Agenda item

Erection of a detached 6 bedroom dwelling with habitable roof-space and basement with associated parking and amenity space including the demolition of the existing detached house, (Resubmission).

In introducing the report, officers advised that the main concern about the application was related to the impact of the scheme on surface water and ground water levels, as a result of the proposal to lower the basement floor slab level by 400mm down into the ground. It was noted that the applicant had submitted a series of documents and investigations undertaken and the information was uploaded on the Council's website on 14 February 2014 for the public. In addition, a 14 days re-consultation was carried out and no comments were received. Officers did not consider that the proposal resulted in any problems relating to surface water.

In response to a query raised about the expiry date of the re-consultation; officers advised that it ended on 18 February 2014.

It was noted in the officer's report that investigation had been undertaken in April 2012 and in view of the severe weather conditions that had recently been experienced, Members wanted to know whether a more recent investigation had been done.

In accordance with the Council’s constitution, a representative of the petitioners and the agent were invited to address the meeting. The petition representative raised the following points in objection to the proposal:

·         Before the widespread buildings of vast basements in Hillingdon, houses generally had footings of about 1 or 2 metres depth, which largely did not cause concern to neighbouring properties

·         Large basement buildings were now being approved consistently by Committee and the Building Control Department was now being expected to deal with issues relating to ground level building, as they had done in the past without seeing the impact on or getting input from the neighbours

·         Large residential basement buildings in particular were of huge importance to neighbours for reasons associated with drainage, construction and damage

·          The Committee must take immediate steps to change this, where large residential basement were concerned and not assume that the public would not understand the detail

·         Asked the Committee to allow public input into the detailed considerations of the this planning application before and after approval, as these were crucial matters, which would affect people's lives and properties and should not be kept secret to the Building Control Department

·         The basements were built to last for over 100 years, so if it took a few more weeks to allow for public scrutiny and representation, then so be it

·         Suggested that the Council and the Committee had the power to allow this but questioned whether they would care to

·         Questioned why the proposed drawings, which showed a clear two level basement drawings were not made publicly available to show what was on the lower of the two basement levels 

·         The size of the westerly face of the proposed basement was now 53% larger than that previously approved

·         The Ground Investigation Report referred to a single level basement to a depth of 3.5metres where as the proposed double basement was stated in the report as 7.6metres deep

·         Questioned whether this important report and its conclusions should now be re-evaluated

·         The data included in the report clearly showed that water was present below a depth of 3.7meteres when it was taken at the existing house from borehole (BH1)

·         The presence of water below this depth to 7.6metres was crucial to the likelihood of the basement to deflect water running down the Copse Wood slope towards neighbouring properties.

·         Urged the Committee to refuse the application on the basis that this huge double level basement on sub-soil and underground water movements in the area had not be properly evaluated

·         Suggested that the Committee should prevent the public from being excluded to detailed underground design considerations, normally reserved exclusively for Building Control. In particular, those that usually threatened to undermine neighbouring properties as it would give neighbours the opportunity to pick-up on any error that may have been overlooked by Building Control on work submitted by overworked "experts."

The agent/consultant raised the following points:

·         It had taken 18 months to develop this application with high financial commitment

·         It had been proposed to just tweak the scheme, however, this had warranted a new planning application

·         Two planning consent already existed, which were slightly different to the application that was currently in front of the Committee

·         The two consent already included double basements and the current application was just seeking to broaden the second consent basement by 400mm

·         Detailed ground water investigation report, flood risk report and structural report had been submitted and reviewed by officers and conditions had been recommended to sustain water impact

·         Site investigation was undertaken in April 2013 in 4 boreholes lasting 5 minutes at three depths and one of which was at 20m; all were dry

·         Water had been added to the borehole to aid drilling

·         The current proposal was asking to increase the depth of the basement by 400mm and to extend the basement to 7.6m deep

·         The proposed development was not in an area with a potential for ground water and it was found that water levels were at their highest in April 2013 when the investigations were carried out

·         Run-off water would be separated with current best practice and the risk of flooding had been identified in accordance with Sustainable Water Management.

In answer to a query raised about the ground water investigation report in 2013, which suggested that water existed in the BH; the agentresponded that at the stage they were involved, the building was just a single-storey and water had been added to the BH to see how much water would move within that BH and the investigations had been undertaken at 7.6m.

Officers confirmed that the BHs had been made in April 2013.

It was also confirmed that the change in the depth of the basement was 400mm and that the previously approved basement was greater than one-storey deep. Officers confirmed the dimensions of the upper basement level shown on the proposed drawing with those in the corresponding plan for the approved scheme. The dimensions being compared were pointed out on the PowerPoint.

The Chairman stated that this was a two-storey building where the applicant was seeking to increase the depth of the basement by 400mm.

The Legal Advisor advised that although Building Control fell outside the Planning Committee's jurisdiction, the scheme would have to be built according to approved plans and if the development was not built to the approved plans, it would be a matter for the Council's Planning Enforcement Team.

The Legal Advisor  added that it would be within the discretion of Members to resolve that certain conditions be brought back to Committee to be discharged but would need to be mindful of the practicalities of that change.

It was highlighted that the Council's Flood Water Management Officer was satisfied with the application, subject to the provision of Sustainable Water Management (Condition 9); acknowledged that the officer had also looked at ground investigation reports provided by experts, and even though Members had not seen these reports, members were satisfied that the Council's officers had. The Committee also accepted that issues regarding the basement had been fully covered by the Flood Water Management Officer and noted that investigation had been carried out during a normal winter.

Inexpressing sympathy for the petitioners, a Member added that there needed to be closer liaison between Building Regulations and Planning.

The recommendation for approval was moved, seconded and on being put to the vote was agreed.

Resolved – That the application be approved, subject to the conditions and informatives set out in the officer’s report.