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Be a beaver

May 13, 2023

I recently read the book Water Always Wins by Erica Gies. A major theme is that to best manage water resources as they flow through our environment, in particular to promote and enhance sustainable water, we need to be imparting a “Slow Water” regime. We need to use management methods that blunt the rushing off of runoff and instead install means and methods that slow the flow, causing it to spread so that more of the water soaks in instead of running off. By these means, Gies argues, we can retain, and restore, the hydrologic integrity of sites, and by so treating a multiplicity of sites, of the watershed, so it would deliver more water supply.

A chapter in the book is about beaver, the undisputed champion in the animal kingdom at modifying and improving the hydrology of watersheds. The instinctive dam-building activities of beaver indeed create a Slow Water regime. They dam the flow, causing water to spread across the floodplain, filling up the “sponge” that landform creates, so storing much more water in the watershed than would occur otherwise. This slowing and retention of the water decreases downstream flooding, as more rainfall is detained/retained rather than zooming downstream. A good bit of this retained water would over time augment downstream baseflow, so improving the riparian ecology. The dams also retain sediment and so improve downstream water quality. All of this also stores carbon, and so helps to blunt climate change.

It struck me while reading that chapter that being like a beaver and creating a Slow Water regime is essentially what we did in the Villa Court project. The 3505 Villa Court project lies between Garden Villa and South 5th Street, in the Bouldin Creek watershed in South Austin. It’s a 13-unit townhome project that was installed on 1.43 acres of formerly “vacant” land. The final layout of the project imparted 67% impervious cover of the land.

In 2010, I was approached by PSW, the developer of many townhome projects in Austin, to help them obtain the water quality permit they would need to execute this development. They related that a senior level person in the City of Austin Watershed Protection Department had told them, “You need a retention-irrigation system.” Won’t bore you with the details of that method, except to say it would have entailed encumbering the back yards of all the townhomes along the downslope edge of the property with tanks to store the runoff, and taken up just about every square inch of greenspace in the development plan to “irrigate” the water gathered into those tanks. I looked at that for, oh, about 2 or 3 nanoseconds, then said, “This is insane.”

I told them, we could provide the water quality treatment for this project with rain gardens, and we could do that without needing any variances. This surprised them, and the folks at Watershed Protection too, as no one had run this idea at them before that. But I showed them that the rules did indeed support the rain garden scheme. Besides meeting the formal water quality management requirements, the rain gardens would capture and insoak the “excess” runoff created by development and keep about as much water on the land as had been soaked up by the land in its “natural” state. This despite a rather high percentage of the land having impervious cover. So we proceeded to be like a beaver.

“Rain garden”, as a formal water quality device, is a term often used for a full infiltration bioretention bed. This device is a vegetated bed of a specialized soil mix that intercepts runoff from its drainage area. Under Austin rules, the volume of water to be captured is termed the “water quality volume”. This is the volume of runoff from the drainage area generated by the “water quality depth” of runoff from the area. The water quality depth required to be captured under Austin rules increases with the percentage of impervious cover over the drainage area tributary to each rain garden. The idea is that the more impervious cover, the more the balance would be shifted from infiltration to runoff of rainfall, so a larger volume of water would need to be captured in order blunt that shift.

The captured water volume would be stored in the bed until it is infiltrated into the soil under and surrounding the rain garden. This process both intercepts pollution entrained in the runoff – “treating” it as it flows down through the biofiltration bed root zone – and retains the water quality volume on site, rather than allowing it to run directly off, so helping to control and mitigate downstream flooding and channel erosion.

The 3505 Villa Court water quality management plan entailed several rain gardens, distributed around the site. Five of them intercepted runoff from rooftops, pavement and green spaces. Another seven captured runoff from a rooftop that could not be routed to one of the other five rain gardens, so that these areas of impervious cover would be “treated”. The project layout is shown in the figure below.

This shows how indeed we intercepted, spread and infiltrated runoff flows. As noted, this restores to some degree the rainfall-runoff response of the “natural” site, as it blunts the increase in runoff immediately leaving the site that installing impervious cover on the site would otherwise impart. This indeed mimics to an extent the impacts that beaver have on a stream, only this is applied in the uplands rather than in a streambed, intercepting and insoaking the increased runoff on its way to a stream. But the ultimate impact is largely the same, damming up the flows, holding – storing – water on the land. And reaping the benefits of that.

Some of this water would infiltrate and ultimately migrate to a stream, to impart baseflow, just as water seeping out of the floodplain “sponge” that beaver create would impart baseflow downstream. As noted, the rain gardens also intercept and store sediment entrained in runoff, just as beaver ponds do, and also intercept and “treat” pollutants that developing land causes to be entrained in runoff. Then too, there would be carbon sequestration in the rain garden beds. So in imparting the water quality management scheme at Villa Court, we were being like a beaver, mimicking the ecological wisdom they evolved to deliver to the landscape.

Now of course the retention-irrigation scheme, entailing interception of runoff and subsequently spraying it over landscape to largely infiltrate the water that would have otherwise run off, would have also helped to maintain the hydrologic integrity of the site. But that would have been acting like a human, using a failure-prone mechanical system, requiring assured power supply, to redistribute the water over the site. Noting that little actual irrigation benefit would be obtained by spraying the captured runoff over the green spaces, because the storage tanks have to be evacuated only a couple days after the rain fell, which had just “irrigated” those spaces. Any sediment removal would have to be accomplished by “actively” cleaning the storage tanks, into which the “raw” runoff would flow. Rather than incorporating the sediment into the plant-soil system on the site just as a matter of course, this would create a “waste” stream that would have to be “disposed of”. Then too, the shallow-rooted turf that would be “irrigated” would not sequester anywhere near the level of carbon that the deep, more biologically complex rain garden root zone would.

All this illustrates we would be well served to be like a beaver in the way we design sites for water quality management, in the manner we did at Villa Court. Damming up water flows to create a Slow Water regime at the site level, holding up and spreading out the flows, infiltrating on the site “excess” runoff imparted by development, rather than it rushing away, so retaining/restoring the hydrologic integrity of the site. And by a multiplicity of such sites in a watershed, we can retain/restore the hydrologic integrity of the watershed. It could fairly be stated that if every site in the Bouldin Creek watershed had been treated like Villa Court was, we would still have baseflow in Bouldin Creek. And that would enhance the ecology of the whole watershed.

Almost like re-introducing beaver to the watershed would. So when considering how to manage storm water as a site is being developed, be a beaver.



March 28, 2022

March 28, 2022

Office of the Chief Clerk, MC 105

Texas Commission on Environmental Quality

P.O. Box 13087

Austin, TX 78711-3087


A petition, styled as the “Pristine Streams Petition”, permit no. 2022-014-PET-NR, has been filed with the Texas Commission on Environmental Quality (TCEQ) requesting that TCEQ adopt a rule that would bar any discharges from TCEQ-permitted “waste” water treatment plants into 23 stream segments that monitoring has found to have very low “native” concentrations of phosphorus. The aim of this proposed rule is to keep these stream segments “pristine”, in regard to their phosphorus concentrations, and thus free of “excess” algae growth that it has been documented “waste” water effluent discharges into such streams will induce.

I agree that such a rule should be promulgated, in an attempt to accomplish its stated aim. This rule is truly the minimal effort that the State of Texas should consider in an effort to blunt degradation of water quality in the waters of the state. It is in fact rather astounding that it would take a petition to get TCEQ to consider such a rule, as protecting “pristine streams” from the sort of degradation due to “waste” water discharges that have been witnessed is really in the “no-brainer” category. But as is reviewed below, establishing such a rule really needs to be just the beginning point of a larger effort to improve the state of “waste” water management in the state of Texas, including – if not especially – in regard to the fate of this water resource that we mistakenly identify as “wastewater”.

You see, a very basic problem that plagues this societal function is that TCEQ insists upon viewing this function through the lens of “disposal of a nuisance”, when really what society needs – in this region in particular, with the looming water supply issues we face – is for us to address this function with a strong emphasis on “utilization of a resource”. As TCEQ appears to “understand” this function, it is required that a full-blown “disposal” system be in place before an applicant can even start to consider the resource value of the water and how best to reuse this water so as to defray demands on the “original” water supply.

The practical outcome of TCEQ’s insistence on the “disposal of a nuisance” focus is that it is difficult to design reuse into the very fabric of development, so as to practically maximize the reuse benefit of this water resource. Which is how we should be addressing this societal function, just as a matter of course.

Under the “disposal of a nuisance” construct, the permitting process is typically a two-part endeavor; first a permit for the “disposal” system, and then another permit to route this water resource to reuse. The “clunkiness” of this process is an open-ended “invitation” to applicants to just throw this water resource away, to just do the “disposal” system and not incur the extra work, and cost, of addressing the reuse part. That is why it has been witnessed that the majority of “land application” systems are in effect “land dumping” systems, with the effluent routed to “disposal fields” – where any irrigation benefit is just coincidental – as the manner in which to make this water “go away”. Indeed, in every reference to the Dripping Springs application to expand its dispersal fields, for example, the proposed fields are called “disposal” fields. Indeed, while Dripping Springs asserts that they intend to reuse their effluent rather than “dispose” of it, it appears that all their efforts to date indeed focus on “disposal”, with no actual reuse system infrastructure being apparent. This is a dynamic that has to be blunted, with the process reoriented to focus on the beneficial reuse of this water resource, if local society is to most effectively address its looming water supply crisis.

Then too it must be recognized that centralization of “waste” water issuing from miles around to one point source treatment plant is the whole predicate for even considering stream discharge as the fate of this water resource. Indeed it is a motivator to just discharge into a stream to “get rid of it”. Once the “waste” water has been gathered to that one point source, stream discharge will always be the “cost efficient” way to “manage” that flow (depending perhaps on whether TCEQ would assign effluent limits that would not degrade the receiving stream’s water quality, which it does not seem inclined to do), especially given the high cost that would already be incurred to gather that flow to the centralized point source. A large majority of the total cost of a conventional centralized “waste” water system is the cost of the collection system, investments that really do nothing but move the stuff around, not really contributing to resolution of the root problem of managing that water resource. So once a community has dedicated a considerable investment to making that water “go away”, they would be less than excited to incur a similar investment to redistribute this water resource from the centralized point source to points were it could be beneficially reused, often being back where the water came from in the first place!

So it is that we should be considering how we can decentralize the “waste” water system, to shorten the water loops so as to minimize the investment dedicated to just moving the stuff around, and better enable designing reuse of this water resource into the very fabric of development. But this runs afoul of TCEQ’s “regionalization” policy, stated in TAC Chapter 26.081. That this holds sway over the institutional infrastructure that addresses this societal function is attested to in Dripping Springs’ “moratorium” ordinance, which states that the city “understands” the conventional centralized system architecture to be the only form of “waste” water system infrastructure that is “blessed” by TCEQ. As if this is religion, not science and technology, so that no considerations of the form and function of that infrastructure that do not conform to the “Book of TCEQ”, Chapter 26, verse 081, is allowed to be countenanced. A moment’s reflection should be plenty to conclude that there is more than one way to skin this cat. But at present it appears that most of our institutional infrastructure will not countenance any such reflection. Again, as if this is religion.

The need for re-examining the infrastructure model is perhaps most critical in exactly the areas such as those where those 23 “pristine” streams lie. A major reason they remain “pristine” is because there has been little development in areas tributary to these streams. So these are places where we have a “blank slate”, where we are not beholden to sunk costs in the conventional centralized system architecture, so could readily entertain another infrastructure model. That was, for example, the situation in which Dripping Springs found itself, yet again they chose fealty to the “Book of TCEQ” over a rational consideration of the full range of options available to them.

One such option is a “decentralized concept” strategy. Cut to its most basic, the decentralized concept holds that “waste” water is most effectively and efficiently managed by treating, and reusing to the maximum practical extent, the “waste” water as close as practical to where it is generated. As noted, this approach would work with, rather than against, the whole idea of integrating reuse into the very fabric of development, as if management of this water as a resource from its very point of generation was a central point. Rather than considering that whole matter as something you might append on to redistribute the water gathered at the end of the pipe, as if the whole matter of this water being a resource was just an afterthought.

This “decentralized concept” idea has been out there for decades, having been the subject of many works considering the concept, much of it funded and conducted under the auspices of EPA. Indeed, a “finding” was issued by Congress in the 1990s that this general approach is a legitimate manner of addressing “waste” water management needs. It is generally understood among those who have chosen to examine this matter that the decentralized concept strategy has the potential to produce “waste” water systems that are more fiscally reasonable, more societally responsible, and more environmentally benign than those systems which implement the conventional centralized system architecture. But in practice any meaningful consideration of the road not taken has been blunted, so that good examples of such practice remain rather few and far between. In no small part due to such circumstances as “regionalization” being an “article of faith” in TCEQ.

However, in the context of “developing” areas, this matter has been presented to TCEQ, and to society’s various institutional actors – city administrations and utility operators, the engineering community, the development community, and the environmental community. An example of this was presented on the Waterblogue in 2014, entitled “This is how we do it” (, considered to be part and parcel of this comment), showing in the context of one development in the Dripping Springs hinterlands how a reuse-focused decentralized concept strategy could work in that environment, in a manner that would not only integrate reuse into the very fabric of the development, thus maximizing ability to defray demands on the “original” water supply, but would also be more globally cost efficient than centralizing that development into a Dripping Springs “regional” system. The fiscal, societal and environmental advantages of this strategy were further reviewed on the Waterblogue in 2016, in the piece entitled “Let’s Compare” (, considered to be part and parcel of this comment). This application of the concept was explicitly reviewed with TCEQ, and it was the conclusion of the folks with whom it was reviewed that this strategy could be permitted under current rules. So it could readily deliver those fiscal, societal and environmental advantages in many developments in the hinterlands, such as those that may be installed on or near the “pristine” streams, NOW.

So it is that there is ample reason to reconsider the “dogma” of “regionalization” and to consider the road not taken. In particular in areas where there is little sunk cost in the ground that must be respected going forward, such as the areas where, in the main, those 23 “pristine” streams are located. Reinventing the “waste” water system infrastructure model in those sorts of areas can deliver systems that are more fiscally reasonable, more societally responsible and more environmentally benign than would be attained by pressing down on the cookie cutter and spewing out the conventional centralized system architecture, without regard to the nature of the circumstances. TCEQ must examine this matter and consider how it can best serve the citizens of Texas in regard to how the “waste” water resource is to be managed, especially around those “pristine” streams.

So again, please do protect those 23 “pristine” streams from “waste” water discharges. This is simply a “no-brainer” thing to do. But also open up the whole process of planning for how growth and development will be managed in such areas, to take a long hard look down the road not taken. As that all the difference could make. [apologies to Robert Frost]

Respectfully submitted,

David Venhuizen, P.E.

Austin, Texas

Cognitive Dissonance

November 1, 2019

Perhaps a child has told us what the deal is.

I have long been mystified about why folks around here behave as they do about the water issues we are facing in Central Texas. For many years, an array of interest groups have been asserting “I’m for the Hill Country, are you?”, that they are dedicated to opposing wastewater discharges into Hill Country creeks, and to moving us toward sustainable water management there. Lately, the flavor-of-the-month with those folks has been the “One Water” idea, that all the water that flows through our communities is a resource to be husbanded, rather than much of it being addressed as if it were a nuisance, to be made to go to that magical place we call “away”. I trust that anyone who has read much of this blog will recognize that is exactly what has been urged upon society here.

But it does not seem that these folks behave in concert with their declarations of how “important” all this is to “saving the Hill Country”, as they have so far not engaged in any real advocacy for the move toward sustainable water. I have often exhorted them to do so, and that always seems to be interpreted, as one of those folks once put it, that I’m “being mean to good people trying to do good things.” So why, I’ve often wondered, do they so often not really act in accord with what they espouse, why do they not actually advocate for the actions that can put what we need to be doing about all that on the ground?

Just as an aside, before we proceed, there is of course the possibility that they just don’t believe that my “prescriptions” for our water issues are “correct”. If so, then I’d challenge them to read this blog and say exactly what they disagree with. And I’d also note that, on occasion when these folks do get at all explicit about what needs to be done, they generally espouse essentially what has been set forth in this blog, that we do indeed need to transform our water resources infrastructure model, to put it generically – again, the “One Water” model. So onward …

A few weeks ago, I happened to watch the PBS Newshour interview of Greta Thunberg, the Swedish teenage climate activist who has been heard from in several quarters lately, perhaps most famously her address to the United Nations. In the course of that interview she said when asked why the climate crisis does not seem to be taken seriously even though people seem to be agreeing there is a problem, “They say one thing and then do another thing. … Cognitive dissonance.”

She went on, “I think it is because humans are social animals. We follow the stream, and since no one else is behaving like this is a crisis, we see that and then think, I should probably behave as they do.” When asked why she doesn’t “follow the stream” herself, she offered, “For me, I’m on the autism spectrum, and I don’t usually follow social coding, so therefore I go my own way, and I think that is a very strong reason why people just continue, because they don’t see anyone else reacting to this.”

So maybe it’s as simple as that. Cognitive dissonance. Folks say they don’t want “bad things” happening in the Hill Country, but when it is set before them what are the ways of proceeding that would blunt all that, they simply cannot seem to bring themselves to actually, explicitly advocate for those ways of proceeding. Perhaps that is because they look around, see that the entire mainstream is behaving as if “business as usual” is the way we “should” approach it – the very mental model that this blog has been dedicated to combating – and they pick up on the social queues and determine that bucking the apparent consensus, that appearing to not be “in the tribe”, would not be a “proper” way to act.

So perhaps I also am somewhere on the autism spectrum, because I also don’t “follow social coding”, as Thunberg put it, and go my own way in the water resources arena. Perhaps I cannot see that “social coding” says one does not so directly challenge the mainstream as I do, and one certainly does not question the behavior of those who assert they are in concert with what I am advocating but then do not act in concert with those assertions. And so each attempt to “enlist” them, to get them to act in concert with their own assertions is simply taken as one more instance of me “being mean to good people trying to do good things.”

Okay, so maybe that is an “explanation” for why nothing that’s been set forth about all this, such as in this blog, has been rallied around by the very folks who have asserted they want to attain the ends that I’ve been asserting those actions would attain. But if that really is the case, isn’t that rather disturbing? Isn’t the logical conclusion here that these people have chosen to be “sheep”, that it is more important to them to “fit in” than to act in accord to their asserted beliefs and aims? How can we accept that all of the “thought leaders” in all of the organizations that have set forth their desires for the how the Hill Country will fare as development occurs there could prioritize not looking like they are not “in the tribe” above attaining the ends they assert they want to attain?

But what is the choice? It is very clear that these folks do not actually advocate for the actions that will lead to attaining the ends they espouse. One very straightforward example is the “waste” water system in Wimberley. Over a decade ago I started advocating that they consider a 21st century infrastructure plan as they considered how to implement an “organized” wastewater system there. Much of that is reviewed here. And five years ago, I laid out rather explicitly for the city management the sort of system concept that might essentially be called a “One Water” adaptation of the conventionally organized system they were pursuing. I did everything but draw them a picture. Yet despite broad dissatisfaction among all the “water activist” types around there with how the city was then planning to proceed, hardly anyone said a word about this option, and certainly no one put forth an iota of effort to press the city to actually examine it. So it was ignored, and the city proceeded with a conventional 19th century infrastructure model, which has since come apart for various reasons. Fast forward – right now these same folks are reported to be scrambling to try to get what has been generally described as exactly the sort of approach I laid out 5 years ago before the City Council commits to hooking the city center up to a conventional centralized system in the adjacent town of Woodcreek. So if these folks were not failing to stand up for a sustainable water approach back then so as to avoid appearing to not be part of the tribe, what was their “reasoning”?

But we should hope there is a way forward. In response to question, “Why do you have hope that we will, as a global society, react?”, Thunberg said, “I think that people are good, people are not evil, at least not everyone, most people, so I think people are just simply unaware of the situation, and people are not feeling the urgency. I think once we would start treating this crisis as an emergency, people will be able to grasp the situation more.” Which would indicate that, here also in regard to our water resources issues, it may just be that these folks are simply not “aware enough” of the situation, that they still need to have their consciousness raised before they will galvanize and act. Again, that runs counter to their own narrative – they already loudly decry the threats to the Hill Country and their “dedication” to blunting them.

So, while it’s an unsettling conclusion, it does appear that there has been no groundswell of advocacy for the sustainable water strategies, such as have been advocated in this blog, due to this cognitive dissonance. I continue to hope that folks will take that under consideration, and evaluate their actual dedication to “saving the Hill Country” in the water resources sphere. Perhaps a real, effective program of advocacy for transforming the water infrastructure model will be embraced when these folks “start treating this crisis as an emergency.” Thank you, Greta.



September 17, 2019

Last June the City of Austin ran a water conservation conference, and among the presentations was a review of Austin Water’s plans to incentivize, or perhaps require, building-scale “waste” water treatment and reuse for all projects housing over 250,000 sq. ft. of floorspace. As that presentation was winding down, the current assistant director of Austin’s Watershed Protection Department came by and whispered, “You were ahead of your time.”

He and I had met in 1986, exactly because I had just written “The Decentralized Concept of ‘Waste’ Water Management”, the first of many versions of that and similar works setting forth the idea that, by organizing the system to treat – and reuse to the maximum extent practical – the “waste” water as close to its source as practical, we would produce an infrastructure model that would be more fiscally reasonable, more societally responsible and more environmentally benign. He was in a business at that time, selling building-scale wastewater treatment units, for whom that basic idea was rather central. As he moved on through stints at various agencies and consulting firms, somewhere along the way he seemed to have “lost” that vision. I recall a conversation on his back patio, about 10 years ago when he was with a mainstreamer national consulting engineering firm, when we discussed how cities would manage water, he opined that my “vision” of decentralizing down to the building or campus scale would never be embraced, rather cities would always stay with the conventional centralized, pipe-it-“away” scheme. So it was, I can only guess, he felt a mea culpa moment, as some version of the very vision I’ve espoused these last three decades was being displayed in front of us as the direction Austin Water is moving.

However … As the presentations, and subsequent discussions with Austin Water folks, made clear, the means by which they expect to implement building-scale reuse is by using the tools of conventional centralized systems. Most particularly the inherently unstable activated sludge treatment technology, which is practically the “knee-jerk” choice of the mainstreamers, pretty much because it is deemed the “reasonable” choice in conventional centralized systems. Which brings us to the idea of appropriate technology for the scale of the system.

A central tenet of the decentralized concept, set forth in that original 1986 paper, is that the nature of the technologies used to assemble the system should recognize that, with distributed systems, there would be many more treatment units to police, so to minimize the total O&M liability, these systems would need to employ “fail-safe” technology. As I set forth in those early writings on this subject, there is a difference between “fail-safe” and “reliability”. A system can be reliable if it has the capability, when properly operated and maintained, to consistently and reliably produce the advertized effluent quality. But “fail-safe” means that the inherent nature of the technology is such that it can maintain reliability in the face of non-optimal operating conditions, because the technology is robust, inherently resistant to “upsets”.

Activated sludge technology is inherently unstable because it depends for its treatment action on very few trophic levels of microorganisms living in concentrations far higher than found anywhere in nature (a trophic level is a rung on the food chain—organisms on a higher trophic level eat organisms on a lower trophic level), thus it is a very truncated ecology that is not inherently sustainable.  The process can only be kept “on track” by maintaining proper operating conditions with constant inputs of energy to aerate the wastewater and monitoring the process to maintain a proper food/microorganism (F/M) ratio. Typically maintaining the F/M ratio requires frequent withdrawals of sludge from the system, on a time scale measured in hours. So failure to pay close enough attention leads to an “upset” in very short order. Therefore, while the process can be reliable, as long as proper operating conditions are maintained, it is not “fail-safe” because it is so sensitive to adverse conditions. Such a process is not really what you want to depend upon in a context like a building-scale reuse system.

So for highly distributed systems, like these building-scale reuse systems, we need to be using “fail-safe” technologies. Before proceeding, note that I always put “fail-safe” in quotes. Nothing is ever completely fail-safe. No matter how robust a technology may be, it will always require proper operation and maintenance if it is to be expected to continue to perform reliably. Again, there are certain technologies that, by dint of their very nature, are rather more immune to adverse conditions than the inherently unstable activated sludge technology, and for which the timing of O&M procedures is not so critical.

While various versions of constructed wetland technology may have merit – the Hassolo on Eighth project in Portland, Oregon, is an example of a project-scale reuse system that employs this technology – for my money the recirculating “sand” filter should be the “workhorse” technology of the decentralized concept. I put sand in quotes, because while the original version of this basic technology did use sand media in the filter beds, modern versions of it use “packed beds” of gravel media, geotextile fabric media, Styrofoam bead media, foam rubber media, etc. To cover all the different media that might be used, a more generic name for this technology is recirculating packed-bed filter.

Reasons why the recirculating packed-bed filter technology is inherently “fail-safe” include:

  • This technology is an attached growth, rather than suspended growth, concept, with the treatment effect accomplished by organisms attached to the filter media, harvesting food from the pollution in the water as it flows on by. Attached growth is far less prone to “wash out” than suspended growth, so the treatment effect is inherently much more robust and stable.
  • The loading rates on recirculating packed-bed filters are quite low, on the basis of microorganism “density” relative to the food source – this imparts a high mean cell residence time in the system – which renders the process more resistant to “upsets” and so enhances the stability of the treatment process. Again it is quite robust.
  • Power is not required to maintain the treatment process. Rather power is only needed to move the “waste” water to the top of the filter bed, and the actual treatment process is passive, imparted as the water flows down through the media by gravity. So, in sharp contrast to the activated sludge process, loss of power does not result in loss of the treatment process. If a power outage were to occur, the biota would sit there, waiting for the flow to resume, with no impact on treatment quality.
  • Flow equalization is inherent in the treatment concept, with the filter beds being loaded at the same hydraulic application rate on the same schedule every day, without regard to how much or how little flow enters the system on any given day. This hydraulic steady state operation renders the process highly consistent and reliable. This is particularly important in buildings with the occupancy patterns of commercial and institutional buildings, with high activity during the day, on weekdays, and little through the night and on weekends.
  • The biology of the system is quite diverse, typically including many trophic levels of microorganisms, and some macroorganisms as well. This characteristic also renders the process inherently resistant to upsets, allowing it to readily accommodate situations where system loading is highly non-uniform, as it will be in this circumstance.
  • The only moving parts are the pumps that dose the filter beds and a passive valve that operates on water level. Again, loss of pump power over the “short term” would have no impact on the treatment process, and a malfunction of the valve can be accommodated for some time before the treatment process may be impacted, allowing the operator to fix the valve essentially at his/her leisure.
  • The pumps are installed inside sealed tanks, setting under water, so would impart no noise pollution.
  • The only odor production might be imparted as the water is distributed over the filter beds. These units are sufficiently well covered so that odors would not be obtrusive.
  • Sludge management is very unobtrusive. The major mode of sludge management is pumping the septic tanks that are the “front end” of the treatment unit. This is typically only required at multi-year intervals and is not time-critical – months could pass between observation of sludge level in the septic tank indicating pumping is needed and the pumping actually being executed without any significant impact on the treatment process.
  • The system, once set up, basically “operates itself” day-to-day. There is nothing to adjust, and only infrequent routine maintenance is required.
  • Operations and maintenance activities for this system are rather simple and straightforward. They can readily be conducted by personnel with minimal training. As long as the control system components are not themselves proprietary, it does not rely upon any one vendor for this service.
  • The major “failure” mode of this technology is clogging of the filter bed. This occurs very slowly, allowing time for the operator to respond essentially at his/her leisure. With insightful design, filter bed clogging can be remediated in very short order.

My approach to building-scale, or campus scale, treatment and reuse was informed by learning from Takashi Asano back about 1990 that the California Title 22 reuse rules basically specified a system composed of a “waste” water treatment unit followed by a water treatment unit, to produce very high quality effluent for “unrestricted” reuse, such as for toilet flush water. Of course, being mainstreamers, the folks who wrote those rules set the water treatment requirements in terms of conventional water treatment plants, entailing coagulation-sedimentation-filtration. But it immediately occurred to me that for small-scale implementation of this concept, perhaps the slow sand filter should be the water treatment plant part of the scheme, for similar reasons that the recirculating packed-bed filter is favored for the “waste” water treatment part of the system.

While sand filtration had been used for water treatment for centuries, the slow sand filter concept as we know it today was first used in Scotland in 1804, and was first implemented for public water supply in London in 1829. It became widely adopted – it was first used in the U.S. in Poughkeepsie, New York, in 1872 – and despite the introduction of more “modern” water treatment processes, it continues to be used for municipal water treatment, including by many large cities, particularly in Europe. Like the recirculating packed-bed filter technology, the slow sand filter is “low tech”, being rather simple to operate and maintain, rather robust and largely “passive”. Indeed, it is these characteristics that make it the go-to water treatment technology in “third world” settings, where operating capabilities may be quite limited. That, of course, also makes it a great choice for distributed systems.

So it is that I suggest that the “standard” treatment unit for building-scale or campus scale reuse projects be composed of a recirculating packed-bed filter for basic “waste” water treatment, followed by a slow sand filter, to produce a near-potable quality water. UV disinfection of the treated water completes the system. A schematic of this sort of system is shown below. Indeed, one of the presentations, by Amelia Luna of Sherwood Design Engineers, at the Austin water conservation confab last June noted this as a good candidate for this duty. Notably, system concepts she highlighted do use the recirculating packed-bed filter unit as the “waste” water treatment portion of the system.RBPF-SSF TREATMENT UNIT

Besides its inherent “fail-safe” nature, this “low-tech” recirculating packed-bed filter/slow sand filter treatment concept would entail significantly less energy use to run it, imparting a much lower carbon footprint. The blowers in an activated sludge plant run 24/7/365, and in the versions using a membrane rather than a conventional clarifier to produce the final effluent – the version certain to be used in a building-scale system – quite a bit of power is also required to force the water through the membrane. By contrast, the pumps in the “low-tech” unit run only intermittently, needing to impart only a modest lift of the water to the tops of the filter beds, so drawing far less power.

It is also quite likely that the installed cost of the recirculating packed-bed filter/slow sand filter unit would be somewhat lower than for the activated sludge unit of the same capacity. Confirming this awaits an opportunity to design a unit for an actual application, but the cost factors seem to favor the “low-tech” unit.

Because there is not a whole lot of economy of scale for installed costs of the “low-tech” facilities, the cost per gallon for a 1,000 gallon/day (gpd) unit would not be greatly increased over the cost per gallon for a 5,000 gpd unit, so this scheme could be just as readily used for smaller projects as for buildings having 250,000 sq. ft. of floorspace. For example, a 250,000 sq. ft. office building might house 1,250 persons, and a 50,000 sq. ft. office building might house 200 persons. The Texas on-site wastewater rules set forth a design flow rate criteria for office buildings of 5 gallons per person per day, imparting a design flow rate of 1,000 gpd for the 50,000 sq.ft. building, and 6,250 gpd for the 250,000 sq. ft. building. If the costs do scale fairly uniformly over such a range of design flow rate, the building-scale reuse scheme might be just about as cost efficient for the smaller building as it is for the larger building. This would make it feasible to cover a much larger segment of the commercial-institutional building market with project-scale reuse than just the “big box” buildings.

Indeed, we have the opportunity here to create Zero Net Water commercial and institutional buildings and campuses. With the water use “intensity” in these buildings – that is, the amount of water demanded relative to the size of the building – such buildings would have adequate roofprint so that building-scale rainwater harvesting (RWH) could provide the “original” water supply, for lavatories and building grounds irrigation, while the building-scale reuse system supplies the flush water. Again, this appears feasible for buildings much smaller than 250,000 sq. ft.

This strategy would be especially beneficial for managing the “nodal densification” proposed by the “Imagine Austin” plan. This suggests that various properties within already urbanized areas would be redeveloped at higher activity levels, or “density”. Implicit in this is that more water supply would have to provided for that “node” and more “waste” water would be generated there. If managed conventionally, this would surely require upsizing water and wastewater lines in that area, which would probably entail “upgrading” the existing lines. For example, the densification of Austin’s downtown area required the installation of a 60-foot deep tunnel to pipe the increased flow of “waste” water “away”. That is all expensive and disruptive. Meeting these increased demands instead with a Zero Net Water strategy – RWH for water supply and decentralized concept “waste” water reuse systems – would obviate all that. Instead of importing more water and draining “away” more “waste” water, the water supply would be gathered and looped around within the “node”, to serve a building or campus of buildings. Then too, growth would be adequately served without increasing demands on our conventional water supplies, which are becoming increasingly strained in this region. RWH would also reduce stormwater management issues in the denser development.

So to summarize, Austin Water should seriously consider appropriate technology as it determines if and how to incentivize, or require, building-scale reuse in commercial and institutional buildings. They should consider implications for cost and reliability. By pursuing this function with systems composed of appropriate technologies, it is more likely that the concept would be more trouble-free, and thus more widely accepted, even embraced, as it becomes clear that we can save water and money by engaging in the fundamental transformation of the form and function of our water resources infrastructure that the decentralized concept strategy accomplishes, creating a system that is more fiscally reasonable, more societally responsible, and more environmentally benign.

A space traveler lands in Austin …

November 26, 2018

In 1999, I gave a presentation at an EPA-sponsored conference on urban infrastructure, featuring “visionaries” focusing on where we were expected to be headed to deal with water resources. Looking back on that presentation, because I’ve been accepted to make a very similar one at the Western Water Summit next year, thought it might be interesting to observe how little of that “visioning” has come to pass, how little has changed in the almost 2 decades since then. We seem to remain stuck on the prevailing, essentially 19th century infrastructure model, which is not serving us too well here in the 21st century. And we are seeing the consequences of that in many places and situations, such as around here in the Texas Hill Country, where the infrastructure model is the whole key to avoiding overt degradation of Hill Country waters with “waste” water discharges. Here is the “script” for that presentation, annotated to give context on what was being shown to the audience.

Our water resources infrastructure:

How we got here, why we’ve stayed so long, and where we’re going

Imagine with me that you are a space traveler who has just landed on earth, right here in Austin.  Since you’ve just gotten here, you know nothing of the traditions that have shaped our water resources infrastructure.  You can only see the results.

You look around and see that these earth people are producing most of the water they use to sustain their lives and societal functions about here (presentation showed location of water treatment plant that has since been decommissioned). This water is treated to potable standards, at considerable expense, and that water is transported in a hugely expensive system of pipes to a far-flung service area, such as way up here (presentation showed service area many miles away from that water treatment plant).

Well okay, you say, they’ve got to have water.  But THEN you see through your beady red alien eyes that they use this expensive water—ONCE!!—mostly for uses that do not require fully potable quality water!  Then it is dumped into another hugely expensive system of pipes to be transported way over here (presentation showed location of Austin’s wastewater treatment plant) to another treatment plant that is also very expensive to build and operate, to be partially treated and then dumped back into the river!  And you further observe that the transport system consists of conduits that sometimes leak and overflow, and of pump stations that sometimes fail, and that the treatment plants these earthlings use employ a very “touchy” technology that is very prone to upsets, so poor quality treatment is not an uncommon occurrence.

You also see that, in this particular case, that system of pipes and pump stations is arrayed over a sensitive recharge zone for an aquifer that serves as the source of drinking water to a considerable population.  You hear that in fact one of those pump stations had catastrophically failed not long ago and polluted that aquifer.

You notice that earth people also have the same attitude toward rainwater that falls on areas that could be used to capture it for direct use.  These could be the best, most pure water supplies available.  But considerable investments have been made to flush rainwater “away” in a “hydraulically efficient” manner.

You look at all this and say, “Huh, what WERE these people thinking?!  Why do they treat all this water to irrigate lawns and flush toilets and supply cooling towers and industrial processes – uses that don’t require such highly treated water – at the same time they’re flushing away all this rainwater and once-used water, at considerable fiscal cost and environmental hazard?”

Then you look at the biosolids that result from the treatment process, and you hear that there is a problem with recycling this resource back into the environment because of contaminants that come from certain industrial processes.  You can’t believe they have organized the system to allow that to contaminate the much more voluminous domestic wastewater solids.

You scratch your little green alien head with your little green alien paw and say, “Why do the people put up with this apparent insanity?  How DID they get here?”

It’s that tradition that our space travelers don’t know about.  The following quote from the 1983 World Health Organization book Sanitation and Disease pretty well encapsulates the situation:

“Those whose job is to select and design appropriate systems for the collection and treatment of sewage … must bear in mind that European and North American practices do not represent the zenith of scientific achievement, nor are they the product of a logical and rational process.  Rather, [they] are the product of history, a history that started about 100 years ago when little was known about the fundamental physics and chemistry of the subject and when practically no applicable microbiology had been discovered…. These practices are not especially clever, nor logical, nor completely effective—and it is not necessarily what would be done today if these same countries had the chance to start again.” [Emphasis added]

This quote dwells on the wastewater system, and this is the field of my expertise, so most of what I have to say [in the presentation] is focused on this portion of our water resources infrastructure.  But as I’ve just reviewed, and as our visionaries [other presenters at the conference] have shared with you these last two days, there may be reason to question water supply and stormwater management strategies as well.

As stated in the quote above, the form of the wastewater system infrastructure is largely the product of sanitary engineering tradition.  City populations were exploding, there was extreme squalor developing, and there was a growing awareness of the connection of these conditions to disease.  So the focus was on piping this stuff to that place we call “away”, the universal definition of which seems to be “no longer immediately noticeable by me”.

Only later, as it was seen that the discharge of raw wastes had transformed rivers into foul, open sewers was treatment at the end of the pipe considered.  I’ve read that there was, in fact, a rather intense debate around the beginning of [the 20th] century among water resources engineers whether it would be more “efficient” to treat wastewater before it was discharged, or for downstream users to suffer higher water treatment costs.

Fortunately, today we have a little more respect for other values provided by our lakes, streams and rivers, and treatment of wastewater prior to discharge is almost universally the norm in this country.  However, having recognized the need to do that, it seems we have never gone back and questioned that “pipe it away and dump it” tradition.  Not only do we seem compelled to pipe it away, we want to pipe as much of it to one place as we possibly can.  This centralized system is the largely unquestioned paradigm controlling the development of wastewater system infrastructure.

As our space travelers observed, if you take a hard look at the system of hardware that has developed from this tradition, there are a number of reasons to question why we continue to do things this way.  For one, we’re spending a whole lot of money just to move pollution from place to place.  That system of pipes and lift stations consumes the vast majority of the capital cost of a centralized system.  We’re also concentrating large flows through one pipe or lift station or treatment center, so by the very nature of the system, the consequences of almost any mishap are catastrophic.

Especially since the larger pipes typically run along the lowest terrain available—our riparian environments—we also create significant environmental disturbance when we install, upgrade or maintain the centralized collection system.

And we’re finally coming to realize that the so-called “waste” water is indeed a water resource that we could be utilizing for non-potable purposes to displace a great deal of demand for highly treated potable water.  We’ve found that, once we’ve piped this water “away”, it’s awfully expensive to pipe the recovered resource back to where it can be beneficially  used.

And if we don’t reuse the water, if we just continue to flush it into aquatic environments, the large point source discharges of “allowable pollution” are often problematic, urging the use of ever more expensive advanced treatment processes.

The centralized system also tends to impose a “one size fits all” management system onto a service area, regardless of local characteristics.  The attitude of this traditional paradigm seems to be, if you’re not on “the sewer”, you’re on your own.  So it is not very flexible, and thus not very responsive to land use decisions.

And any upgrades or major extensions of the service area typically entail large-scale projects with long lead times for planning and financing, so the system is also slow to respond to land use decisions.  In a dynamic development environment such as we have here in Central Texas, this can lead to some pretty sorry performance of the management system.

Well, if all these problems are so obvious, if this system is indeed “not especially clever, nor logical”, why have we stayed with this paradigm for so long?  It’s because of the institutional barriers that are arrayed against change.

In my view, the nature of the engineering business is the most problematic institutional barrier.  Billable hours are god.  So it’s really hard to muster much impetus to incorporate new methods and ideas unless the individual engineers go out and learn about these on their own.

That is, unless the firm can talk the client into funding its learning process.  But I’m sure you can see the obvious “image” problem this would create.  The firm has undoubtedly sold itself to the client as the people who can solve its problem, so how would it look if they said, “Hey, there’s some other ideas that ought to be entertained, but we need some hours in our contract to learn about them”?

The result is that most engineering firms are not proficient in anything except business as usual.  I’d venture to guess the percentage of firms that could design, say, effluent sewers or sand filter systems is pretty small.  And even fewer could actually visualize alternative management concepts in which these technologies would fit.  Because of this situation, most firms have a strong vested interest in seeing that their projects focus on the conventional management paradigm.

Added on to this, the sanitary engineering field is, rightfully so, rather conservative.  There are, after all, serious public health and environmental implications at stake here.  But this conservative nature results in any methods and strategies outside the prevailing paradigm, no matter how well justified, being very slow to be embraced.  In what other field, I wonder, is stout defense of the status quo at the expense of vigorously pursuing better and more economical ways of doing the job seen as the best way to maintain and expand your business?

One aspect of that conservatism that has often been used as an excuse for not pursuing alternative strategies is that it’s perceived as difficult to get them permitted through the regulatory agencies.  I don’t believe that’s as much of a problem as it once was.  The so-called alternative methods have been kicked around long enough now that many, if not most, regulatory agencies are at least open-minded about them. [Sadly, in the intervening 2 decades, that has not always been borne out.]

In fact, if there is an expectation that other methods and strategies may result in systems that are less costly, friendlier to the environment, and would have societal benefits, an obvious place from which to stimulate change are the regulatory and funding bureaucracies.  But these institutions tend to concentrate more on process than on substance. Then too, the people in these bureaucracies have been indoctrinated in the same tradition that holds sway among the engineers that submit plans to them.  So these bureaucracies tend to accept those plans without a whole lot of critical questioning about cost and resource efficiency. [As we are now seeing in places like Dripping Springs and Blanco.]

Financing is another significant institutional barrier.  Regardless of the true global costs of various options, institutional arrangements for financing projects are often highly biased toward traditional strategies.  Typically, one who wishes to investigate anything besides “the sewer” is largely on his own and is looking at paying for the ENTIRE management system.  If one hooks up to “the sewer”, on the other hand, the buy-in cost is often a small fraction of the total costs, with the operating entity financing the rest through bonds and grants.

Another significant barrier is the entities that operate the systems.  That’s easy to understand – these guys are immersed in making sure that their existing systems are being operated and maintained properly so they don’t get their butts in a crack.  And basic human nature is also at work here—people are comfortable with the familiar and fear the unknown.  If you go to these people and suggest that they should reorganize their management system and retrain their people to accommodate new methods and strategies – well, that’s not going to make the hit parade with many of them.  At least not without a concerted effort to educate them on how that would be better for the community they serve, and ultimately on down the line for them as well.

And that brings up education.  If education is the key to proliferating better ideas in this field, then perhaps what we have here is a massive failure of the educational system.  It is indeed true that, until fairly recently, engineers who work in this field had not been taught anything but the traditional methods and strategies in their university studies and continuing education courses.  But for many years now, opportunities to learn about other ways to skin this cat have been widely enough available that just about any firm that does a significant amount of wastewater system work could have become expert in other methods and strategies. [That this has not really happened in the intervening 2 decades speaks volumes about how massively the education system has indeed failed.]

And finally, system users are another group that must be addressed.  It can be reasonably argued that the user shouldn’t care how the system hardware is arranged as long as the system is “transparent” to him or her, if all he or she has to do is flush the toilet and pay a fee.  But there is an almost universal fear that proposals to implement “alternative” systems would be rejected by the people that would be served by them.  It seems to come across that any alternative system is “experimental” or a second-class option.  We have a situation right here, in the suburban area of Westlake Hills [which was planning to sewer parts of its jurisdiction at that time], where some citizens are opposed to an effluent sewer system.  Their attitude seems to be fairly well encapsulated by what a lady actually said to me one time when discussing the possibility of a decentralized wastewater system – “Why don’t we just pay more and get a real sewer system?” !!  Also, as long as some funding agency is willing to pony up the lion’s share of the cost, why should the users be particularly interested in assuring that the most cost effective option is implemented?

That’s a lot of reasons to stay “stuck”, isn’t it?  So where do we go from here?

Despite all these barriers to change, a paradigm shift is coming and things are beginning to change, albeit at a snail’s pace. [As we’ve seen in the intervening 2 decades, the pace has indeed been that of a very slow snail.]  I believe that eventually society will come to embrace a “decentralized concept” of management, an idea that I’ve been exploring and discussing since 1985.  That year, in fact, I obtained a permit from the state of Texas for what may have been the very first decentralized concept system ever permitted.  So much for the excuse that you can’t get these things through the regulators, huh?  Unfortunately, that project died in the development bust we had here in 86 and 87.

This decentralized concept will be the antithesis of the conventional, centralized management paradigm.  Under this new paradigm, we will focus on utilization of a resource rather than on disposal of a nuisance.  Rather than look for the most efficient way to make it “go away”, we will look for the most efficient way to reuse the water and the nutrients it contains.  In general, decentralization of the treatment system is the key to achieving this goal.

Decentralization will eliminate a majority of the expense of installing, upgrading and maintaining the far-flung centralized collection system, allowing a far higher percentage of society’s investment to be focused on removal of pollutants rather than on just moving it around, and on reusing these reclaimed water resources.

Decentralization will allow segregation of industrial flows.  Sludge can be classified by source and the biosolid product from “safe” sources will be more easily marketable.  I envision the use of septic tanks or hydroseives located at the source of wastewater generation to be the basic sludge production devices.  While the many dispersed sources of sludge creates a management challenge, timing of sludge handling is not critical with these technologies, and I believe that sludge handling will be less problematic than it is now at centralized plants.

Removal of settleable solids at the source of generation also means that conveyance facilities can be small diameter effluent sewers.  These are less costly to install and maintain, and they practically eliminate infiltration and inflow to the sewer system.  So besides eliminating the cost of interceptor mains and lift stations, the decentralized concept also entails a local collection system that is more economical and eliminates the pervasive problem of high wet weather flows.  Typically, the savings in the local collection system by itself will more than pay for the septic tanks required to allow the use of effluent sewers.

To assure that operations and maintenance of many dispersed treatment facilities is not an untenable problem, treatment technologies will be chosen that are inherently low maintenance.  The small scale of the system will make it cost efficient to design in safeguards against catastrophic failure, and modern remote sensing capabilities will allow the operator to readily monitor the progress of chronic problems.  In short, the treatment system will be far more “fail-safe” than conventional plants, which typically employ the inherently unstable activated sludge technology, and so they won’t need to be placed so far “away” or be watched so continuously.

Some think that newer methods like membrane technology will be the best choice for dispersed treatment systems, and these methods may have a place, but I believe that the workhorse technology of decentralized concept systems will be updated versions of an ancient art – sand filtration.

This technology offers inherent stability, is easy to monitor and control, and, on the rare occasions it’s needed, can be serviced and put back in action in short order.  It’s also capable of producing near-potable quality water, appropriate for a variety of beneficial reuse applications.  Finally, it is a technology that is actually much MORE amenable to use in small-scale treatment centers than in larger plants.

Reuse opportunities that can be entertained without too much institutional resistance are subsurface drip irrigation of any greenspace, surface irrigation of controlled areas, flush water supply to non-residential buildings, and industrial processes that are not highly sensitive to source water quality, or that already employ point of use treatment in any case.  Perhaps after demonstrating that we can indeed control the system and consistently and reliably produce a near-potable quality effluent, we might expand our options to include surface irrigation of uncontrolled areas, flush water supply in residential buildings, cooling tower makeup supply, a wider variety of industrial processes, and perhaps even laundry water supply.

While I see the decentralized concept as where we’re headed, of course we’re not going to abandon the prevailing paradigm and adopt a new one overnight, regardless of how unclever or illogical the prevailing paradigm may seem – society just doesn’t operate like that.  But we do need to begin critically examining our opportunities to move in that direction.

I’ll close with an example of such an opportunity.  There was an article in the local paper a couple weeks ago about the Austin city government’s efforts to direct growth eastward, to what is termed the “Desired Development Zone”.  A problem pointed out by a developer who is planning a project out there is the need to expand and upgrade the city’s water and sewer system in that area in order to handle the growth.  It was reported that this developer needs $10 million worth of infrastructure improvements.

I spoke with [then Assistant City Manager] Toby Futrell after her talk [at the conference] yesterday, and she confirmed that the City is not considering decentralized management as a possibility anywhere in the Desired Development Zone.  Now if we so blindly follow the traditional paradigm, if we simply settle for the status quo, that will be another $10 million invested in piping it “away”.  Another $10 million invested in adding to the problem of long-term regional water supply shortages, another $10 million invested in moving pollution from place to place, in exacerbating point source pollution, and in adding to the biosolids reuse problem.  But in this case we have a somewhat clean slate.  Here there hasn’t been decades of investment in the traditional paradigm that must be respected.  Here we have the opportunity to consider the costs and benefits of building in a new paradigm from the beginning.

This is how we need to start thinking EVERY time a significant investment in our water resources infrastructure system is considered.  The problems are not technological, rather a matter of mustering the political and managerial will to break through the institutional barriers.  We can invest in the past, or we can invest in the future.  The choice is ours.


If we just would use global cost accounting …

October 20, 2017

I was chatting with a friend awhile back, and he asked me what projects I was working on. I told him about a meeting I’d just had with some folks proposing to develop a piece of land near Bulverde, just northwest of San Antonio, an area in which water supply is a critical issue. My reason for talking with these folks was to offer a sustainable water management concept to serve their development, entailing the strategies we have been discussing in this blog:

  • maximizing rainwater harvesting for both water supply and as a component of stormwater management;
  • a decentralized concept “waste” water system focusing on practically maximizing the resource value of this water, mainly for irrigation supply, but in this case perhaps also for toilet flush water supply in the commercial and institutional buildings planned for this project; and
  • an LID/green infrastructure stormwater management system that would hold much of the increased runoff caused by development on the land rather than “efficiently” draining it “away”.

The developers’ major focus in this particular meeting was the wastewater system. They wanted to understand the fiscal implications of pursuing the decentralized concept strategy vs. connecting to an area-wide conventional wastewater system, which would entail a 13,000-foot line to be extended to this property (and, I presume, one or more lift stations, given the topography of this area). But they also seemed very leery of the “hassle factor” of dealing with the Texas Commission on Environmental Quality (TCEQ) to permit a stand-alone decentralized concept system for their development. They perceived this permitting process would not be as “clean” and “easy” of an institutional process as “simply” joining the existing conventional centralized system. So the impression I got was that the cost implications would have to lean rather starkly in favor of the decentralized concept strategy if they were going to even investigate what permitting and running it may entail.

And this is where the tale becomes rather frustrating. As I related to my friend, one of the guys did a “back of the envelope” calculation of the cost of the 13,000-foot connection to the conventional system, which came out to be very similar to the rough ballpark cost I’d offered for the decentralized concept strategy, given the number of connections they were projecting. It was unclear if his estimate included anything but the connection line. It appeared not because he was just multiplying a cost per foot figure – offered by an engineer connected to the conventional wastewater system, I presume – times the length of the line.

As I told my friend, I began to identify costs we would need to include if we were to arrive at an “apples to apples” comparison with the decentralized concept strategy. That approach serves up a complete wastewater system – collection, treatment and reuse – while that 13,000-foot line by itself is only a partial collection system, not including all the internal collection lines (and lift stations, if needed) within the development. It also does not include connection fees, the buy-in to the centralized treatment plant capacity and any system improvements needed between the point of connection of this project to the centralized collection system and the treatment plant. That charge would likely accrue not to these developers, but to the builders, as each building or neighborhood connects to the centralized system.

Then I noted to my friend – I was really on my soapbox now – that their accounting also totally ignored the value of the water resource embodied in the “waste” water. And the eventual cost of upgrading/expanding the area’s water supply system, driven by the need to provide all the irrigation (and toilet flushing?) water for this project – and by extension for many other projects in this fast developing area – if all that “waste” water were dumped down the drain instead of reused to defray those demands. Both the costs of upgrading the water system facilities and of accessing new water supply to run through them – which in this area gets us into that whole issue of raiding remote aquifers that we’ve looked at in a previous post.

Then too, being a distributed system, it may be quite practical to install the decentralized concept system in phases, matched to the level of imminent development. So a considerable portion of the ultimate total cost of that whole system might be put off till later, saving the “time value” of the money not expended up front to get the development started. Unlikely the developers will factor those savings into their decision.

All in all, I told my friend, from a global perspective, there are a lot of cost factors that “should” be considered to get to that “apples to apples” comparison. But it is to be expected that at least some of them will not be considered as these developers make their fiscal comparison. And that is because folks don’t look to a global cost accounting when making those decisions, rather they only look at the costs that they would directly bear themselves, fairly immediately. Thus these guys’ preoccupation with that 13,000-foot extension, to the apparent exclusion of those other cost factors, as that’s the very visible immediate cost they’d bear to be able to actuate their development.

There’s also the “hassle factor” beyond the TCEQ permitting process. These developers are very leery of having to set up an entity that would handle on-going operations, maintenance and compliance monitoring of a stand-alone decentralized concept system. They most definitely would not want to be involved in running any such operation themselves; indeed, few if any developers would be. That is not their business, and they quite understandably don’t want to be bogged down in it.

A solution to that problem would be for the owner-operator of the area-wide centralized system, the Guadalupe-Blanco River Authority (GBRA), to become the owner-operator of distributed systems within this area. What GBRA is actually selling is a service, not a connection to a specific type of system. That just happens to be the manner in which they are presently organized. GBRA could just as well obtain revenue from operating and maintaining distributed systems. This concept has in fact been posed to them a few times, dating back a couple decades. But GBRA appears stuck in its mental model, always has been and apparently still remains so invested in its current business model, operating the centralized system, that it will not entertain whether it would be more globally cost efficient to provide that service by other means. This too warps the perspective of the developers, who perceive that under the centralized plan they can “just” install their collection lines, pay their fees, and then they are out of the wastewater business. While if they go with the decentralized concept strategy, no matter how much more globally cost efficient it may be, they would have to take on duties they’d rather not get into – organizing, if not actively running, a wastewater system.

This situation facing these developers and that wastewater system operator is a ubiquitous problem in our society. As I’ve noted on this blog in another context, “Society has not figured out how to send to those who incur the first costs the signal sent by the global life-cycle costs. The result is that choices are made which may well serve the short-term interests of those who bear those first costs but poorly serve the long-term best interests of society.” That may be exactly the outcome here.

As was noted in “Motherless in Bee Cave”, everyone is invested in their “deal of the moment”, focused on what they perceive best serves their bottom lines in the short term. So we have this situation where society would be paying more to degrade the cause of sustainable water than, if it followed the lead of global cost accounting, it could be paying to bolster sustainable water, saving money while saving water. How we can “get around” all these deals of the moment and make those global evaluations the basis for decisions on water management is a mystery. One of many this society must solve if it is to remain sustainable.


Tom Brady’s Complaint

December 2, 2016

The Dripping Springs wastewater discharge permit is now before the Texas Commission on Environmental Quality (TCEQ), which will determine whether or not to grant the permit and allow discharge into Onion Creek, an environmentally sensitive Hill Country stream. The issues with that course of action have been discussed here, here, and here, reviewing and highlighting the many fiscal, societal and environmental factors which rationally would be brought to bear on such a decision. If TCEQ holds to form, however, very little of that will actually have any bearing on the decision. Rather, the decision would hinge pretty exclusively on whether Dripping Springs has conformed to a process and has presented a plan of action that TCEQ deems would meet the wastewater treatment standards that TCEQ has chosen to impose. Standards which seem to be limited by that process, and so have been called to question as being equal to protecting water quality in Onion Creek.

Which takes us to Tom Brady’s complaint. The NFL succeeded in depriving the New England Patriots quarterback of four games out of his career pretty much completely on the basis of “process”. Similarly to the manner in which TCEQ will review the Dripping Springs permit, the legal review of Brady’s case centered on whether the process fell within the nominal bounds of the agreement between the NFL and the players’ association. The NFL was never required to produce any objective proof that what Brady was accused of participating in – underinflating footballs he used in a playoff game – ever even happened! (Anyone who actually understands the Ideal Gas Law will attest to that.) Thus Tom Brady’s complaint is that he was “judged” and “convicted” with no proof of wrong-doing having been required by the controlling institutions empowered to rule on the propriety of the NFL’s decision.

Before proceeding, I hasten to note that this is not a “fandom” thing. Indeed, anyone who knows me knows I’m a diehard Green Bay Packers fan, no fan of the Patriots. While I respect Brady’s abilities and accomplishments, this is not about the man, this is about the level at which we allow our society to “function”.

To the point here. The “machinery” of society sits still for this matter being executed at the level of “process”, pretty much devoid of substance, in an arena so central to the American psyche as football. What hope is there, then, for meaningful pushback against similarly ignoring the actual impacts on society, subsuming them to “process”, in an arena that most people don’t want to ever even think about – what happens to their wastewater after they flush the toilet?

The “Tom Brady’s complaint” of anyone who has chosen to consider the actual fiscal, societal and environmental factors surrounding Dripping Springs’ approach to wastewater management is that the controlling institutions who will permit that strategy will not take most of that into account. As noted, the decision will be based only on conformance to a “process”, rather than on a consideration of actual causes, effects, and outcomes. Thus, just as Tom Brady was afforded no forum for a consideration of the factual basis for what he was accused of participating in, the deflation of footballs, local society has no forum for the review of those fiscal, societal and environmental impacts, no way to bring them to light, to be prudently and factually considered.

In particular, TCEQ will absolutely not require any showing that the infrastructure model Dripping Springs is dead set on pursuing is the “best” way for them to proceed, by any measure. That infrastructure model – a conventional centralized wastewater system, routing flows from miles around to one point – is the whole predicate for even considering a discharge, so in a way is the whole problem here. Indeed, that model entails a number of fiscal, societal and environmental liabilities, as have been reviewed here, so reconsidering that infrastructure model could offer many benefits to Dripping Springs and its citizens and development clients.

But the TCEQ process allows Dripping Springs to utterly ignore all those fiscal, societal and environmental factors, that a thinking person would consider central to any such far-reaching decision. And indeed it is far-reaching. Once Dripping Springs commits to extending and perpetuating the prevailing 19th century centralized infrastructure model, that will cement into place for generations to come a mode of management that will hamstring efforts to move local society toward sustainable water. It will instead “institutionalize” the low water use efficiency that is characteristic of that 19th century model.

It appears that all the machinery of society will sit blandly by and allow this “triumph” of process over substance. No one appears much interested in lobbying TCEQ to broaden the scope of what would be deemed important to consider. Not downstream interests, not the affected citizenry – who will be financing the city’s overpriced strategy – and not the “leadership” of society, such as local legislators and city and county officials.

So, being empowered to blindly follow their mental model, never being even asked, much less compelled, to question its underpinning – that is, to actually examine those fiscal, societal and environmental factors – Dripping Springs is being allowed to close out a major avenue to deep conservation. Recall that is defined (here) as water use efficiency that is “built in” to the water infrastructure model, that will deliver that efficiency just as a matter of course, year after year. Losing this opportunity to attain deep conservation will be a disservice to local and regional society.

Again, as long as all concerned simply sit by and allow these matters to be considered solely on the basis of a “process” that ignores the underlying facts on the ground, we will all suffer Tom Brady’s complaint – a “sentence”, in this case on society, will be carried out without ever having considered the things that really matter. In Brady’s case, whether any “crime” actually happened; in ours, whether we will proceed to develop in a manner that moves us ever further away from sustainable water – and be more costly and more environmentally problematic.

With apologies to Steve Earle, I guess this is just America V 6.0, “It’s the best that we can do.”


Let’s Compare

September 26, 2016

A water management tragedy is playing out around the Hill Country community of Dripping Springs.

As reviewed in a previous post, the city has predetermined, apparently without any meaningful analysis of options, that it will extend wastewater service to large developments being planned around the city by doubling down on the prevailing 19th century infrastructure model. The plan is to increase capacity at its existing centralized treatment plant and to extend sewer trunk mains to major developments to the east, west and south of the city. The city believes this “requires” them to apply for a permit to discharge effluent from the centralized plant into a branch of Onion Creek, on which are downstream sites of a goodly portion of the recharge of the Edwards Aquifer, and along which reside a goodly number of people who are concerned about the impacts of this discharge on the creek. Recent information indicates that discharges into the creek would also recharge the Trinity Aquifer, a source of their water supply, right about where the wells serving the city are located.

The level of treatment which the Texas Commission on Environmental Quality (TCEQ) appears likely to permit for Dripping Springs will not require reduction of nitrogen. That can lead to algal blooms in the creek, degrading water quality and the visual quality of the riparian environment. Recharge of nitrogen laden water would be a problem in drinking water withdrawn from wells. It appears the permit will also not require consideration of contaminants of emerging concern (CECs), such as pharmaceuticals, also problematic in drinking water. They may also impact life in the stream. Cases of sex changes in fish have been observed in waters receiving discharges containing CECs.

In response to widespread criticisms of their discharge permit, the city asserts that “most” of the effluent would not be discharged, rather would be routed to irrigation reuse. Some on city-owned facilities, but since those are quite limited, mostly it appears by routing it back to the developments generating much of the increased flow to the city’s plant, to be used for irrigation there. However, no reuse lines running to those developments are shown in the city’s Preliminary Engineering Planning Report (PERP), dated July 2013, which a city spokesperson stated is still their “official plan”. Since it’s clear this long-looped, far-flung centralized reuse system would be quite costly, it appears the city has not yet calculated the full cost of their “disposal” focused conventional centralized strategy with reuse just appended on at the end.

A 21st century option to this very roundabout method was reviewed in “This is How We Do It”. That decentralized concept would obviate the long-looped, high-cost system of pipes and pump stations to first make this water supply “go away” and then to run it back to where it was generated in the first place. Rather, a tight-looped reuse system would be integrated into the development – irrigating the neighborhood where the wastewater is generated – as if reuse were a basic principle of water management, instead of just an afterthought to a disposal-centric system down there at the end of the pipe. Reuse would be cost efficiently maximized, and being designed into the development would not be optional, so would most definitely save on using potable water for irrigation. This is a model which the city and the developers of the large projects around it have so far refused to consider.

Dripping Springs also contends it must centralize all wastewater flows because it aims to implement a direct potable reuse (DPR) scheme, providing additional treatment to bring this wastewater to potable quality and introducing it into the city’s water supply. They assert this is the “ultimate” scheme for reuse of this water. DPR, however, is a rather problematic strategy. The costs would be prodigious, and the city does not own, thus control, the water system that supplies the city; an independent water supply corporation does.

There are also social equity issues with this scheme. Even if it were to integrate its water system into a DPR scheme, that water supply corporation does not, and will not, provide water to some of the outlying development, so in the process of serving that growth, the existing citizens would be expected to drink the reclaimed water produced by those who generate it but won’t have to drink it.

It’s an open question if the water supply situation in and around Dripping Springs is, or will become, so dire that the city would ever seriously consider the extreme costs, and the other complications, of going to DPR. Arguments can be made that increased water supply could be more cost efficiently, and safely, provided locally by building-scale rainwater harvesting, so the actual utility of DPR is questionable. From all indications so far, a DPR system in Dripping Springs is just theoretical. Perhaps not the best argument to ignore anything but a conventional centralized wastewater system, without any regard for the consequences.

So let’s compare the two approaches to expanding the Dripping Springs wastewater system to serve those large outlying developments, to see what those consequences may be. They can be compared on fiscal, societal and environmental grounds.

More Fiscally Reasonable

As reviewed in “This is How We Do It”, the decentralized concept appears to be far more fiscally and economically efficient than the conventional centralized system is projected to be. That analysis was admittedly limited, meant only to be illustrative, and more work is needed to put some meat on that skeleton, but the comparison was stark.

To review, a sketch plan was created – see the figure below – and a cost estimate derived for this decentralized concept strategy in a neighborhood in the Headwaters project, to the east of Dripping Springs. The estimate was $8,000 per house for collection, treatment and redistribution of the reclaimed water throughout the neighborhood, to provide irrigation of front yards, parks/common areas, and parkways. Since these areas would be irrigated in any case, an irrigation system would need to be installed in any case. The drip irrigation fields in those areas would therefore not entail much additional cost. So the estimated global capital cost of the decentralized concept strategy was $8,000 per house, or about $8 million total for the 1,000 houses planned in Headwaters.

Headwaters neighborhood ww sketch plan

[click on image to enlarge]

From the city’s PERP, the estimated cost in 2013 of the “east interceptor”, to convey wastewater from Headwaters to the city’s centralized plant, was $7.78 million. Spread over those 1,000 houses, that yields a cost of $7,780 per house. This one line by itself costs almost as much as was estimated for the complete decentralized concept wastewater system, yet all it does is move the stuff around.

To complete the centralized collection system requires installation of all of the local collector lines, manholes, and lift stations within Headwaters, an additional cost likely north of $10 million. Then there would also be a buy-in cost for a share of the treatment capacity at the centralized plant, likely a few million more. So it seems pretty clear that the basic conventional centralized strategy would be more than double the cost of the decentralized concept strategy, which is again a complete system, including reuse. Yet for that much greater cost, they get only collection and treatment, still having to pay for any reuse of this water.

One wonders, in what other arena would the prospect of getting more function for less than half the cost not be compelling? But in this arena, that prospect does not seem to even be noticed!

Dripping Springs insists that little, if any, of the water would be discharged; instead facilities would be installed to route it to irrigation reuse. That would entail pump stations, transmission mains, storage facilities, distribution lines within the areas where the water would be irrigated, and the irrigation systems. What all this would cost has apparently not been addressed; as noted, the city’s latest PERP is utterly silent on this. To just get the water back to Headwaters, for example, would likely entail a cost similar to the “east interceptor”. Clearly, the cost of enabling reuse under the disposal-centric centralized infrastructure model would be much greater than the cost to integrate reuse into the very fabric of development, as the decentralized concept does.

Then too, the energy demands of the decentralized concept system would be much lower than for the centralized system. The multiple distributed treatment units would use less energy in total than would be required to run the centralized activated sludge treatment plant. Little if any energy would be required to pump wastewater to those distributed units. In contrast, wastewater would run through multiple lift stations to get to the centralized plant. The tight-looped distributed reuse system would require little energy, as the water would only be pumped short distances. In the long-looped centralized strategy, much more energy would be expended to get water from the centralized plant to far-flung points of reuse. These energy savings also impart a fiscal advantage to the decentralized concept.

As it is turning out, however, that analysis of Headwaters is “theoretical” because it appears that Dripping Springs is no longer planning to install the “east interceptor” and run the wastewater from Headwaters to its centralized treatment plant. It appears they will also not build the “west interceptor” to run Scenic Greens, another major development in the city’s hinterlands, to its centralized plant. Instead these developments will be left to implement and independently run stand-alone wastewater systems.

Still, the analysis of that Headwaters neighborhood is indicative of what may be generally expected in any of the outlying developments that Dripping Springs does include in its centralized system. So it remains a general indication of how the decentralized concept would be more fiscally reasonable, likely far more so.

The wastewater systems within Headwaters and Scenic Greens are presently planned to themselves be smaller-scale disposal-centric conventional centralized systems. Effluent will likely be run to “waste areas” within the development rather than to areas that would be irrigated in any case – “land dumping” this water resource. These satellite treatment plants are exactly what Dripping Springs has asserted they are centralizing to avoid, thus the decision to not include Headwaters has societal dimensions to it. Leading us to …

More Societally Responsible

Dripping Springs will face a clear temptation to “cut corners” on the centralized reuse program that’s just appended on to an otherwise “disposal” focused system exactly because it will cost them so much. But under the decentralized concept, reuse will be practically maximized, most cost efficiently, because it’s designed into the development, serving the local and regional water economy well just as a matter of course, no further effort or expense required.

A decentralized concept system would be inherently simpler to plan and finance. Each distributed system would serve a small area, a neighborhood, to be built out in short order. Contrast this with planning large-scale facilities over an area-wide system, with much less definite growth projections.

And because investments are so focused, the costs of planning, designing and implementing the wastewater infrastructure could be readily “assigned” to those who directly benefit from that development – the developer would directly fund the building of those distributed systems. Unlike the conventional centralized system, which is typically financed by loans and bonds, spreading the costs among the whole of the city’s citizenry and/or ratepayer base. So the decentralized concept could be more equitably financed; existing residents would not be compelled to be the “bank” for development.

Then there’s the “time value of money”. With distributed systems, only the infrastructure needed to serve imminent development would be installed, neighborhood by neighborhood, so cost would closely track actual service needs. In the conventional centralized system, on the other hand, facilities that will not be fully utilized for years to come are routinely installed; dollars paid today for something you don’t need for years, foregoing all other investments that money could fund in the meantime. In Headwaters, for example, buildout is expected to take years, but to centralize it, the “east interceptor” and associated lift stations, sized for that ultimate flow, would have to be installed up front of serving the first house.

And this is all money “at risk”. If, for example, we were to experience another “crash” such as occurred in 2008, the pace of development might slow down, even stop altogether for a time. But once the money is borrowed and the system built, the payments would be due whether development came on line to fund those payments or not. So whoever financed that infrastructure would be “on the hook” to make those payments. If these facilities were publicly financed, it would be all of the ratepayers, and/or taxpayers, who would be called upon to pony up. This could balloon their wastewater rates and/or tax bills. All that would be avoided under a decentralized concept strategy, which assigns that risk to the developer, who would be putting relatively small amounts at risk at a time.

If the management needs of each area were considered independently, there would be no need for a “one size fits all” approach. But the conventional centralized system is a one-trick pony; either an area is sewered and the “waste” water is piped “away”, or – sorry, that’s the one trick – it’s left unmanaged. Under a decentralized concept strategy, the needs of each area can be considered independently. Some areas might be connected to an existing centralized system, some areas may have distributed systems, some areas may use individual on-lot systems, with all of those systems under unified area-wide management. So one management entity could accommodate each development in the most cost efficient manner, with systems best suited to the characteristics of the area and the type of development planned for it.

This would eliminate the “balkanization” of wastewater management Dripping Springs said it’s centralizing to avoid, not wanting a bunch of independent operators running systems around it – or installing unmanaged on-lot systems. On its present course, however, balkanization is just what will happen. Having had to abandon centralizing Headwaters and Scenic Greens, each relatively close in to Dripping Springs proper, highlights that it’s clearly a pipe dream to centralize the whole of Dripping Springs’ far-flung extraterritorial jurisdiction. They will continue to accept a proliferation of independent operators and unmanaged wastewater systems. Under the decentralized concept, they wouldn’t have to; they could manage it all, effectively and cost efficiently.

Independent systems could also be required for any “industrial” wastewater generators that might locate within the service area. Each such generator could be required to tailor its treatment to the characteristics of its wastewater flow. And also to the reuse opportunities inherent in the operation at hand, or that may be offered by co-located activities.

The decentralized concept is inherently growth-neutral. Each distributed system serves only a limited area of known imminent development. The centralized system, however, creates large-scale infrastructure covering an area that would grow over time. Since this infrastructure needs to be installed, and financed, up front of any development over that larger area, that creates an impetus for growth, indeed for higher intensity growth, to pay for those large-scale facilities. The infrastructure funding “tail” is allowed to wag the pace and nature of development “dog”.

The “out of sight, out of mind” nature of the conventional centralized system, taking the water far, far away from the neighborhoods where it’s generated, has at times resulted in wastewater management failing to get adequate funding to do the job well. Many cities, MUDs, etc., have a story or two about that. But with the system right there in the neighborhood, there would be constant vigilance to assure that proper management effort is always applied, that adequate funding to maintain the system is always provided. Of course, some may question if keeping the wastewater in the neighborhood is an undue “hazard”. But as reviewed in “This is How We Do It”, these distributed systems would be rather less likely to create any problems than the wastewater systems now routinely used in hinterlands developments, which do not seem to be causing much alarm, so that objection is rather disingenuous.

A little noticed feature of the decentralized concept, the system could readily accommodate any level of water conservation found to be desirable, or necessary, in the future. Employing the effluent sewer concept, the “big chunks” are retained in the interceptor tanks, and only liquid effluent is conveyed to the treatment centers. So cutting the flow, no matter how drastically, would not cause any problems in these collection lines. In conventional sewers, on the other hand, if “too much” water conservation were practiced, the sewers would be “starved” of the liquid flow needed to move solids through the lines. During severe droughts, some utilities have had to haul in water to flush sewer lines because the wastewater generators were “too good” at cutting their water use. Stagnation of sewer flows can cause a buildup of hydrogen sulfide in the sewers. That’s a potentially deadly hazard to sewer workers and can degrade sewer system components. Another whole field of risk that would be completely avoided under the decentralized concept.

Another societal issue is vulnerability to pollution, an inherent quality of the type of wastewater system being used. This leads us to a consideration of the differences in environmental impacts between the two infrastructure models.

More Environmentally Benign

Scale is a major driver of environmental vulnerability. In the conventional centralized system, large flows run through one pipe or one lift station or one treatment plant, so the consequences of any mishap – like a line break, power outage, flow surge, flood damage – are potentially “large”. With distributed systems, flows at any point in the system remain “small”, thus the potential consequences of any mishap remain “small”. Eliminating all of the large-scale collection lines outside the neighborhoods, the decentralized system has shorter runs of smaller pipes, minimizing vulnerability. Then too, with a distributed system, any mishap that may occur would only affect a small part of the overall system. All the other independent distributed systems would not be impacted at all.

In any case, decentralized concept infrastructure would be much less likely to experience problems to begin with. Effluent sewers are built “tight”, with no manholes, and there’s short runs of small pipes, so infiltration/inflow and exfiltration/overflows would be somewhere between minimal and non-existent, while conventional sewers are inherently leak-prone, typically leaking more as they age. Decentralization also minimizes, perhaps can eliminate, pump stations in the collection system, removing a major source of (sometimes major) bypasses that plague centralized systems.

The distributed treatment unit employs a highly stable, very robust technology – the high performance biofiltration concept – which is highly resistant to upsets and, by the very nature of how it’s built and operates, does not allow bypassing of untreated wastewater. The conventional centralized plant, employing the inherently unstable activated sludge technology, is a point of high vulnerability where any sort of mishap, flow surge, etc., could lead to a bypass or poorly treated water running freely on through the treatment plant.

In a conventional centralized system, the larger sewers typically have to run in the lowest topography, the riparian zones. Thus these areas are torn up to install the sewers, and often to repair or upgrade them, creating environmental vulnerability. In the decentralized system, since flows are not highly aggregated, riparian areas can typically be avoided, eliminating this vulnerability.

Also, with the collection lines being small and shallowly buried, far less disruption is entailed when installing the sewer lines, wherever they are located, and reclaimed water distribution lines can typically be laid in the same trench, making their installation non-disruptive. Since the system would be expanded by adding new distributed systems rather than by routing ever more flow to existing treatment centers, there would never be a need to upgrade collection lines, eliminating that on-going disruption.

All these factors impart a far lower vulnerability to environmental degradation with a decentralized concept system. Indeed, centralization is a “vulnerability magnet”, gathering the stuff from far and wide to one point, where again any mishap can cause “large” impacts.

Backward – or Forward?

Carrying the promise of being (far) more fiscally reasonable, more societally responsible, and more environmentally benign than the “disposal” focused 19th century conventional centralized infrastructure model, it is nothing less than a water management tragedy that Dripping Springs, and the developers of the large projects around the city, will not consider the 21st century decentralized concept infrastructure model. Preferring the “comfort” of the familiar, they will extend and perpetuate that 19th century model, incurring the high costs of implementing it and the even higher costs of appending on at the end of the big pipe a far-flung reuse system, along with all the societal and environmental ills it entails. Since this infrastructure has a service life of several decades, this retreat into the past will cement in place an infrastructure model that may hamstring progressive water management in this area for generations to come.

This is a tragedy that local society does not have to endure. It merely requires the boldness and wisdom to move forward, instead of backward. To explore the full range of options, of infrastructure models, that the city and the surrounding developers have at their disposal. Their refusal to do so is a free choice. There are no imperatives “forcing” them to forego such an examination, not fiscally, nor societally, nor environmentally – as just reviewed, all those factors highly favor the decentralized concept. And not regulatorily. TCEQ has confirmed the decentralized concept can be readily permitted.

There is nothing really new here. This is just a re-framing, in the current context, of the forward-looking ideas, ideals, concepts and principles that have been set out for society’s consideration for decades. Perhaps here and now, with the “urgency” of an Onion Creek discharge in the mix, society will chose to act on it.

Indeed the question is, will we continue to fall backward, or move forward?


A Rain Garden’s Adventure – UPDATE

September 7, 2015

… from concept to the future

The Problem – our back yard floods when we get large, sustained rains.


Drainage from the lot across our back fence pools in our back yard because our house blocks drainage from our back yard toward the street. To blunt the breadth of this ponding, particularly for it to lap up on the back patio, we decided to install a rain garden, that will pond and infiltrate a lot of the flow within it, instead of it spreading over the yard.


The logical location for that rain garden is, of course, the low point, where ponding first appears. So that set the location, in the area in the picture above that is ponded.

What is a rain garden?

Informally, a “rain garden” is any vegetated low spot where runoff gathers and infiltrates into the ground. So in that sense, much of our back yard is a rain garden. As a formal term of art, a rain garden is a bioretention bed. That stormwater management tool is an excavation that is filled with an “engineered” media into which plants are installed. Water gathers in the excavation, filling the pores in that media and ponding up over it, to the overflow depth of the bed. Below is a generalized schematic of a bioretention bed.


Of course, since water ponds here instead of running off in any case, in terms of hydrology installing a formal rain garden – a bioretention bed – in this yard is rather gratuitous. But as noted, the aim was to have more of the water pond in the rain garden excavation, with less spreading across the yard and onto the patio. And also, as I am an avid advocate of Low-Impact Development – for which the bioretention bed is a prime tool – to also create an example that practices what I preach.

Creating Our Rain Garden

Having determined the best location, the low spot where ponding in the back yard begins, I cut the edge and removed the turf. This created an excavation about 4 inches deep, which I then lined with 4-inch cut stone blocks.


The next step was to dig out the rain garden excavation which would be filled with the engineered media. I decided a media depth of about 8 inches would be a good compromise between providing storage volume, limiting the depth plant roots would have to extend to get into the native soil, and “preserving” my back. I wheelbarrowed all the excavated material, including the turf dug off the top, out to the front yard, where I had long planned on installing a raised bed. Below we see the excavation, ready to have the media installed. Note the tree roots I cut out when digging out the bed. I laid those in the bottom of the excavation before installing the media, to create a sort of hugel culture bed for the rain garden plants.


I decided on a media obtained from a local yard named JV Dirt, a specialty mix they created that includes expanded shale in the mix. This increases the water holding capacity of the media. Since the media must be coarse/sandy so that water will readily infiltrate into it when runoff starts to gather in the bed, the ability of the media to hold water in the plant root zone over the media depth will be limited. The expanded shale “absorbs” water, which it then releases as the soil around it dries out, so that more water would be available to the plants through extended periods of no rain.

It took two runs in our pickup truck to get the media here. We wheelbarrowed the media into the back yard, dumped it into the rain garden excavation, and leveled it out. The finished product is seen below:


I decided to add some compost and mix it into the media, to provide a “better” planting bed, that would support the plants better than the “bare” media, which contains limited organics and nutrients. This is by design, actually, because often a bioretention bed is installed with an underdrain and acts as a biofilter, so that “excess” nutrients in the media may flow out of the bed, a sort of “compost tea”. As those biofiltration beds are installed to treat the runoff to protect water quality, regulations for those installations limit the nutrient content of the media. In our case, though, the water infiltrates into a deep soil in a “non-sensitive” watershed, so leaching of nutrients from the media here is not an environmental hazard. And besides, this is a rain garden installed “outside” of the regulatory system, so adding compost to our media was “okay” in that sense too. The bed with the compost mixed in, ready for planting, is shown below:


The next step was to decide what plants to install. We wanted the bed to be an attractive landscape amenity, so we chose a variety of plants that would provide various colors and plant shapes. We also chose plants that were going to be available at the Wildflower Center’s spring plant sale. I consulted lists of plants recommended for rain gardens put out by the Wildflower Center, Texas A&M, and the City of Austin, and came up with this planting plan:


The general plan is to have a ring of smaller plants around the edge and some central plants that would grow taller and spread out some. I was told by an expert landscaper friend that the flame acanthus would “overwhelm” a space this small, but I decided to give it a try anyway.

So when the Wildflower Sale came along, we got the plants. I wanted to install all 1-gallon plants so that they’d have a more well-developed root system, but had to settle for 4-inch plants for the red columbine and the plains coreopsis.

The planting begins:


Here we see me – and our cat Joey – at the “Bon Jovi point” (“Oh, we’re halfway there …” 😉


And finally I get to the last plant – yea!!


I then covered the surface of the media with a thin layer of mulch, to both hold down “weed” growth and to blunt drying out of the media over extended periods with no rain.


With that, the rain garden is finished!! And I cracked open a Real Ale Fireman’s 4.

Into Operation

Lacking rain, I spot watered each plant every other day or so to get them established. Particularly important with the coarse/sandy media all around the plants. Below we see the bed about a week after planting. All plants are doing well.


It was a few weeks before we got a “significant” rainfall. When we finally did, we saw the rain garden begin to pond – with no ponding over the rest of the yard. It works!!


A few days later, we got a big enough rain that the bed completely filled up to the top of the rock border. As we see below, again with minimal ponding outside the bed.


This was the beginning of a series of larger rainstorms through May and June, including the big Memorial Day floods. So the system was really put to a test.

When we got a much larger rainstorm, there was still some ponding over the yard outside the bed too, as we see below, but clearly more of the water was contained within the rain garden.


And each time the rain garden filled up, it would drain down in less than a day, so the plants were not standing in water for too long. Here we see the rain garden in “mid-drain”:


Then we got a week of intermittently heavy rainfalls. The rain garden filled up and the ponding spread over the yard 3 times that week:


And then the rain garden filled up a 4th time. With the ground so saturated, the rain garden drained more slowly this time. All told, this spate of rainy weather resulted in the plants being in standing water for several days. The “too small” red columbines got completely covered – for too long – and they were clearly “toast”. The Texas betony also failed to keep stems above water after a few days of ponding.


In the picture below, we see the impacts on the plants of having been in standing water for several days. Being young plants, not having developed significant growth and an extensive root structure, they were perhaps not “prepared” for that. Or it could be that some of these plants are simply not really very good choices for a rain garden.


One of the purple coneflowers appears to be dying, and the yellow columbine and flame acanthus appear to be struggling mightily. The bunch grasses appear to have survived, the skullcaps look a bit worse for wear but are still standing tall, one of the coreopsis has lodged, the other looks fine. The gulf coast penstemon and – especially – the inland sea oats seem not to have been bothered at all.

Below is a more closeup view of the flame acanthus, yellow columbine, purple coneflower and the now “toasted” red columbine. And just at the edge of the view, the now “flattened” Texas betony. The flame acanthus appears highly compromised, but the two bunch grasses appeared be surviving, for the present.


The rains were relentless, however, and the bed flooded and flooded again. As noted, with the soil – not only below the bed but all around it – so saturated, the bed was draining more slowly, leaving the plants in ponded water for days on end. One by one, the plants began to fail. Until only the inland sea oats and the gulf coast penstemon survived. I’m guessing the bunch grasses would have made it if they had been big enough to have foliage above the water, but they weren’t, and so they succumbed. Leaving us with a very impoverished plant palette in a mostly bare rain garden bed. We filled it in with potted plants, “to keep up appearances” 😉


It was a case of very bad timing, of a spate of heavy rains before the plants could become well established. Still, as we saw, the rain garden basically “worked” as it was expected to, containing the runoff up to the point that it was overwhelmed, and infiltrating it into the soil, holding water on the site and bolstering deep soil moisture.

Then the spigot shut off, and we did not get any rain for about 2 months. Note all the leaf fall at the end of August, showing how drought-stressed the trees are. And still the inland sea oats and gulf coast penstemon hung on. So we know those, at least, are very robust rain garden plants.


We’ll put in more plants in the fall when the temperatures moderate, about the time of the Wildflower Center fall plant sale. We’ll keep on watching and tracking the plants, and updating this document. Please follow along with us and watch to see what the future holds for this rain garden. Which plants will survive, and thrive? Which will have to be replaced? How will it look, and perform, over time?

On to the future …


The fall Wildflower Sale is here, so yesterday we got more plants for the rain garden and planted them. The rain garden now looks like this:


The added plants include more inland sea oats and another gulf coast penstemon – the survivors from the original planting – and switchgrass, yellow Indian grass, American beautyberry and Turk’s cap. If the promised El Nino ever brings us any rain, we’ll watch and see how these do.

When installing these new plants, I encountered a very “hard” media, needed to use my geology pick to create the plant holes. I attribute this to the rain garden media being “settled” by the repeated and prolonged ponding in May and June, then being “baked” for a couple months with no rain. I will observe how readily the water infiltrates – if we ever get any big rains that fill it up – to see if the media may need to be “aerated” to restore its permeability. That may be a maintenance program that needs to be considered for rain gardens in this climate. We’ll see.

Continuing to watch …


… and Stormwater Too

October 14, 2014

In the last post, we reviewed a decentralized concept “waste” water management strategy which can render the “waste” water system more fiscally and economically efficient for both the developer and society while also focusing on beneficial utilization of that water resource, rather than on making a perceived nuisance go “away”. In this post, we look at specifically how stormwater can be managed to attain those same ends, as was generally reviewed in “Stormwater Management Can Be ‘Green’ Too”.

As we did when reviewing “waste” water management, we’ll use that neighborhood in the proposed Headwaters project on the outskirts of Dripping Springs as an example of how we might husband the stormwater resource. A Low-Impact Development (LID) scheme for a stormwater management system is sketched onto the neighborhood plan in the figure below. Two strategies are employed in that scheme, with the aims being to defray demands on the potable water system and to hold at least as much rainwater on the land as would have infiltrated on this site in its “natural” condition:

  1. Integrate water quality management of runoff from the rooftops with rainwater harvesting to obtain direct use of that runoff to meet irrigation demands over the back yards of each lot.
  2. Provide water quality management of runoff from the ground level surfaces using bioretention beds, which would retain and infiltrate runoff from the areas tributary to each bed.

Headwaters neighborhood WQ sketch plan

[click on image to enlarge]

Recall from the last post that reclaimed “waste” water would be used to irrigate “public” spaces – front yards, parkways, a neighborhood park – leaving irrigation of back yards, the “private” spaces, to other means. Under the stormwater management scheme shown above, runoff from rooftops would be captured in a water quality tank integrated into a rainwater harvesting system so that this water could be used to irrigate these back yards. The system integrating these functions is illustrated in the figure below.

Rooftop WQRWH scheme_CROP

[click on image to enlarge]

The rules governing water quality management on this project would require a “water quality volume” (WQV) to be sequestered and treated, while runoff volumes in excess of that amount could overflow and leave the site. The water quality (WQ) tanks shown in the figure above are sized to hold the WQV calculated for the rooftop runoff. The rules require that the WQV must be evacuated within 48 hours, so that this tank capacity is again available to capture that volume from another storm. Typically, under such a scheme, the water in these tanks would be drained “away” over that period and so would not be available to provide irrigation supply, since little if any irrigation would be required within that 48-hour period.

Under the scheme illustrated above, however, these tanks would drain into the rainwater harvesting (RWH) cisterns, which would be buried in the back yard, and only when those tanks were full would water pond up in the WQ tanks. The water in the RWH cisterns could be held there as long as required until needed for irrigation, for which a high efficiency subsurface drip irrigation field would be installed. Thus much of the water that would have been “disposed of” would instead be retained and used to meet irrigation demands.

Note that the RWH cisterns could be installed at the homeowner’s option, required only if the homeowner does plan to irrigate the back yard. If the RWH cisterns were not there, the water quality management concept employing the WQ tanks would still operate in a “normal” mode, as this method is set forth in the applicable rules. As reviewed below, the arrangement shown in the figure above simply enhances that “normal” water quality management scheme.

It does that is by capturing, and retaining on the site, a somewhat larger portion of the roof runoff than would be retained if the RWH cisterns were not there. The WQ tanks would drain into the RWH cisterns until they are full. Typically the RWH cisterns would not be full at the start of most storms, since the typical inter-storm period is long enough that some portion of the water in the RWH cisterns would have been evacuated to run the irrigation system. In that case, the volume captured would be whatever amount is required to fill up the RWH cisterns plus, if that storm produced more than enough rain to fill them, whatever amount ponded up into the WQ tanks, up to the their overflow level. Only the water that had ponded up in the WQ tanks would be drained in short order, with the rest being retained in the RWH cisterns until irrigation was needed.

The majority of the rainfalls over the annual cycle are less than the depth that would generate runoff equal to the WQV and so fill the WQ tanks. Many rainfalls may not even cause water to pond up into the WQ tanks at all, rather all the roof runoff from that storm may flow into the RWH cisterns. Thus a large portion of the rainfall onto the roof would be slowly infiltrated into the soil, through the irrigation system. That water would evapotranspirate rather than flow “away”, just as most of the rainfall over the annual cycle would have infiltrated into the area of soil now covered by the house roof. This greatly blunts the impact of placing impervious cover on the site and so provides a level of water quality protection superior to a system that simply sequesters and releases the WQV within 48 hours, as current rules require. And it does this while also providing a water supply for irrigation. Again, the stormwater management function is integrated with the water supply function, rendering each of them more efficient.

This scheme also proposes that whatever volume does pond in the WQ tanks would drain from them into the drip lines. Knowing the flow rate of the drip emitters at the head created by the ponding depth in the WQ tanks, the number of emitters required to drain the WQV in 24 hours can be calculated, and that many emitters made available to receive this water. Note that this would be done regardless of whether or not the homeowner were to install the RWH cisterns, so that even in that case, the WQV would be largely stored in the soil, enhancing long-term soil moisture, instead of directly flowing “away”.

With this arrangement, draining the WQ tanks in 24 hours, the WQV would also defray any stormwater detention volume that may be required for this project under rules governing the control of peak runoff rates. That would decrease, gallon for gallon, the size of any detention facilities that must be built, another savings for the developer.

As noted, any irrigation system in the back yard would be a subsurface drip irrigation field, fed by a pump in the RWH cistern. This would render the irrigation process most efficient, so that the harvested water would provide as much irrigation benefit as practically attainable. When installed in conjunction with improving the soil to support landscaping in the back yard, a subsurface drip irrigation field would not be significantly more expensive than a less efficient spray system covering the same area. Any installation cost difference would deliver long-term value to the homeowner.

The RWH cistern volume needed so that the back yard could be irrigated with just this water supply can be determined by running a rainwater harvesting model. A fairly cost efficient installation would be two concrete tanks (modified septic tanks), each having a capacity of 2,500 gallons, so that the total RWH cistern volume would be 5,000 gallons. The details won’t be belabored here, but the model will show that, presuming the house roofprint is 2,000 sq. ft. and that the landscaping is composed of plants needing a “low” amount of irrigation, this system would cover the irrigation demands of an area the size of this back yard in all but such severe drought years as 2011 was around here.

About that low water demanding landscaping, if the homeowner wanted a back yard covered mainly with turf, as is often the case – for instance, to provide a playspace for children – then this would urge using the sort of drought tolerant turf offered by Native American Seed under the name Thunder Turf or by the Wildflower Center under the name Habiturf. The irrigation demand profile suggested by these bodies to maintain this turf in a fairly lush condition was presumed in running that rainwater harvesting model. To whatever extent turf would be displaced with shrub beds, ground cover, etc., these plants also should be drought-tolerant natives. This illustrates the need to move to more regionally appropriate landscaping as an overall part of water management strategy here.

Before proceeding to consider the general strategy for managing runoff from ground level surfaces, note an optional “wrinkle” suggested in the figure above for managing driveway runoff. If driveways were constructed using permeable pavement, in essence they would create their own water quality management system. The rain falling on the driveway would not run off, rather would infiltrate through the pavement surface, to be held in a gravel bed below until it infiltrated. That bed would be sized to hold at least the WQV calculated for the driveway pavement area. Until that bed filled up, no runoff would flow “away”. Again, over the annual cycle a majority of the rainfalls have a depth less than the WQV capture depth, so would not produce runoff from this pavement. This impervious surface then would have a rainfall-runoff response somewhat similar to the area of natural soil it displaces.

The driveway pavement could be composed of pavers, porous asphalt, or porous concrete. Being a fairly small area of pavement, any cost bump over a “normal” concrete driveway – the typical installation – would be “small” for each home. This would be defrayed by there being less impervious surface draining to the other ground level stormwater controls, decreasing their sizes, and thus their total costs.

A variation of this would be to make the driveway a rainwater harvesting system as well, by installing material below the pavement that would hold a significantly greater volume than the calculated WQV. This could be done by installing a deeper gravel bed to create more void volume. However, there are a number of products on the market made just for the purpose of creating a water storage volume below a paved surface which may provide this storage more cost efficiently. This stored water could also be used to defray irrigation needs.

Now to the management of stormwater runoff from ground level surfaces. As shown on the overall development plan above, bioretention beds would be built downslope of all developed areas. These beds would intercept and treat an amount of runoff from each storm up to the WQV calculated for the area tributary to each bioretention bed, and would also infiltrate that WQV. The general scheme for construction of the bioretention beds is shown in the figure below, on this particular site taking advantage of the sloping ground on which those beds would be arrayed.

Bioretention bed section detail_CROP

[click on image to enlarge]

The berms built to contain the bioretention beds could use material excavated on the project site for roads and house foundations, providing both on site “disposal” of this spoil and a cost efficient source for that material. The core of the berm could be the poor quality subsoil, while the top and downslope surfaces of the berm would be covered with salvaged topsoil so that those surfaces could be effectively restored to prevent erosion. All such disturbed surfaces on the project site would be restored with native grasses and/or wildflowers so that no long-term irrigation of those surfaces would be needed. The bioretention bed surfaces would also be restored with native plants, chosen to endure both short-term inundation and long-term dry spells. With good planning, these plants would enhance and blend in with the vegetation on the slopes below the developed areas to provide a pleasant viewscape from the house yards.

A bioretention bed stores the WQV until it can be infiltrated into the soil below it. A combination of the void volume in the bioretention media and a ponded depth above the media provides this storage. The minimum required footprint of the bioretention bed is determined by the infiltration rate of the soil underlying the bed. The height of the berm would be set so that the bioretention bed surface would run far enough up the slope to provide the required area. Any runoff into the bioretention bed in excess of the WQV would overflow the berm, either as sheet flow or through defined overflow weirs, in which case provisions would have to be made to avoid erosion due to those channelized flows.

By capturing and infiltrating the WQV in these bioretention beds, we would be holding on the land at least as much rainfall as would have been infiltrating under the “natural” condition of this land. The way these beds would be constructed, they could be rather cost efficiently “oversized” relative to the calculated WQV to retain more runoff. It would indeed be good to hold more rainfall on the land, since the “natural” condition of this particular property is rather hydrologically degraded, the legacy of poor land management practices by previous generations. This scheme for stormwater quality management can thus help to “heal” the land as well as provide superior water quality management. This strategy will greatly blunt the degradation of water quality over this watershed that the placement of development on this degraded landscape could readily impart.

Another benefit of this scheme is that, with the thin soils covering this landscape, much of the water that infiltrates below the bioretention beds would probably not be retained in the soil over the long term, rather it would migrate to rock shelves or other slowly permeable strata and move downslope, where a significant portion of it may emerge at seeps. This is why it is important to provide the high level of pretreatment that a bioretention bed can impart, which along with migration through the soil will deliver a highly “renovated” water to the seep faces.

This is a benefit because these seeps could flow into streams, increasing and extending baseflow in the creeks downstream. That would benefit the riparian environment generally, but in this particular area, it could provide another benefit. The creeks which drain this area run through the Recharge Zone of the Edwards Aquifer, and in creek beds are where a large majority of this aquifer’s recharge occurs. Understand that under a conventional stormwater quality management scheme, which focuses on making the runoff flow “away” after short-term detention, adding impervious surfaces would make creek flow more subject to “flash” hydrology, with a large flow surge following a storm and then no flow between storms. Those large flow surges would more readily flow on by recharge features in the creek beds, and so would less “efficiently” recharge the aquifer. Therefore, extending the period of flow at a lower rate – that is, enhancing baseflow at the expense of quickflow runoff – would enhance recharge, and so enhance the water supply obtainable from this aquifer.

As for the cost efficiency of this strategy, notice in the overall neighborhood plan there are no storm sewers. Indeed, flows would only be channelized in the street gutters, flows which are directed into bioretention beds where they are spread out and infiltrated. It has been typically observed that this sort of stormwater management concept, centered on distributed green infrastructure rather than gathering runoff into more centralized end-of-pipe devices, is significantly less expensive, even as it does a better job of water quality management. Add on the water supply value the suggested scheme provides and this approach is no doubt significantly more cost efficient, both directly for the developer and globally for society.

In summary, this stormwater management strategy of integrating rooftop runoff with rainwater harvesting and capturing, treating and infiltrating ground level runoff provides superior water quality protection while also augmenting water supply. Overall, just as for the “waste” water management strategy reviewed in the last post, this integrated stormwater management strategy offers a win-win-win for society, for the developer, and for the residents of this project. It is another aspect of the sustainable water strategy that should be considered for all development in this region.