DRAINAGE OF GISBORNE

Gisborne Times, Volume XXVII, Issue 2511, 26 May 1909, Page 3

DRAINAGE OF GISBORNE

Mr Marchant Submits a Septic Tank System.

Southern Expert Says the Borough can be Sewered 'for £58,000.

At a special' meeting of the Borough Council*last evening, Air. F. AV. Alarchant, C.E., submitted the following •scheme for the sewerage of Gisborne: GENERAL FEATURES OF THE TOAVN AREA. The town of Gisborne, situated on an alluvial flat, having its area divided into three separato sections by the Taruheru and AVaimata rivers, renders it a special case to deal with. On the AVhataupoko and Kaiti areas the natural inclinations of the ground are such that good gradients can be given to the sewers. In the old'borough area, it is generally speaking very flat, and hero recourse must*" be had to pumping the sewage. At present, the population of the whole borough is estimated as being about 7000, inhabiting about 1300 houses.

as arranged is that no night staff would ho needed at the power station. On the Whataupoko and Kaiti blocks are three very small low-lying areas , on which are built about 20 houses altogether. The sewage from these must either be pumped or disposed of by a septic tank for each , area. The cost of pumping has been allowed for in the estimate. If, however, the septic tank system is allowed by the Health Department ,the estimate given for tlio whole scheme can bo reduced by nearly £2OOO. I am certain there is no objection whatever to tho use of tanks in these small areas, the only thing necessary is that tho effluent should be carried below low water mark. SEPTIC TANKS.

Subject to the reservation under tho preceding heading, there would be two main septic tanks for the whole of the town area. One would bo set on Stanley Road and the other by the breakwater. Tho former would have sewage pumped into it,' the other would receive it by gravitation. At Stanley Road, the effluent from tho tank would gravitate out to the beach, and be carried by cast iron piping secured to timber piling out about 60 feet beyond low water mark, and discharged below that level.

The water supply of the town consists of a 15-inch pipe, 20 miles in length. The quantity of water delivered by this materially delimits the quantity of sewage the sewer pipes must carry. At certain points of the old borough, subsoil water will be met with. This would be shut out by taking great care in the pipe jointing and testing the work for water-tightness; but there is always a risk of leakage under such circumstances, so that ample power for pumping must he provided. The scheme proposed and the sizes of pipes arranged will allow for many times the flow of sewage which would be discharged by the present population. GRADIENTS AND SIZES OF SEAVERS.

At the breakwater tank it would have a cast iron pipe laid in a trench cut in the papa rock, and concreted all round. Tho effluent from this tank would thus bo carried about 20 chains seawards from tho breakwater, and discharged below low water mark.

The action and practical experience of these tanks must be considered. All sewage flowing into them when properly designed and proportioned is divided into three parts. Roughly speaking, about one-third is disposed of in the form of gas, about another third passes out in solution, and tho remainder is left in tho tank, By building these tanks in two compartments, as should always bo done, the sludge difficulty is almost, if not quite, entirely eliminated. One tank I designed some years ago has received tho sewage of 2000 persons for four years. One compartment only has been used, and there is not more than 6 inches depth of sludge in it. The large Christchurch tank, which has been in use. for some three years, has little or no sludge, so I am informed bv the Drainage Engineer there. “At New Plymouth a tank has been in use for about five or six years. It is situated in the centre of the town, with houses within 40ft of it. Iho effluent discharges into the Huatohi stream, about lo feet wide and fa to lo inches deep. At the point of discharge the effluent looks like soapy water, and in 20 feet or so it is co-nnngled null the clear water of the stream and entirely disappears, without offence. At Timaru we have a largo doublecliambcred tank discharging its effluent into the sea, through a cast pipe, mi timber piling. Houses within three chains of the tank. There is no smell and nothing whatever to be seen of the effluent as it is discharged below low water mark. . Gisborne. - effluent from the Sil’wSt cSofthau «»«*« “) VhVnow mdh 'iXlied hy disclar'rimam'pn, and other source, T lc _ ..-hen it is remembered Hat a.i the sewage cn"han delivered charged ls nmcli l 55 inches bv the water supply P 1 no gets diameter and 20 nnks ’ £ioll 1 something of the l would tho ana water into which it eventually Sons.

The town would be sewered strictly on the separate system, whereby the sewage only is discharged by the sewers, leaving the storm water from house roofs and ground surfaces to be discharged by surface channels and natural water-courses. This system cheapens the work very materially, and is now almost. exclusively. employed. All street grit and dust"is excluded from the sewers. The consequence is that the pipes need only be quite small, and can be. set at very small inclinations, and still keep perfectly clean and unobstructed. The reason is, that all the closet and house wastes conveying solid matters of lighter or much the same specific o-ravity as the water, do not teruh to settle in the pipes, but either float or are carried along by a very gentle curl<?Th'e minimum gradient fixed for the sewers in the old borough is Ift rUninc; or 1 in 528. None of the pipes in * this area would be less than 9m. This size is fixed because it lends lt.c.i better to .cleaning by flushing if required than would a smaller pipe. 1 This stated gradient is small m on compared with older ideas of what such gradients should he, hut they work admirably well when grit and dust aie oX l ll have in my charge on a sewerage system a 9in pipe, set at a f in 550, which has discharged hous^ sewage for many years past without reqiddSg flushing, and st.ll remams pcfectly clean of CliristExpenence in the nax eiu> church is just the same. late Mr. C. Napier lien, y i n reporting on the seweiage o Vm-th W A , also a very flat city, quotLi'Sno oxa’mnles oh A—ticis- ono'o”them being a 4in pipe on a gradient of 1 in 1000 and tvl. el. d - 01 \m,thci na example maybe quoted, where a 9in pipe discharged and that again into an 5 1000. -i loPl on a gradient ox 1 m xuu There carried the sewage of 1600 houses and the rainfall from the house rods ’’“S'e eases arc quoted because those be ukd of much greater boro andinchnation than is desirable 01 necc- V tJ whole of the borough area amounts to Tho°'r«u-t of'ccrjing the pipes on a inimum safe ora client where puinpin L , is required, is that the cost of eonstruction and the lift for pumping aie both "lit mhiimnm depth at which rarwors would bo »t would be o feet ' W» g 1 f I, ? o^’ , Sm S ' m!se commotion. S d av«agi deplb of tbo sower ...a.us would he under 7 - SYSTEM OE PUMIING KLGOh MENDED. It is proposed to raise the .sewage power from the borough water m.ams, would continually • drive a From the accumulator, power would be transmitted by ordinary post and linos to four .pumping pomtj. A? Tl, p would also bo engine'plant Oi zo o.n-i rierahv, installed, using suction gas gonerai.y, „... ,i town’s gas when dosiied. I hi. <rine would drive a second dynamo, als connected with the tr v these means all sui plus power could bo usefully employed Wlin<r hack on the ga.s p ant if the wate ever failed in sufficient ei . Two small pumping stations m lo\ Ann.punt toad.. ing points would -he on G y S T)n Stankyßoad a large septic tank would be built, and' all the sewage of the old borough would be pumped mt tb TbG svMem ef electrical pumping as applied to sewerage work is a great success. It is entirely automatic, an fs very much cheaper m constructive cost and working expenses than found S 'ln°Christcliurcli it is giving the greatest satisfaction, and in ijew belli" adopted m -rcfdoimo to otliei . .- -/.....A <-,f i (listnbu.t-cy.u-, . , , . .. 4>. r , gi-qfc-n

MANHOLES. These would be set at frequent into'--street level. If M nns.^ rnatic .*»ft-nr properly, «t!dng C p^ s ™ out of actioU * aUd 11 becomes useless. VENTILATION. I„ Timaru we" seal everything so that no -wit or dust finds its way into tho sewers. Ventilation is provided to Jj tall steel stand pipes, seton jho - line', , and coininectcd Aiitli the nnn_ holes by -pipes height 3£ So &S tt " offence. eSTIMA TES. wlLr^^^Srou^eoSiei^^ SSjSS? Si^^^hWeivgineering supervision, and contm o . Ci The whole of this sum might not be Z Swicffm S' t paid, although he St he tho only honso-mvnor nr a lo, s & of the scheme, .an main sewSSSi% -;S£ HOUSE CONNECTIONS. Tho beat systorn for dealing wi* +l,cse is to lay them up to the stieci, boundary at the same time a| Ah «,nins are laid, and execute them as uart of the scheme. This inakes on ! {caving house-owners to pay the whole + df the connection between th I Sin and building.. If tho connections i ■ Sl'MlfAlO •

ouglily satisfactory and completely modern work for the estimate given. The working expenses should be under £4OO a year for repairs and supervision, as the scheme would be almost entirety automatic, requiring only a minimum of oversight and attention. It is useless to enlarge upon the value of a scheme of sewerage in a town. Towns a quarter of tho size of Gisborne have sorely felt the need, and have established such to their groat benefit.

SPECIAL MEETING OF BOROUGH

COUNCIL

A special meeting of the. Borough Council was held last night to receive the report from Mr. F. W. Marchant on tho sewerage of Gisborne. There were present : His Worship the Mayor, mid Crs. Kirk, Maynard, Barton, oiavzon, Collins, Smith, Pettie, Harris, and. Somervell.

After the report had been read by the Town Clerk, Cr. Kirk said that as the report had been read Mr. Marchant was to be congratulated upon the report, which was most comprehensive and free from wearisome technicalities. He ventured to say if the report were adopted that it would bo endorsed by the ratepayers when it was put before them. On this occasion 110 did not think there was any likelihood of the loan for drainage being rejected. The Mayor suggested that Councillors should ask Mr. Marchant questions. In reply to the Mayor, Mr. Marchant said that provision was made for the reticulation of every street in the borough. The cost of house connections would he anything from £l2 to £ls; that would be for a small cottage. This would include a connection from tho main, and tho borough’s contribution he set down as £3 per house. In answer to Cr. Smith. Mr. Marchant said that it was his intention to run the pipes in the middle of the road, but in order to save the streets it would bo possible to instal two smaller pipes, one on each side of the road. He thought tho system of back drainage was a good one, but it bad its drawbacks, as ono man’s sewerage passed through another man’s property. He had allowed liberally for the cost of pipes. They could .get them for about £2OO a schooner load from Auckland. The pipes would all be earthenware. At the Hutt, Wellington, they were using pipes from Auckland. In answer to Cr. Harris, Mr. Marchant said that all the -drain 1 age of the area in the vicimty of Kahutia Street would have tobe pumped into a septic tank in Stanley Road, the level of the water in which wouM be above high-water mark. To Cr. Somervell, Mr. Marchant said that lie "did not think the amount of £4OO per year for upkeep was too low an estimate. If they allowed for the old borough, 10,000 jieoplc. using 30 gallons per day, a 7 horse-power engine driving a dynamo would be more power than they wanted, lie was absolutely certain ol what be said al>out the septic tanks. ~ ~ To Cr. Collins : The tanks were divided into two; but they would never in -Gisborne require filter beds, no matter what increase of population they had. \t New Plymouth he bad watched the effluent from the septic tank, and likened it to soapy water, which, after troino- for a few yards in the totally disappeared- The electric system of pumping was being largely used in new works in the Ohl Country and was in use in Christchurch. The oldci schemes of pumping were but wore very expensive. The an alignments for electrical pumping were simSty in themselves. Tho pmnp.na plant mentioned in his veport "ouW r,ilow for a population of at feast 30,000. There was little objection to a system of direct- sewage, except sentimental ones. Septic tanks were used to make sure of eliminating any possible appearances of any sewage on the beach. Even with tho pumping plant a system of direct sewage was v , but be strongly recommended the s>s torn of septic tanks. It -as unposs ble to have a drainage scheme by gianta tion in Gisborne, and he thought the system of electrical pumping was the best The cost of each tank would not be more than £ISOO. and if they did not instal the- tanks they niigbt possffilv save about £2OOO on the who 0 scheme. An outfall sewer carried out HOT below low water mark would be “ite sufficient. Ho did not holmvo in tho tanks with only one compa.t

thoy hud- already resolved to be submitted’ to a board of experts, .lib; own idea, wa.> that if they thought the scheme a' satisfactory and economical one, that they should place it before the ratepayers without submitting it to ai board of experts, <but only to the Chief Health Officer. He thought that the Council could congratulate itself on having got a report to'show them that a system of drainage could he installed in Gisborne for £58,000, when the most economical thev had received up to the present was £107,000. He thought that the, scheme was the host that had come before them, and if they could be reasonably agreed on this, then submit it to the Chief Health Officer for his consideration.

Cr. Pettie thought that the report should he printed and given to Councillors to consider the question before next meeting. Cr. Collins asked if there was not a resolution passed by the old Council to place the different schemes before a hoard of experts. The Mayor said that there was no resolution, and they had a clear field to work on.

Cr. Smith moved, and Cr. Clayton seconded, that the reports h e printed and circulated to Councillors, and that the subject be discussed at next meeting. ... Crs. Somervell and Harris supported the motion, which was carried. Other Councillors agreed with the suggestion to let the ouestion of drainage take precedence over other business at next meeting of the Council. Considerable discussion took place on the question as to whether there had been a resolution passed that Mr. Mareliant’s scheme should he submitted, with others, to the suggested board of exports, Crs. Pettio and Somervell affirming that such was the case. Eventually Cr. Kirk gave notice of motion that if any such resolution did exist, it he rescinded. He also moved that a copy of the report lie forwarded to Dr. Mason.

Cr. Collins seconded the motion, stating that at least such a proceeding was onlv a matter of courtesy.

The motion was agreed to. On the motion of Cr. Pettie, seconded by Ct. Somervell, a hearty vote of thanks was passed to Mr. Marchant for his attendance, and for the courteous'manner in which he had answered their numerous questions. Other Councillors expressed their appreciation of Mr. Marchant’s courtesy and patience with the Council, and of the great amount of information lie had given them.

Mr. Marchant thanked the Councillors for their kind remarks, and said that he was only too pleased to be able to give them any information.

m ~£- Cr Harris: All tho water slop?, etr tarn the house would he taken m th To'Cr S Coilins: It they mod a lot of antiseptics iu tlio towcra*® they wowd destroy the micro organistn.s “CSNuvorTHo tely certain that with tho septic tank s>sSm there would he. nothing, m Ho slightest degree obnoxious on .the b Ho had seen several places, and tnerc 1 nt even discoloration m the ivas not , u; e wero somc houses in KaUi’ and AVhataupoko which might %r<S E cS°; Ho .lid not think thev would ever have to H-un tl tanks out under any circumstances. ,r & Kirk : ‘“Wages should not exceed £250 per year, and there was nttlc “'Tnir’o r‘ot’¥... <">>'. who °r/ 0 Vct'tie • He would suggest that the, should tel \vhatnpoko?andKaiti. Workihson these linos they oug t to P CO ngested XSZXJStM 'fiU* at t" Cr. Kirk, Mr, Mediant out tl,o schomo. T)w scptic t„„k sysio estimate a, itood nun, to . >"J^ 0 ’ W „ E when ainkins. , 1,1 , r,'':V«,oVXr%S init would. rail through the pip<;s- ,^> rc {&“ JlUfS'lS, the puiupiust fstations. that he was very ,°f’ / ’ Air Marchant s propleased to lun t i u , feeling nonneed waitilvinsl out. The iSu , SSS had object.. d to t\ 0 Thu Mavor said it uajihl Scmo was .V 1«% one .1