BOROUGH SEPTIC TANK.

Hauraki Plains Gazette, Volume XXXIX, Issue 5326, 14 September 1928, Page 3

BOROUGH SEPTIC TANK.

UNSATISFACTORY CONDITIONS. INVESTIGATIONS BY THE MAYOR. 1 Recently an inspection of the Pac- <• roa Borough septic tank disclosed the - fact that the installation was pot g‘vl. iijg satisfaction, and the Mayor (Mr ■- W. Marshall) set about investigating - the conditions. As a remit of his investigatiops the following report was presented by Mr. Marshall to the Borg ough Council meeting last night i “Aie a result of the unsatisfactory 3 conditions disclosed during the re,cent . flood. I have gone thoroughly into •| every phase of. the septic tank in|stal--8 lation. In this investigation I have 7 had the valuable assistance of Mr. RP. Worley, civil engineer., who made a special trip to Paeroa for this purpope. and- willingly gave any opinion or assistance asked for, “I have also made a trip to Auckl land to personally loc ; k into certain ‘ related matter?. The: tank has been e in for six years, and iti should be understood) that a large septic tan|k 5 must have regular, attention, with the removal of the sludge and mat 6 growths a?: required. The periods of 7 time for this work vary greatly, a.nd f apparently no definite rule can. be I laid down.; but it should have been done at leas.t epee a year. This has not been done, anjd the position has II been aggravated by a willow leg 5 blocking, the effluent s flap valve and " permitting river silt to- enter. Foi 11 the time being, however, thit; has 11 been remedied by completely cleanIng out the whole ta,nk at a coist of a approximately £lOO. 0 “My investigations have disclosed, among ether things, the following e fa.cts ’ s “ ‘That it is impossible to decludge ' the tank by gravity ; and! neither the e sludge: nor mat can be removed.- wi-th-n out dewatering. H “ ‘That the maximum storage capa- ' city of the tank with the preset sewerage inflow is 15 hours between: " lo,w wa.ter spring, tide leivel and the level of roof of tank, while th e high6 e?t computed flepd level is 9.20 ft above -the highest tank storage level. y The tank will, however, continue to e discharge; while .the head of water in[ n the sewer is abo.ve the head of water in the river; but -if the flood levetLof. e the river is very high, and -the period f ing which the discharge valves are 0 closed are protracted, the sewerage will be forced out of the lowest openings in the town sewerage system, - which, Cjf course, are the gully traps, e or cesspits in the low-lying properties, e An;d if these outlets are: nPit adequate, 1 manhole lids in the: Idw areasl will be a lifted. Both these effects were produced during the last flood, and lasted r for. two. days. e “ ‘That owing to ;a,n ofetructiqnj in the lowest flap valve o>n the effluent ■ pipe, in the river, river water and 1 silt have entered the tank. At pre:2 ent, if this happen# it cannot be - remedied ojr controlled during flood 3 time. A considerable quantity of - river water also' enters past the flap » valves, which are not watertight unj der. less than a 4ft head. “ ‘That the tank and tank manholes are submerged during high flcjod.’ Tq remedy these matters T Suggest: “ ‘That the tank now be used as .a, liquefaction, tank instead of a septic \ tank. That it be half -emptied monthly and cleaned but every three j months. “‘For keeping the sewage level down at flood periods, dewatering, , and removing sludge apd- mat, tha.j a j Maceman’s No. 4 vertical, centrifugal r pump be installed in -the fir.;t sludge - manhole, with a 12-in flap valve set ’ in wall of the tank fqr dewatering, (. an;d the sludge passed through existing sludge valve. That the whule be pumped to a height 21in, above highest computed flood level a,nd carried ■ in 6in spiral pipes to .the effluent j' manhole otn a grade of 1 in 100. The effluent manhole be altered and raised L to 12in above highest computed flood level, with a wooden penstock on the effluent pipe on the tapk side of the manhole. This wojuld enables the material pumped to be discharged through existing effluent pipe, and if ’ dhring flood time the river, water wa.s j found to be entering the tank, the closing of this penstock would, imme diately shut it off. That the highest i level flap valve on effluent pipe be r removed, and that the second brae be 1 clamped clcked. j j “ ‘The engine and pump to be hows- . ed in pumphouse having con.cr.ete , floor and corrugated ’»on wa-Us and roof. . “ ‘That a, low stop-bank be built round tank, with a small -flood-gate, to keep floqilwater off rcofi and manholes. “‘That a bar grid be: placed nea,r ; inlet end bf tank to patch: large solid 1 .articles, which sopietimes- enter and 1 which would damage pump impeller. ' ‘“That in cave of damage to pump 1 at a critical time, a spar e impeller and a. suitable han,d pump: should be ‘ kept in the pumphouse, s so that the, manhole: could be dewatered and a 1 new impeller fitted quick l ly.’ "Estimate: My approx imate estimate for the work, incltr ding necessary alterations to manholes, labour, and fixing plant— providijnjg it can be done. by| our own men, —an d a suitable second-hand engine; purchsised, fs £275. “Addeindum : The advisability of installing an electric moto r was; thor- ! oughly investigated; but. it necessitates a special high ten® icjti line and a transformer, at an additional cost of approximately £3oo'. The possibility of installing a pump to; deal with stormwater has al?;o ; been, frilly inquired into, beieaues the puiripho'use would suit both purposes, and. if the electric line and motor, were put .in, a. stormwater pump capable of throwr ing. 200 1 ,000 gallons Cjf water pier hour could be installed for an adilitionaJ £125.” In movinig the adoption eff the repbrt Cr. Silcepk congratulated the Mayor on its thoroughness. It was quite, evident that thie reiriort had taken up a lot of ,times and thought, and he considered it viery complete. Cr, Edwards- also extended: his! congratulations. He kniew ’that the Mayor had devoted a. tremendous

amount of .time on the work, and the report was very thorough. Cr. Flatt said that the report was a valuable especially so aS it dealt with the shifting of floodwater. In. thanking .the councillors for their remarks the Mavbr said bat the. sewerage of the. town wa>> a serious matter, especially if anything went wrong. He had given a good deal of time to t>he matter. He wihed to thank the councillors for -their whalehear.ed support a.nd co-operation. The report was adopted.