Discussion Forum
Garden Street (3a)

From Richard Hull
Sunday, 13 July 2008

Objection to reconstruction of retailing wall

  1. Given the scale of the proposed reconstruction at least two further structural surveys should be commissioned through an impartial and transparent tendering process.
  2. The structural report commissioned by the applicants does not make sufficient exploration of water springs and water seepage at the site. In particular, it should be noted that all surveys were conducted during times of mild weather, and not during the several days following heavy rain when the strongest water presence would be expected.
  3. The structural report does not constitute a sufficient cost-benefit comparison of (a) the proposed major reonstruction, and (b) ongoing remedial repairs and maintenance.
  4. Further structural surveys addressing points (2) and (3) above should be commissioned by the Council through an impartial and transparent tendering process.

Objection to the Development application

1. The Flood Risk Assessment is insufficient with respect to the analysis of the risk from Groundwater Flooding and Springflow. This is especially incompetent as the structural survey of the physical integrity of the existing retaining wall explicitly cites water-damage as a cause of deterioration of the existing wall.

1(a)  The data informing the risk assessment is the survey conducted by Strata in March 2007. This consisted of only five bore-holes and six trial pits, and a "site walk-over".

1(b)  There is no copy of the full report from Strata, only the information allegedly derived from it.

1(c)  There is no specific date for the Strata survey - merely "March 2007". There is also no report of the time elapsed between drilling the bore-holes and test-pits, and the measurement of water depth in the holes.

1(d) There is no description of the weather conditions prior to and during the Strata survey.

1(e) It is possible that the Strata survey was conducted at the same time as the intrusive structural investigation of the retaining wall, conducted March 12th 2007 by Barry Green Associates. The report on that survey describes the weather conditions as 'Mild with occasional showers'. It is also possible and likely that the bore-holes and test-pits were drilled and mesaured on this single same day.

1(f) The summarised data from the Strata survey on the depth of water encountered in the bore-holes and test-pits merely makes assumptions about the source of the water being below the capping clay stratum. No testing of this hypothesis was conducted.

1(g) In other words, the applicants do not appear to have a conducted the required rigorous survey of the risks from ground water and springflow.

1(g)(i) Such a rigorous survey would have been conducted during, and for fourteen days following a sustained period of heavy rain, as that is precisely the time of greatest risk from groundwater and springflow.

1(g)(ii) A rigorous survey would have conducted a more thorough search for springflow than the "site walk-over"; e.g. historical records dating before the construction of the retaining wall; hydrological surveys of the land above the site, etc, etc.

1(g)(iii) A rigorous survey would have drilled more bore-holes and test-pits, and would have left them in place for fourteen days, with water level measurements being taken at least twice a day.

1(g)(iv) A more rigorous survey would have tested the hypothesis that the source of current groundwater seepage into bore holes and test-pits is below the clay capping stratum.

1(h) In conclusion, the suggestion in the Flood Risk Assessment that there are only low risks from groundwater and springflow are unsubtantiated and irresponsible.

2. Block F is totally out of keeping with the current character of the site; and it will substantially detract from the visual attractiveness of the current heritage character of the site

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