it then, but the first signs of what NASA now calls the "MEGA DROUGHT" were already boiling up out farther west in the beautiful blue Pacific, and it was headed straight for the West Coast. MeanMesa has covered this part of the story in previous posts:

Well, the bumbling weight lifter is no longer the Governor in California having been replaced by the current, "painfully common sensical" Democrat, Jerry Brown, in the 2011 election. However, quite predictably, solving the state's now critical water problem has now become a rather complex "catch up" process.

In the "Infrastructure" post [above] MeanMesa proposes a plan to elevate available water resources in the Columbia River to provide the possibility of irrigation in the Central Valley. Of course this effort is not motivated by a deeply held concern for the plutocrats running the corporate agricultural empires there but, instead, by the produce prices MeanMesa is encountering in the near by, neighborhood whole foods grocery.

The plan laid out in that "Infrastructure" post is rather complicated, but, of course, imminently realistic. It is complicated by the necessity of boosting that river water high enough to reach the elevations found in the Central Valley and doing so at a cost justified by the losses we might anticipate without it -- at least, without doing something.

However, in this post we will address a slightly different challenge for California and the MEGA DROUGHT -- specifically the challenge of providing fresh water to San Diego. [LA and other coastal California cities may also be quite interested.]

Unlike the worried industrial farmers in the Central Valley, San Diego needs fresh water at sea level. This means that there are no mountains to climb, and that may well make things significantly easier. Very understandably, San Diego has turned to the desalination of Pacific Ocean water as a possible solution.

Have a look at some current reporting on this plan.

Nation's largest ocean desalination plant
 goes up near San Diego;
 Future of the California coast?
By Paul Rogers

 [Excerpted. Read the entire article - San Jose MERCURY NEWS]

The crews are building what boosters say represents California's best hope for a drought-proof water supply: the largest ocean desalination plant in the Western Hemisphere. The $1 billion project will provide 50 million gallons of drinking water a day for San Diego County when it opens in 2016.

Graphics from Mercury News article.

Desalination plants
 aren't a good solution for California drought
Michael Hiltzik
LA Times
April 24, 2015
[Excerpted. Read the entire article  here - LATIMES/Hiltzik]

The plant, the largest of its kind in the U.S., is designed to provide San Diego County with about 50 million desalinated gallons a day, about 7% of its water needs.

The San Diego County Water Authority has committed to purchasing the plant's entire output for 30 years — a deal that was crucial for Poseidon's financing — for about $2,100 to $2,300 per acre-foot, plus inflation. An acre-foot is 325,851 gallons, or about a year's usage for one or two five-member families. The county agency, therefore, will be paying at least $110 million a year, whether it needs the plant's water or not. San Diego water bills are projected to rise by an average of $5 to $7 a month to cover the cost.

The county judged that it might pay about that much in the future for other imported water, which makes the commitment look like a long-term hedge against a continuing water crisis. But desalinated water is far more expensive than other existing sources. San Diego currently pays $923 per acre-foot for treated water from the Metropolitan Water District. The Pacific Institute reported in 2012 that San Diego could obtain recycled water for as little as $1,200 per acre-foot, and that the marginal cost of water obtained through conservation and efficiency measures was as little as $150.

That's what happened to Santa Barbara, which began building a $34-million desalination plant during the drought-stricken 1980s. By the time it was completed in 1992, the rains had returned; the facility went through a few weeks of pilot testing, then was mothballed and partially dismantled. The city is now contemplating restarting it at a cost of $40 million, plus $5 million a year in operating costs. That would place the cost of desalinated water at about $3,000 an acre-foot and drive up average monthly household water bills to $108 from $78 today.

Pay attention to the water costs and statistics mentioned in the articles:

San Diego  - current price - 1 acre foot = $923

San Diego - desalinated water - 1 acre foot = $2,100 - $2,300
San Diego - desalinated water's portion of total water needs = 7%
San Diego - desalination plant production = 50 Mn gallons/day
San Diego - construct one desalination plant = $1 Bn
[desalination production: 50 million gallons per day = 150 acre feet +/- per day]
San Diego: if 50 Mn gallons per day = 7%, 700 Mn gallons per day = 100%

Both the LA Times article's author [this is good reporting...] and the San Diego County Water Authority are assuming that the drought conditions experienced by the system currently will mitigate within a few years. 

Importantly, this is NOT what the NASA research is predicting.

The costs are high, but perhaps more troubling, the desalination plant program will be producing only 7% of the city's water requirements. The NASA prediction deals directly with the availability and access of both that 7% and the other 93% of San Diego's water needs in the near future. Further, considering the number of "little blue dots" appearing on the map [above], the cities and State governments of California are getting ready to really dump some serious cash into desalination plant construction.

We don't have an annual operation cost for the San Diego plant, but the smaller plant in Santa Barbara mentioned in the article is estimating $5 Mn per year.

Well, MeanMesa has little appetite for simply promoting hopeless doom and gloom, so there will have to be some sort of alternate solution proposed in this post.

Changing Channels on the "Big Picture"
Maybe $1 Bn desalination plants are not the answer.

While LA Times reporter, Mr. Hiltzik, was clearly sounding an alarm about the proposal to start allocating so much money to this type of solution, his article pretty much stopped there. Now, we may as well go on ahead and consider a possible alternative.

Let's call it:
"the tube."

The "tube" idea has been bandied about before -- notably at the discharge of the massive Kenai River in south central Alaska. The "dream" was to collect water up north and then transport it to California through giant tubes laid down along the ocean floor. For starters, this would have been a very, very long pipe. Next, when this plan was being "played with," California was still in pretty good shape with respect to water so it garnered very little serious traction.

Although it is still thousands of miles to Kenai from San Diego, some other important conditions have changed -- bringing the "tube" idea back "onto the table." 

MeanMesa focused on the Columbia River in the previous post, "Infrastructure," so we'll simply return to this same water source while describing this plan. There are a number of good sized rivers much closer to San Diego than even the Columbia, but it is a good "bench mark" because its flow statistics are so thoroughly studied and well documented.  

Let's start with a few ideas about water and tubes.

hydraulics of water flowing through a tube
Figure 1 [Graphics - MeanMesa]
The simple tube arrangement shown in the diagram [right - Figure 1] looks promising enough, but right away we encounter some problems. If the level of supply water in a river is the same as the top of the tube, it would have little inclination to flow through the tube instead of just flowing down the river as if the tube were not even there.

Further, a pump large enough to power a 30 ft. diameter stream of Columbia River water through a tube all the way to San Diego would be an immensely large pump depending on lots of moving parts and requiring an enormous amount of power -- it would probably be cheaper to simply go ahead and build the desalination plants.

Finally, when water passes through a long pipe, the pipe itself begins to create a "head loss" which makes the system require even more "pumping" to over come it. Different pipe materials produce this "head loss" at different intensities, but none of the "head loss" charts include data for the type of pipe material proposed here.

Capturing fresh water in Columbia River Estuary
Figure 2 [Graphics - MeanMesa]
The plan appears remarkably similar to the design proposed in the previous "Infrastructure" post, but there are some important differences. Instead of requiring a series of very large hydraulic ram pumps to be strung sequentially across the mountains between the Columbia River and the Central Valley, this plan calls for a simple pipe -- a "tube" -- to be laid along the ocean floor with one end in the Columbia River and the other end in San Diego Bay.

The "tube" would not be a steel pipe in the common sense at all. Instead, it would be manufactured from very light weight plastic film attached to a more durable style of an external plastic mesh jacket. It could be laid in much the same manner as cables are laid today. 

Think of a slightly modified design similar to the exhaust duct tube used when installing a clothes dryer -- except, of course, 30 feet in diameter.

Such a plastic "tube" could be rolled up as a flat form to make it easier to unreel it from a ship's deck. It would remain in this flattened shape until the fresh water from the river began to inflate it as it made its way through the tube.

As mentioned before, various pipe materials create "head loss" corresponding specifically to each material. This tube with a carrier pipe fabricated entirely from nice, "slick" plastic should create a "head loss" significantly lower than, for example, steel or copper pipe. This will be important as we consider such a long pipe run from Washington to California.
sub-ocean tube carrying fresh water to San Diego - details
Figure 3 [Graphics - MeanMesa]

At first one might think that a flimsy plastic tube might not be able to contain the water pressure of such a flow. However, nature helps out on this one. The exterior pressure of the sea water pressing on the outside of the tube will be almost exactly the same as the internal pressure being generated as the fresh water flows along through the inside.

Our tube will need to be fairly tough -- enough so to avoid being punctured or suffering serious abrasion from being moved around by ocean floor currents. However, protecting the pipe from this will be the job of the protective jacket. Think of the mesh fabric of a durable fish net permanently connected to the tube's outer surface.

During the process of unrolling the pipe, several small stabilizing collars can be attached to the tube at intervals as it is being laid. These would anchor the pipe by entangling stones or plants to prevent the ocean floor currents to whipping the tube strongly enough to rip it. Although the precise route of the tube is not particularly important, it will need to be anchored to the ocean floor well enough that rogue currents won't be able to whip it around and damage it. 

As the tube fills with fresh water from the river, it will assume an elliptical section [Figure 3] which should further stabilize it on the ocean floor.

[MeanMesa is assuming that the plastic materials required to manufacture the pipe and jacket are either available now or can be developed rather quickly if the market were to emerge. Like wise, the mechanism and process to lay it in the ocean should not be very dissimilar to that used for laying cable.]

How This Works

At this point we could delve deeply into the hydraulic equations with which we could precisely calculate what our tube was going to do after it was in place. Relax, we're in concept mode here. There are, undoubtedly, plenty of hydraulics engineers looking for work out along the West Coast who are absolutely just "itching" for a chance to actually build something. We can leave the number crunching and head scratching to these eager beavers. 

Across the country there's almost no building going on at all, now. Without a Congress our nation's tax dollars are accomplishing very little beyond quietly evaporating and reappearing in the pockets of the billionaires. We are producing very little besides more sky scrapers full of millionaire hedge fund managers. Aggravating things even more, hydrologists are practically worthless for the weapons export industries.

We could, for example, take one of our "modern" US trains to tour the Columbia's estuary in person -- if we had enough time. [The average speed of a "modern" US train is 68 mph.] Perhaps it's just better to stick to our CRTs and word process key boards -- lost in dream fantasies. There is something  classically romantic about imagining not dying when the climate finally croaks for good.

Still, in any event we should complete our alternative plan. Let's look at how our tube approach can function.  

Highway 101 crosses the Columbia estuary from Astoria on the southern bank to Megler on the northern side via a highway bridge. This section of the estuary is routinely dredged to provide depths required for both ocean and river traffic. This bridge is important because the Columbia River's discharge into the ocean at this point is calculated at 6,000 cubic feet per second. [USGS.gov/report/0433] The bridge is designed structurally to withstand a maximum flow rate of 9 miles per hour, although the average flow rate could be significantly lower.

[image Estuary Partnership]
Just as was the case with the very large hydraulic ram pump proposal ["Infrastructure"], fresh river water for San Diego can be captured from the Columbia River flow just before it enters into the brackish water in the estuary. The environmental impact of this water capture is minimal due to the fact that the fresh water in the river mixes with the salt water in the estuary only a few miles  farther down stream to the west.

When we consider a likely elevation for the inlet funnel to concentrate river flow [Figure 2- above], the higher above estuary sea level the better. This means that the funnel structure will benefit from being placed further and further inland in order to take advantage of "total dynamic head" increases derived from the higher elevation at the inlet.

Remember: the outlet in San Diego Bay will be at sea level or just below. The water flowing in via the pipe will still require the standard purification process in a city water plant. Columbia River water is "fresh" water because it is not salty, but it is not "potable" water. It must be pumped from such a reservoir for treatment before it becomes "drinking" water.

The Columbia's heavy flow and extreme elevation drop over a short distance, 2.16 feet per mile (40.9 cm/km), give it tremendous capacity for hydroelectricity generation. In comparison, the Mississippi drops less than 0.65 feet per mile (12.3 cm/km). The Columbia alone possesses one-third of the United States's hydroelectric potential.[WIKI - Columbia River]

Although the WIKI quotation lauds the River's hydroelectric potential due to its relatively high drainage grade, the same energy potential can be directed at creating water flow through the tube. Moving water has inertia. It is this inertial energy which is used to drive the large hydraulic ram pumps in "Infrastructure," and it is this same energy which, when flowing River water is captured by the concentrating funnel, will serve to provide the level of dynamic head necessary to move fresh water through the pipe.

Intuitively we should probably assume that the tube will fill gradually over a period of hours or days. Additionally, the first fresh water emerging from the tube will do so at a very low flow rate. However, as the flowing water in the tube gradually develops its own kinetic inertia, the flow's delivery rate in San Diego should increase and then stabilize at a standard flow rate.

The flow rate used in the design parameters for the Highway 101 bridge was 9 mph. We can assume that this flow rate was calculated as the maximum during periods of high flow [storm surges]. From this we are comfortable at estimating a more common flow rate of the River at around 6 mph. This suggests that the water passing through the concentrating funnel feeding River water into the stilling chamber and then into the San Diego bound pipe will be "attempting" to flow at this rate -- 6 mph.

6 mph/60 minutes per hour = 1/10 mile per minute
 = 530 feet per minute = 9 feet per second

Size of opening of the inlet gate of concentrating funnel = 
1,200 feet across X 15 feet high = 18,000 sf

Now, the structure will not be able to deliver to the pipe any quantity close to the theoretical amount of water suggested by these figures, so let's arbitrarily conclude that the actual amount of water which will actually be able to be "pressurized" [flow concentrated] will amount to only 10% of this theoretical maximum. This figure will establish a rough estimate at what quantity of flow might be introduced into the pipe.

funnel opening: 18,000 sf X River flow: 9 feet per second X 10% "efficiency" =
 16,200 cubic feet per second of water entering the tube at the estuary

Almost done!

Thanks to the [Bernoulli] head loss from such a long pipe we cannot reasonably expect this quantity and flow at the San Diego "end" of the system. Instead of being overly optimistic, lets estimate the the flow rate will have diminished significantly by the time a gallon of Columbia River water finally reaches San Diego. Let's set our estimated flow rate at 1/3 of the flow entering the pipe from the estuary funnel, or: 

16,200 cfs [inlet] X 1/3 = 5,400 cfs [discharge at San Diego]

Finally, it's time to compare the amount of fresh water being delivered in this manner to the amount of fresh water the proposed desalination plant could produce in 24 hrs:

desalination production: 50 Mn gallons per 24 hours
tube delivery: 5,400 cfs X 3600 seconds per hour X 24 hours = 19.9 Mn cf
 and, 7.48 gallons per cubic foot X 19.9 Mn cf = [roughly] 149 Mn gallons per 24 hours

The "tube's" annual operating and maintenance expense would, presumably, be quite a lot lower than the desalination plant's. Plus, recall that in Figure 2 [above] there were three additional hubs already installed in the discharge of the stilling chamber -- waiting for additional tubes to be installed if it turns out that San Diego likes the numbers on the first one.

Now, all we need is a Congress.

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