Sewer Layout

Laser generators have replaced the board system to line and grade sewers. Various laser generators were specifically designed for sewer installation. These generators projects a concentrated low cottage light beam of such quality that little diffusion (or light spread) occurred in distances usually encountered in installation. The light beam essentially replaced the stringline in the transfer of the line and grade Input power was supplied by an A.C. source and output sewer was in the low range of 1 to 5 milliwatts. Care was exercised sewer when laser equipment was in use, since eye injuries resulted from staring directly at the light

source.

Laser generating equipment was adjusted and positioned and an adjustment was provided to incline the beam at a slope equal to the grade of the sewer. Two basic locations were generally used for the positioning of the laser equipment, in the trench bottom or on the ground surface. The equipment was placed in the trench and positioned in such a manner the laser beam described the centre of the sewer. The initial alignment of the laser generator was accomplished by the erection of several grade boards. As each pipe section was installed, a special target or the template was placed on the pipe's end and the vertical and horizontal alignment chocked. The beam projected through previously placed sewer sections was also used to provide line and grade for trench excavation and placement of the bedding materials. The light beam was periodically checked against surface control points to insure its correct horizontal and vertical alignment. The laser was subject to refraction as it passed through the atmosphere. This was primarily function of humidity, the sewer lines were consequently vertilated as works progressed. (Ref. 11).

Set Up

When a surface set up was used, the laser generator was positioned on the sewer centre line and the light beam functioned in the same manner as the stringline in a springboard system. A

grade pole was then used to transfer line and grade into the trench bottom. This method had the advantage of providing a but the beam was not available for contiquick check against grade reference points nuous check in the trench with use of laser equipment, the generator was protected against bump. A slight shift in alignment of the light beam was unnoticeable at first, but the errors were magnified as the sewerline installation progressed. (Ref. 14).

Maintenance and Inspections

Sewer systems were inspected to ensure that they functioned properly. Inspections were on an annual or semi-annual basis, but were always conducted following major storms. Systems that incorporated infiltration were most critical since poor maintenance practices rendered them inefficient. Inspection of pipes, covered trenches and wells was accompalished by close circuit television, and still photographs were obtained by taking a picture of the monitor and mounting a still camera along side the T.V. Camera and triggering it electronically.

Basins

Infiltration basin surfaces were sometimes sacrificed to break up silt deposits and restore top soil porosity. This was done when all sediment had been removed from the basin floor. This operation was eliminated by the establishment of grass cover on the basin flow and slopes. Such cover helped maintain soil porosity.

Storm Drainage

As much storm water runoff as possible was collected and rapidly discharged through a system of pipes to the nearest outlet. The major problems encountered

were:

(1) High peak flows in storm sewers and streams required larger facilities at higher cost,

(2) Lowering of water tables had

detrimental effect on existing vegetation and in low lying coasted areas, permitting salt water intrusion,

(3) reduction in base flows in receiving streams, affecting aquatic life,

(4) excessive erosion of streams and sedimentation of lakes due to higher discharge velocities,

(5) increased pollution of receiving streams and lakes due to industrial fall out on roofs, fertilisers from lawns and deter is from streets and paved areas being conveyed directly to the streams and

(6) flooding, run off quantities which had been experienced rarely now occurred much more frequently.

Minor Systems

The minor system consisted of carefully designed closed and open conduits, with capacity to handle run off from a storm expected to occur with a certain frequency. The major system was the route followed by run off waters when the minor system was imperative or inadequate. The lack of a properly designed major system often led to flooding causing severe damage. Sub-surface disposal of storm water, like land treatment of waste water was cost effective alternative to conventional discharge into surface water. The impact of sub-surface disposal of infiltrated storm water on the quality of the ground water was an essential consideration. (Ref. 12).

Design

A combined storm water sewage conduit was economically designed. A framework for the analysis of pollution control investments was made. A rational method for determination of the optimal design specification provided for correct projections as the pay off matrix. The relationship between projection uncertainty, interest rates and scale economics received particular attention. The method was applied in some recent sewage treatment plants and the results were compared to the more traditional design specifications in the preliminary design reports. Over design in the face of flow uncer⭑ tainty carried higher penalties than the underdesign under the prevailing interest

rate conditions. A new technique for sewer flow routing was developed using synthesis. This approach was based upon a bumped mathematical model to describe unsteady, non sewer flow. (Ref. 13). Conclusion

System analysis and synthesis techniques were applied for designing and maintenance, of sewer and storm water networks. This technique was applied to multilevel branching sewer networks. The model was compared to other routing techniques through the use of example sewer network. State variable modelling was not only limited to sewer flow routing but was also applied to overland flow, linear and reservoir networks were populations and

reservoir modelling operation. Combined beneficial for regional served large areas.

A range of potential costs for the control of overflows was worked out. Cost estimates were worked for the control of runoff from combined sewer service areas based on a single design storm and control strategies. Capital costs varied with amount of storage and degree of treatment provided. These costs were next compared with similar estimates for new and upgraded municipal sewers and treatment systems were modified accordingly. Water pollution control agencies are advised to become more strict about pollution from treatment plants. An important factics is to reduce the amount of waste generated in the first place. The evaluation and acceptance of alternative sewage system is advocated as reliable and cost effective. Pressure and vacuum sewers, and home aerobic units for primary treatment. are recommended.

References

(1) Chaturvedi A. C.: Priorities in Environmental Engineering Education, Asian Environment, Makati, Philipines, 1982, p. 12.

(2) Sixth Annual Report, Council on Environmental Quality, Washington D.C., 19, p. 12.

(3) Pollution Control in 80's, Proceedings Fourth World Congress on Water Resources, Buacus Aires, 1979, p. 24.

(4) U.N.E P.- Industry and Environment,

Special Issue No. 1., 1930, p. 16. (5) Chaturvedi A. C., Environmental Management in 80's. Proceedings First International Congress Industrial Pollution and

on Control,

Singapore Society of Civil Engineers, 1982, p. 32.

(6) The State of the Environment, Selected Topics, U.N.P/C.C., 9/3 Report, 1981, p. 14.

(7) Knees A. V. Economics and Environment, Pengnia Books, New York, 1977, p. 18.

(8) Chaturvedi A. C. Storm Drainage in India, Proceedings International Conference on Urban Storm Drainage, Hampshire, W. K. 1978, p. 26.

(9) Balaziku O.F., 1979, Economics of Pure Air, Nankara Dunika, Kiev, U.S.S R. 1979, p. 24.

(10) Chaturvedi A. C Structural Designs for Water Pollution Control, Proceedings International Conference, Asian

Institute of Technology, Bangkok,
Thailand, 1979, p. 40.

(11) Theys J. Enviror.mental Assessment of Socio Economic System Plenum Publication Corporation, 1978, p. 28. (12) Sentor D. and Boyd G. B., Water Pollution Aspects of Street Surface Contaminants, Report E P.A., RAZ72-081, U.S. EPA Washington, 1972, p. 16.

(13) Chaturvedi A. C. Urban Regional and National Planning in India, Proceedings International Workshop, International Federation of Automatic Control on Environmental Aspects, Kyoto, 1977, p. 102.

(14) Collins P.S. and Ridway D.W., Urban Land Runoff characteristics. Urbani

sation and Water Quality Control Proceedings American W.R.A. No. 20, 1948, p. 12.

(15) Chaturvedi A. C. Disposal of Radio Active Waste in India, Proceeding International Workshop in Water Quality Management Asia Aque Tech., Manila, 1980, p. 44.

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to IS: 1536

Branch:

米糕

Way back in 1943, I joined as a junior officer in the Auxiliary Fire Force of the then Calcutta Fire Brigade crowded with an influx of British Fire Officers, all imported from Great Britain to keep His Majesty's Flag flying aloft in this subcontinent in the face of Japanese straffing from the East.

Several of these brand of imported experts were real characters to remember with fun. One of them was Company Officer W. M. K. Carr, a character straight out of some comical strip. A sozzler par excellence with a temperament only comparable with oriental Norwester

was

His first question to me was "Are you married, my boy ?". I was only 21 and notwithstanding the fact that rankwise he was just a step ahead, he took the liberty of addressing me 'boy'. Perhaps, taking into count his age. Anyway back to Carr's question, my firm answer "No". "Fine! Never get married. have tried thrice those lousy stuff with no success-bloody direty, monotonous filth stirring business-Day in and day out and you are done. No, never get married. Why should you? Don't believe in women. Don't even go near them, they are all very same though in different garbs and appearances. I tell you again. I have tried thrice and all ended in bloody hell. And why should you buy a car and ruin your money and energy after it when taxis are available aplenty? Isn't it? Ha-Ha-Ha. Lock, when you need a ride, whistle a taxi stop, take a good ride and finish with paying to meter. No bloody maintenance, changing tyres, getting spares, charging the battery and frequent refuelling. Isn't it? Don't believe them. Believe in drink and music only. They never betray".

"But dogs toɔ, are equally trustworthy. Aren't they? I chipped in. "Hellworthy'. My foot. I had a Labrador, the bugger was darn food of sozzling. One night both of us had a tremendous booze and after the bottle was empty the bastard

The Author

would still want more. And you know what the hell that sone of a bitch did? He bit me thrice the same night asking for more and more of grag'. And I killed the bastard to finish it once for all next day. No more dog after that. Any better than women you think? Hell with it

all".

Of course, I had no answer to this poser. But enjoying nevertheless.

Carr and myself were quartered in adjacent bachelor flats ard both lived in

our own ways of life with no lady to take care of bed and kitchen. Carr was found of drink and music (!) I was food of book and games. But his music? Good God! Something a veritable torture to ear and elegant tastes. He was his own composer and tune setter and whenever he revelled in his musical extravaganze in accompaniment of his out of tune quitar and corvine voice rending the coiling of the roof, from the adjacent flat I invariably felt that Doomsday was on.

Those of repeated compositions are mostly the unprintable. But as a specimen I just give my readers a few rather printable lines hereunder :