Reconstruction of Pattissery Dam under Chengalar Scheme: Dam and Appurtenant works
In Pambar river basin, the Chengalar watershed is faced with severe drought situation during summer season when the crops grown in Kanthalloor and Keezhanthoor villages need water for irrigation. The soil is highly fertile for paddy, sugarcane, vegetables and hybrid varieties of fruits like orange, apple, strawberry etc. According to final verdict of Cauvery Water Disputes Tribunal, Kerala has been allocated a share of 3 TMC of water for Pambar sub basin. The share of Chengalar scheme is 0.80 TMC.
In order to cater to the irrigation needs, the possible solution in this catchment is to store water during the monsoon months and also to facilitate for storage of water from rainfall received during summer months by way of balancing reservoirs.
This concept has been conceived years back by way of constructing a small dam (Pattissery Dam) having a storage of 0.075 Mm3. The present system and existing canals (2.20 km length) are able to irrigate 36 Ha only. This reservoir capacity is insufficient to cater to the needs of the existing utilizable ayacut.
This proposed scheme aims at increasing the capacity of reservoir to 1.00 Mm3 and thereby irrigating an area of 515.20 Ha. In order to increase the storage capacity, additional water spread area was acquired on the upstream of the existing dam and is in the possession of Irrigation Department, requiring no forest clearance.
Vide Agt No 04/SEPCM/2014-2015 Dated 11-07-2014; the site has been handed over to the contractor, M/s Paulose George Construction Company for a time of completion of 24 months.
Earth work had been completed on 21.08.2015. Excavation of rock had been completed on 02.01.2016 and cleared for geological mapping. Geologists mapped the location 4.01.2016 to 6.01.2016. Assessment and recommendation of geologists.
1.Block III (Ch: 36 to 61.00 m) non over flow portion had been achieved foundation grade levels.
2.Block I and II (Ch: 61 to 91.00 m) indicated the presence of moderately to high weathered rock mass with thin bands of hornblende biotite gneiss. And they recommended to drill exploratory boreholes to ascertain the depth of hard rock having 6.00m continuous rock mass
Photograph showing nature of rock mass in initial foundation level Block 1 & 2 areas
3.On examination of additional exploratory boreholes, they recommended foundation grade level as 1553.795 in block I and 1554.295 in block II.
Profile of rock strata on the right bank
Excavation had been continued to the recommended foundation strata and geological mapping was done on 1.7.2016 and 19.01.2017 and approved foundation strata and recommended for concreting. Due to the nature of foundation strata, with the recommendation of GSI, the design has been revised by IDRB.
As per revised design revised A.S has been accorded vide A.S No. 58/2019/WRD dated 24.01.2019. Revised T.S has been accorded vide T.S No. 1/TS/CE, PII/2018-2019 dated 11.02.2019 of the Chief Engineer, Project II, Thiruvananthapuram. Supplemental Agreement number 4 to the Principle Agt No 04/SEPCM/2014-2015 Dated 11-07-2014, has been executed on 16-04-2019 with a time of completion of 24 months. Concreting of block I, II, III(B), IV is in progress. The work will be completed within 1 year with respect to the climatic conditions
1.Total quantity of concrete executed at site comes to 12500.00 m3.
- Physical Progress of work- 34.00 %
- Financial progress: Total value of work done – 13.60 crores out of 42.90 Crores (Including Pending Bills)
Expenditure updated in EMLI ( Effecting all deductions) – 12.882 Crores
2.Total Payment done to the contractor – 1.67 Crores