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Elegant water drainage methods: Levi Plaza in San Francisco and elsewhere

Walking to the Embarcadero in San Francisco provides an opportunity to visit Levi's Plaza Park, a tranquil and beautiful refuge that makes the nearby traffic almost disappear. On a very rainy day in San Francisco this January, we visited the empty park, walked around, and admired the brooks, fountains, and an ingeniously designed drainage system. The physics of drainage revolve around the hard fact that the erosive power of water is proportional to the fifth power of the water's velocity--double the velocity and the erosion goes up 32-fold! (See our discussion below)

My photographs show the diversion of water flow along the walkway margins, with elegant rip-rap breaking the velocity and swales directing the flow of water towards larger streams, a pool, and, ultimately, large drainage pipes.

Drainage is always an issue when installing large outdoor sculptures. In our work, we want to avoid water pooling at inappropriate places around the piece and also to prevent nearby erosion. Freeze-thaw cycling in New England makes the drainage issues more complex.

-- Edward Tufte

Water bars: An explanatory engineering report with photographs

On dirt roads and hillside trials, washouts are a common problem. Rivulets of rain water erode the earth. Such erosion can be reduced by "water bars" that gently cut across the downward grade of the road to divert the water sideways. Made from rock and earth, water bars sometimes resemble diagonal speed bumps, big lumps on a farm road or trail. This article proposes construction of flexible water bars to divert the etching flow of water and also to avoid the speed-bump effect.

Thom J. McEvoy's article on flexible water bars appears in this month's Farming: The Journal of Northeast Agriculture, a magazine published on newsprint filled with ads for tractors, timber mills, greenhouses, and classes in dairy science. Perhaps many viewers of this board subscribe and have already read the article.

Waterflow physics is intriguing: "the amount of sediment a given flow can carry increases as the fifth power of the velocity." Do many things in Nature vary in proportion to the Ponzi-scheme fifth power? Waterflow sediment is a powerful force; the velocity squared of kinetic energy will get you every time (recall the velocity difference--500 mph--between the Columbia and the piece of foam).

The article begins with a straightforward engineering diagram (in cross section and in plan) that nicely explains what is going on. The source for the diagram is indicated. The plan-view uses appropriately varying line weights. Note that in the cross-section, the arithmetic for the height of the water bar (a used conveyor belt!) is not in error by very much since the 2 by 6 dimension for the timber planks is the nominal pre-milled dimension. Those readers unfamiliar with cross-section and plan-views will have to think a bit to understand what is going on, at least if they want to keep their dirt roads from eroding out. (Every grade school should teach every student how to read engineering and architectural plans.) Also some pictures later in the article will clarify the diagrams for those who can't read plans. On the opening page of the article, the tone-deaf typography of the various titles brings in the routine and unfortunate contributions of commercial art: 4 levels of hierarchy (woodsy-forest font, then all caps, caps and lower-case, and text font) in a bloated size compared to the diagrams, table, and photographs in the article. Except for the designer typography of the titles and subtitles, the presentation has a good direct unmediated quality in explaining a new engineering solution to a practical problem.

The table belongs in the text; there's no need for a big production for a simple table of 14 numbers. Perhaps a little graph would better indicate the nonlinear relationship.

Two pictures make things perfectly clear. It would be helpful to put the pictures on the opening page, in parallel with the engineering diagram.

Note that detailed sources, citations, and author biography are provided.

Source: Farming: The Journal of Northeast Agriculture, December 2003, pp. 59-61.

-- Edward Tufte

Erosion as fifth power of velocity

ET's question: "Waterflow physics is intriguing: the amount of sediment a given flow can carry increases as the fifth power of the velocity. Do many things in Nature vary in proportion to the Ponzi-scheme fifth power?"

The thermal radiation of an ideal black body increases at the fourth power of its absolute temperature.

-- David Cerruti (email)

How about the sixth root of intermolecular distance?

Nonradiative fluorescence resonance enrgy transfer (FRET) is a phenomenon exploited to measure intermolecular distances in chemistry and biology. The FRET efficiency (probability of energy transfer) between a donor and an acceptor fluorophore varies with the sixth root of the intermolecular distance.

-- Alex Merz (email)

Experienced water-bar informant

After several years of working with sedimentation and erosion control issues, I find this is an intriguing idea and an excellent article.

Waterbars are traditionally constructed with soil, which is bermed to resemble a speed bump. Without regular maintenance, as mentioned in the article, these must be considered temporary measures, as the waterbars themselves either erode or collect enough sediment to become ineffective (or a combination of these). The 2002 Connecticut Guidelines for Soil Erosion and Sediment Control do not have this technique as a suggestion- perhaps it should be considered. My experience with waterbars is in their application on both forestry/logging roads and at construction sites. There are many instances where the "flexible diversion" technique would probably be an improvement over the earthen berm approach, and I would be interested in working with Edward or someone else in the Connecticut area to experiment with and document this. If it works well, this would be a great way to address temporary erosion problems at (at least) construction sites, and do it in a way where the diverter could simply be dug up at the end of a job and moved to the next job site.

Some design considerations:

1. If the subject roadway is crowned (high point in the middle, sloped to each side), a constant 3" reveal for the rubber belt may not be appropriate. In this case, the belt could be designed as a "V" in the plan view, with the point aimed uphill and water diverted to both gutters. (Perhaps a second cross section view, across the road, could address this and other sloping issues.)

2. The CT Guidelines recommend waterbars be used only where the drainage area to each waterbar is 1 acre or less (if greater, try something beefier). To calculate, consider both the roadway itself and all surrounding land that drains to it. Also, soils vary widely in their erodability, so space accordingly.

3. The CT Guidelines suggest the deflection angle be about 120 degrees, where McEvoy suggests a 100 degree minimum. Regardless, riprap or some other energy dissipator for the outfall is crucial--otherwise you've just moved the problem somewhere else.

4. Lastly, the comment above about frozen ground is important. In areas subject to frost, consider the potential effects of frost heave and possibly dig deeper with the base than is specified in the article, especially if the installation is intended as permanent or semi-permanent.

-- Mark Kasinskas (email)

Water bars actually built and at work

Two water bars are now in position here, it finally rained, and the water bars worked as claimed.

It is of course a sample size of n = 1, but since the water bar is based on the universal laws of Nature, a large sample is not required. When the underlying theory is weak and incomplete, the subject matter is very complicated, and the treatment effects are small (as in testing of new drugs), then big samples are needed, as empirical experience replaces theory. This is the big difference between physical science and medicine (or social science).

A really heavy rain would help us see the technique's limits. As statisticans know, you never get a greater reduction in estimated variance than when you go from n = 1 to n = 2. Especially since the estimate of the variance is infinity for n = 1. Or, another way to look it: estimates of the slope are better if the observations are far apart.

So much for water-bar philosophizing.

Below is a picture of a fairly steep dirt and stone road with our two water bars, constructed following the plans at the top the thread.

-- Edward Tufte

Graphs vs. tables in Texas

This application looks useful for us down here in Texas, too—especially in the eastern half of the state. But I’m interested in whether a graph would have necessarily been better than the table showing optimum distance between water bars at various road grades. A small table might better convey the information to folks who aren’t used to reading graphs. Certainly not all farmers read graphs particularly well.

I would think the table would also be the better approach when only discrete values of one variable are likely. For example, in a publication for chicken farmers, I once replaced a graph illustrating 0.3 percent mortality by total number of chicks with this simple table, in which each number in the first column is a typical total flock size at commercial chicken farms in Texas:

If you have
this many birds:
then 0.3%/day
is this many:
16,000 48/day
64,000 192/day
128,000 384/day
192,000 576/day
256,000 768/day

By using this small table instead of the graph, I not only saved readers the trouble of doing a trivial calculation but also avoided a subtle version of “chart junk”—there is no point in illustrating 0.3 percent of 100,000, because no commercial operation would have a flock of that particular size (at least that’s what the resident expert says).

Of course, with road grades, the possible values are continuous and the relationship to distance between bars is nonlinear. But I’m curious: if you were to graph this, which variable would you choose for the x-axis—road grade, or distance between bars?

Oh, one other thing—I did set the small table directly where it belonged in the text. I’m not sure whether this was before or after I had seen ET’s display of the ancient astronomer’s depiction of the rings of Saturn, but I was working from the same principle.

-- Cliff Tyllick (email)

Unnecessary graphs in scientific publications

Cliff Tyllick makes an important point. I often referee papers in which the authors want to put an unnecessary graph to make a simple point that can be more clearly expressed in one short sentence.

-- Athel Cornish-Bowden (email)

Paving and drainage

It is always good practice (if not obvious) to check out drainage issues during a good rainstorm.

Regarding the stone-edged asphalt walkways at the Levi Plaza, I think E.T’s “rip rap” at the asphalt edge is more decorative (i.e. design element) than functional (i.e. energy dissipator). The stone border is; however, an example of aesthetics and good engineering practice working in tandem. According to one Magic Book of prices, granite pavers cost approximately 8 times as much as a 3-inch layer of asphalt paving. The stone border also serves as a tactile indicator of the pavement’s edge. Similar tactile borders are mandatory in many situations such as a train platform edge.

One concept to enhance drainage under pavement is either asphalt-treated or cement-treated permeable base, both of which we have placed beneath new apron and taxiway pavement. Any asphalt or concrete producer can manufacture these products, and neither product requires any special equipment to place. One of my co-workers has suggested using permeable base as a sidewalk/pavement material in certain applications which require both paving and drainage—not as a base material—but as the actual pavement surface. is a link to a lengthy technical document on permeable base. (The direct html code linkage sends the user to 404-Land.) Either cut-and-paste this link or click as follows: go to>REPORTS AND PRODUCTS>2002 Project Reports>Project Number 02-01: Stabilized and Drainable Base in Rigid Pavement Systems>Design and Construction Guide.

Any “hardscape” requires a good stone base and optimally also includes a perforated underdrain system enveloped with washed stone and filter fabric. The underdrain would discharge by gravity to a storm system or a rock outfall.

Stormwater detention (holding back stormwater in a controlled manner to avoid flooding) is a big topic in paved urban areas. A wise stormwater engineer once called turf “green concrete” when describing turf’s stormwater storage capacity. By comparison, indigenous prairie plants, with their extensive root systems and above-ground plant structure, offer tremendous stormwater capacity and erosion control.

For walkway paving in the sculpture garden, I would probably use grass pavers. A recent Google search turned up nearly 50,000 hits. Such a product would allow drainage, support the occasional vehicle and meld better into the landscape than asphalt.

-- Jon Gross

Drainage breakthrough at Santa Anita racetrack

USC soil expert Jean-Pierre Bardet helps to solve the drainage problem on the synthetic track at Santa Anita.
By Diane Ainsworth

A machine works on the synthetic surface at Santa Anita.

Benoit Photo
When Santa Anita unveils its newly surfaced racetrack this weekend, jockeys, trainers, owners and horses will thank soil mechanics expert Jean-Pierre Bardet, chair of the USC Viterbi School of Engineering's Sonny Astani Department, for coming to the rescue.

Bardet was called in during December to solve a drainage problem on the synthetic track after a heavy rainstorm turned the course into mush.

Collaborating with Australian racetrack builder Ian Pearse, founder and president of Pro-Ride Racing, the pair began experiments on a new additive to make the surface more water repellent and more stable.

Pearse added a polymeric binder that he designed for racetracks in Australia to give surfaces a cushiony texture. The binder replaced wax, which is used in synthetic racetracks all over the world to repel water.

"Santa Anita's synthetic surface was created from a unique blend of sand, fibers, recycled rubber tread and wax," Bardet said. "When the track became saturated from rain, the horse-track officials added coarse sand to try to fix the problem, only that made it worse. They thought the sand would add stability - and make the track less mushy - but it didn't."

So Bardet began testing clumps of the synthetic material in his Kaprielian Hall lab.

Wax, which bonds with sand grains, is a common ingredient in synthetic surfaces because it holds sand grains together and allows water to flow vertically through it. But Bardet discovered that the wax did not properly coat the sand mixture, which was clogging up the base of the racetrack, seven inches below the surface. That base is made of a porous asphalt, but wax can clog and seal it up, like a clogged drain, when it settles to the bottom.

Pearse's polymeric binder comes as a water-based emulsion that contains billions of micron-sized particles of polymer. When mixed with the sand mixture, the water evaporates and the polymer coats the sand grains. The coated sand displays a new behavior; it repels water and holds together, Bardet said. This binder proved superior to a wax-based mixture because it was able to adhere to and coat the silt.

"When you heat up wax and put it on sand, wax may not always adhere to the sand. They don't bond," Bardet said. "But you can mix a liquid emulsion with wet sand. When the water evaporates, the polymer droplets will coat the sand and silt particles and make them water repellent."

Santa Anita's racetrack woes go back to 2006, when the California Horse Racing Board mandated that California's five major racetracks install synthetic surfaces to reduce the number of injuries.

Santa Anita replaced its one-mile course last summer with a springy new surface called "Cushion Track." The surface was specially designed with a new microcrystalline wax that could withstand the hot temperatures in Southern California. The synthetic surface had enjoyed rave reviews from the press, which claimed it could retain its performance in the presence of temperatures of 110 degrees F or higher.

Four months later, after the first heavy rains in December, Bardet was called in to find a solution to the synthetic material, which had become unstable due to drainage problems. He was put in touch with Pearse, who had been trying to convince professional racetracks to use additives other than wax. Pearse was known for his patented binder; Bardet was known for his work in experimental soil mechanics.

Bardet spent most of the December holidays in his lab, hunched over buckets of the problematic synthetic material, measuring its permeability under various conditions to understand why waxed materials had failed in unexplained ways.

He added more wax, temporarily improved permeability and each time noticed that wax had clogged the drainage of his testing equipment. He filled up countless Petri dishes of the material, then poured water over the samples, one at a time, to see how well the water drained through. When he replaced wax with Pearse's liquid polymer, he noticed encouraging results.

"Finally, we got a better binder than wax. It adhered quite well to the sand as well as silt," he said.

Work began on Feb. 6 to resurface the racetrack with the polymeric binder, which is manufactured in the United States. The surface was leveled uniformly to correct all the numerous alterations it had gone through as crews tried to keep it operational under adverse conditions.

The upgrade may not be a permanent solution, Bardet said, but it will solve the problem temporarily without interrupting the current spring meet.

Bardet, Pearse and racetrack officials will reassess the situation after April 20 to determine how well the modified surface has held up. Until then, it's business as usual. Nothing will be noticeably different, aside from the racetrack's slightly darker color.


-- Virginia Tufte

Elegant water drainage method and speed bump in Luquillo, Puerto Rico

Luquillo, Puerto Rico is a small town about one-half hour east of San Juan, on the coast. While walking around downtown, we saw this example of unusual surface drainage, inverted speed bump, and instructions at the point of need—all in one! It's a clever and unusual detail that I don't recall ever seeing before.

This detail, which occurs at street intersections, does two things. First, it drains one quadrant of the intersection to the adjoining curb lines and storm inlets. Second, like a conventional speed bump, it forces traffic to slow down at the intersection. It is rather unforgiving as a speed bump—witness the many gouges that passing vehicles have left.

Curb and gutter typically act together as a drainage structure. Our state’s Department of Transportation even categorizes combination curb and gutter as a drainage item in its book of standards.

-- Jon Gross (email)

Road ripples

Do the rhythmic road ripples (that wear into roads after a few years of use) at 90 degrees to the flow of traffic subtly serve as both speed bumps and mini-swales?

(Surely civil engineers don't call them "rhythmic road ripples." Could a Kindly Contributor provide some explanations and links about RRRs?)

-- ET

rhythmic road ripples

The stretches of washboard or corrugated road that shake vehicles are distinct from "shoving". Washboarding is apparently inevitable on gravel, sand, or dirt roads in dry areas. The Wikipedia article on washboarding has links to more detailed explanations.

-- Dave Nash (email)

New Canaan drainage

We visited an old modern house in New Canaan, Connecticut
last summer and, among other things, checked out the drainage.
Here are some drainage research pictures:

This imaginative house and grounds, where construction started 60 years ago,
could be not built by an individual today given inland wetlands regulations.
Nowadays, only a developer building 8 cookie-cutter Mega-MacMansions
on these grounds could afford the mandated costs.

-- Edward Tufte

Manhole Covers: From Drainage System Component to Sublime Art

Consider the cast-iron construction castings embedded in the streets, curbs, parkways and elsewhere. For background, the Wikipedia article is a good place to start. A typical manhole cover consists of an embedded frame and a removable (solid) lid or (open) grate.

Neenah Foundry’s catalog is available online at It contains pictures, drawings and much technical information. For a historical perspective on design:

“Not much is known about the history of construction casting design. For many years past, manufacturers quietly produced castings in accordance with owners’ specifications without much more apparent involvement than that. But with the massive road building program of the 50’s and 60’s, and the accelerated infrastructure development during the same period, the relationships between the specifier and the casting manufacturer began to change.”
When I started working for a general contractor in 1995, one of the first impressions was the tremendous variety of construction castings available, from manhole covers to tree grates and everything in between. Both of the two main suppliers in our area have catalogs of construction castings approximately 300 pages long! Yet, upon careful examination, each item has subtle differences applicable to certain situations.

How does such a catalog swell to 300 pages? Some of the various options include: low height frames, sloped frames, frames with or without ribs, concave or convex grates, “bicycle-safe” grates, vane grates, riser rings, non-rocking lids, locking lids, vented lids, gasketed lids, lift-assist lids, secondary covers, square/rectangular/circular configurations, trench drains, various duty ratings, hydraulic considerations, surface textures, custom lettering/artwork and so on.

Something as mundane as a manhole cover in the street can rise to sublime art, especially in Japan. A recent Google search (double quotes included) for “Japanese manhole covers” turned up over 6,500 hits. Without the double quotes, there were 43,600 hits. This photo site has examples and this Japan travel site has others. A stunning array of artful manhole covers from France is available here. Historical examples from the United States are available in a book from M.I.T. Press, Manhole Covers, which is available from

Even the material itself—cast iron (or ductile iron in some cases)—has a utilitarian beauty. Here, a series of photographs shows the protective black iron-oxide silicate forming to stop further corrosion over approximately 6 months. Compare this process to “weathering steel” (also COR–TEN® B or ASTM A588 steel) which forms a stable surface under most circumstances. The aesthetic value of rust has been discussed elsewhere in these message boards, .

Foundries are promoting custom artwork for manhole covers, from just custom lettering to elaborate logos. For storm drains, agencies are starting to install castings with an image of a fish with a notice such as “Drains to River,”—another example of instructions at the point of need.

The next time you travel or walk through an older part of town, look down—you might just see something interesting....

-- Jon Gross (email)

Elegant sewer outfall

The remarkable photo below is used with permission of For scale, I estimate the width at the base to be 67± inches wide.

The Falls Street Tunnel is a hundred-year-old brick-lined sewer built to discharge sanitary effluent into the river from the communities above the gorge. In the 1990s it was identified as the worst source of pollution in the Niagara River, and an interceptor sewer was built to redirect its dry weather flows to a treatment plant upriver. In wet weather, however, the combined sewers still overflow into the Falls Street Tunnel and dump raw effluent into the river.”
The rest of the site is well worth exploring, and includes reproductions of original drawings. For more information on sewers, the site is a masterpiece—from history, regions, materials, methods, engineering and so on. The Romans even had a goddess of sewers. Who knew?

-- Jon Gross (email)

Drainage poem

From a poem by John Betjeman, In Westminster Abbey, 1940:

Think of what our nation stands for
Books from Boots and country lanes
Free speech, free passes, class distinction,
Democracy and proper drains.

-- Edward Tufte

Drainage detail for weathering steel

The Richard J. Daley Center in Chicago is a major landmark, mainly for the abstract, untitled Picasso Sculpture, now iconic and beloved—but once extremely controversial. North of the Picasso rises a tall municipal office building designed by C.F. Murphy Associates. The plaza and sculpture are visible via Google Street View. Look north from 64 W Washington St., Chicago, Illinois to see the plaza.

The building and sculpture are constructed from weathering steel (brand name COR-TEN®), whose protective oxidation people neither understood nor appreciated at the time. This photograph shows an important drainage detail for this weathering steel structure—without this trench drain at the cruciform column base—oxidized steel draining from the building would stain the granite sidewalk. Manufacturer U.S. Steel recommends the following:

“Special attention must be paid to the drainage of storm water to prevent staining of surrounding structures, sidewalks, and other surfaces.

COR-TEN® Steel must be kept free from debris such as leaves, pine needles, etc. These waste products retard the wet/dry cycle necessary for COR-TEN® Steel and corrosion is accelerated.”
Chapter 4 of this Texas study of weathering steel on bridges shows problematic drainage details with appropriate solutions.

-- Jon Gross (email)

Elegant Drainage: Sidestream Elevated Pool Aeration

The Chicago area has a significant waterway system, which includes various rivers: Chicago, Fox, Calumet, and Des Plaines; and various channels, among them: Chicago Sanitary and Ship, North Shore, Illinois and Michigan, and Calumet-Sag (“Cal-Sag”). The Cal-Sag Channel runs “sluggishly” from the Little Calumet River on the far South Side of Chicago generally westerly to the Chicago Sanitary and Ship Canal in Lemont, Illinois. The term “Sag” refers to low valleys left by retreating glacial water.

To improve water quality in the Cal-Sag Channel and connected waterways, the Metropolitan Water Reclamation District of Greater Chicago (MWRD) constructed five innovative Sidestream Elevated Pool Aeration (SEPA as in “see-puh”) Stations. The July 1994 issue of Civil Engineering describes the SEPA Stations in detail. Please read this excellent, concise and illustrated article, if you read nothing else.

There were several important design criteria for the SEPA Stations:

Not obstruct marine traffic, as former installations were in-channel.

Operate only when necessary.

Be simple and economical.
The SEPA Stations have improved the Calumet River System both qualitatively and quantitatively. Dissolved oxygen measures the quality of a body of water in general, and the ability to sustain life in particular. The SEPA Stations oxygenate the channel or river water as follows: high-capacity, low-head screw pumps lift approximately half the channel or river flow up to elevated, shallow pools. The water then flows down through a cascade of 3 to 4 weirs. The oxygenated water then discharges back into the river or channel, slightly downstream. While both the pumping and the cascades oxygenate the water, the pumping actually adds more oxygen than the cascades. The numbers are impressive, as the SEPA Stations:
Pump up to 1.3 billion gallons (4.92 billion liters) of water each day.

Elevate water up to 15 feet (3.66 meters).

Add up to 25 tons (22.7 tonnes) of oxygen each day.

Have eliminated approximately $300 million worth of secondary and tertiary water treatment.
Government agencies, educational institutions, and others have studied the entire Calumet Region extensively. Chicago State University offers the Calumet Environmental Resource Center (CERC), an impressive resource library. For example, here is a comprehensive report on the Chicago and Calumet River systems. CERC has also posted a technical report of a long-term study of the SEPA Stations after construction. Scroll to the end of the document for photographs and diagrams.

Here is a boater's guide to traversing the SEPA Stations westerly, from the Calumet River to the Little Calumet River, and then to the Cal-Sag Channel. The trip continues northeasterly through the Chicago Sanitary and Ship Canal and ends at the Chicago River's South Branch.

The latitude/longitude coordinates below link to aerial views of the SEPA Stations from Yahoo Maps. Be sure to click on the “satellite” or “hybrid” button to see the aerial view. To see impressive higher resolution aerial views via Microsoft Live Search Maps, click on the “here” links below. Be patient—these are high-resolution images that require time to load. Since Live Search Maps links to street addresses and not latitude/longitude coordinates, the “here” links require a little extra work—but the views are worth the effort, especially for SEPA Stations 1 and 5. In Windows, the F-11 key acts like a toggle switch to decrease (or restore) administrative clutter from the screen. Once at the “here” link, grab the vertical frame divider at the series of ten vertical dots with the mouse, and drag to the left to increase the map width to full screen. Select the “Bird’s Eye” option at the top and zoom/pan as needed:
SEPA Station 1 at 41.6687N 87.5620W is directly west of here, where Torrence Avenue crosses the Calumet River in Chicago. This Station is part of a wetland and bird sanctuary. Countless discarded blue crayfish claws (probably invasive) litter the east bank—crustaceans sustaining the avian population. Amid sounds of train whistles, the site offers natural tranquility against a backdrop of industry.

SEPA Station 2 is the smallest station, at
41.6629N 87.6245W just west of the intersection of West 127th Street and South State Street, here in Chicago. Look for a series of four weirs parallel to the Little Calumet River—this one is a little hard to spot.

Louis S. Viverito (former MWRD Commissioner and current Illinois 11th District State Senator) SEPA Station 3, at 41.6528N 87.6785W, southwest of here, which is east of Western Avenue on the north Cal-Sag Channel bank—a series of circular weirs in a park setting in the City of Blue Island. This SEPA Station gives commuters an aesthetic treat as they walk from two nearby parking areas to the Metra commuter rail station.

Harry “Bus” Yourell (former MWRD Commissioner) SEPA Station 4 at 41.6781N 87.7958W is east of here, which is just east of Harlem Avenue on the north Cal-Sag Channel bank—just south of the Water’s Edge Golf Course in the Village of Worth. Click on this link for an awesome panoramic view of the whole area.

SEPA Station 5 at 41.6978N 87.9468W, is approximately 1,800 feet west of here. You will need to scroll west from this location until you reach the intersection of the two channels. A lighthouse marks the confluence of the Cal-Sag Channel and the Chicago Sanitary and Ship Canal. The elevated pool—as metaphorical boat—“floats” above the wave-like cascading weirs. This SEPA Station is no longer open to the public, though I was fortunate to visit this facility during construction.

The SEPA Stations epitomize elegant water drainage methods: aesthetic structures, aeration with minimal equipment, and reclamation of the urban waterway. Yes, the SEPA Stations even form the occasional background for wedding pictures! Now that’s elegant.

Besides the on-line information linked above, two books proved helpful in writing this post:
Solzman, David M. (2006) The Chicago River: An Illustrated History and Guide to the River and Its Waterways. 2nd Edition. Chicago: University of Chicago Press. This author is an associate professor emeritus of geography and anthropology at the University of Illinois at Chicago and a professional photographer. This book is packed with information and pictures—essential for anyone interested in the Chicago River and associated waterways.

Mueller, James A., William C. Boyle, and H. Johannes Pöpel. (2002) AERATION: Principles and Practice. Boca Raton, Florida: CRC Press. Chapter 8 Aeration Systems in Natural Waters is devoted almost entirely to the SEPA Stations: theory, history and performance. As evident from the title, the rest of the book details principles of this crucial water and wastewater treatment method.
Finally, here are two photos:
First, looking southeast at the concentric weirs of SEPA Station 3.

Second, looking east at a weir and elevated pools in the foreground, and the pump station in the background at SEPA Station 4.

-- Jon Gross (email)

Elegant Drainage: Elevated Modern house (with aesthetics, romance, controversy, entertainment, and more.)

The “Old Modern” house, Phillip Johnson’s “Glass House” in New Canaan, Connecticut was constructed around the same time (1949 to 1951) as the Farnsworth House by Mies van der Rohe, a mentor of Johnson. Nephrologist Edith Farnsworth, M.D. commissioned Mies to design a weekend dwelling for Dr. Farnsworth to enjoy the surroundings and play music. The Farnsworth House actually inspired the Glass House.

Although functionally and stylistically similar to the Glass House, the Farnsworth house floats above ground on LeCorbusier’s pilotis, in the ironically coincident Plano, Illinois, about 60 miles west of the Sears tower. In 1946, Mies researched the 100 year flood level, reportedly about 3 feet (0.9 m) above grade. Mies placed the floor level at 5 feet 3 inches (1.6 m) above grade thinking this would keep the house safe from any floodwaters from the nearby Fox River. The columns do serve their intended purpose—keeping the house from flooding, except for a couple of past incidents.

Unfortunately, increased development has decreased area stormwater capacity and the Fox River occasionally floods the lower patio. The National Weather Service has much flow data available at a Fox River monitoring station at Algonquin, about 48 miles upstream of Plano. Look here for an example of a United States Geological Survey monitoring station with real-time flow data along the Naugatuck River in Connecticut.

Dr. Farnsworth and Mies were linked romantically until controversies over costs and design soured the relationship. The resultant lawsuit from Mies for non-payment and a countersuit from Dr. Farnsworth for alleged malpractice—were finally settled out of court. This play documents the liaison between Dr. Farnsworth and Mies. Actor and architecture enthusiast Brad Pitt visited the site to assist during the 1997 flood. Country musician Kenny Chesney even made a music video there—though Mies must be muttering something....

Dr.  Farnsworth sold her house to Lord Peter Palumbo in 1972—a devoted steward who spent many hundreds of thousands of dollars to sustain the house. When the house became too burdensome for Lord Palumbo, it was auctioned for a reported $7.5 million in 2003. There was a fear that a prospective owner would pluck the house from its idyllic location next to the Fox River and move it elsewhere. During the dramatic auction, The National Trust for Historic Preservation won the auction, and thankfully, the Farnsworth House is safe from acquisition for the foreseeable future.

Photograph of the Farnsworth House during the 2007 flood is courtesy of the Landmarks Preservation Council of Illinois.

-- Jon Gross (email)

Another fourth power in physics

As David Cerruti says, the amount of energy radiated by a black body is proportional to the fourth power of its absolute temperature. It is also true that the intensity of light scattered by small particles is inversely proportional to the fourth power of the wavelength of the incident light. Thus, blue light is scattered more than red, and the sky appears blue.

-- James Scott-Brown (email)

Physics of "washboarding" of roads

A friend from college sent me this link on washboarding, published in Physical Review Letters, 99, 068003 (2007)

Washboard Road: The Dynamics of Granular Ripples Formed by Rolling Wheels

I quote the authors’ conclusions:

We have established that washboard roads exist with a simplified system with no suspension or tire. We have also found that the diameter of the wheel and the size of the grains are unimportant to the phenomenon. Finally, washboard patterns were obtained with a blocked wheel (which couldn’t spin), means that the moment of inertia of the wheel is unimportant as well.

Overall, the only relevant parameters are:
m, the mass of the wheel (per unit of width), in kg/m
ρ, the density of the bed, in kg/m3
v, the velocity of the wheel, in m/s
g, the acceleration of gravity, in m/s2

-- Jon Gross (email)

Elegant water drainage in Austria

I found a drainage system superior to your water bar solution on a recent trip to the Austrian Alps. A simple I-beam is embedded into the path (see images 1 & 2). Traditionally, these drainage channels were built out of wood (image 3) with a particular elegant solution found here While I like your water bar for its simplicity, I do see them problematic since they present a barrier someone can fall and stumble over. Embedding the drainage flush with the path eliminates this problem.

-- Hermann Zschiegner (email)

Threads relevant to architecture:

Threads relevant to nature studies:
Theoretical speculations on leaving the flatland of paper and computer screens and working now in real-land and space-land.

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