Archive for September 2014

THIS IS HOW WE DO IT

September 24, 2014

In the last post it was asked if Dripping Springs and developers there could bust out of their 19th century approach to water resources management. In this post, we look at how they can do that, reviewing a plan for a decentralized concept wastewater system, with the reclaimed water used for irrigation. And in the next post we’ll look at a stormwater management plan based on distributed Low-Impact Development (LID) techniques, integrated with rainwater harvesting to also supply irrigation water. This integrated water management strategy is a 21st century approach.

To address our 21st century water challenges, the over-arching goal of employing these strategies is to pretty much take irrigation off the potable water system. It is typically expected that, averaged over the year, about 40% of projected water demands would be for irrigation. So if we attain our aim, the actual water required for new development could be only 60% of the currently projected demand. That would drastically reduce the strain on existing supplies from local groundwater and the Highland Lakes, and it would blunt the need to develop new supplies, like schemes to import water to this area from the Simsboro Aquifer. That would be very expensive and likely unsustainable over the long term, as reviewed in “One More Generation”. Decentralized concept wastewater systems and LID stormwater management can therefore help to move us toward sustainable water in this region.

A neighborhood in the proposed Headwaters project is used to offer an example of these techniques. This is one of the developments in the hinterlands around Dripping Springs to which the city is proposing to extend an interceptor and take their wastewater “away”. An overall draft plan for Headwaters is shown below. The neighborhood we’ll focus on is along the first side street you come to as you run on down the main road entering the project off U.S. Hwy. 290. This street and one cul-de-sac off of it are fronted by 29 houses.

hd conceptual yield study - full plan 2014

[click on image to enlarge]

 

DECENTRALIZED CONCEPT WASTEWATER SYSTEM

Before proceeding to review the details within this neighborhood, let’s look at how the decentralized concept strategy works with the “time value of money”. The development-scale conventional centralized wastewater system currently permitted for this project would have the treatment plant located in the lowest area down toward Barton Creek. So if the development were to begin with lots on the “higher” end, closer to Hwy. 290 to minimize the length of the main road and waterline to be initially installed, then they’d have to build a long run of wastewater interceptor main down to the treatment plant site, all of which would have to be sized to carry the flow from all of the development that would eventually occur along its route. This would impart a large “carrying charge” since much of that development wouldn’t be built for many years, thus much of that investment would lie “idle” for a long time. If, on the other hand, the first neighborhoods to be developed were down close to the treatment plant site, then a long run of road and waterline would have to be built, also imparting a “carrying charge”. As we will see, under the decentralized concept strategy, the whole wastewater system for each neighborhood is self-contained, built on a “just in time” basis, so one could start development anywhere desired without incurring “carrying charges” for that function.

Back to that example neighborhood, a plan approximating its layout is shown below, along with a decentralized concept wastewater system to serve those 29 houses. The plan utilizes the three essential tools of the decentralized concept to simplify the system, to make it more robust, to reduce its costs, and to maximize water utilization efficiency:

  • Effluent sewerage.
  • “Fail-safe” treatment.
  • Beneficial reuse of the water resource.

Headwaters neighborhood ww sketch plan

[click on image to enlarge]

Effluent Sewers – Simpler and Less Costly

In an effluent sewer system, wastewater from a house runs through the house drain into an interceptor tank (primary septic tank). These interceptor tanks hold and digest the settleable solids, so that only a liquefied effluent would run to the treatment unit. This allows use of small-diameter effluent sewer lines. These can run at very small and variable grades, typically with the lay of the land, in shallow, narrow trenches.

The interested reader can find a thorough review of the effluent sewer concept and its advantages here. But basically we use it because it is less expensive than conventional large-pipe sewers that have to run on larger and uniform grades, and it creates a simple, easy sludge management system – just pumping the interceptor tanks at multi-year intervals. Because the whole system is contained within the neighborhood, the overall cost of the collection system would be significantly less than a conventional collection system. That system would include not only the more costly lines within this neighborhood but also the large interceptor mains outside the neighborhood leading to the centralized treatment plant, the lines that would incur those “carrying charges”.

Ideally the area tributary to a treatment unit would be those houses that could drain by gravity through an effluent sewer system to the plant location. But where the topography dictates, one or more interceptor tanks could drain to a pump station, as shown in the drawing, to be pumped from there to the treatment unit, or to a point in the pipe system where gravity flow could take over. Such pump lines would also be small-diameter pipes installed in shallow, narrow trenches. Where they run parallel to the effluent gravity sewer, they would be in the same trench, so the cost of the pressure sewer would essentially be just the cost of the second pipe in that trench. Also an effluent pump station would be simpler and less problematic, and significantly less costly, than a conventional lift station, which would be needed at that point in a conventional centralized system.

“Fail-Safe” Treatment is Essential

The concept of “fail-safe” treatment bears a bit of explanation. I always use quotes in setting forth this tool, as nothing is ever completely fail-safe. Every sort of treatment unit will need proper operations and maintenance (O&M) in order to continue to function over time. However, there are some treatment technologies which, by their very nature, are resilient and robust, whose failure modes are slow and gradual, so can consistently and reliably produce a high quality effluent even in the face of temporarily poor operating conditions. One such technology is a variant of recirculating sand filter technology that I have labeled the high performance biofiltration concept. The interested reader can go here to get a thorough rundown of how this concept works and why it is highly robust, able to run with minimal routine oversight.

That’s a sharp contrast to the inherently unstable activated sludge process that is almost exclusively used by the mainstream in their centralized plants. And it is essential to a strategy entailing many small, distributed treatment units. Using activated sludge plants as distributed treatment units would be a disaster, as the O&M liabilities would be untenable. The high performance biofiltration concept, however, can run with little active oversight over long periods, so policing multiple plant sites would not create a great burden. This simple operating concept also uses far less energy than an activated sludge plant.

This treatment system will consistently and reliably produce an effluent quality better than that produced by most municipal treatment plants, including removing well more than half of the nitrogen from the wastewater. Recall from the last post that nitrogen was identified as a problematic pollutant, so care must be taken to remove it before any of the reclaimed water might seep into a creek.

Maximizing Irrigation Reuse, Minimizing Pollution

The reclaimed water coming out of the treatment unit would be routed into subsurface drip irrigation fields, arrayed as much as possible to irrigate areas that would be irrigated in any case, so maximizing the reuse value of this water resource. As the plan shows, much of the reclaimed water feed pipe could run in a common trench with the effluent sewer pipes. So the cost of much of this distribution system would basically be just the cost of the second pipe in that trench.

As noted, this decentralized concept plan aims to take irrigation demands off the potable water system. The plan shows dispersal of the reclaimed water is focused on front and side yards and parkways, in the “public” spaces, leaving the back yards – the “private” spaces – unencumbered by the drip fields, allowing the owners to install patios, pools, etc., there. (As will be reviewed in the next post, those private areas could be irrigated with harvested rainwater, integrating that into the stormwater management scheme, so taking that irrigation off the potable water system as well.)

The area of drip irrigation field is based on a design hydraulic application rate onto the drip fields of 0.1 gallon per square foot per day, about the average year-round evapotranspiration rate in this area. This plan provides more than enough space in areas that could be beneficially irrigated to meet that criterion. Note however this rate dictates that, on average, the field would be under-loaded through the heat of the summer and over-loaded through the winter. Thus, the drip field would act like a “drainfield” through part of the year, and indeed on any days at any time of year when a significant amount of rain fell. This may raise a concern about public health and environmental protection.

With the high quality effluent produced by the high performance biofiltration concept, and adding on UV (ultraviolet) disinfection as a safety factor, subsurface dispersal would pose no public health hazard. The water would be sequestered below the surface so contact potential would be extremely low. And any water that percolates through the soil, perhaps eventually to emerge at seeps as is likely in this topography, would have been completely “renovated” by passage through the improved soil that would be installed over the drip field areas.

Regarding environmental protection, the nitrogen concentration of the wastewater will be knocked down in the treatment unit, so it would be loaded at a rate more closely matching the uptake of nitrogen by plants covering the drip fields. Over the annual cycle the vast majority of the reclaimed water entering the drip irrigation fields would exit by way of evapotranspiration into the air instead of percolation down into the soil, where it could perhaps migrate to seeps and on into streams. So the potential mass loading of nitrogen into streams would be inherently very low. In any case, it can be expected that most of the nitrogen in the reclaimed water that is not taken up by plants would be eliminated by in-soil denitrification, gassing off the nitrogen into the atmosphere in the same manner it is eliminated in the treatment process. The soil is also by far the best medium for eliminating/assimilating the contaminants of emerging concern, such as pharmaceuticals, which would be so very problematic if the effluent were discharged to a stream.

Indeed, critics of dispersing the reclaimed water in uncontrolled access areas as shown in the plan – front and side yards, parkways, a park – would be hard pressed to show why this would be unsound practice in regard to either public health or environmental protection. As reviewed in “Slashing pollution, saving water – the classic win-win (but ignored by society)”, our controlling institutions allow – indeed they support – the spewing of water over the surface that has been questionably treated in home-sized activated sludge units subjected to a meaningless level of oversight, and then is rather questionably disinfected in a drop-feed tablet chlorinator, all over Hill Country watersheds. And many other houses have subsurface drainfields dispersing water into the soil, with no organized oversight at all. Contrast that with what is posed here – a professionally managed, highly robust and resilient treatment unit with subsurface dispersal at irrigation rates after highly effective UV disinfection – inherently far less problematic.

By the same token, concerns about marketability of a development with this sort of wastewater management system ring hollow. Again, there are all those houses being sold with that (smelly) activated sludge unit sitting right next to the house, with the poorly treated water sprayed around the lot. Whole large subdivisions, including some within Dripping Springs’ jurisdiction, employ that as the wastewater management strategy, and the builders don’t seem to be batting an eye. Indeed, it is the builders who insist upon installing the relatively cheap activated sludge and spray dispersal system, who refuse to consider using a “fail-safe” treatment unit and drip irrigation. So to suggest that the decentralized concept scheme would negatively impact on marketability is disingenuous, to say the least.

Back to real issues, irrigation of front and side yards with the reclaimed water would relieve the homeowners of water bills to irrigate these spaces. But, as noted, the amount of water each house would produce as wastewater would leave these areas under-loaded through the peak irrigation season, IF a conventional turf and/or high water demanding “exotic” plants were used to create those front yard landscapes. This suggests another strategy to match the needs of the landscape to the water made available through the wastewater system – a regionally appropriate landscaping aesthetic/ethic. A front yard landscape employing native and native-adapted plants, such as shown in the picture below, could thrive on the amount of water the wastewater system could provide, so no draw on the potable water system for additional irrigation would be needed through the peak irrigation season.

OLYMPUS DIGITAL CAMERA

[click on image to enlarge]

This sort of landscape might be institutionalized as the “face” of this development, displacing the sterile patch of water-guzzling turf that is the “stock” aesthetic in such places. The developer might deliver the home to the buyer with a basic native plant palette in place over the mulched and improved soil bed, as required to support drip dispersal of reclaimed water. The homeowner might be given an account at a participating native plant nursery and some assistance/instruction in native plants so that he/she can enhance the landscape as desired, creating buy-in to this aesthetic.

What Does It Cost?

Rough cost estimates were made for the effluent sewer system, the treatment unit, and the reclaimed water feed system shown in this neighborhood plan, yielding an estimate of about $8,000/house. To complete the entire system, the cost of the drip irrigation fields would have to be added. It is called to question however if those are not, in part at least, costs that would be borne in any case, given that much of the area shown on the plan as irrigation field might be irrigated anyway. It can be argued that, in this terrain, amended soil would cover the front yards and parkways to support improved landscaping without regard to whether it would be needed to support environmentally sound drip dispersal of the reclaimed water. Indeed, minimum soil depth on lots for landscaping is required under the Fish & Wildlife MOU that would allow this development to use water delivered by the Hwy. 290 pipeline from Lake Travis. And installing drip lines in this amended soil would not be significantly more costly than a spray irrigation system, which the drip fields displace.

While hard to compare without more details than I currently have, it is expected that these costs compare well with what would be needed to implement the conventional centralized system. The conventional collection system within this neighborhood would incur a similar cost to the effluent sewer system within it, with the interceptor tanks included, and then to that you’d have to add a share of the cost of the interceptors and lift stations needed to get wastewater from this neighborhood down to the centralized treatment plant. That plant would no doubt cost less per gallon per day of capacity than the small decentralized plant, but here again the centralized plant would be sized for the flow at buildout. So the total cost would be much greater, with the capacity that would not be fully utilized for many years imparting a “carrying charge”.

Also, under the centralized plan, the dispersal of the treated water would be a “land dumping” operation, with the cost of the dispersal system not providing any benefit other than making that water go “away”. So the entire reclaimed water distribution system and the entire dispersal system would all be extra costs, instead of displacing irrigation systems that would otherwise be installed anyway. As well as wasting all that water, while the homeowners would purchase potable water to run their irrigation systems.

If, instead of implementing their development-scale conventional centralized system, the developers connected to the City of Dripping Springs system, it does not appear that their cost situation would be much, if any, better. The estimated cost of the “east” interceptor that would receive wastewater from Headwaters is $7.78 million (per the Dripping Springs PERP dated July 2013). While of course that interceptor would eventually serve other development, its major reason for being in the Dripping Springs plan is to incorporate Headwaters into the city’s proposed conventional centralized system. Dividing that cost by the planned 1,000 lots in Headwaters, the cost per lot is $7,780, by itself almost as much as the rough estimate for collection and treatment of the wastewater and redistribution of reclaimed water under the decentralized plan. This would be in addition to the internal sewer network, including several lift stations, within Headwaters. There’d also be a charge for buy in to the city’s treatment capacity.

Of course, this all presumes that the city could have that interceptor and the lift station(s) associated with it on line, as well as its treatment plant expanded, before the first house in Headwaters becomes occupied. As Headwaters has filed a preliminary plan for its first phase of 208 lots, that is an open question. Dripping Springs has not yet even released its revised PERP, thus has not even begun the permitting process at TCEQ, which can be expected to run about a year. If all goes well, that is; it could get longer.

Also note that it would be only those 208 lots, not 1,000 lots, that the developer could spread the buy-in costs over. But the entire $7.78 million must be put in the ground up front, along with the $8+ million for the treatment plant expansion. And the estimated cost for permitting is another $1 million in up front money. It will not be the developer who will be prevailed upon to cover all these costs, rather they will be covered by bonds, the payments for which will doubtless be spread over the entire city’s ratepayer base. So there is an aspect of social equity to be considered here too, as existing ratepayers will be required to help pay the costs incurred due to growth. Which, it has been asserted, will never pay back through tax revenues what it costs to install and maintain the infrastructure needed to actuate it, at least if that continues to be the conventional infrastructure.

A note about operations and maintenance. Understand that all of the decentralized concept systems would be under unified management, either by the MUD organized by the developer or as an integral part of the Dripping Springs wastewater system. While it won’t be belabored here, it is expected that the O&M costs of the decentralized concept systems would be less, perhaps significantly so, than for the conventional centralized system.

All things considered, the price of the decentralized concept system appears likely to be a sweet deal for the developer, even without taking into account the “time value of money” benefits of installing the wastewater system infrastructure on a “just in time” basis, to serve only the neighborhoods slated for imminent development. And because of the social equity issues, it would be a sweet deal for the existing citizens of Dripping Springs as well.

A WIN-WIN-WIN

Then add on the reuse benefits, displacing irrigation demand from the potable water system, which will further benefit all the citizens of the area by delaying, perhaps obviating, the need to implement a very costly long-distance “California-style” water transfer scheme that would greatly increase water rates. Altogether this is a win-win-win. So clearly it would be in the interests of Dripping Springs and the developers there to give meaningful consideration to a decentralized concept wastewater management strategy.

 

Advertisements

Can Dripping Springs, and developers there, bust out of the 19th century?

September 8, 2014

Or will they choose to remain stuck there. Because, you know, that is a choice they are free to make.

It’s a simple proposition, really. If your aim is to maximize use of the water resource we mistakenly call “wastewater” to defray demands on the area’s water supplies, then it just makes sense to design the “waste” water system around that principle. It doesn’t make sense to instead use a large majority of the money dedicated to this function to build a large-scale system of pipes and pump stations focused on making what’s misperceived as a nuisance to go “away”, then to spend even more money on another large-scale system of pipes and pumps to run the reclaimed water back to where it came from in the first place!

That’s the standard MO of our mainstream institutions, like the City of Dripping Springs and the engineers who advise it and developers whose projects would feed into the city’s centralized wastewater system. This centralized management concept was a response to the conditions considered paramount in the 19th century. The industrial revolution was in full force, city populations were exploding, the stuff was littering the streets, creating a stench and a serious threat of epidemic disease. The response was to pipe it “away”, to be deposited in the most conveniently available water body. Later, as it was realized those water bodies were being turned into foul open sewers, creating a threat of disease in downstream cities that withdrew their water supplies from them, treatment at the end of the pipe was considered, and eventually adopted as the standard.

The intellectual leadership of the centralized pipe-it-away strategy was centered in well-watered areas like northern Europe and the northeastern and midwestern areas of the US. So the resource value of that “waste” water was never part of the equation. This water, and the nutrients it contains, was viewed solely and exclusively as a nuisance, to be made to go to that magical place we call “away” – the working definition of which is apparently “no longer noticeable by me.” This centralized pipe-it-away strategy became institutionalized as the manner in which cities manage wastewater.

Of course, that strategy flies in the face of the circumstances confronting us here in Central Texas in the 21st century – that water, all water, is a valuable resource which we can no longer afford to so cavalierly waste by addressing it solely and exclusively as if it were just a nuisance, simply because that is what the prevailing mental model dictates. Rather, it’s imperative we practically maximize the resource value of that water, using it to defray demands on the area’s water supplies, which are being stressed by both chronic drought and population growth.

In the Texas Hill Country, we also have an issue with surface discharge of wastewater, even when treated to the highest standards that the Texas Commission on Environmental Quality (TCEQ) has so far formulated. And before proceeding I’d note that this issue would remain even if the whole system were to operate perfectly all the time. But of course, it will not; there will inevitably be “incidents”. Which brings up the issue of the vulnerability created by centralization. I’ve often said, not entirely tongue-in-cheek, that the real point of regionalization – TCEQ-speak for centralizing flow from as far and wide as can be attained – is to gather all this stuff together at one point where it can really do some damage. Indeed, the whole organizational strategy is a “vulnerability magnet”. Large flows being run through one treatment plant or one lift station or one transmission main means that any mishap may create large impacts.

Back to the issue with discharge in the Hill Country, the major problem is those nutrients in the wastewater, in particular nitrogen. A discharge of the magnitude that an expanded Dripping Springs system would create, centralizing wastewater flow from developments for miles around the city in every direction, would make the receiving stream effluent-dominated. This would be partly an artifact of the drawdown of local aquifers drying up springs and thus reducing natural streamflow – again highlighting how critical it is to defray demands on these local water resources – but in larger part due simply to the magnitude of the wastewater flow. Highlighting the problematic nature of “permitted pollution” when the flow has been centralized so that, even with low concentration limits, the mass loadings may still be “large”. The nitrogen would cause chronic algal blooms in the creeks, making them very green most of the time, and then depleting oxygen in the water when the algae die off, degrading the riparian environment.

This is deemed an aesthetic affront by downstream landowners. But even more critical, the stream that would receive Dripping Springs’ discharge is Onion Creek, a major source of recharge to the Edwards Aquifer. That’s a sole source aquifer supplying water to about 60,000 people and is the source of Barton Springs, which is home to endangered species. So there’s great antipathy to any plan by Dripping Springs to discharge.

The “standard” option is to continue to “land apply” the effluent from its wastewater treatment plant – “irrigating” land for the sole purpose of making the water go “away” rather than to enhance the landscape or grow a cash crop – which the city does under its current permit. This practice is more accurately termed “land dumping”, and in this region, in this time, it is an unconscionable waste of this water resource.

At least discharge would have some utility, providing more constant flow in the creek, enhancing the riparian environment, and a more constant recharge of the Edwards Aquifer. That is, it would have utility if the water were to be treated to a standard that would preclude the “insults” noted above.

In regard to nutrients, that is technically possible – albeit unlikely to be required by TCEQ – but it would be quite expensive. Burnet discovered that treating to a higher standard to allow them to discharge into Hamilton Creek, which eventually flows into the Highland Lakes, would add about $10 million to the cost of their treatment plant. But that still won’t attain the high removal rate demanded for discharge into Hill Country creeks that recharge the Edwards Aquifer.

But nutrients aren’t all there is to be concerned about. There are also “contaminants of emerging concern” – pharmaceuticals, in particular endocrine disruptors. What it would cost to make discharge “safe” in this regard is an open question – another subject for another time. Suffice it to note here that TCEQ has no standards addressing these pollutants, thus there is no requirement to even consider what might be “safe”.

The latest word is that the overwhelming dissatisfaction with a discharge scheme has urged Dripping Springs to drop its plans to seek a discharge permit – for the present. It’s unclear if that means it would just expand its “land dumping” system (a rather costly proposition, due to the land requirements, so Dripping Springs might soon decide that’s just too expensive and would request a permit to discharge). Or would the city pursue any and all opportunities to route the treated effluent to beneficial reuse? Likely mainly within the developments generating the flow as few other opportunities have been identified, the 8-acre city park being the only one mentioned in the version of the Preliminary Engineering Planning Report (PERP) the city released last summer.

Which brings us to how the city would create a system plan predicated on beneficial reuse of this water resource to defray demand on other water supplies. The city appears to be leaning toward simply appending onto the already costly 19th century conventional centralized wastewater system another whole set of costly infrastructure to redistribute the water, once treated, back to the development that generated it. Note, however, that as TCEQ presently interprets its rules, the city will still be required to have a full-blown “disposal” system in place regardless of how much of that water they expect to route to beneficial reuse, making that whole concept somewhat problematic if indeed no discharge option would be sought. This focus of TCEQ rules, as currently applied, on “disposal” of a perceived nuisance, to the exclusion of focusing on integrated management of water resources, is an issue for any sort of plan the city may consider, highlighting the need to press TCEQ to reconsider that focus.

Indeed the city’s centralized plan would be costly. Dripping Springs is keeping its present engineering analyses close to the vest, but according to the version of the PERP released last summer, the three interceptor mains in that plan – denoted “east”, “west” and “south” (leaving us to wonder what will be done with development that may occur to the north) – and their associated lift stations would have a total cost of about $17.5 million. These are costs, along with the estimated $8.1 million for treatment plant expansion and an estimated $1 million for permitting, that must be sunk into the system prior to being able to provide service to the first house in the developments this system would cover. Then there is the cost of centralized collection infrastructure within the developments, to get their wastewater to those interceptors, no doubt running into the 10’s of millions at complete buildout.

And for this, all they get is “disposal” of a perceived nuisance!

With, as noted, the issue of how the water would be “disposed of”, if it is not discharged, still to be resolved – and paid for. If it is to be redistributed back to the far flung developments generating the flow, the facilities to do that will add many more millions to the overall cost of the complete system.

Far less costly, in both up-front and long-term costs, would be the creation of a 21st century system that would be designed around reuse, rather than “disposal”, of this water resource right from its point of generation. The city could pursue a decentralized concept strategy, focused on treatment and reuse of this water as close to where it is generated as practical, obviating the high cost of both the conventional centralized collection system and the reclaimed water distribution system.

Entailing a number of small-scale systems designed into rather than appended onto development, it is highly doubtful that the city could unilaterally impose that sort of system. The large developments around Dripping Springs are all planning – indeed they have obtained TCEQ permits for – smaller conventional centralized systems within each of them, featuring “land dumping” as the intended fate of the water. In fact, Dripping Springs has “sponsored” the permit for one of those developments, so is actively promoting this strategy. The development agreement with another large project specifies that the wastewater generated in that development must be run into the city interceptor whenever it is built, despite the development-scale system being in place. So if the city does develop interceptors that would drain wastewater from those developments to an expanded centralized plant, then these development-scale systems would be stranded assets, sunk costs incurred simply to allow development to begin prior to completion of the city interceptor, then to be abandoned, basically wasting the fiscal resources required to install them.

It’s clear then that Dripping Springs could pursue a decentralized concept strategy to expand service capacity to encompass those developments only if each of them were to cooperate in planning, designing, permitting and implementing the decentralized system, instead of those development-scale centralized systems they’re presently planning to build. But of course, unless Dripping Springs presumes a leadership role, the developers have no impetus to consider that. They must presume they’d have to abandon any sort of development-scale system and run their wastewater “away” into the city’s centralized system whenever interceptors were extended to their properties.

To pursue a decentralized concept strategy it must be determined how such a system would be organized and how it could be permitted, given the “disposal”-centric focus of how TCEQ wields its rule system. This is a complex subject that does not well lend itself to this medium. Complicated by the decentralized concept remaining “non-mainstream” despite it having been out there for quite a long time – I defined the decentralized concept in 1986, and it was “ratified” as a fully legitimate strategy in a 1996 report to Congress, among other milestones – so its means and methods remain largely unfamiliar to regulators, engineers and operating authorities. Further, being designed into rather than appended onto development, the details would be sensitive to context; while there are recognized organizing principles, there is no “one size fits all” formula.

For the interested reader, a broad overview is “The Decentralized Concept of Wastewater Management” (in the “Decentralized Concept” menu at www.venhuizen-ww.com), and a basic review of those organizing principles are set forth in this document, reviewing wastewater management options in the nearby community of Wimberley. But a review of exactly how to design a decentralized concept system for any given project in and around Dripping Springs is properly the subject of a PERP for each project, not something that can be credibly described here, absent any context. The means and methods are, however, all well understood technologies that can readily be implemented to cost efficiently maximize reuse of this water resource. [Note that a stab at detailing exactly how to do a decentralized concept system in the context of one of the development in Dripping Springs’ hinterlands is offered in the next post.]

Highlighting that the most salient feature of a decentralized concept strategy in the context of this region is the “short-stopping” of the long water loops characteristic of the conventional centralized strategy, so that reuse of the water resource would be maximized at the least cost. It is this 21st century imperative that should motivate Dripping Springs and the developers working in that area to explore the decentralized concept. A necessary part of that exploration is to press TCEQ to consider how it interprets and applies its present rules, and perhaps to consider the need for “better” rules that recognize our current water realities. None of this can be served up for the city or the developers as a fait accompli in this medium; it is a job they have to undertake. One which we all need them to undertake, for the benefit of this region’s citizens, current and future.

But from all indications to date, it does not appear they will even try – they just can’t seem to expand their mental model of wastewater management to encompass it. The result of which is that most of this wastewater will live down to its name for a long time to come, driving us ever further away from sustainable water. So the question is posed: Can Dripping Springs, and the developers there, bust out of the 19th century – or will they choose to remain stuck there?