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The Pumpers and their Myths

The Saga of Lake Merced

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. This report was originally published in April 2001.  The Water Committee of the Lake Merced Task Force had issued its report concluding that pumping from the Westside Basin Aquifer was having a negative effect on lake levels.  Three Task Force members, including representatives of the golf courses and cities in San Mateo County using aquifer water for both irrigation and domestic purposes, supported by the San Francisco Public Utilities Commission (PUC), wrote a 'minority report' denying this claim. This report was intended to put to rest the most egregious of the "pumper's" arguments.  At the time this was issued we received some criticism for the aggressive tone we had taken.  But we had done our scientific homework; every point here was supported by at least two professional hydrologists. We don't hear these arguments any longer.  Since this report was written the golf courses have signed an agreement to use tertiary treated water for irrigation, Daly City has let a contract for the first recycled water plant in the northern San Francisco peninsula, and several San Mateo County cities have signed  conjunctive use agreements with the PUC.  How much of this is due to our holding their feet to the fire we can not say. Certainly the CalTrout petition was primary in bringing the parties to the table. But this didn't hurt. Our advice to others engaged in these battles: It may help a little to be polite, but we doubt it.  However, whatever you do get your science right.

 

The Water Committee of the Lake Merced Task Force recently issued their report describing the conditions leading to the demise of Lake Merced^[1]. Three members of that committee filed a ‘minority report’ objecting to certain terms of the full committee report^[2]  These three were Michael Carlin, head of planning for the San Francisco Public Utilities Commission, Patrick Sweetland, Manager of Water and Wastewater Resources for the City of Daly City, and Robert Maddow, attorney for three of five private golf courses drawing water from the aquifer for irrigation^[3].  Together this team is hereinafter referred to as “The Pumpers”.

This minority report attempted to accomplish two goals:

To disassociate the demise of Lake Merced from any action by The Pumpers related to pumping water from the supporting aquifer, and

To remove any timetable for action in the recommendations.

On the surface these may appear to be relatively innocuous terms. The Water Committee’s recommendations were after all supported, and we seem sure to get around to implementing them someday. This argument carried some weight with members of the Task Force not familiar with the history of the relationship between The Pumpers and Lake Merced. In fact this minority report represents just one more step in a continuing program, intentional or not, of misinformation, partial information, obfuscation and delay that has resulted in The Pumpers continuing their activity unabated for a period of many years, as well as the continued demise of Lake Merced ^[4].

 
Mr. Carlin has led the way in obstructing efforts to understand and to resolve scientific issues that have been raised.  He has refused to support a review of the most recently developed model of the aquifer and its relationship to Lake Merced ^[5].  As of this writing Mr. Carlin has failed to release $150,000 allocated to the Public Utilities Commission by the San Francisco Board of Supervisors specifically for this purpose, indicating that he’s “not sure that is the best use of these funds."^[6]  Mr. Maddow has grasped every data point, no matter how ill founded, to support his claim that pumping by the golf courses has little or no impact on Lake Merced.  Mr. Sweetland leads in believing, or at least purporting to believe, that there isn’t any problem now nor any threat of problems in the future.

An example of positive engagement, Olympic Club style

Mr. Maddow’s recent offering of support for Lake Merced was quoted in the San Francisco Independent:^[7]

“The (Olympic) club has always said that if someone comes up with a proposal for recycled water that meets our quality and quantity needs at the cost requirements of California water law, we will definitely consider it. ”

That is truly generous of you, Mr. Maddow.
 

Now to the myths.

 
Lake Merced is indirectly connected to the Westside Basin aquifer
 

The neat part about this myth is not so much that it’s not true, as by some definitions of ‘indirect’ it is true. Rather, it is irrelevant. The Pumpers have quickly confused the words ‘indirect’ and ‘insignificant^[8].’  Now if I kick you and, being angry but noting that I am much bigger than you, you kick your neighbor instead of me that is indirect. If you don’t kick very hard that is insignificant. The Pumpers kick hard.

 
Myth No. 1: The decoupled lake myth
 

So what do The Pumpers mean by ‘indirect’?  The first definition provided was that the groundwater level in the aquifer is lower than the bottom of Lake Merced to the south of the lake. The connection is direct, The Pumpers explained, at the north side of the lake where the water table height remains above the lake bottom. The lake and the aquifer are in this case ‘coupled’. The lake and the aquifer are ‘decoupled,’ however, south of the lake where the water table has fallen below lake level^[9].  By this definition, then decoupled equals indirect.
 

It quickly became apparent that the decoupling argument is more than a little dangerous as, if true^[10], it leads to a second question, that is: Why is the water table lower than the lake bottom to the south of Lake Merced?  The explanation is clear, that is, that the water table has been significantly lowered where The Pumpers are most active, at the golf courses and in Daly City, both south of Lake Merced.
 

Myth No. 2: The two-aquifer myth
 

A new definition was needed. Let’s try this one: There are really two aquifers, a lower aquifer (the Merced layer) and an upper aquifer (The Colma layer), in the Westside Basin. These layers are separated by a semi-permeable layer of clay, also called an aquatard, that limits the flow of water between the two layers. Since The Pumpers pump from the lower aquifer they claim that their activity has little if any effect on the upper aquifer, and consequently no effect on Lake Merced.
 

That’s an interesting theory. Let’s see if it holds water.
 

The Westside Basin aquifer lies between two bodies of salt water, San Francisco Bay and the Pacific Ocean. It is further bounded to the west by the San Andreas fault. There is one and only one route for fresh water to get to the lower aquifer, that is from the surface, i. e. rain and/or imported water, e. g. from Hetch-Hetchy, used for irrigation. If pumping from the lower aquifer continues at a rate that exceeds the rate at which rain water reaches that aquifer salt water intrusion will inevitably follow.
 

Some estimates indicate that the water being pumped from the lower aquifer is more than 40 years old. Is it a coincidence then that 50 years after the significant increase in pumping that occurred in the late 1940’s and early 1950’s the level of Lake Merced began showing the impact?  The consequence of pumping has required a significant time to become apparent. If the definition of ‘indirect’ is based upon a time delay then the relationship is in fact indirect. It is obviously not insignificant.
 

Let’s suppose, however, that through some geologic action a layer of fresh water were captured deep underground, and that some fortunate happenstance moved a confining layer of clay in place. John Suen was one of three hydrologists retained by the Westside Partners^[11] to review several planning documents^[12]. In his report to the Partners Dr. Suen observed:^[13]

“The author of the report^[14]stated that the pumping from the deep aquifers would only have an indirect effect on the water table, because most of the extracted water would come from horizontal movement. This is only true if the aquifer is completely or almost completely confined. In this case of the West Side Basin, the extent and continuity of an ideal confining layer is uncertain at best. The existence of a truly confining basin-wide layer is rare and unlikely. ”

Dr. Suen continues:

“Regardless of the existence of a confining layer, the pressure distribution within the aquifer must gradually return to natural equilibrium. Simply put, the extracted water must be gradually replaced by recharge of fresh water from the surface; otherwise, the aquifer would be invaded horizontally by the surrounding seawater. This process may take many decades before any degradation of water quality is noticeable. ”

Myth No. 3: The clay layer myth

As Dr. Suen pointed out, the existence of a true confining clay layer is “rare and unlikely. ”  Toni Pezzetti, a representative of the hydrology consulting firm CH2M-Hill, described the condition of that layer as follows:^[15]

“A cross-section drawn through the Lake Merced area shows . . . that the clay appears to be thin or absent at the Olympic Club wells. The absence of the clay in an area of high groundwater pumping would increase the impact of this pumping on the ground-water in the upper unit and water levels in Lake Merced. ”

Mr. Sweetland found an impervious clay layer at the bottom of his well:

“As for the recent core samples taken from the vacant lot just north of 2171 Junipero Serra Boulevard, a series of clay layers were determined at various drilling depths. The impervious clay layer was found at minus 636 feet and continued to minus 656 feet when drilling was ceased^[16].”

Obviously a clay layer so located is not going to protect Lake Merced.

Myth No. 4: The dry lake myth

Having failed in these attempts, The Pumpers made a final try:  “If the relationship between the Lake and deep aquifer were direct, then Lake Merced would be dry”^[17] by the first of May.

This apparently profound observation is based upon the fact that the amount of water taken from the aquifer in four months equals approximately the volume of water in Lake Merced. This conclusion would be accurate in that special case where the boundaries of the lake and of the aquifer were coincident^[18]. That is, were Lake Merced to cover the entire aquifer then the first gallon of water taken from the aquifer would reduce the level of Lake Merced by one gallon, and so forth until the lake were empty.

However, anyone who has tried to bail out the moat around their sand castle at the beach quickly realizes that the water visible at the surface is just a small part of the much larger volume of water stored in the surrounding sand.

The Lake Merced goes-inza’s and goes-outza’s

CH2M-Hill, a consulting firm employed by The Pumpers, is creative in their own way in the generation of new myths. One of these rests on what is called the ‘water budget’ for Lake Merced. This budget measures the sources of water going into the lake (the goes-inza’s) and the destination of water going out of the lake (the goes-outza’s). Maintaining the level of Lake Merced depends upon some understanding of these factors, and it may make sense to look at the big numbers first.

Myth No. 5: The ‘we can’t help it’ myth

The biggest source of water supporting the lake is precipitation. On average the lake receives about 20. 4 inches of rainfall a year^[19]. The area of Lake Merced is about 270 acres, so that rainfall provides a direct contribution to the lake of about 460 acre/ft. per year. (An acre/foot is enough water to cover an acre of land with a foot of water, 325,851 gallons. )

The biggest loss of water from Lake Merced is evaporation, averaging about 27” each year^[20], or about 610 acre/ft per year. That leaves about 150 acre/ft of water, or about 5% of the total volume of water in Lake Merced, to be contributed from other sources.

Since about 80% of the inflow and more than 90% of the outflow are precipitation and evaporation^[21], it seems, according to Ms. Pezzetti, that the level of Lake Merced is outside human control. Ms. Pezzetti’s conclusion misses two major points, first that the amount of rainfall in the northern peninsula hasn’t gone down, and second that the rate of evaporation hasn’t gone up for at least several centuries^[22]. Yet something has changed, as Lake Merced has been a lake for all of this time and something kept it in place, at least until quite recently.

Myth No. 6: The disappearing watershed myth

This myth is one of which Mr. Carlin is particularly fond, having repeated it in a recent interview^[23]. and again in testimony before Supervisor Tony Hall’s public hearing on Lake Merced (March 2001). The claim is that pre-development there was a watershed supporting Lake Merced of more than 6,600 acres, and that this has been diminished through urbanization to a mere 600 acres. More than 90% of the water formerly available to Lake Merced has, according to this theory, simply disappeared.

That observation misses a number of facts:

1) The 600 acres indicated as current watershed is contained entirely within the peripheral roadway and includes only the lake shore, Harding Park golf course and the lake itself. The fact that even more open land is present across the road, in the golf courses, and along Brotherhood Way is left out of this calculation.
 

2) If the entire 6,600 acres is considered just about half has been ‘urbanized’, that is covered with housing, roadways, parking lots and other impermeable surfaces^[24]. The amount of permeable land upon which water falls remains about equal to half of the pre-development total. Furthermore, impervious areas that are not connected to the storm water system and that runoff to adjoining pervious areas can significantly increase the amount of rainfall recharge in those pervious areas.

 
3) Finally, urbanization in this area occurred largely in the 1950’s, with major construction such as ParkMerced, Stonestown, San Francisco State University and Westlake Village in place well before 1960^[25]. Yet Lake Merced maintained its level fairly well into the mid 1980’s, long enough for the long-term impact of urbanization to begin to show.

The image of 6,600 acres receiving rainfall and swooshing it into Lake Merced is itself a myth. Rain falling on open spaces as far away as the Top of the Hill in Daly City, the cemeteries in Colma, and the farms at the foot of San Bruno Mountain does have an influence on Lake Merced as it percolates into the supporting aquifer. That relationship too might be considered indirect, but it certainly isn’t insignificant. Because of the sandy soils – even sand dunes to the north of the lake – the predevelopment rainfall-runoff patterns are unclear. However, the lack of a surface outlet to the lake suggests that rainstorms did not produce large runoff events but largely percolated into the groundwater system.

 

The Westside Basin goes-inza’s and goes-outza’s

 
Let’s take a look at the bigger picture, the aquifer that supports Lake Merced, and the water budget for that aquifer.

 
Ultimately all of the water we use comes from rainfall. Were there 6,600 acres in the region (accepting Mr. Carlin’s estimate), and 20. 4 inches of rainfall in a normal year, we would average about 11,220 acre/ft of new fresh water in the region each year. Since The Pumpers are pumping 11,370 acre/ft of water each year^[26]you can see that we’re in trouble already. Fortunately the Westside Basin’s area is much greater than 6,600 acres.

 
Myth No. 7: The urbanization myth

 

The urbanization myth contends that increased population, greater demands for potable water, and the reduction of pervious land surface have combined to create a water budget deficit for the Westside Basin aquifer. In fact that aquifer is in deficit, in the area south of Lake Merced probably at least 1,000 acre/ft. per year. However, it is not these factors that result from urbanization that have led to the demise of Lake Merced. This region has been urbanized for fifty years now, and until relatively recently Lake Merced was able to hold its own.

 
The fact is that the 6,600 acres suggested by Mr. Carlin is itself a fiction intended more for display than for analysis. The actual area of the Westside Basin is closer to 25,000 acres^[27], probably a little more, producing something over 40,000 acre/ft. of fresh water in an average year. That, parenthetically, is about equal to the amount of water used for all applications in the Westside Basin, an estimated 38,935 acre/ft annually^[28]. Careful harvesting of this replenishable resource could potentially supply a significant percentage of the water requirements for the region. Clearly this opportunity has not been explored with adequate vigor. Unfortunately, a great portion of the available rainfall runs into storm drains, is mixed with household wastewater and sewage, and after treatment is poured into the ocean. This represents a potential source of additional fresh water, a source that is only now beginning to be recognized^[29]. More of this water evaporates, or is absorbed by plants and released to the air, a process called transpiration. After all losses are considered less than one fourth of the total, approximately 8,600 acre/ft a year, finds its way into the aquifer^[30]. This is augmented by such things as leakage from pipes, seepage from Lake Merced into the aquifer, and deep percolation of applied irrigation^[31].

 
The discharge of water from the aquifer is similarly complicated. The Pumpers remove the largest amount, an estimated 11,370 acre/ft each year. Other losses include discharge to surface streams, outflow to the Ocean and/or Bay, and a tiny amount that seeps into Lake Merced^[32].

 
It is clear, then, that urbanization per se is not the problem. In fact there is enough fresh water available to meet municipal requirements in the Westside Basin. Rather there are two issues that must be addressed if a solution to the maintenance of Lake Merced, and of the Westside Basin aquifer, is to be achieved. First is the opportunity to recover more of the available rainfall through improved conservation. Second, is the need to stop using potable water for low-grade applications, i. e. , irrigation of the golf courses and cemeteries.

Myth No. 8: The return of the irrigation water myth

The golf courses and the cemeteries who use aquifer water for irrigation claim that the impact of their pumping is really quite limited. They suggest that much of the water that they spray on their lawns returns to the aquifer as it seeps through the soil. In fact that return is likely to be less than 25% of the water pumped, a relatively small amount in terms of the overall water budget of the aquifer.

 
There are at least two problems with this ‘return of the water’ myth:

 

First, The Pumpers can’t have it both ways. Either the pumping comes from a confined aquifer, as in the two-aquifer myth, or it doesn’t. If the aquifer is confined then water sprinkled on lawns is no more likely to recharge that aquifer than water from Lake Merced. While it is true that water pumped from the deep aquifer that recharges the shallow aquifer may produce a short-term benefit for Lake Merced, in the long term the result is the same. If, on the other hand, there is no confining layer, as the report cited above indicates is the case at the wells near Lake Merced, then pumping has an immediate and deleterious impact on lake level.

 
More importantly, this myth misses the main point. That is, if The Pumpers weren’t watering with water pumped from the aquifer they would be watering with recycled water, brought from another source. They would them be adding 20% to 25% of their irrigation water to the aquifer rather than taking 75% to 80% away.  The truth is that every gallon of pumped irrigation water replaced by recycled water represents a gallon of water added to the aquifer.

Myth No. 9: The ‘We have some new data’ myth

Until quite recently there has been a general scientific consensus that Lake Merced is a surface manifestation of the Westside Basin aquifer. That conclusion was confirmed by a number of research studies conducted by reputable agencies such as the United States Geologic Survey ^[33] and Geo/Resource Consultants
^[34]. CH2M-Hill, in an in-house memorandum, ^[35] reached that same conclusion.

 
Recently, however, CH2M-Hill developed a model of the Westside Basin that reversed this conclusion. Based on this model CH2M-Hill concluded that pumping from the aquifer has only a minor impact on Lake Merced, and that the golf courses continued use of water pumped from the aquifer has an impact on lake level about one-fourth that earlier estimated^[36].

 
There is of course no data to support this new finding, as Mr. Maddow claims, only speculation. Careful review of the CH2M-Hill model, by a qualified hydrologist,^[37] has revealed serious errors in that model’s calibration. These errors have been described in a letter to Jim Hartley,manager of the Sacramento office of CH2M-Hill, with a copies to Mr. Carlin and Ms. Pezzetti^[38]. No reply to this letter, or to follow-up phone calls to Ms. Pezzetti, has been received. No attempt has yet been made to reconcile these models although that step has been encouraged by a number of professional hydrologists.

 
It was suggested that a small amount of work be done to reconcile these differences, and the San Francisco Board of Supervisors allocated $150,000, a major part of which was intended for this purpose. Mr. Carlin has as of this date not relinquished these funds on the dubious grounds that no such work is needed, as he puts it “The models say basically the same thing. ”

 
Again The Pumpers seem confused. Do you want ‘new data’? Then the new model clearly demonstrates the error of the old. Do you want to avoid addressing the issue of calibration? The two models say basically the same thing. It’s hard to keep up.

Myth No. 10: The we don’t really have a problem myth

Mr. Sweetland has been a particularly aggressive advocate of this myth^[39]. This myth, in two parts, first states that the lake level went down during the drought of the early nineties and has now returned to its normal level. The second part discards concern for salt water intrusion of the aquifer. We really, Mr. Sweetland observes, have nothing to worry about.

 
Myth No. 10a: The lake level is normal myth

 
The table below illustrates the fallacy of this myth^[40]

 

Lake Level in 1962	Lake Level in 1982	Change in 21 years	Average Annual Rainfall
24 ft. 10 in.	24 ft. 4 in.	loss of 6 in.	20.65 inches
Lake Level in 1982	Lake Level in 2000	Change in 19 years	Average Annual Rainfall
24 ft. 4 in.	19 ft. 6 in.	Loss of 4 ft. 10 in.	20.73 inches

There was a serious drought in the mid- to late-seventies^[41]. However, during 20 year period from 1962 to 1982 the level of Lake Merced stayed nearly even, with an annual rainfall about equal to the long-term average. In eighteen years since 1982, however, the lake has gone down nearly 5 feet, while the average annual rainfall has remained about the same. While there was a serious drought during the mid-90s, after several years of normal rainfall the lake has not recovered.

 

The difference between these two twenty-year periods is not the droughts, it’s the condition of the aquifer, and the lowered groundwater levels that The Pumpers have caused, that has led to the decline in Lake Merced.

 
Myth No. 10b: The no chance for salt water myth

 
The second part of that myth states that Dr. Suen is wrong again, there is no risk of salt water intrusion into the deep aquifer. In fact there is salt water intrusion going on now, and has been for many years. CH2M-Hill estimates that in the twenty-year period 1976 to 1995 27,200 acre/ft. of salt water entered the aquifer from the ocean^[42]. This represents approximately 3% of the total estimated capacity of that basin. Note that when salt water intrudes sufficiently to reach the wells water from those wells is useless for any domestic purpose, including irrigation, and that process is very difficult, expensive and time-consuming to reverse.

 
Is that salt water approaching the wells now?  The Bookman-Edmonston report is not quite so sanguine as is Mr. Sweetland:

“Chloride is the major anion in ocean and bay waters, and increasing chloride ion concentrations in groundwater may be the first indication of saltwater contamination. Chemical data for samples from most municipal supply wells in the Westside Basin do not show clear trends or substantial increases in chloride ion concentrations (Figure 3.4). In some wells, however, chloride ion concentrations have been increasing gradually. For example, several wells in Daly City indicate an average increase in chloride of between 0. 5 and 1. 0 milligrams per liter (mg/L) per year (Figure 3.4a)^[43].  The Regional Water Quality Control Board noted this trend, and in a letter from Ron Gervason to Mr. Sweetland observed^[44]:

“Based on our review of the report, we have the following comments:

“1. Although there is limited data, several Daly City wells are showing gradual increases in chloride concentrations (see pages 3-5, 3-8 and Figure 3.4a). Implementation of measures to prevent saltwater intrusion is strongly urged.

“2. The integrity of Lake Merced must be preserved. However, despite years of study, the understanding of the connection between the lake level and the water table is still uncertain. Therefore, we urge the implementation of the Tier 1 Tasks, especially those related to maintaining Lake Merced.

“3. Existing beneficial uses listed in our Water Quality Control Plan (Basin Plan) for Lake Merced include Cold Freshwater Habitat, Warm Freshwater Habitat, Water Contact Recreation and Non-contact Water Recreation. There is also the potential Municipal and Domestic Supply beneficial use. A 1993 San Francisco Water Department Planning Study concluded that a lake level of 26 feet was needed to maintain the beneficial uses of the lake. Recent water level data indicates the lake levels are between 19 and 20 feet, significantly below this level. Therefore, it appears that the existing beneficial uses are impaired. ”

No response to that letter has been received as of this writing. Today the lake level has declined another foot, the beneficial uses have been further impaired, and while a brighter future is promised, none of the recommended monitoring activities have yet been implemented.

 
Where can that water come from?

 
It is clear now that:

1) Increased use of rainfall and reclaimed water could create a positive groundwater budget that would restore the level of Lake Merced and avert the risk of seawater intrusion.

 
2) Conservation efforts are inadequate, and a significant amount of first-quality water is used for low-order applications. The result is a deficit budget for both the Westside Basin aquifer and Lake Merced.

3) Steps needed to remedy this situation represent rather small amounts when compared with the overall hydrology of the Basin.

So what action is needed?

1) Use recycled water to irrigate the golf courses The five golf courses pump an estimated 1,310 acre/ft. of water from the aquifer^[45]. The total take from the aquifer by the golf courses is then more than the current estimated annual overdraft for the aquifer south of Lake Merced.

 
2) Use recycled water to irrigate the cemeteries. While the amount of water involved here is not known with the same accuracy, it is estimated that cemeteries and other irrigators use an additional 1,700 acre/ft. of water pumped from the aquifer each year. While the effect on Lake Merced from conversion to recycled water will be delayed due to the distance from the lake, the contribution to avoiding salt water intrusion will be significant.

 
3)  Implement a “conjunctive use” agreement between San Francisco and Daly City. That simply says that in rainy years Daly City would buy more water from the Hetch-Hetchy system, at advantageous rates, that would otherwise be spilled into the ocean, allowing the aquifer to recharge. In dry years that banked water would be withdrawn, maintaining a balance in the Hetch-Hetchy system and slowly restoring the Westside Basin aquifer. An average reduction of 20% in Daly City pumping would add another 800 acre/feet of water to the aquifer.

 
4) Increase the capture and infiltration of rainfall. Better conservation of available fresh water is a much needed program not currently on anyone’s agenda. In fact, conservation was not listed as an “area of concern” by the Westside Basin Partners when they put together the Westside Basin Groundwater Management Plan. This needs to change.

The final myth

The golf courses claim that they are the Good Guys, taking an insignificant amount of water from the aquifer, much of which is safely returned^[46]. The bad gorilla is Daly City, pumping more than 4,000 acre/ft. of water from the aquifer each year. The fact is that irrigating with recycled water would add some 3,000 acre/ft. of water to the aquifer. Daly City would need to reduce pumping by 75% and replace that water with another source of potable water to achieve the same result, denying us all a valuable replenishable resource. As the demand for water in Northern California continues to grow failure to tap into a natural resource of this size is simply unconscionable.

 

Unfortunately, little is being done to implement these programs. After many years of delay, The Pumpers spend more time defending their myths than in creating solutions.

 
Lake Merced Task Force

Water Committee Report

April 5, 2001