| | MMi Li | Hl =8 Ww aks i a ene pee 4 weet oe Ov 4 eS i ¢ —— eo a ee THESIS. DESIGN OF SEWER SYSTEM FOR OAKwOOD. 1 . ce f uL oO”. M p Nacker. ——_ June, 190s. 4 meals -l- Oakwood is a new town recently platted, and is a portion of section 15, Tp. 4 M., R. 2 W., traversed as follows: beginning at intersection of North side of what was originally the Lansing and Howell plank road, and the township line between Tp. « Ne Re 2 We. and Tpe 4 Ne Re 1 Wes thence N 48.60 to quarter post: thence W./2.533 thence S. 22,25 to said plank road; thence S. 703 E. £).2755 to place of beginning. The first thing to consider in this design is to deciace on the kind of system to be installed; whether com- tined or separate. In this partioular case, the ground is quite rough, and all.the storm water drains to practically only two places. One place is known as lot no. 46, and is a triangular lot facing Oakhill ang Evergreen aves. as may be seen from the accompanying blue print. The other place is intended to be a park, and is quite a little lower than lot 46. The trianguiar lot, however, collectg only a con- paratively smali amount of the water. In the first place, the lot does not drain as large an area, it is higher than 102922 2. the park, and the water soon percolates to the lower place; water standing on the lot cnly during, and for a short time after, very heavy rains. thus, a part of the system will be combined, and the rest a simple sanitary system. ihe park may be drained with ordinary drain tile since to all present indications, there will be no houses or other buildings neeaing sewerage in its vicinity. ihe sewer tile of the systen as designea is low enough so that. the drain tile may be tappea into it at any convenient place or places. The water collected on lot -@ that does net per- colate through the soil may be conducted away by placing a catch basin on the lct ard@ conducting the waiter irto the sewer line or Evergreer aie. it is necessarv to put the catbh basin on the lot because the surface of the lot is a little lower than thah o. the street. These two places, howe.er, do not collect ali the water, since the whole North end oi the plat is drained into a low, marshy pond. Part of this pond is included ~3- in the plat, our of course, is not diriued into lots. Some day, it might become desirable to drain this pond and divice it into lots, but it is not lookec for within the life of this Systen, and hence no account will be taxen ci it. Beyond what its above spoken of, no special pro- ,ision will be made tor drainirg ott the storm water; be- cause there will be only a very light flow of sewage in any case, and the six inch tile which will be used (ior rea- sons gi:‘en later), has a capacity many times the flow, and thus takes care of a great amount of water which will be Caught in the rcanholes and lampholes along the line. In order +o facilitate in deciding on the streets in which to run the sewers most ad\antageously, a contour map was made. Insteac of following out the ordinary method of tracing out the contours in the field and locating points along the same, ievels were taken at each lot cor- ner and also at places where there was a sharp change of grade in the surface of the ground. ihen points along the respective contours were plotted on the map by interpolating its level in between two adjacent levels taken at lot cor- ners. A blue print of the original plat was secured, anc from this print, a tracing was made of the plat in -Llack ink, and ther the contours were plotted on this same tracing in red irk. ihus the two naps were combined in one. The. reason for using the red 1nx on the tracing was that when the blue print was made, the contour lines would not prin: out as white and distinct as the more important lines of the pla. and sewer lines, which were traced in black, and thus avoid the conpusion of so many iines on such a comparatively smal] scale tracing. This method is not as accurate as the one ordinariy used, but since its purpose is to present to the eye the general lay of the land without the details, it answers all requirements. Most important of all, ihe cuestion of time was one of the chief factors which led to the use of this method; it taking but a little nore time to plot than the usual method, while it greatly reduces the amount of field work. Let it be understood that the inaccuracy is -6- due to the plotiing. The levels were accurately taxen and recorded in the fiela notes for use in plotiing the street profiles which must be done with greater accuracy. Having this contour map, the designer was able to trace out with the eye the natural water courses of the land, and select streets that woula most nearly follow these cours- es and still give service to all of the lots. Jhen after laying out a preliminary system from the contours, he could take the field notes in which the levels are more accurately given, and make a detailea examination to nake sure that the System is the most economical one. ihis latter statement is general and applies more particularly to places where the slope of the ground is very flat. In this particular case, all the grades of the ground surface were so pronounced ard sharp that little comparison with the field notes was necessarve In some instances wheie the suriace is flat, the designer has the choice of either of two directions, but in this case, neariy ali the grades are steep, and there is but one choice. -6- After tne preliminary lines and courses haa been laia out as above, the aesigner went over the ground where the sewers were to be laid in order to detect any difficulty which might arise, and which was not shown on the ocrtour Map. ‘here was no trouble of this sort found, bui note was taken of the piaces where the sewers could te laid shal- low (where the lots were considerably higher than the streets) and where it would be necessary to lay them deep. The way the levels were taken helped this matter of depth considerably for the reason that they were taxen at the lot corners at the side of the street and gave, as a general rule, the mean level of the lot and street. However, the direction of the slope had to be kept in mind, that is whether toward the street or away from ii. The location of the sewers are shown on the plar. It was desirgable to locate the lines where one line may serve two rows of lots. Such i8 generally the case, but in the case of the line in alley no. 2, it was impossible to make this line serve the lots facing Evergreen a\e., -7- oecause these lots were al*ogether too low to discharge sewage into the alley line. !n most cases where connec- tiors are made from both sides of the street, the line was placed in the middle of the street. The alley line is also an exception to this since there has been laid, previous to this design, a water main six ieet iron the basi sice o! che ailey. In streets such as Miles ave., the sewer line was placed twenty four fee. trom the side just so as 10 clear the side walks and trees. ihe levels tor all this work were refered toa bench mark on the North East corner of the water table on College Hall, to which rearly all the surveys made in this vacinity for a long. time past, have been connected. It wee was thought that in case it was e.er aesirable to cumpare or refer this survey to any other, it would be more con- venient to have them all retered to the same datum which was one hundred feet below the above berch wark. ishis tench mark or Lollege Hail was quite a distance from the plat oz CVakwood so before taking any levels, a bench mark was made on. the root of a large white oak tree on the Last side ~~ of Abbot roac ana neaily oppesste iot corner no. 1, by chopping a bench cn the root, and driving a large nail in until the head stood about $/16" above the wood. ihis, on account of the growth oi the tree would soon becone un- reliable, but it sas only used tor a short time; and on later occasions to dc any leveling it is necessary to refer to the original bench mark. A large stone would hate been much better for the purpose, but suck could not be found. After making the contour map, and devernmining the location of the system, the cuestion of grades and depths was next in order. a set of profile drawings of the streets in which the sewers were to be laid was made from the levels recorded in the field note bock. A hori-.ontal scale of iifty feet to the inch, and a vertical scale of ten feet to the irch was used in plotting the proiiles, thus any grade or unevenness was greatiy exaggerated in the drawing, making it possible to piot the grades with more accuracy. jhen conmencing at the :ower end of the line, that is, at the river, because the height at that place was first determined, being neariy the mean -G- that is at the ri.er, because the height at ihat place was first determinea, being nearly the mean level of the waters the prade line was drawn at some con‘erient ¢race which, commencing at the surface o!1 the ground at the ricer, would soon run the line deep enough to be below frost and any surface disturbances of the ground. Then the grade was changed ard some grace was chosen which would keep the line, as nearly as possible, parallei to the suriace. The ground cetween the river and Oakwooc ts of such a grade it- self, that the same grade may be used from the change otf prade a shoit aistance from the river (spoxen of above) all the rest of the way to the plat. The first grade line chosen was taken at such a grade so as to bring it at about se:en feer below the surface at the manhole on Miles ave. near lot corer no. 150. (See map.) It was found that this depth at this man- hole was not sufficient to give the proper tall trom the marhole on Evergreer ave. along the \alley Court line --- the surface along here being very nearly level, and part of -10- the way, at a reverse grade. So 2 lower grade had to be chosen that would give the recuired fall. After this no particular difficulty was experienced in fixing the grade, except on Evergreen ave. where, as may be seen from the profile drawing, the suriace was o1 such a disadvantageous character that a few trials were made before a suitable grade was found. The average depth was about seven feet beiow the ievel of the adjacent lots so as to be low enough to take sewage from the cellars. By examining the profile, it will be seen that for a short distance on Evergreen ave. the line is shallower than this, and in oroer to ren- ecy it, the whole line to the river woula have to be lower accordingly because the vrades now used between there and the river are already as small as it is advisable to al- low. This line as above mentioned, is too shallow for the celiars on one side of the street for a distance of one lot front which is lot no. 1&, but is plenty low anough for the lots on ihe opposite side of the street so that -— oe 78 TT Na” —_ -lj)- all it afiects is only one lot. A dilterence of a foot in depth clear to the river would ade coesicerabdly to the to- tal cost so that it was thoughtbest to make a litile sac- rifice on the part of this one lot and save the extra ex- pense of changing the oertire line to the river. The line to the river is already deeper tham is desirgable because after it leaves Oakwood there will be no more connections to be made into it, and hence all that would be necessary would be to keep it below the frost line, but, as saia be- fore, it would not alicw fall enough on tne \ailey Court line. The method of commercing at the outlet and werk- ing upstrean was used so as to avoia the use of fractional or unusual grades. On the other hand, ii there are two points on the line that are absolutely fixed, and it is necessary to run a line between them, to ail probability a fractional grade would be necessary, anc thus cause a loss of time in seiting the grade stakes. On the proiile drawing, distances Letween the points ~l]y- QO. charpe of grade are giver. These distances. as piven, are as accurate as can be determined by scaling and cal- culating irom the map. ihey are ail supposed to be correct to the nearest foot cr twe, and in some cases it was possible to get closer results than these. In othee words, they are as accurate as can ne determinea without going into the field ana laying out the line, and then actually measur- ing the different lengths such as they come. Any small error in the distances will affect only the heights of the manholes at the several intersections. The dis- tances on the line from Cakwood to the river are absolute- ly correct and are just as it is intended to lay out the line. The lires on the streets must be laid out by running the lines parallel to the respective street lines, and at their proper distances from the street lines as given on the plan, and then let the intersections come as they will. ‘lhe maximum error as recorded in any case is probably not Over two feet, and hence, even on a ten percert grade, will not atfect the height of the manhole nore thar two -]5- tenths of a foot :rom the calculated elevation gi\en on the drawing. Then when it is taken inio consideration thai the error is a compensating one, the7zis no probability of any trouble from this source. Manholes are placed only at intersections and occasionally on curves becuuse any trouble on a curve is hard to locate, and it was thought that this would be helped somewhat by putting in manholes where it could te more readily gotten at. At al] the changes of grade, lampholes were placed. No fiush tanks were put in the deaa ends because they are expensi.\e, and all the flushing that Will be necessary can be done through the lampholes at the ends with water from the nearest hydrant, conducted through fire hose. On account of the peculiar topography of the North erd of the plat, it will be seen that there are six lots facing Fern st., that are not provided for in this sys- vem. All of these lots lie on a steep side hill, and ac- cording to present inaications will not be built upon for ~)ae several years. there is no outlet to this district ex- cept bv a very round about way along a ditch which runs Eastward and Southvard and over other property. Henoe the ° most economical and most desireable system, if the needs ae- manded it, would include a septic tank on the North side and at the East end of Fern st. Fern st. is at the base of the side hill, and is practically level, the East end be- ing slightly the lower. Now as to the size of the sewer, we use Kutter's formula | (a1 .6- 200281 1s€11 y ie 6 oo ee eee - ( + [41.6 1. 29261 | -2. where n is a factor depending on the roughness of the tile which is taken at 0.015 in this case; R,is the hydraulic radius; S, tne slope. 0 - \ x (area), where © is the quan- tity of flow in ou. ft. per minute. Calculating on each lot being occupied by six persons, we have a total population of 6 x &4 - 504. We assume that we have a flow of O.O16& cu. ft. per minute ag maximum flow. 604 x .0152 - 8.1648 cu. ft. -15- per minute as the total maximum flow in any line of the system. From the formula, a six inch tile on a 0.6% grade (which is the minimum grade used on a six in tile) is capable of Carrying about 22 cu. ft. per minute. Theretore 4 six inch tile is realy larger than necessary to theoretically car- ry the total amount of sewage, having a margin o1 safety cf 22 - 6&2 = 13.6 cu. it. per minute. On account of prevent- ing clogging by roots etce, no tide will be used less than six inches in diameter. Therefore no further calculations need to be nade regarding the sizes of the pipe. Fror Oakwood to the rier & inch tile is to be used for the reason, that a 0.4% grade is about as iarge a grade aS can be used in order to have the manhole near lot corner noe 150 low enough, and this grade is hardly allow- able on a six inch tile. The larger size also doubly pre- vents clogging. The estimate is taken from contract prices at which previous similar contracts have been let in other places. ihe excavating, laying, and filling is taken at -16- t5.5C per rod, and. the Price of six inch tile at l2¢e, and eight inch tile at l5&y per itt. The M. A. C. let a coniraci once for the excaiating, laying, ard filling as low as €1.26 per rod, but this is extraordinarily low. It ig merely gi.en to show how Cheap the work nay be done under favorable conditions. ‘The cost of digging, laying, and fillire for both six inch and eight inch wall be calculated at the same pricesince the trench is about the same size and the laying recuiring about. the same amount Of labor. The following is considerea to be a fair average cost: 6591 ft. of 6" tile: 35.64 -----L_-e $2175 .CC 17V76 f[t. of 8" tile © 36¢ ------_- 640 .CO 20 lampholes & #5.00 - --~---+---+--+uH- Le 10C .CO <2 manholes ® ®30.C0 --~-------+-- ~~860.00_ Total - - - - ©5575 .00 MICHIGAN ii UN nn ER ITY LIB Nl il ii i IV 3 12 03196 71 Mic HIGAN State ANTHTA TTT ooo | | | | MICHIGAN STAT E UNIVE RSITY i il) vi iil i 3 03 STAT i UNIVERSITY LIBRARIES J MT it NE || WNP Ii\| AN | 293 03196 7171 / ~ oe . Se — = - = . _ - = = z = Fe va os ~~ - he - te > Ph, : h = 1 iN ‘ 7 : ) tS E B IES TATE UNIVERSITY LI! Hi TM HM Hl Hill 3 03196 7 | 29 9 171 MICHIGAN S$ WH os 7