Statement of evidence of Jonathan Williamson (hydrogeology) for the New Zealand Transport Agency

Transcription

1 Before a Board of Inquiry under: the Resource Management Act 1991 in the matter of: applicant: Notices of requirement for designation and resource consent applications by the New Zealand Transport Agency for the Ara T hono P hoi to Wellsford Road of National Significance P hoi to Warkworth Section New Zealand Transport Agency Requiring Authority Statement of evidence of Jonathan Williamson (hydrogeology) for the New Zealand Transport Agency Dated: 23 January 2014 Paula Brosnahan (pbrosnahan@furthernorth.co.nz) Luke Hinchey (lhinchey@furthernorth.co.nz)

2 TABLE OF CONTENTS STATEMENT OF EVIDENCE OF JONATHAN WILLIAMSON FOR THE NEW ZEALAND TRANSPORT AGENCY... 1 QUALIFICATIONS AND EXPERTISE... 1 MY ROLE... 2 EXISTING HYDROGEOLOGICAL ENVIRONMENT... 2 METHODOLOGY OF THE ASSESSMENT... 3 ASSESSMENT OF HYDROGEOLOGICAL EFFECTS... 3 RESPONSE TO SUBMISSIONS... 5 Impact on bore water... 5 Groundwater modelling predictions... 6 Drying of wetlands... 6 Artesian bore... 7 RESPONSE TO ITEMS IDENTIFIED BY THE BOARD... 7 CONCLUSIONS... 8

3 1 STATEMENT OF EVIDENCE OF JONATHAN WILLIAMSON FOR THE NEW ZEALAND TRANSPORT AGENCY QUALIFICATIONS AND EXPERTISE 1 My full name is Jonathan Lindsay Williamson. 2 I have a Bachelor of Science (BSc) in Earth Science (1993), and a Master of Science and Technology first class honours (MSc(Tech)[I]) (1995) in Hydrology and Geology from the University of Waikato. I am also a Certified Resource Management Act Decision-Maker (valid until June 2015). 3 I have 18 years specialist technical expertise in hydrology, hydrogeology and irrigation engineering covering a wide spectrum including data collection, manipulation and analysis; testing and investigations; modelling; engineering design; construction contract management; report writing; community and stakeholder consultation; resource consent hearings; and technical working panels. Previous projects I have been involved in include: 3.1 The Statement of Interest and Ability phase and Interim Project Alliance Agreement phase of the Waterview Connection Tunnel and Great North Road Interchange project. My role was lead hydrogeologist responsible for a team of four hydrogeologists assessing the potential impacts of the tunnel on local groundwater conditions for ground settlement assessment (by others) and impacts on stream base flows. 3.2 The East Taupo Arterial project, where I provided catchment hydrology and stormwater design advice to Fulton Hogan Limited. My role in that project involved a technical review of the catchment hydrology simulations and applications for culvert design. 3.3 Contact Energy Limited s proposed Tauhara II Geothermal Power Development. In this project I provided evidence relating to groundwater effects from the operation of the development. 3.4 I reviewed and provided evidence at the joint Auckland Regional Council (ARC) / Manukau City Council Hearing on the groundwater and settlement predictions for the proposed Ihumatao Quarry expansion, which adjoins Auckland International Airport s proposed northern runway. 4 In a broader sense, I have undertaken numerous groundwater resource sustainability studies for many regional councils nationally. 5 My evidence is given in support of the New Zealand Transport Agency s (Transport Agency s) Notices of Requirement and applications for resource consent lodged with the Environmental Protection Authority for the

4 2 construction, operation and maintenance of the Ara T hono P hoi to Wellsford Road of National Significance P hoi to Warkworth Section (the Project). 6 I am familiar with the area that the Project covers. I am the author of the Hydrogeology Assessment Report that informed the Assessment of Environmental Effects (AEE) lodged in support of the Project. 7 I have read the Code of Conduct for Expert Witnesses as contained in the Environment Court s Consolidated Practice Note (2011), and I agree to comply with it as if this Inquiry were before the Environment Court. My qualifications are set out above. I confirm that the issues addressed in this brief of evidence are within my area of expertise. I have not omitted to consider material facts known to me that might alter or detract from the opinions expressed. MY ROLE 8 I was the lead author of the Hydrogeology Assessment Report and the Groundwater Modelling Report, with much of the analysis and report drafting undertaken by Gillian Holmes, Tim Baker and Brendan Feather under my supervision. I visited the Project area during the investigation phase to familiarise myself with the lay of the land and understand the relationship between potential hydrogeological features, and the sites identified and available for drilling investigations. During the investigations phase I provided advice on piezometer construction details and hydraulic test setup procedures. EXISTING HYDROGEOLOGICAL ENVIRONMENT 9 Several contrasting hydrogeological regimes are found within the Project area. The regimes are strongly influenced by the underlying geological units. 10 The majority of the Project area is characterised by the steeply and incised elevated terrain of Pakiri Formation (part of the Waitemata Group), which comprises interbedded sandstone and mudstones. 1 Groundwater in the Pakiri Formation is strongly influenced by the incised valleys, with groundwater typically being elevated along ridgelines and depressed along valley sides and floors. Perched and leaky water tables may be present at higher elevations than the local water table in discrete localities, reflecting the interbedded nature of the sandstone/siltstone formation, with the lower permeability siltstones typically providing the basal layer for perching Hydrogeology Assessment Report, Section 3.1 (page 8). Hydrogeology Assessment Report, Section 3.3 (page 10).

5 3 11 Northern Allochthon is found within the Project area, which comprises highly sheared mudstones, siltstones, sandstones and limestones. Permeability of the Northern Allochthon is typically very low, and groundwater is typically observed as a line of seepage or minor springs at geological boundaries between units within the formation. 12 The majority of valleys in the Project area have been infilled with deep, soft estuarine and alluvial sediments comprising clay, silt, peat and fine sand. METHODOLOGY OF THE ASSESSMENT 13 The methodology that was undertaken for my assessment is summarised as follows: Desktop study to determine existing groundwater levels, current groundwater use and abstraction and groundwater/surface water interfaces; 13.2 Core drilling and geological logging; 13.3 Piezometer installation; 13.4 Groundwater level recording; 13.5 Hydraulic testing in piezometers to determine aquifer hydraulic conductivity; 13.6 Groundwater model development and calibration; and 13.7 Predictive simulations using the groundwater model to assess potential groundwater impacts. ASSESSMENT OF HYDROGEOLOGICAL EFFECTS 14 The potential impact of the Project on groundwater may arise from deep excavations below the groundwater table, which can impact on the natural groundwater regime in the following ways: 14.1 Drawdown - Groundwater drawdown 4 and associated ground settlement that may have the potential to impact on existing structures and services; 3 4 Section 2 of the Hydrogeology Assessment Report provides more detailed information on the study methodology. Groundwater drawdown is the reduction in groundwater level in shallow unconfined aquifers, or the reduction in groundwater pressures in deeper aquifers (which are usually semiconfined or confined by overlying strata).

6 Surface water resources - Reduction in groundwater levels that may affect stream baseflow regimes, and alter present inflows and outflows from springs, streams, rivers, ponds and wetlands; 14.3 Groundwater quantity and quality - Reduction in groundwater quantity (yield) and quality at existing abstraction bores through the alteration of groundwater flow patterns; and 14.4 Migration of existing contaminants - Potential to spread contaminants residing in areas of past landfilling and/or contaminated sites through groundwater drawdown in these areas. 15 My assessment of the Project s construction and operational effects on groundwater concluded that: 15.1 Drawdown resulting from Project construction will be confined to a narrow 700m corridor parallel to the indicative alignment 5, with the majority of drawdown occurring within 160m of the corridor; There are only two private bores indicated in the Auckland Council database for the taking and use of groundwater within 2km of the indicative alignment. The maximum drawdown impact simulated in these bores is only 0.5m. Both of these bores are over 150m deep and I therefore consider 0.5m of impact to be less than minor; The reduction in stream baseflows due to predicted groundwater diversions at the Project s proposed cuts range from approximately L/s (0.02m 3 /day) to L/s (9.8m 3 /day). This reduction represents up to 2.6% of the baseflow in the larger streams and up to 46% of baseflow in the smaller streams. However, the smaller streams assessed are so small that they are more likely intermittent wet areas from wet season groundwater seeps rather than continuously flowing streams ; I consider the Project s potential effects on groundwater quality to be less than minor. My view is primarily based on the very slow groundwater infiltration and flow rates due to the low permeability of the Waitemata Group materials, and the very small volumes of water that will be diverted at the cuts; 9 and A preliminary design alignment assessed by technical experts that may be refined on detailed design within the designation boundary. Hydrogeology Assessment Report, Section 4.2 (page 28). Hydrogeology Assessment Report, Section 4.3 (page 30). Hydrogeology Assessment Report, Section 4.4 (page 31). Hydrogeology Assessment Report, Section 4.5 (page 32).

7 I consider the Project s construction and operational impacts on groundwater to be minor because of the surface water containment system 10 developed for the Project, 11 the underlying groundwater system being so impermeable, and the fact that any diverted groundwater will be redirected in natural watercourses through the surface water drainage system Based on my assessment of effects, I considered that no mitigation or monitoring was necessary for groundwater impacts because of the very low likelihood of any significant impacts, the fact that there are no affected third parties, and because any diversions are routed through the Project s stormwater system or back into natural watercourses. 13 RESPONSE TO SUBMISSIONS 17 I have read the submissions lodged on the Project that raise concerns about groundwater and I address these below. Impact on bore water 18 Two individuals and one group of submitters raised concerns about the impact of groundwater level reductions on water level and quality in their bores With respect to the Slowater Lane and Puhoi Close Residents Association bore users, 15 the key points to note are: 19.1 I considered the bore discussed in the Association s submission as part of my analysis of groundwater drawdown. The groundwater model encompasses the area of the bore and extends a few kilometres to the west My analysis indicated only a minor groundwater impact on the location of the Slowater Lane bore. Drawing ES-102 shows the modelled groundwater drawdowns derived from the proposed Project cuts to the northeast of Puhoi. Drawdown is indicated at less than 0.1m at this location. I consider such a drawdown to be negligible and consider it would have no material impact on operation (level or quality) of the water supply bore, particularly A system of stormwater diversion, collection and treatment devices. As outlined in the Construction Water Assessment Report, Section 4.4 and Section 4.7 (pages 40 and 47). Hydrogeology Assessment Report, Section 4.6 and Section 4.7 (page 34). Hydrogeology Assessment Report, Section 4.8 (page 34). Donnellan (104542); Pickering (105561); and Slowater Lane and Puhoi Close Residents Association (105741). Pickering (105561); and Slowater Lane and Puhoi Close Residents Association (105741).

8 6 given the depth (305m) and available drawdown (298m) in the bore Mr Donnellan s groundwater concerns related to bore water: We also have a bore and take bore (and roof) water routinely for drinking water and are concerned at air and water and ground-water pollution from the proposed SH1MW (page 3) I understand (as I have not inspected the site and it is not consented) that Mr Donnellan s bore is located along his property boundary adjacent to Woodcocks Road. In this location, the Project will have no impact on a groundwater supply bore because there are no road cuts in this area, hence no mechanism to alter groundwater pressure profile or flow dynamics at the depth of the bore (130 m). Groundwater modelling predictions 22 Fernbrook Farm (106186) raised concern as to how the groundwater modelling used to arrive at the estimated effects on the environment will be measured during and post construction, and how the Project construction methodology will be amended if these estimates are exceeded. 23 I do not consider measuring the groundwater effects during construction to be necessary. The simulated effects for groundwater are negligible, even when considering the sensitivity of model hydraulic conductivity within a reasonable range. The likelihood of levels exceeding the range estimated is low and the consequence should levels exceed those predictions is still, in my opinion, insignificant because of the very small level of change possible. Drying of wetlands 24 Two submitters have raised concerns regarding drying of wetlands due to changes in aquifer conditions As discussed in Section 4 of my Report, 19 the reduction in stream baseflows due to predicted groundwater diversions at the highway s cuts range from approximately L/s to L/s. This reduction is a very low flow (from a trickle to a garden hose at half pressure) and unlikely to be detectable over and above the influence surface runoff generated flows Calculated from data contained within the Auckland Council bore database. Donnellan (104542), Section 4.2. Thaller (105691); Lee Family Trust (105559). Page 27.

9 7 26 Accordingly, I do not expect any impact on wetlands. Any diverted groundwater will return to the natural watercourse downstream of the new road. Artesian bore 27 Mr Thaller has raised concerns about an artesian bore on his property Loss of artesian pressures (and impact on wetlands) is not possible in the area of Mr Thaller s property as there are no road cuts proposed (only embankment fills) in this area and hence no possibility for groundwater drawdown or depressurisation to occur. Drawing ES-115 from my Hydrogeology Assessment Report shows the proposed works in this area and indicates no drawdown anywhere in the vicinity of Mr Thaller s farm. RESPONSE TO ITEMS IDENTIFIED BY THE BOARD 29 The following comments respond to Items 71 to 76 of the Board s directions from the Summary of the unresolved items identified by the EPA s contracted technical experts and the Auckland Council. 30 In Item 71, the Board asks for identification of all permitted groundwater users and further consultation. In my view, consultation has been undertaken with affected landowners and my Report does not identify any significant modification to groundwater as a result of the Project. 31 In Item 72, the Board notes that Auckland Council record permitted activity surface and groundwater takes in the Council s consent database, but acknowledges that this record is not complete because there is no compulsion for permitted activity users to supply information about their takes. The Transport Agency has undertaken extensive consultation with affected and adjacent landowners. Other than the submitters identified above, no issues related to groundwater takes have been raised. Furthermore, because the impacts on groundwater as a result of the Project works are minor, I do not consider additional surveying or consultation to establish whether other permitted activity users exist is necessary. 32 The Board asks (in Item 73) for legal descriptions of where short-and long-term groundwater diversion is to take place. Legal descriptions cannot be provided at this stage, as detailed design for the Project has not yet been completed. 33 In Item 74, the Board asks for a monitoring and compliance methodology for monitoring groundwater drawdown and potential ground settlement should high groundwater flows be intersected in the cuts. As set out in my Report, it is my view that monitoring is not required for this Project because there will be no discernable effects on groundwater. 20 Thaller (105691).

10 8 34 The Board requests (in Item 75) more detail on groundwater piezometric surface and flow directions in the vicinity of the groundwater diversions. My assessment has not identified any potential issues related to groundwater diversions, and I do not consider further information is required. 35 In Item 76, the Board requests sensitivity analysis on groundwater drawdowns and on potential settlement affects. Again, it is my view that no further analysis is required based on the conclusions in my Report. CONCLUSIONS 36 The hydrogeological regime of the Project area comprises very low permeability rocks with no appreciable shallow aquifers within the depth range of Project excavations (60m). Most bores in the area are greater than 150m in depth and provide only very small yields (< 1 L/s). 37 The most significant hydrogeological potential impact from the Project is the reduction in stream baseflows or groundwater flows to wetland areas. However, because of the very low permeability rocks encountered in the Project area, groundwater flow rates are very low and any water intersected will be rediverted into the same watercourse through the Project s surface water containment system. I consider impacts to these watercourses, which would only be experienced during drought anyway, to be less than minor. 38 I do not expect impacts on existing groundwater users, groundwater quality impacts or construction and operational impacts due to the following reasons: 38.1 Very low permeability and hence flow rates of the rocks; and 38.2 The surface water containment system will deal with any groundwater diversions and discharge them back into natural watercourses. 39 Based on the data available to me from my hydrogeological investigation and modelling analysis, the scale of effects from any changes to the groundwater regime through the development of the Project will be less than minor. Information provided by submitters has not changed this opinion. Jon Williamson 23 January 2014