REFERENCE NO. : PIQ / 019 PUBLIC INQUIRY QUESTION RAISED BY: The Inspectors DATE: 20/02/17 RESPONDED BY: Ben Sibert DATE: 10/03/17 SUBJECT: Engineering Proof of Evidence Elucidations The attached document provides updates to provide responses to questions of elucidation raised by Mr Wadrup in correspondence dated 20 February 2017.
Engineering Proof of Evidence Elucidations Ben Sibert, BEng CEng FICE MIStructE MCIHT Welsh Government, Engineering Design Contents 1. Introduction... 2 2. Clarifications... 2 Page 1
1. Introduction 1.1 This document provides updates to provide responses to questions of elucidation raised by Mr Wadrup in correspondence dated 20 February 2017. 2. Clarifications 2.1 Evidence Section 4.38: Question: Given that the inquiry will need to justify the CPO of land necessary for the construction of the road, what justification is there in the provision of a dual carriageway rather than a single carriageway which would cater for the traffic demand? Am I correct in seeing this link road as one simply connecting to gyratory junctions rather than linking to unimpeded dual carriageways? 2.2 Evidence Section 4.38: Response: I have clarified in my evidence in section 4.38 that the reason for the choice of a dual two lane link road is on the basis of a) Strategic WG decision and b) to be broadly consistent with the advice of TD 9/93. At The Plan stage of the Scheme, the Glan Llyn link was established as a dual lane highway as shown in the Stage 2 Scheme Assessment Report Volume 2, Drawing No. M4OA-01-00-DR- C-XX-0164 Section C sheet 1 of 3. Matthew Jones has explained further the strategic reasons for the choice of a dual two lane carriageway. 2.3 Evidence Table 3: Question: a) Traffic forecasting report figure 10.6. It is not clear what the do-something flows are predicted to be on the length of the proposed motorway between junction 23 and 23 A. These are quoted at 15,400 and 20,300 vpd east and westbound, but that seems to be impossible looking at the adjacent figures. b) I cannot reconcile table 3 in the proof with figure 10.6 in the report. For example, J23-Glan Llyn is shown as 52,200 vpd in the proof but 54,000 in the report. Similarly, there is a slight discrepancy in the projected flow between the docks and J29. Clarity required please. c) It would be useful to have a comparable table setting out the 2022 flows for the do Page 2
minimum situation on the existing M4 West of J23A, that is traffic flow ranges compared to predicted traffic. 2.4 Evidence Table 3: Response to point a): The forecast Do Something opening year 2022 two way AADT on the proposed new motorway between junctions 23 and 23A is 54,000. The figures are quoted on Figure 10.6 of the Revised Traffic Forecast Report (Doc. 2.4.13) where the label is closer to the proposed new Glan Llyn Junction. The figures 15,400 E/B and 20,300 W/B (Totalling 35,700 two way AADT) are the Do Something flows for the proposed new dual two lane trunk road link connecting to the reclassified M4 to the west of the west bound free flow link from the M4. These figures therefore include traffic travelling from the M4 to the reclassified M4 as well as traffic travelling from the M48 to the reclassified M4. Refer to the extract from Figure 10.6 is included below for clarity as new Figure 14 to my evidence: Forecast 2022 Traffic on the Dual two lane Trunk Road Link Forecast 2022 Traffic on the M48 Forecast 2022 Traffic on the proposed new motorway between Glan Llyn Junction and J23 with the M48. Figure 14 Extract of Figure 10.6 from Revised Traffic Forecasting Report (Doc. 2.4.13) Page 3
2.5 Evidence Table 3: Response to point b): There is an error in the data in Table 3 which I have identified in my list of errata for my evidence (WG 1.5.4). The Core Scenario Forecast 2022 AADT figures between J23- Glan Llyn and Docks-J29 should be transposed. A corrected table is given below: Carriageway Standard Opening Year AADT flow ranges from TA 46/97 Core Scenario Forecast 2022 AADT All D3M Minimum Maximum J23 Glan Llyn Glan Llyn - Docks Docks J29 D2M up to 41,000 D3M 25,000 67,000 54,000 54,500 52,200 D4M 52,000 90,000 Revised Evidence Table 3 Proposed New Motorway Traffic Flow and Cross Section 2.6 Evidence Table 3: Response to point c): Additional Table 3a below provides summary of the Do-Minimum forecast traffic flows along the existing M4 north of Newport, with figures taken from Figure 10.6 of the December 2016 Revised Traffic Forecasting Report (Doc. 2.4.13), compared with the opening year AADT flow ranges from TA 46/97. Section of existing M4 Existing carriageway Opening Year AADT flow ranges from TA 46/97 2022 Do Minimum Forecast two way configuration 1 Minimum Maximum AADT. J29-J28 D3M 25,000 67,000 118,200 J28-J27 D3M 25,000 67,000 111,200 J27-J26 D3M 25,000 67,000 112,900 J26-J25a D2M up to 41,000 76,300 J25a-J25 D2M up to 41,000 98,500 J25-J24 D3M 25,000 67,000 106,900 J24-J23a D3M 25,000 67,000 89,200 Additional Evidence Table 3a Do Minimum Traffic Flow and Cross Section for the Existing M4 North of Newport. 2.7 Evidence para 4.72: Question: Do any of these reduced verge and central reservation widths compromise forward SSSD for the design 1 Note that the existing M4 cross sections do not match exactly the D3M and D2M requirements of TD 27/05 Figure 4-1a. Page 4
speed, for example southwest of Duffryn and east of the proposed viaduct? 2.8 Evidence para 4.72: Response: There are no stopping sight distance (SSD) departures from standards which are directly related to the reduction of the central reservation (CR) width nor the reduced carriageway width over the River Usk Crossing. There are seventeen permitted relaxations to SSD including those at Duffryn and east of the River Usk, plus two more on the River Usk Crossing and thirteen around Magor. There are a total of eight departures from standards relating to SSD, although none of these are attributable directly and only to the reduction in widths of CR and verge. These are located one at Castleton Interchange, one at Docksway Junction and six around Magor Junctions 23 and 23A. 2.9 Evidence para 4.110: Question: There is no mention of the effect that the viaduct would have on shipping bound for the quay sides along the River Usk upstream of the viaduct. As I understand it, this is theoretically is an area within the Port of Newport. 2.10 Evidence para 4.110: Response: As shown on Amendment Scheme Order Schedule 3 (Doc. 2.4.20) and Figure 6 in my evidence, the crossing of the River Usk would provide for 33.54m of clearance between Mean High Water Springs tide level of +6.49mAOD and the soffit of the bridge. The Statutory Harbour Authority for navigation on the River Usk is the Newport Harbour Commissioners who have objected to the Scheme (OBJ0071). Their objection does not relate to the bridge crossing of the River Usk. As described by Jonathan Vine (WG 1.22.1) in his evidence, the bridge over the River Usk would not impede shipping activities on the River Usk. The Navigational Risk Assessment Workshop discussed the risks of collision with the River Usk Crossing in the vicinity of the River Usk. The Newport Harbour Commissioners were represented at the Navigational Risk Assessment Workshop and, with agreement from the other parties present, deemed the navigational clearance provided over the River Usk to be more than adequate for the Page 5
vessels currently using the River Usk. Following the workshop the Navigation Risk Register (Doc. 2.4.14 10) was updated to record that the clearance provided in the bridge design was a Project Specific Mitigation Measure for the risk and hazard of vessel collision with the section of bridge over the River Usk during both the Construction and Operation phase. 2.11 Evidence para 4.136: Question: Presumably no borrow pit would be located within any SSSI area? 2.12 Evidence para 4.136: Response: Correct, there are no borrow pits within any SSSI area. 2.13 Evidence para 4.175: Question: As the proposed channels are to be lined, it follows that they cannot filter water vertically through the subsoil. That being the case how do the channels empty, other than through wind and evaporation forces? I can understand the attenuation principle but I need clarity on how the water (potentially polluted) would discharge into the adjacent areas. 2.14 Evidence para 4.175: Response: Along the embankments on the Gwent Levels, the water which would run off from the carriageway surface in to the grass lined channels would be conveyed by gravity by way of the longitudinal fall of the carriageway and embankment levels to intake chambers. From these intake chambers, the water would be piped in to the water treatment areas, commencing with the forebay pollution control lagoon, then in to the attenuation and permanent dilution lagoon and then in to the reed bed before discharge to the water course. Further details of this all of these features can be found in the Drainage Strategy Reports as Appendix 2.2 to the March 2016 ES (Doc. 2.3.2) and Appendix S2.2 to the September 2016 ES (Doc. 2.4.4.). I note in particular that Figure 2 to Appendix S2.2 shows a typical arrangement of the collection of water from the grass lined channels to the Water Treatment Area, showing the location of intake chambers. The intake chambers and direction of fall of the grass lined channels are also shown Page 6
on the Highway Drainage and Reen Mitigation Drawings, Figure R2.5 to the ES and its supplements, with the latest list of drawings given in Section 7 of my main evidence. 2.15 Evidence para 4.249: Question: Why would the Welsh Government need any easement rights to maintain the ditches which would lie inside the CPO. Should that be referring to ditches which lie outside the boundary? 2.16 Evidence para 4.249: Response: Across the Gwent Levels, the highway fenceline and land in the CPO have been drafted to minimise the encroachment of the highway on to the SSSI land. This would be achieved by placing the highway fenceline close to the earthworks embankment and leaving essential mitigation measures of field ditches and reens outside the highway fenceline. As shown in Figure 15 below, which is an extract of the Typical Cross Section drawing, the CPO includes for Title, Essential mitigation and S250 rights to provide for construction and maintenance of the field ditches. The arrangement for replacement reens is similar. Refer also to: a) The Design Options Report (Doc. 6.2.4); option H1; Appendix C, figure 2 b) The Alignment and Junctions Report (Doc. 6.2.1); Appendix A Cross Sections - Typical Sections Drawings M4CaN DJV-HML-ZG_GEN- DR-CH-0001. Page 7
New Evidence Figure 15 Extract from Typical Cross Sections Drawing from Alignment and Junctions Report (Doc. 6.2.1) 2.17 Evidence para 4.260: Question: Obviously, some clarity is required in respect of this paragraph, for example with whom would the agreement be made? 2.18 Evidence para 4.260: Response: In the majority of cases the modifications to the CPO relate to changes as a result of objections and through consultation with land owners and are contained within the draft CPO footprint. The intention of the Welsh Government is to seek the agreement of the relevant land interest to the modification and advise the Inspectors accordingly. If written agreement were not achieved, and if there is no additional land is involved, the Welsh Government would still submit the modification to the Public Local Inquiry and would propose to the Inspectors that the CPO be made including the modifications. 2.19 Evidence para 5.12: Question: With no agreement in place can it be assumed that the proposed modification would still be recommended? 2.20 Evidence para 5.12: Response: Yes, as described in response to question on section 4.260 above. Page 8