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San Francisco Great Sewers M. Garnett "Cloaeina. goddess c.t the ti<Ji\ \u25a0 Whose table streams beneath tbe city glide." 50 pang the poet Gay of the guardian deity who in the old Roman myth ology presided over the city's pewcrs. At the first blush it would seem that the bard flung this little flower of poesy at the muse's feet either in a self-defensive spirit or else in a playful attempt to justify, his pat ronymic. But the fancy was not with out its basis in fact. Viewed in the light of the chief object to be attained even a city's sewerage system may as sume a somewhat poetic aspect. The transforming of squalid, noisome sec tions of the town into attractive neigh borhoods, thereby bringing health and possibly wealth and happiness to the general resident and property owner, as well as to the r«al estate dealer, is an aim not exclusively prosaic From this viewpoint the importance of the comprehensive system of sewer age projected for the new San Fran cisco can hardly be exaggerated. The execution of the design, now well un der way. will conform, with slight modifications, to the plans of former City Engineer C. . E. Grunsky and his associate. Marsden Manson. When finished it will give San Francisco a sewerage unsurpassed if not unequaled by any other American metropolis. It will even go far to justify. In one es sential at least, the application to our own fair city of that somewhat Delphic distinction, the "Paris of America." Yet comparatively few of the tax pay er? who are footing the bills for this huge enterprise have the faintest con ception ejther of the nature or of the progress thereof. Of all the civic improvements to be completed under the bond issue of $18. 200,000, voted on May 11, 1908, none is more essential, nor more sorely reeded for the city's welfare, than the contemplated sewer construction. Before the scope of the latter, the $4,000,000 appropriated for the purpose seemed to fade into insignificance. But with the competent -supervision now in force the sum will probably suffice. And a contrast of the new order of things with the old should edify the general reader. In the matter of sewerage and sewage disposal San Francisco has lagged fur ther behind European and other large American cities than is generally real ized. Though sewerage systems, as now understood, date only from about .the middle of the nineteenth century, even in London going back no further than 1659. in Paris to the completion of her system in 1893 and in Boston to the municipal control in 1823, all Im portant cities in Europe and in the United States have for years managed their sewage problems with something like adequacy. In tnose municipalities both the combined and separate sani tary systems are in general use. Puri fication works, filter beds, or chemical treatment, as adjuncts, to dilute the sewage, have been adopted wherever 1 this .could not be properly delivered Into river, bay or ocean. But San Francisco, with all her unrivaled ad vantages of drainage areas, sloping lands, abundant points of outfall into the deep, swift tides of the bay and ocean, has gone on her merry way ap parently indifferent to the Importance of thoroughly flushing the general body civic — to say nothing of the body politic. And this is all, the more re markable in view of the influence sewerage improvements have been found to have on the general death* rate of cities. In some instances a re duction of 25 per. cent In tiie rate of death from pulmonary diseases -alone lias .followed the introduction of mod ern sanitary systems of sewerage. The defects of the old system may be gaid to have been felt, rather than seen. A stroll along the water front on a' warm day, or the necessity of waiting on a street corner near one "V those numerous storm water 'inlets. How Mammoth Mains Are Being Constructed to Give the City the Greatest System in America lurking under the curb, has often con vinced the San Franciscan that some thing was radically wrong with his sewerage. Had he known the truth, however, he probably would have been roused 'into defensive action long be fore May "11, 190 S. The perfume em balming the atmosphere he vaguely attributed either to the low tide or to the lack of a sewer flushing rain. But he seldom even suspected that under lying the most populous parts of the city was a network of old brick, pipe and wooden sewers, often on streets without gradients, or with downgrades in both directions from the storm water Inlets at the street corners. As no water could/ flow into these in takes-they were, of course, useless, and, in the dry season, vilely malodor ous. In fact, it was found in 1893 that in the district bounded by TayloV street on the east, Broderick on the west. Washington on the north and Hayes on the south there were 1,080 storm water inlets, of which 149 were absolutely worthless. And many more w.ere rendered unnecessary by the fact that they received water from a negli gible area of street surface. The cost of these superfluous inlets, or catch basins, to the property owners was about $90 . per superfluous catch basin. * In the less densely settled districts such as the Islais creek, the Precita creek, the Visltaclon valley. Washer woman's bay, Lobos creek,' Presidio and ocean beach watersheds, the sew-, er deficiencies are not so serious, and are more easily remedied. . There the discharges are either through . marsh lands into natural streams, or else Into tide water, where extensions are easily feasible. Where, however, there Is a long bay frontage, as in the North beach region, the sewers now in use empty into the bay wherever they hapr pen to hit the water line, and offer difficulties not readily surmounted. Old Construction Faulty As a type of faulty construction, and lack of comprehensive plan, the sew erage of 'the "terba Buena watershed is especially interesting. This is the low, flat part of the city north of Mar ket street, whose water, frontage was once Montgomery street, and whose watershed includes the slopes of the hills to the north and west. It em braces tbe most \u25a0 important business section ef the city. About 120 acres of it consist of filled in land. Under almost every street and alley in this historical district is the old 3x5 foot sewer, and at every street crossing the typical sewer intersection. Streets running north and south with level sur faces are not. rare. In 1890 a common outfall at Washington street was made for these sewers, and for the Market street sewer, as -far north as Jackson street. The sewage from the west, in-, eluding the intersections by the lower Market street main of all the sewer contributions from Geary street "to Sacramento street, .was also intercepted' and discharged at the foot of Wash ington street, at tlfe low water line under the wharf. . The sewers on Bran nan, Folsom, Howard and . Mission streets likewise'have their outlets un der'the wharves or piers' of the^ater front- As a means of savorizing' these frequented/parts: of .the city, it is doubtful if -.this method ..--.'0f... sewage disposal arouses the enthusiasm- of either the regular or volunteer deni zens of the water front. • •~ ; It Is: in the Mission' bay; watershed, 1 the draicage basin tributary ..-, to. Mis sion bay, that the problem of effective" sewage disposed seems to be most diffi cult- This: area includes the.* heart of the city, the "entire Mission ; and crn" addition, and almost all of its sew age' reaches -the. open waterway' in Channel street the lack of rain and of water ; circulation -In * the old Mission ; creek causes a noisome nuisance - that would i almost resurrect the dead. It will not cease \ to offend : until some "other, outfall,' contemplated on the new 'plans,' ; is found "for,- the . sewage of 'this .district. Furthermore, 1 : the] inability of the principal sewers;of • this, watershed, -namely,- the- Channel street and : Brannan street;" mains, .to care for the "contributions- therefrom Is aggravated by. the nonconformity of the Brannan street sewer grades with those of the sewers the Brannan street conduit intersects. The latter are often from one to three feet higher than the bottom of the former. In the tunnel under the south slope of Rln con hill there is an offset of about 12 feet, and the bottom grade for a con siderable distant^ slopes the wrong way. That under the conditions here roughly sketched San Francisco' has won the distinction of the most health ful metropolis in America seems to put a heavier debt of gratitude than is generally acknowledged upon her trade winds, generous, sunshine and \u25a0 other climatic blessings, j^--. .Despite, then, the many favorable features in the problem, the board of public works and the city engineers have grappled with a task more for midable than ; can , be easily realized. This new system will drain the entire watershed east of the main ridge that divides the city into two great slopes and has its northern limit near Fort point. The western,' or ocean slope, in addition to the project adopted in 1899 for the Richmond distrlct,_and yet to be completed, will have branches in the west Richmond, upper Sunset, lower Sunset and Ocean View districts. The last includes the Lake Merced region, and extends southward to the'« county line. > The drainage and sewerage problem for this vast area is still further com plicated by the city's peculiar topog raphy. Her nature, like her art, is not yet an unmixed blessing. And. this truth is illustrated, as far as sewer construction is concerned, by .the fact that the sloping ground, hillsides and hilltops, which can be, easily drained by gravity flow, are often separated from the low flat areas, where it is almost Impossible properly to collect the sew age without the aid of pumps. The unanimity of scientific , opinion, how ever, that the ultimate discharge into the deep waters of the bay or ocean was the only practical method of sew age disposal has greatly aided the"so lution. In general terms trie, present plans call for a combined system of storm water relief outlets, consisting of main conduits, fed by tributaries carrying rain water, a . certain amount of soil water entering by leakage,, and dilute sewage. It is expected that this, sewage^ will be rendered, quite inoffensive. by\ the small percentage thereof »in : the out flow. In addition to this combined sys tem there | will be ; separate . sanitary systems, disconnected • entirely, from the storm water outlets, and discharg ing into | pumping stations,". whence | the sewage will be sent I into ; the : principal relief mains,'; through 'which fit .will be swept on to the various points \>f out fall. 'And besides this disconnected system a combination of storm water and sewage carrying ducts is X designed' for districts that ; have seemed \ to , the engineers to_ demand them. * Wherever the; condition", of -the old sewers 'war rants they will be* retained to supple ment the new system. ' \u25a0 \u25a0' Except the great -Division street con duit,.which is rectangular in 1 shape, all mains, throughout s ;the ? city,: will 1 be either • circular .- or 1 oval, varying 1^ from \u25a0abdut.B feet in diaxheter.f or the! former to about 3 % by>6 Yt, j feet for the ; latter. These will all Tbe tof J reinforced ''fion-i crete, and in many Instances lined' with', vitlrifled brick.; For.; the supplementary and t sanitary "-systems v , ironstone - pipe will be used.; ranging- from • 6 ; inches to 2 feet In diameter.; ,\u25a0;--'' - }- -I This separation system was rendered necessary,^ in >\u25a0 the ? ; Yerba'^Buena \u25a0; and Mission flat : subdistrlqts % by -',tbe";;j fact that : much • of ? the * surf ace ": lies s below city base^ . ' And \u25a0;' In"? most • of * the > »cean slope districts 'both? sewage ; and'storra water /will "be Yi. intercepted - s ': and •T, dis charged f: into ,7 theTocean ,; at • the Point '. Lobos v.'ou tf all, -i where i; th c y: ocean ward 1 fl ow -' is Vaway J from • the £ beach:'; -f As 1' a large 7 .; part? of this 2 beach 4is \u25a0= a"- public : playground^lt|isiimperatiye.to^ keep; it -as-freelas possibleTfroml pollution.: .'-.• * . - ..The j maln'skeyJ to'ithe^ sewage- prob- ; ±. lem ,* presented'; by.: : this comprehensive system was founded; ln the selection of the points of outfall for the various drainage areas. A closs study of the tides and their velocities resulted in the choice of the following. projections into deep, swift water: Off North point, where ; a large pumping station and. screen house , will be situated and where there is a discharge in 36 feet of water at 1,200 feet or more from the water front line;- off Hunters. point, in a like depth; off the ocean shore, just west of Bakers beach, at the foot of Twenty-seventh avenue; off the foot of Scott street, in «at least; 36 feet of water, sufficiently far from , the shore. When it is considered that about one cubic mile of water passes through the Golden gate each .way every; day, and that- to this vast outflow is added the rivers tributary to the bay, San Fran ciscans need lose no sleep over the ulti mate fate of the sewage, j Providing for the Future Further than this, two other points have.been chosen -to provide for the concentration of all sewage 'reaching; the northern city front, shouldUhecity. outgrow the present plan. > These fare Fort Point and Point Lobos. :;; The for-, mer wlllreceive the'sewage from a" dis trict comprising the greater part of the residential section and the entire busi- 1 ness portion (of the city. At I Point Lo- ' bos the sewage from most of the ocean slope will ultimately be delivered.'; And ' the Scott | street outfall will , take . care S of nhe' Harbor View.: district; until Forts Point is brought" into" use; for tne ulti-* mate discharge.; The importance of this latter, point- sufficiently explains , why: the greatest possible' area". will be made tributary to the North* Point : outfall,, and why Hunters point will be permit ted to provide f or the ; rest. ,' . : ; The: main. lntersecting sewer of v this whole system- is --what fs technically known :as :the'iNofth point : outlet. ';its position was determined by, the outfall : at North point, north 'Of Telegraph hill," and; the intercepting .point- on 1 the ibid line'of Mission creek. \u25a0 l lt,wiH'run from 1 . Valenciavfstreetito^Division street; at: Eighteenth,:, follow/-; the ~best^ adapted to : the , purpose ; arid\reach..the , water front f romlSansome street. : ; The sewers ; from \u25a0' the j west ) and? a plentiful number of ;- storm "f water : relief " outlets ". .will discharge into' it all along Its .course.'- 1 ';" •'/-:;;;*\u25a0;: -.--;•':• \u25a0'\u25a0'i- : -' : ''"'--'' ; '-' ;< Of ; the conduits \u25a0 that >will, carry, efflu- entslfrbm'each. of 4 the storm water out lets to the open water in Channel; street* or ?. to :. the ; bay J the" chief : ; and £ most .; im-^. portls the great sDivision;street sewer:;, This T.wlll r.lisZ serpentine \u2666 course along? Division* street sf ronrj Eighteenth-; toithehead of the 7 old Mission creek^ or ; . under]'; way, Its t middle -3 section,! khownfasiß,- almost 1 completed^a* more or;iess'.detalled/descrlptlon;;of Its con-" struction-'may;S interests they general, reader.^: v ..;.; ;-7.-;>!V* -: -••-':\u25a0;.;.. -.;\u25a0.•-. \u25a0' \u25a0. \u25a0'\u25a0-":•'.. "'\u25a0\u25a0, ~ v;l.lke ! 'all the main conduits i and stornri' .water sewers in.the riew.system.'it'is toi be built throughout of reinforced con crete and lined on the bottom with vit rified brick. Section A runs from Chan nel street; to Kansas, section B thencf toiTehth and section -C continues the outlet to Eighteenth and Division. Th 6 first two sections are practically Iden tical ' in construction and dimensions— that : is, of three parallel compartments or Inverts under a common roof of re inforced concrete. For section C, which does not have to. provide for as much volume and . velocity ; of storm, water, two compartments, of : slightly larger dimensions have been found sufficient. A description of section. B, the only one near; completion, will servo to illus trate the type. . This section, then, crescent . shaped, following the line. of Division street, is. 1,400 ; feet in length. Its total width from outer- wall , to outer wall is 32 feet.: .Through each of its three com partments about seven ; giants 8 feet . Z Inches in height; could; walk, abreast withouf crushing one another's feet, and such is its strength that'the heavi est .locomotives of the Western Pacific, whose tracks cross Its roof near Ninth street,: can pass; without disturbing the concrete. . . : . • - Its ;, ventilation \ia > amply, insured by manholes at intervals of about 140 feet. I 'And it is flanked on fioth sides through out' most of Itsilength" by a sanitary system of ,12 inch; pipes, also well aired by.: chimney 'shaped; manhole's. ; In Its main ' dimensions \ andi^in; its power to • resist strain it 'surpasses the'; famous Cloaca ,• Maxima lot « Rome, which with ; its eccentric i'and solid blocks of uncemented stone '• Is ; still . the wonder of the I civilized ;; world. .The compara tively modern origin br , concrete sew- ', ecage . has:, as. yet furnished ; no. test Vof the : enduring ; quality <of this material; for>the'purppse. JBut , it is\ believed that unless the action' of whatever salt 'and otherichemicalslthe:.water tobe carried may iContainf is more^serious than 'ft'is r expected : to jbe, the endurance .of ( San . Francisco's'-new.^sewerage. system will suffice^f or her; development. . - -T...That this "huge 'section JB" has-been ' rushed'; through . to ? compleVbn , in , what, is. said to be the shortest-: time ever.re quired a'; great - city ;;contract ;of ' similar -exactions ; is ; due , largely \to ; the ' methods \u25a0 of ; operation ' and of inspection employed lon j th e :\: \ Job; ,~ \ Despi te i many ''-\u25a0 obstacles vof -unfavorable X. weather land " of (experimentation necessitated by; lack. - of precedents; the whole work has re quired; less ;. than ; 10 ; months. \u25a0; , ..'As Jshown |in A the pictures .: the . con struction^has (followed the .line: of the old€sewer Hhat "J debouched at stre c t.T; "Along ; th is " cour se : a*h vge di teh \ ;had -Übibe;; dug \u25a0": by u pick:; and- shovel; "\u25a0'- : Lagging^and, piles: to; prevent the :sides > fromVcaving«:and^to" support 'the* outer ; [sheathing > f orAthe'i'cbncrete; had V to be drlven.\;,.;Ofteh,ithe4triple.'rbw; of /piles ' \u25a0f br^the; foundation .were forced 1 i the j h'eavyi planks \ arid i brick *of Ithe I old f ;sewer.". Theinext'step was the placing .The*' San '^ 'Francisco Sunday CaU ana connection of the iron rods to re inforce the concrete, which was emp tied from "buggies" to make the con cave bottom of -the inverts. Then the reinforcing rods for the walls were set and wired, the. mudsills of 2x4's Were laid, the wooden forms to hold the con crete In place were stood against the rods, bolted, braced by "spreaders" and "purlines" . and finally the concrete walls were poured, tamped and allowed to; set. 'On. the wooden tops then ad justed a similar process of forming the reinforced concrete roof of the Inverts was begun. At the end pf two weeks, the time. specified for the "setting" of the concrete, the forms and tops were removed and carried forward to be used for the 'continuation of the construc tion. Thus -the contractor strovecto minimize, the waste of time and ma terial ias consistently -as\ the require ments of speed and efficiency would Where; Inverts Separate The 'most interesting! part of the whole work from an engineering view point is shown, in the "picture Jof the fork and .distribution "or equalization chambers at the Tenth; street end of the* conduit. • Here the north Invert, is separated- ; from the: other . two and brought around. in a curve to meet the sewer that will run . along Tenth street to' the bay. ; The chief -compartments are continued to the'end of the old main and will be merged into section C. . All .three inverts are widened and heightened at -least a foot. and a half Where .the -branch begins the roof is supported \ only by two reinforced con crete * columns, 16 inches In Thus An ', the 'open . space left at the v in tersection the waters flowing from the Tenth: street main: and, from section C the- Division : street extension, will be distributed , and i; sent through: the in verts of section B.^ In the picture the construction;; and' the efficient activity of the carpenters. Iron workers and la borers! are {clearly: shown." • • •\u25a0 " \ To* calm "the /possible fears of Vail skeptics , as ;to the £ carrying capacity of ;these : great; inverts be it = understood that .they are made and "graded' to pro vide , for j the itorrents ' from ' the ' heaviest rainfall • overran t area ; of >. five .square miles <ln the' Mission; and iPotrero dis tricts...^ More scientifically the" 1 three rcompartments will have a carrying: capacity of 1,701 second feet and will provide for a velocity of 7.51 feet per second. The one compartment of the Tenth street branch will have a quantity capacity of 620 second feet and a velocity provision of 7.5 feet par second. Much credit for the process and ef fectiveness of the work is due not only to the dynamic superintendent em ployed by the contractor, but also to the quiet young engineers or active In- opectors who car* for the clty*» Inter ests. It Is these latter who make the surveys, lay the lines and levels, scan with lynx eyes every detail of the con struction and often , suggest Its prac tlcal execution. The- Merchants* asso ciation, legitimate heir of the Civic league, is also on the job by proxy. Occasionally one of their scouts hap pens along with a criticism or word of advice, which, if deemed practical. i 3 observed by the Inspectors. Thus har- ~ mony is the watchword, and the work. Is rushed as merrily as Its unsavory nature and the complex character of the labor employed have permitted. Until recently representatives of many foreign climes were fo.und side by side on*., the job. Greeks. Ifallans. Servians, Syrians were mingled with Scotch. Irish. English, Germans. Americans and here and there a Native Son, generally of Irish extraction. But the recent en forcement of the ordinance that all employes on a city contract must be either citizens or- able to prove their serious intention. of becoming such has eliminated the "foreign" element strict ly so called. In- view of all tha serious problem* involved in this huge sewerage system, and of its benefits to the community, its successful completion should reflect undying credit upon Its designers. Be fore the actual work could be begun, careful studies had be, made of drainage areas, soil water planes. water consumption. rainfall rates, storm water capacities. Infiltration. ~ run ' off rates, grader, and numerous other theoretic and practical details. But the condition of the work already underway seems to insure the satis factory solution of the most serious problems involved. The progress made In. the large Intercepting sewers of the eastPotrero, in the North beach inter cepting: sewer, in the tributary main In Fifth, Howard and Sansome streets; In the construction of tbe Sunset, Rich- . mood - and other districts of the city, argues strongly'for the efficiency of the^ present methods of operation. As theC^ system has '. been planned for an esti- * mated population of a million souls, It is safe to assume that the San Fran ciscan of the future will have less cause to worry over sewage disposal and will breaths a somewhat more Sabean at mosphere than did his less fortunate