Test Valley Borough Council – Northern Area Planning Committee – 10 July 2014 ITEM 13 APPLICATION NO. 14/00300/FULLN APPLICATION TYPE FULL APPLICATION - NORTH REGISTERED 10.02.2014 APPLICANT Lord Simon Tanlaw SITE Upper Mill House , Monxton, Andover, SP11 8AP, ABBOTTS ANN PROPOSAL The construction of a replacement weir AMENDMENTS Additional information received: 06.03.2014 07.03.2014 21.03.2014 09.05.2014 CASE OFFICER Miss Emma Jones Background paper (Local Government Act 1972 Section 100D) 1.0 INTRODUCTION 1.1 The application is referred to the Northern Area Planning Committee at the request of a Local Ward Member due to the widespread interest in this matter. 2.0 SITE LOCATION AND DESCRIPTION 2.1 Upper Mill House is situated to the east of the village of Monxton. The existing weir to be replaced is situated to the west of the existing dwelling and its residential curtilage. The site of the proposed replacement weir lies just outside the boundary of the Amport and Monxton Conservation Area. 3.0 PROPOSAL 3.1 The construction of a replacement weir. 3.2 The planning application proposes alterations to the existing weir that was constructed at the point where the Pillhill Brook branches away from the mill stream. The information supporting this planning application advises that prioritising flow into a single channel, the Mill Leat (watercourse running directly to the south of the dwelling at Upper Mill House), during low flows will make the Pilhill Brook (overflow carrier) more resilient in flood flows. The existing weir is notched to allow a small flow through into the overflow channel. Inspection of the site on the 4th December 2013 found that this small flow caused the overflow channel to run for approximately 50m before running dry. The existing weir is constructed from reclaimed flint, dressed stone, rubble, concrete bags, butyl liner and topsoil. The replacement weir will be constructed from reclaimed materials from the existing weir, plus the structure is to be constructed with geotextile supported with chestnut posts with a finish of imported clean gravel. Test Valley Borough Council – Northern Area Planning Committee – 10 July 2014 The supporting information advises that the final height of the new weir will be constructed at a lower height than the existing line of bagwork which forms the existing weir crest. The existing bag height across the weir crest varies but the lowest point of the new weir will be approximately 50mm lower than the existing weir crest bag height and 100mm above the existing notched section. The new weir will pass more water in flood flows than the existing weir. 3.3 The additional information received on the 6, 7 and 21 March 2014 provides clarification on the heights of the proposed replacement weir in relation to the existing weir, and clarification on the sections provided on the originally submitted plans. The additional information from the applicants agent also sets out the following; “I have been monitoring the situation with regard to the river level in relation to the upstream properties. Even with the unprecedented rainfall we have had recently, there was no repeat of the flooding of the upstream fields of last spring, which was alleviated at the time in a matter of hours, by cutting weed in the Mill Race (even though the weir had already been lowered), thus showing that particular flooding was not due to the weir height at that time, but due to the weed growth which was partially blocking the Mill Race downstream. This was observed by the Environment Agency on site, and by upstream property owners. The conditions in the field upstream adjacent to the Southern Water pumping station seem to have nothing to do with the weir. Indeed, the river level adjacent to that field appears to be 450-600mm lower than the top of the river bank. This points to the flooding in that field being groundwater and sewage overflow. The new weir is designed so that the greater the volume of flooding, the greater amount of water will flow over the weir into the old river course, and will be substantially more than has been allowed into the old river course during the last few months of exceptionally high rainfall. The proposed weir height is to be a good 600mm lower than the original height of the weir as renovated by Mr Burgess. It has been agreed with the Environment Agency that the Mill Race should be the primary water carrier. The Mill Race is better able to hold a flow in drier conditions than the old river course, which owing to locally lowered groundwater levels, results in it drying up every summer through to October/November. Since I have been re-involved with the site, I have observed a healthy trout population in the Mill Race, and seen water vole on several occasions and kingfishers regularly fly its length and fish from specially constructed perches. There is no loss of wildlife and the river valley within the property is being managed to the complete satisfaction of the Environment Agency and Hampshire County Council Biodiversity officer. The whole essence of having a weir is to ensure that there is a flow of water from the western end to the eastern end of the Upper Mill House property. Test Valley Borough Council – Northern Area Planning Committee – 10 July 2014 There is not enough flow in the Pillhill Brook to service both the Mill Race and old water course together. There is also not enough volume of water during the summer and early winter periods to preserve a flow in the old river course alone, owing to depleted ground water conditions. The river bed dries up, as it is much wider and the ground in the bed becomes porous. Even with a reasonable flow over the weir in December the water sank into the ground after flowing approximately 200m, leaving the main straight section of the river completely dry. Surely it is better, as has been agreed by most of the official bodies, to keep the primary flow in the Mill Race with an improved structure which will enable more water to overspill the weir in times of flood than at present.” The relevant Parish Councils, neighbours and interested third parties were notified of these additional submissions on the 26 March 2014. 3.4 The additional information received on the 9 May 2014 provides a copy of the Flood Defence Consent which was issued by the Environment Agency on the 26 March 2014for the proposed development. 3.5 The application is accompanied by a Flood Risk Assessment (Cain Bio- Engineering Ltd January 2014) and a Method Statement (Cain Bio-Engineering January 2014). 4.0 HISTORY 4.1 13/01556/FULLN; Retrospective application - Construction of access bridge across the Pilhill Brook overflow carrier – Permission – 23.04.2014 5.0 CONSULTATIONS 5.1 Design and Conservation; No objection. 5.2 Ecology; No concerns over the potential for this proposal to adversely affect biodiversity. Until recently there was an existing weir in place, preventing water flow through the southern channel. This weir has been partially removed, allowing a proportion of water to flow along the southern arm of the stream before this re-joins some 360m to the east. The proposed weir appears to be designed to avoid any significant reduction in water flow along the northern branch of the watercourse during normal flow levels, but to enable water to divert along the line of the southern watercourse as water levels rise. The proposal will not affect any statutory or non-statutory site for nature conservation, nor is it likely to affect any legally protected or notable species. By enabling the southern channel to take water, this is likely to increase the diversity of habitats present over that which is present at the moment and may thus result in a net gain to biodiversity. 5.3 Hampshire County Council as Lead Local Flood Authority; Hampshire County Council has no objection to the application which is also supported by a Flood Defence Consent from the Environment Agency. Test Valley Borough Council – Northern Area Planning Committee – 10 July 2014 The Flood Risk Assessment indicates no increase of flood risk from the reconstruction of the weir. The new weir appears from the drawings submitted to allow a larger volume of water to pass over the weir at times of high flow in the river. Currently, Hampshire County Council have received reports of sewerage flooding upstream of the weir caused by high ground water inundating the pumping station but no reports this winter (November 2013 to March 2014) of fluvial flooding in the location upstream of the weir as far as the Andover Road bridge. In the interests of clarity, Hampshire County Council have received reports from a resident about fluvial flooding in the property upstream of the Andover Road bridge, the resident explained that this is caused by capacity of the Andover Road bridge. In the reports of flooding received by Hampshire County Council, over the last 18 months, no evidence has been received of internal property flooding. 5.4 Environment Agency; No comments to make regarding the planning application. 6.0 REPRESENTATIONS Expired 09.04.2014 6.1 Abbotts Ann Parish Council; No objection. 6.2 Monxton Parish Council; Monxton PC objects to the application unless certain conditions are imposed and enforced; 1. The U-shaped design is changed to V-shaped and the depth of the weir is constructed such that sufficient water is allowed to flow down the Pill Brook river in the winter months to prevent flooding when levels are high.