Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...
Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...
Retrospective Evaluation of Cured-in-Place Pipe - (NEPIS)(EPA ...
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water <strong>in</strong>dustry conferences. A senior STW manager, George Hedley, chaired the Department <strong>of</strong> the<br />
Environment’s Committee responsible for materials used <strong>in</strong> sewer and water ma<strong>in</strong>s networks. In 1980, it<br />
conducted a survey <strong>of</strong> sewers <strong>in</strong> 240 locations distributed across its territory from Shrewsbury <strong>in</strong> the west<br />
to Scunthorpe <strong>in</strong> the east and Cheltenham <strong>in</strong> the south. The result<strong>in</strong>g analysis relat<strong>in</strong>g age, size,<br />
construction material, depth and condition led to a comprehensive estimate <strong>of</strong> rehabilitation needs and<br />
costs which had an <strong>in</strong>fluence on the National Water Council and the Department <strong>of</strong> the Environment and<br />
the direction <strong>of</strong> its Water Research Centre <strong>in</strong> develop<strong>in</strong>g sewer rehabilitation strategies.<br />
The reputation developed by STW <strong>in</strong> the 1980s for its expertise <strong>in</strong> the practice <strong>of</strong> rehabilitation was such<br />
that it became respected consultants provid<strong>in</strong>g eng<strong>in</strong>eers and managers to guide overseas water agencies<br />
such as the Delhi Jal Board and the Bombay Municipal Corporation <strong>in</strong> sewer clean<strong>in</strong>g and ma<strong>in</strong>tenance,<br />
condition assessment and rehabilitation. The expertise cont<strong>in</strong>ued after privatization when STW<br />
purchased Haswell and Partners, a specialist consultant firm, and transfered operations eng<strong>in</strong>eers and<br />
managers <strong>in</strong>to the consultancy firm dur<strong>in</strong>g a period <strong>of</strong> reorganization. Haswell Consult<strong>in</strong>g Eng<strong>in</strong>eers<br />
ceased to trade <strong>in</strong> 2005 and residual staff were transfered back to Severn Trent, some f<strong>in</strong>d<strong>in</strong>g<br />
opportunities <strong>in</strong> Severn Trent Services, Severn Trent Water’s sister company.<br />
STW has experienced significant difficulties with flood<strong>in</strong>g. In 2007, flood<strong>in</strong>g cost the company U.S. $50<br />
million and affected more than 140,000 customers <strong>in</strong> and around the Gloucestershire city <strong>of</strong> Tewkesbury.<br />
It is <strong>in</strong>volved <strong>in</strong> extensive network monitor<strong>in</strong>g and dra<strong>in</strong>age studies, which will have future network<br />
ma<strong>in</strong>tenance implications.<br />
In the period s<strong>in</strong>ce privatization, AMP1 through AMP4 (1991-2010), Severn Trent undertook a<br />
significant program <strong>of</strong> sewer renewal (Table C-4). Accord<strong>in</strong>g to OFWAT statistics, it renovated 630 km<br />
(391 mi) <strong>of</strong> critical sewer and replaced 414 km (247 mi). OFWAT commenced report<strong>in</strong>g volumes <strong>of</strong><br />
renovation work on non-critical sewers <strong>in</strong> 2001. Recorded volumes <strong>of</strong> non-critical sewer work with<strong>in</strong><br />
STW are surpris<strong>in</strong>gly low, a little over 25 km (16 mi). Follow-up discussions with contractors suggest<br />
that more work has been undertaken <strong>in</strong> this area and so, as discussed <strong>in</strong> the Thames Water report, the<br />
under and over report<strong>in</strong>g to OFWAT may be mislead<strong>in</strong>g and it may be reasonable to suppose that the<br />
overall volumes <strong>of</strong> non-critical sewers l<strong>in</strong>ed may be similar to the volumes <strong>of</strong> critical sewers l<strong>in</strong>ed.<br />
Conflict<strong>in</strong>g reports were received from STW about its rehabiliation and replacment volumes <strong>in</strong> AMP4,<br />
which perhaps confirms the difficulties <strong>of</strong> classification and <strong>in</strong>terpretation described earlier. Accord<strong>in</strong>g to<br />
STW, <strong>in</strong> AMP4 it rehabilitated 31 km (19.3 mi) <strong>of</strong> critical sewer and 10 km (6.2 mi) <strong>of</strong> non-critical sewer;<br />
it replaced 25 km (15.5 mi) <strong>of</strong> critical sewer and 97 km (60.3 mi) <strong>of</strong> non-critical sewer.<br />
Table C-4. STW and U.K. Sewer Renovation Rates for 1990 to 2010<br />
Asset<br />
Management<br />
Period<br />
Severn Trent Water All U.K. Water Companies<br />
Critical<br />
Sewers<br />
Renovated<br />
km<br />
Non-Critical<br />
Sewers<br />
Renovated<br />
C-7<br />
Critical<br />
Sewers<br />
Renovated<br />
km<br />
Non-Critical<br />
Sewers<br />
Renovated<br />
Water<br />
Ma<strong>in</strong>s<br />
Rel<strong>in</strong>ed<br />
km<br />
AMP1 90-95 79 NA 509 NA 10,639<br />
AMP2 95-00 221 NA 711 NA 9,670<br />
AMP3 00-05 63 13 505.4 350.5 9,255<br />
AMP4 05-10 271 11 1162.5 1356.7 6,238<br />
Sub Total 634 >24 2887.9 >1707.2 35,802<br />
Proposed AMP5 10-05 96.1 161 769.4 3358.9 1,126