20th June 2005 - esperance.wa.gov.au

TECHNICAL REVIEW Hydrogeology - Esperance Waste Management Facility Environmental Referral

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Title: Independent Technical Review of Esperance Waste Management Facility Env Referral

For: Shire of Esperance Date: 17/5/2018 Ref: 2188 ESP Esperance Landfill PER ITR Rev 1

1 Background

The Shire of Esperance’s existing Wylie Bay domestic and commercial waste management

facility (WMF) is nearing capacity and a new WMF is now required to meet the Shire’s future

needs. After a selection process involving several potential WMF sites on Shire, Crown and

Freehold land, a preferred site has been selected on Lot 12 Kirwan Road, Merivale,

approximately 13 kilometres (km) from Esperance (the Site).

The Shire commissioned Talis Consultants (Talis) to prepare an Environmental Referral

document (the Referral) for the Environmental Protection Agency (EPA) so that the EPA

could set an appropriate level of formal assessment needed to approve the Project. As part

of the approval process, Talis presented Phase 1 of the Referral to the Department of Parks and Wildlife (DPaW) and the Department of Agriculture in June 2017, and DPaW responded

later that month (DPaW 2017).

The EPA advertised the Referral for public comment and on 9 January 2018, the EPA

compiled and summarised about 80 public submissions on the Referral into a letter to Talis

requesting further information. The Esperance Merivale Tip Action Group (EMTAG), is a

notably active local community group who are opposed the location of a WMF on the Site.

On the 22 January 2018 Talis Consultants responded to the EPA in a letter that addressed

each of the comments in turn (Talis 2018a).

The EPA has subsequently advised the Shire that, in light of the high number of public

submissions on the Referral, the Shire will be required to prepare the highest level of

assessment this project; being a Public Environmental Review (PER).

Following community concerns, specifically regarding the veracity of the hydrogeological

studies and interpretation, the Shire voted to engage and an Independent Technical Review

of the hydrogeology to help inform what knowledge gaps and further hydrogeological

investigations are needed in the PER to give the EPA sufficient information to assess the

approvability of the proposal in accordance with Ecologically Sustainable Development

principles.

The Shire has engaged Don Scott and Len Baddock of Pennington Scott (Groundwater

Consultants) to undertake the Review.

This contained document represents an Independent Technical Review of the

hydrogeology and hydrology factors relating to suitability of a Referral to construct a

waste management facility Lot 12 Kirwan Road, Merivale. This review has been

prepared by Pennington Scott, who confirm that they have no prior or ongoing

conflicts of interest in this Referral or with the Shire or Talis.


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1.2 Documents included in this Review

Pennington Scott were originally engaged by the Shire on 23 March 2018 to review the

following five (5) documents prepared by Talis. These documents collectively constitute the

Referral:

1. TALIS CONSULTANTS 2017b. Esperance Waste Management Facility – EPA

Referral – Phase 1 Hydrogeological Investigation. CMS17230 – dated Jun 2017

2. TALIS CONSULTANTS 2017c. Esperance Waste Management Facility – EPA

Referral – Phase 1 Hydrogeological Risk Assessment. 19.1c – dated Jun 2017

3. TALIS CONSULTANTS 2017d. Esperance Waste Management Facility – EPA

Referral – Supporting Document – Phase 2. CMS17230 – dated 20 Oct 2017

4. TALIS CONSULTANTS 2018a. Esperance Waste Management Facility – EPA

Referral – Phase 2 Hydrogeological Risk Assessment. V1a – dated Mar 2018

5. TALIS CONSULTANTS 2018b. Esperance Waste Management Facility – Response

to EPA Request for further information TW17082 – dated 22 Jan 2018

As part of the review process agreed between the Shire and Pennington Scott, on the 3rd and

4th of April 2018 Don Scott (Pennington Scott) presented the preliminary findings of the

review in a series of meetings to key stakeholders in Esperance ahead of finalising the

contained document. Key stakeholder meetings included the following:

The Esperance Shire Council;

Department of Agriculture;

Department of Parks and Wildlife (DPaW);

The Esperance Merivale Tip Action Group (EMTAG); and

Subsequently with Talis Consultants in Perth on 16th April 2018.

During the meeting and subsequent site visit with EMTAG, EMTAG presented Pennington

Scott with a further five (5) documents (listed below) to be considered. In consultation with

the Shire, the scope of this review was expanded to also consider, and where necessary

provide comment on, supplementary information contained in the following documents and

the EMTAG site visit:

6. CHALMER, P 2017. Siting of Landfills, Best Practice Environmental Management

EPA Victoria 2015

7. DEPARTMENT OF PARKS AND WILDLIFE 2017. Letter to Mathew Scott (Shire of

Esperance) Re. Review of Hydrogeological Report for the proposed waste

management facility – Lot 12 Kirwan Road – dated 30 June 2017;

8. EMTAG 2017a. Summary hydrogeological investigation comments Merivale Rubbish

Tip – dated 24 June 2017;

9. EMTAG 2017. Merivale Rubbish Tip, New Information;

10. SHIRE OF ESPERANCE 2017. Letter to Greg Mair (Dept of Parks and Wildlife) Re.

Review of Hydrogeological Report for the proposed waste management facility – Lot

12 Kirwan Road – dated July 2017.


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Pennington Scott delivered an electronic first draft of this Technical Review (Rev 0) to the

Shire on 27 April 2018. On May 1, Don Scott again visited Esperance to explain the findings

if the draft to key stakeholder groups, including the Shire and EMTAG in Esperance, and

later to Talis in Perth on May 4. Following those meetings, each of the stakeholders

provided a list of their proposed clarifications and corrections on the draft for Pennington

Scott to consider for inclusion in this final draft (Rev 1).

1.3 Terms of reference for this review

We understand that the Shire has considered several other potential WMF sites before

choosing Lot 12 Kirwan Road, Merivale as the preferred Site. We also understand that the

site selection process itself involved consideration of factors other than hydrogeology. The

terms of reference for this review, however, are limited to consideration of the

hydrogeological factors associated with establishing a WMF on the Site at Lot 12 Kirwan

Road. This review specifically excludes consideration of any site other than the Site on

Kirwan Road and excludes consideration of the Site selection process itself. Specifically, this

review is to consider:

the quality, accuracy and appropriateness of the existing geological and

hydrogeological investigations and risk assessment contained in the Referral;

Identify any knowledge gaps or inconsistencies that might lead to an ambiguous or

erroneous analysis of the perceived level of environmental risk presented in the

Referral;

recommend a hydrogeological investigation scope for the PER to address the

knowledge gaps and inconsistences sufficient to enable the EPA to weigh the

acceptability of the proposal.

Technically, the Referral is a contaminated site, and thus the review will consider the

adequacy of the hydrogeological factors within each of the following categories:

Source: whether the Referral has gathered sufficient knowledge of the nature of the

contamination source (i.e. the landfill leachate)?

Pathway: whether the Referral sufficiently understands the site hydrogeology to be

able confidently predict the fate of contaminant leaks or overflows to the

environment?

Receptor: whether the Referral has adequately identified the potential environmental

receptors and is able to confidently quantify and qualify the risks to those receptors?

Containment design: how robust is the landfill containment design to mitigate leakage

and overflows. What are the key design risks and limitations?

Monitoring plan: is the monitoring plan adequate to recognise foreseeable forms of

leakage or overflows of contaminants to the environment early enough to enact

contingency measures?

Contingency Plan: has the Referral adequately provisioned for an effective

contingency action plan to efficiently and effectively capture, contain and remediate

any contaminants before they reach sensitive receptors?


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Where appropriate, the investigations will be considered against the framework of the four

core Ecologically Sustainable Development principles contained within the Australian

Intergovernmental Agreement on the Environment (1992), which include:

• the precautionary principle;

• the principle of intergenerational equity;

• the principle of conservation of biological diversity (later enshrined in the Environment

Protection and Biodiversity Conservation Act); and

• the principle of improved evaluation, pricing and incentive mechanisms.


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2 Review Findings

2.1 Containment Design, Monitoring and Contingency Action Plan

This existence of relatively high permeability sediments beneath the Site is not best practice

for siting of a WMF according to Chalmer (2017). However, Figure 1 shows the potential

distribution of relatively high permeability spongolite and shore line facies sedimentary units

within a 30 km radius of Esperance may be quite extensive (after Johnson and Baddock,

1998). Furthermore, not all communities are fortunate enough to be in environments where

it’s possible to find a site for their WMF that meets all these best practice hydrogeological

criteria. For example, many coastal communities in Western Australia are underlain by

extensive karstic limestone, and yet they still manage to design, maintain and monitor WMFs

according to ESD principles. Nonetheless, where the hydrogeological conditions are not ideal

for a WMF, greater emphasis must be placed on the design and implementation of the

containment system, plus the adequacy of early detection monitoring systems and effective

contingency action measures if a leak should occur.

We are comfortable that the proposed triple layer liner design for the WMF at the Site has

proven to be effective in hydrogeological environments that would otherwise be less

favourable than the Site at Kirwan Road, Merivale. Nonetheless, albeit rare, an inescapable

fact is that liner failures do occur and when they occur can cause serious environmental

consequences and/or require costly mitigation measures.

When liner failures occur, its often due to poor construction technique or materials; or due to

post construction activity. Our concern in this case is to whether appropriate clay (free of

spongolite contamination) can be sourced locally for the clay layer (refer to geology section

below). We recommend that the PER include an inspection and testing program to ensure

that the source of clay is appropriate.

Landfill leachate represents a cocktail of different hazardous pollutants from hydrocarbons,

organics, coliforms, salinity, chemical compounds, heavy metals, trace elements, corrosive

wastes. Each of these products has different density, solubility, attenuation (mobility),

dispersion and absorption characteristics in the environment. The most mobile

contaminants, however, are likely be those that are miscible in water and these will travel

fastest and farthest in the environment. The direction and maximum rate that these

contaminants could potentially travel from the WMF over time should be predictable using a

distributed and properly calibrated mass transport numerical groundwater model based on

the movement of fresh water.

The Referral proposes a groundwater monitoring network and the key parameters to monitor.

It also includes leak detection system built into the liner itself. As part of the PER we would

expect baseline monitoring of key parameters be undertaken at quarterly intervals to define

background seasonal fluctuations upon which set trigger levels for a Contingency Action

Plan. The monitoring network presented in the Referral includes site bores, however the

baseline water quality monitoring should also include several off-site bore/spring locations

downgradient from the WMF.

Overall the engineering recommendations provided by Talis are sound, but additional

monitoring and leakage contingency need to be addressed if this site is chosen.


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Figure 1. Hydrogeology 30km around Esperance (adapted from Johnson and

Baddock 1998)

2.2 Geological setting

The Site is shown on Figure 2 and is located on the Lower Sandplain, underlain by the

Pallinup Siltstone beneath a cover of aeolian sand up to a few metres thick. Talis have

classed the Pallinup Siltstone as ‘Bedrock’, and in the Conclusions have stated that the

Pallinup Siltstone comprises hard rock geology, which is not appropriate for a sedimentary

formation that has not been extensively lithified. Pallinup Siltstone is up to about 80 m thick

based on geophysics in the Bandy – Coramup Creek area (Baddock, 1995b). It is underlain

by either granitic bedrock or the Werillup Formation which is probably restricted to broad

channels between basement ridges and consists of fine to coarse grained sand, lignite and

carbonaceous clay.

The Pallinup Siltstone comprises three facie units; Spongolite, Sand/Silt and Siltstone

(Johnson and Baddock, 1998). A Sand/Silt facies overlies or interfingers with the Spongolite

facies, and while present in the Bandy Creek – Coramup Creek area (Baddock, 1995b), it

does not extend to the Site, although it potentially could form a narrow apron of sand

surrounding the granitic ridge. The Spongolite facies is present at the Site, and comprises

clay with layers of hard, brown spongolite. Spongolite is a sedimentary rock composed of

SITE


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siliceous sponge spicules, which are silica needles forming a sponge skeleton, with common

coral fossils, and is notable for its low density. It formed in warm Eocene seas in locations

sheltered from wave action.

The Spongolite facies is around 30 m thick, with about 30 m present in bore EWD2-95

located about 21.5 km east of the Site (Baddock, 1995a) and it extends to 29 m depth at

CBC5 located 9 km to the N-NW (Baddock, 1995b). It extends to about 32 m depth in GW17

at the Site, with a transition into the underlying Siltstone facies. The thickness or portion of

spongolite making up the spongolite facies is likely to vary significantly over the area, with

thickest developments probably associated with shallow marine channels that were more

protected from waves by granitic islands that existed at the time of formation. Below the

Surficial Sand, about the upper 10 m of spongolite facies is highly weathered to a clayey fine

sand and silt or sandy clay. Talis failed to recognise the spongolite in their core logging

(except in GW18), where they appear to have described it variously as siltstone

conglomerate, silt/sandstone, sandstone or mudstone, and often seemed to confuse

spongolite (spicule sponge) as quartz pebbles.

Spongolite frequently contains open porosity (loosely compacted spicules), cavities (voids)

and connected preferred flow conduits (macro-pores) typically present below the highly

weathered zone. Talis have assumed that the voids are associated with dissolution of

carbonate rocks, and while this is true for many areas with carbonate rocks, it is not the case

in the Esperance region where spongelike is extensive. Carbonate does not tend to be

preserved within the Pallinup Siltstone in the Esperance area, although it is locally present in

the Werillup Formation. Voids and macro-pores in the spongolite have developed essentially

through the combined effects of enhanced horizontal flow along structural weaknesses

(faults, joints and bedding defects) by tunnelling erosion of loose spicules and development

of “sink holes” (vertical macro-pores) in the voids left behind by decaying tree roots.

Although silica minerals such as quartz are resistant to chemical dissolution, the fine silica

spicules of the sponges do show signs of dissolution and reprecipitation elsewhere as a

cherty silcrete nodules in the Spongolite. The combined effects of physical macro-pore

development and chemical dissolution of the Spongolite can create a landscape exhibiting

“karst-like” features such as sink holes and springs, albeit without the large dissolution caves

and collapse dolines structures that characterise karstic carbonate environments.


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Figure 2. Site and wetlands downgradient upon the coastal plain.

Cavities were common in cores drilled by the Talis at the Site. Voids are described in most

of the holes drilled, encountered at depths from 4.4 to 16.2 m with a thickness 0.18 to 1.37

m. It is possible that instead of voids, these zones may represent intervals of spongolite that

is honeycombed with abundant macro-pores. Many of the holes experienced loss of

circulation (drilling mud flows into the formation) when drilling at depths from 3.5 m to 13.5 m,

probably due to the presence of voids and macro-pores.

Talis state that the voids are discrete and disconnected, although they did note that several

of the holes drilled intersected voids at similar depths and that these features may be

connected. However, it is evident that macro-pores present within the spongolite are

extensive with a good degree of connection at many sites, as demonstrated by the frequent

loss of circulation when drilling at the Site and large sustainable bore yields that can be

obtained at other locations (e.g. EWD2-95). Further evidence for interconnectivity of these

macro-pores is shown by a dye test undertaken by EMTAG that involved pouring dye into a

sink hole west of Mount Merivale which was observed to emerge from a spring located

1.8 km to the W-SW within 24 hours.

The “sink holes” that are found within the Pallinup Siltstone, are apparently areas of

subsidence normally no more than a few metres in diameter, as shown by Figure 3. These

sink holes probably develop over areas with thick spongolite that has extensive development


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of macro-pores left behind after decayed root systems of now cleared vegetation. These

vertical macro-pores are likely to be widespread and represent vertical drains that lead from

the surface to the deeper spongolite facies.

Figure 3. “Sink hole” developed above a vertical macro-pore west of Mount Merivale.

The Siltstone facies comprises siltstone, shale and fine grained sandstone, which is dark

brown to green grey, carbonaceous and micaceous. Up to 35 m of the facies was

intersected at Coramup – Bandy Creek in CBC-1D to 65 m depth where the base was not

intersected, while a geophysical survey suggests it is about 50 m thick in the Coramup –

Bandy Creek area (Baddock, 1995b). The Siltstone facies is present at the Site, but only

GW17 appears to have reached the facies at about 32 m depth (it is the deepest hole drilled

to 34.5 m).

Granitic basement underlies the sedimentary deposits of the Pallinup Siltstone and Werillup

Formation. The basement tends to form north-east trending ridges in the subsurface, with

some outcrops often forming rounded hills, such as Mount Merivale east of the Site. Talis

note a small bedrock outcrop in the south-western portion of the Site, which could form a


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sub-surface bedrock ridge extending from the SW corner of the site toward the proposed

WMF. This bedrock ridge probably does not go as far as the WMF as shallow bedrock was

not intersected in any holes drilled about the Site. An EM geophysical survey over the Site

would be an effective method in mapping of bedrock topography and possibly some

attributes of the sedimentary cover.

Reference is made by both Talis and EMTAG to the Doombup Shear Zone which is located

just east of the Site. This shear zone is a Proterozoic feature present within the granitic

bedrock and does not cut through the sedimentary cover. However, it is possible that it may

have been a zone of bedrock weakness later incised by a stream to form a valley within

which the Werillup Formation was subsequently deposited.

2.3 Hydrogeology

Aquifers at the Site are formed by the Pallinup Siltstone Spongolite facies, and the Werillup

Formation where present. Perched groundwater may be present within the Surficial Sand

overlying the Pallinup Siltstone. Schematic hydrogeological cross-sections are presented by

Figures 4 and 5, and location of the sections are shown on Figure 2.

2.3.1 Surficial perched groundwater

Talis is correct in considering that there is potential for shallow seepage within the Surficial

Sands following rainfall. However, their assertion that the low permeability of the clays/silts

is likely to prevent a superficial perched aquifer is incorrect as perched groundwater can

occur in sand above this layer. A perched groundwater system was not recorded on the Site

during the Talis investigation, however, there is evidence for perched groundwater in SW02,

SW03 and SW05 about the proposed WMF. In these holes a water level of 4 to 5 m depth

was recorded, which is around 8 and 11 m above the watertable within the underlying

spongolite aquifer, and fresh quality water was yielded from SW02 and SW05 (0.449 and

0.259 ms/cm respectively) indicating separation from the deeper watertable. These

observations were made in March 2017, following a wet period in February (around 120 mm

of rain over 5 days), and therefore may represent temporary perched groundwater. Talis

have therefore under-estimated the risk of groundwater seepage as part of a perched

groundwater system that can develop following periods of heavy rainfall. Flow through a

perched groundwater system can potentially migrate from the WMF in the case of overflow

and direct it toward nearby creeks, the escarpment, or flow deeper into the spongolite aquifer

via macro-pores.


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Figure 4. Section 1: SW – NE hydrogeological cross-section.

Figure 5. Section 2: W-NW – E-SE hydrogeological cross-section.


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2.3.2 Permeability of the Spongolite aquifer

Spongolite can be a permeable aquifer due to the presence of macro-pores, although it

would be highly heterogeneous. Macro-pores act as preferred groundwater transport

pathways through the Spongolite. Areas with thick development of spongolite would form

zones of higher transmissivity compared to surrounding areas with less spongolite, and it is

likely that permeability of the spongolite aquifer will be variable across the Site. High bore

yields are possible from the spongolite aquifer, such as bore EWD2-95 drilled into the

spongolite facies about 21 km east of the Site which produced 106 m3/day for a steady

drawdown of 1.1 m (Baddock, 1995a). Talis have assumed that the Pallinup Siltstone is of

low permeability, which has not been substantively proven for the Site and is contradictory

observations at other locations. In Section 6, Talis do conclude (correctly) that ‘groundwater

flow paths would be through these secondary opening features and would likely increase the

overall hydraulic conductivity of the aquifer’. They consider that it can be described as a

‘semi-confined fractured rock aquifer’, but comparison with a karstic aquifer would be more

accurate, although without the larger scale caves and doline structures characteristic of a

karstic limestone terrain.

Values for hydraulic conductivity of between 0.063 and 0.38 m/day have been derived for the

Pallinup Siltstone at the Site from slug tests of 6 monitoring bores. Slug tests, however,

cannot be regarded as a substitute for conventional pumping tests as they can only

determine the characteristics of a small volume of aquifer surrounding the well, which may

have been disturbed during drilling and bore construction (Kruseman and de Ridder, 1990).

Slug tests can also be an unreliable method for assessing permeability if the bore is not

adequately developed to remove any mud-cake formed on the hole walls during drilling.

Pumping tests would be a better method for assessing aquifer hydraulic conductivity, while

recording of the drawdown at monitoring bores would allow some assessment of permeability

variation over the site.

Permeability of the weathered profile described as the Upper and Lower Cohesive Horizon

by Talis will be low over most of the Site as found by Talis. Triaxial permeability testing

found values for hydraulic conductivity of 3.4 x 10-8 to 1.0 x 10-8 m/s (0.003 to 0.0009 m/d) for

low plasticity clay/silt, and 9.5 x 10-9 to 1.1 x 10-9 m/s (0.0008 to 0.0001 m/d) for high

plasticity clay/silt. However, it is likely that zones of higher permeability do exist, and may

comprise more sandy zones, shallow spongolite with macro-pores left by the decay of tree

roots after widespread land clearing between the 1970 and 90’s. EMTAG have reported that

farms in the area do not use excavated dams for water as the clay is porous and does not

hold water, suggesting that the clay permeability at the larger scale may be greater than

suggested by the laboratory permeability tests on small samples.

2.3.3 Werillup aquifer

The Werillup aquifer would be confined (isolated) by the overlying Siltstone facies of the

Pallinup Siltstone, although some leakage connection down the side of the bedrock ridge is

possible where there could be a thin margin of sandy material. Due to the confining beds of

the overlying Siltstone facies of the Pallinup Siltstone, the risk to this aquifer from the WMF is

probably low. It would, however, be appropriate to demonstrate if the Werillup Formation is

present and if there is potential for hydraulic connection with the overlying aquifer.


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2.3.5 Watertable depth, and groundwater movement

Groundwater flow patterns, watertable levels, artesian pressure heads and groundwater

throughflow in the lake systems around the Esperance region are in a dynamic equilibrium in

response to the changing climate and vegetation cover. One of the largest regional

hydrogeological impacts around Esperance has been the widespread clearing of native

Mallee vegetation for pasture lands that has occurred since 1960 in response to a

government policy of releasing Crown land to develop the state’s agricultural production.

The rate of land clearing around Esperance peaked between 1970 to 1990 following the

enactment of the Esperance Land Development Act 1968 (AGO, 2000). By 1980, the State

Government had largely reversed its policy on land clearing after recognising its link to rising

watertables and dryland salinity. Any hydraulic changes potentially caused by the proposal

need to be considered within the context of seasonal and historic land clearing variations in

groundwater recharge.

The results of recent drilling by Talis on the Site suggest that watertable depth is between

3.1 m (GW03 at SE corner) and 15.5 m (GW02 at SW corner), while beneath the proposed

WMF it is about 14 m deep. Water levels measured in shallow (SW) bores SW02, 03 and 05

would appear to have intersected perched groundwater within the Surficial Sand, as the

levels are well above other deeper holes.

Groundwater within the Spongolite aquifer is recharged by the infiltration of rainfall.

However, the rate of infiltration is probably highly variable over the Site depending upon

ground conditions. Development of perched groundwater within the Surficial Sand is

probably an important part in the recharge process by creating pools of groundwater that can

drain toward and down macro-pores which are probably present over the Site. The presence

of the Surficial Sand in conjunction with vertical macro-pores enhances the risk that

pollutants that might leak from beneath the WMF liner would reach the watertable. The

importance of sink holes and horizontal macro-pores is demonstrated by EMTAG (2017a) in

the observed rapid drainage of surface water at a nearby property to the east following a

heavy rainfall event, where an estimated 24 ML of water drained down a sink hole over about

16 hours in September 2017.

There is some uncertainty of the direction of groundwater flow from beneath the proposed

WMF. Overall, groundwater flow is to the south-southwest toward the escarpment as shown

by Figure 6, although from the south-eastern portion of the site groundwater probably flows

due south toward Doombup Creek. Talis concluded that the granitic bedrock outcrop does

not appear to affect the flow direction, although if groundwater flow is essentially parallel to

the bedrock ridge then its influence would not be apparent. If the bedrock forms a ridge in

the subsurface it could still separate groundwater flow passing on either side. Groundwater

flow downgradient of the proposed WMF appears to diverge into two flow directions.

Beneath the eastern portion of the WMF groundwater flows to the southwest and south,

passing east of the bedrock ridge, while from the western portion of the WMF groundwater

possibly flows to the west-southwest, passing west of the bedrock ridge. This suggests that

the bedrock ridge may be influential in groundwater flow.

Talis estimated a seepage velocity at the site of 2.59 m/year and concluded that groundwater

would take approximately 579 years to travel 1.5 km from the proposed WMF to the Site

boundary, based on a hydraulic conductivity of 0.38 m/day and the hydraulic gradient of

0.0054. This assumes a homogeneous (practically impermeable) aquifer while the

Spongolite aquifer is highly heterogeneous with flow rates through macro-pores potentially


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several orders of magnitude greater. The dye test undertaken by EMTAG demonstrates that

groundwater could potentially migrate from the WMF to the Site boundary within a few days,

flowing through horizontal macro-pores in the spongolite. It is therefore clear that Talis may

have underestimated the magnitude of groundwater flow beneath the Site.

The watertable beneath the escarpment has likely risen in response to increased

groundwater recharge after historic land clearing several decades ago. As a direct

consequence of this watertable rise, the rate of groundwater discharge from springs in the

creek valleys and along the escarpment would have also increased. By the same token, it is

likely that the blue gum plantation on the Site has locally reduced groundwater recharge

rates relative to open cleared farmland as the trees matured. In any case, the Australian

Federal and State governments have set a precedent that considers measures that either

mitigate the rate of watertable rise or return the watertable to its pre-clearing condition are to

be considered as being environmentally desirable.

2.3.6 Groundwater receptor environments

Groundwater from the Site discharges to Doombup Creek at the south-eastern end of the

location and probably at the base of the escarpment extending up to 3 km west of the creek.

Groundwater discharges either as seeps that can cover large areas low in the landscape or

at springs. Seeps represent the slow discharge of groundwater from the general aquifer

material, while the springs are probably mostly related to groundwater discharging from

macro-pores within spongolite and seem to occur higher in the landscape to the seep areas.

The most at-risk areas from groundwater migration from the WMF are therefore Doombup

Creek and along the escarpment. Below the escarpment groundwater flows beneath the

coastal plain through Superficial formations probably toward the coast through the Lake

Bannitup / Doombup wetland system. It is unlikely that groundwater will flow into the Lake

Warden system further to the west, although this has not been demonstrated. Talis make

the same conclusion when they state that the site ‘is not directly hydraulically connected with

the Esperance Lake nature reserve’ (presuming this refers to the Lake Warden Nature

Reserve). Strictly speaking, the area is hydraulically connected with the Lake Warden chain

of lakes through the Superficial aquifer, but the hydraulic gradient is probably not toward this

system.

2.3.7 Water quality

The ANZECC (2000) guidelines for fresh and marine waters recommend that dairy cattle

should drink stock water that contains less than 2500 mg/L TDS, while beef cattle should

drink water with less than 4000 mg/L TDS. Cattle however may tolerate drinking water with

salinities up to 7,000 mg/L TDS for short periods of time, albeit that they will show a decline

in the animal’s condition.

From the monitoring bores installed by Talis it’s apparent that the groundwater salinity within

the Pallinup aquifer beneath the Site is brackish, ranging between 1,100 mg/L and

3,700 mg/L TDS. By claiming groundwater is unsuitable for stock use in the Referral, Talis

have therefore understated the beneficial value of groundwater in the area.

The groundwater salinity around the Site is largely suitable for stock watering and is currently

used by all landholders in the area for this purpose.


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Figure 6. Groundwater contours for June 2017 for Lot 12 Kirwan Road.


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2.5 Predictive groundwater simulation

As an aid to problem solving in groundwater investigations, computer numerical models

provide a powerful tool for the rationalisation of spatial and temporal variability of field

conditions (e.g. variations in aquifer permeability, wetland and spring discharge, pumping,

etc.). The development of a numerical model also facilitates sensitivity analyses that assist in

understanding the dominant parameters and mechanisms within an aquifer system. The

modelling process is a method of simulating groundwater regimes by a system of

mathematical equations based on Darcy's law for groundwater flow. The process requires,

primarily, definition of the following characteristics of an aquifer system:

aquifer geometry, including lateral and depth extent;

aquifer hydraulic properties - permeability, specific yield etc.; and

regional head distributions or fluxes - rainfall recharge, throughflows, spring and

wetland outflows and borefield abstraction.

The use of predictive computer numerical models in problem solving can overcome the

difficulties inherent in assessment of hydrological systems using classical analytical methods,

which mostly assume aquifer homogeneity and are more applicable to the interpretation of

localised aquifer response.

The quality and accuracy of numerical modelling predictions is critically dependant on the

quality of the Conceptual Site Model (CSM) which comprises: the hydrogeological

conceptualisation; assumptions and parameters to be used in the model; as well as the

ability of the selected modelling code to simulate these conditions. The Australian

Groundwater Modelling Guidelines (NWC 2012) was developed to provide confidence and

consistency in the use of modelling for regulatory purposes.

The Referral includes Landsim 2.5 Model simulations prepared by Talis. The Landsim code

was developed by Golder and Associates in the UK as an in-house semi-analytical model to

simulate, primarily, the performance of different landfill lining systems and is application

described in the user manual at http://www.landsim.co.uk/forms/landsim%202_52006.pdf.

Reference to the Landsim manual specifically recommends that the model should not be

used in situations where the following site limitations occur:

• “The receptor should not be far from the site as the model output becomes less

precise with increasing distance”; and

• “Landfills located on highly sensitive aquifers are likely to require the use of more

sophisticated flow and contaminant transport models”

The Site fails to meet either of the above criteria and we also believe the application of

Landsim modelling itself fails to meet several key requirements of the Australian

Groundwater Modelling Guidelines insofar as:

• Model Objectives: The Australian Groundwater Modelling Guidelines require that the

purpose and modelling objectives be clearly articulated. In our opinion, the objectives

and limitations of the Landsim model are not made clear and it is left to the reader to

determine what interpretation and value to attribute to the model outcomes. While the

Landsim model is designed to simulate the performance of the liner system, its

application appears limited by the fact that is neither a proper solute transport model, nor

a spatially distributed numerical model in accordance with the guidelines;

http://www.landsim.co.uk/forms/landsim%202_52006.pdf


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• Model Conceptualisation: The model does not appear to be designed to fit any specific

Conceptual Site Model. For example, the regular rectangular model domain clearly is

unrepresentative of any natural aquifer system boundaries, usually referred to as

“boundary conditions”, and therefore cannot simulate regional flow paths from the WMF

to any specific receptors such as nearby creeks, boreholes, wetlands or groundwater

dependent ecosystems;

• Model parameterisation: The vertically and spatially homogenous, isotropic and

practically impermeable parameterization (K = 1.41x10-9 to 3.42x10-8 m/s) of the

Pallinup siltstone in Appendix C clearly misconceptualises this aquifer and particularly

the spongolite facies within the Pallinup siltstone. Also, the model doesn’t include the

underlying Werillup formation

• Model assumptions, calibration and limitations: None of these have been

comprehensively articulated in accordance with the guidelines

We recommend that the Landsim model needs to be upgraded to be consistent with a

Conceptual Site Model, its objectives and limitations need to be more clearly defined and its

use be limited on the design and performance of the liner system only.

The PER still needs a defensible distributed groundwater simulation making use of a proper

groundwater flow and solute transport model with a capacity to predict the likely groundwater

flows patterns from the WMF to receptors and to demonstrate the effectiveness of

contingency recovery systems. The modelling should be undertaken in accordance with the

Australian Groundwater Modelling Guidelines and use a recognised groundwater modelling

platform such as the Feflow or Modflow family of models.


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4 Comments and Conclusions

We have identified no hydrogeological fatal flaws that would otherwise preclude this Site

from use as a WMF, although the occurrence of relatively high permeability spongolite under

the Site would not be considered best practice for the siting of a WMF. Nonetheless, many

WMFs are in hydrogeological environments that are less ideal than this Site but manage to

be acceptable according to ESD principles based on the robustness of their containment

design and implementation; the adequacy of their monitoring plan and trigger levels; and the

demonstrated effectiveness of their contingency recovery system in the event of a liner

failure.

The Referral, as it stands, fails to deliver us with confidence that:

appropriate clay resources for the liner (that are free from spongolite) have been

demonstrated locally to construct of the containment system as designed;

the baseline hydrogeology is sufficiently understood to develop an early detection

groundwater monitoring plan; and

Talis’s understanding of the Site Hydrogeology and model simulation is insufficient to

facilitate the development of an effective leachate recovery strategy in the event of a

liner failure.

Specifically, our review of the hydrogeological aspects of the Referral documents concludes

that:

the Phase 2 of the Referral failed to address most of the issues that were raised by

DPaW after its review of Phase 1 of the Referral;

the Referral greatly understates how rapidly groundwater could migrate from the

WMF to the surface environment south of the location should the WMF liner fail;

The regional hydrogeology, and the nature of the spongolite facies of the Pallinup

FM, is described in the following public documents: GSWA (1998) Esperance –

Mondrain Island 1: 250,000 hydrogeological series map sheets’; GSWA investigation

holes in the Bandy Creek – Coramup Creek area; and Esperance Water Deficiency

drilling. The hydrogeological knowledge from these documents hasn’t been

adequately captured in the Referral. The drilling on the Site failed to adequately

define the extent and hydraulic properties of the spongolite aquifer;

The Landsim semi-analytical unicell modelling presented in the Referral was not a

spatially distributed numerical model and therefore is incapable of meaningful impact

assessment on downstream receptors or the simulation of the effectiveness of

potential leachate recovery measures.

4.1 Recommended Hydrogeological Scope of Works

We recommend that Talis engage the services of a hydrogeologist for the Public

Environmental Review phase of the project. The Scope of Works for the hydrogeological

investigations should include the following:

Surface EM geophysical survey to identify any shallow bedrock and allow better

characterisation of the site hydrogeology;


Page 19

At least two aquifer test bores constructed into the Spongolite aquifer for pump

testing. The existing monitoring bores would be good for observation points during a

pump test;

An optional deeper bore may be drilled to test the stratigraphy of the Werillup

Formation and completed as a monitoring bore. Test pumping of this bore would be

a low priority as the risks to this aquifer are likely to be low;

Although Talis’s assumption in the Referral that groundwater flow from the Site is

toward the coast and not towards Lake Warden seems likely, this nonetheless was

not demonstrated. It is desirable that several additional monitoring holes be

constructed south of the location toward and about the escarpment and Doombup

Creek to better map groundwater flow and for ongoing water quality monitoring;

All monitoring and production bores should be constructed in accordance with the

NUDLC (2011) “Minimum Construction Requirements for Water Bores in Australia”.

Specifically, the annulus of each bore must be sealed with a cement grout above the

water table in order to properly seal off connection with potential perched aquifers;

The existing core should be relogged, as it appears much of the previous descriptions

have misrepresented the lithology;

A regional water bore census of existing groundwater users should be conducted,

including depth to water, water quality and status. Talis refer to testing of some

private landholder bores and tanks in surrounding area (Section 7 of the Referral), but

have not provided details for the landholder bores, only output from a DWER bore

search was provided;

The PER will need to include a Contingency Action Plan to be actioned if

environmental triggers are exceeded in the Monitoring Plan;

Contingency measures should include interception bores to pump contaminated

groundwater from the aquifer and prevent it from migrating further from the site;

The contingency plan should include commitments by the Shire to implement the

actions; and

The effectiveness and appropriateness of contingency actions needs to be

demonstrated through a numerical groundwater flow and solute transport simulation

model, which must be developed in accordance with the Australian Groundwater

Modelling Guidelines.


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5 References

DEPARTMENT OF THE ENVIRONMENT AND ENERGY 1992. Intergovernmental

Agreement on the Environment

AUSTRALIAN AND NEW ZEALAND ENVIRONMENT AND CONSERVATION COUNCIL

2000. National Water Quality Management Strategy – Australian and New Zealand

guidelines for fresh and marine water quality. Paper No.4

AUSTRALIAN GREENHOUSE OFFICE (2000) Land clearing a social history. The national

carbon accounting system. Technical Report No4

AUSTRALIAN NATIONAL WATER COMMISSION 2012. Australian Groundwater Modelling

Guidelines. Waterlines report series No.82

BADDOCK, L.J., 1995a. Esperance water deficiency area bore completion reports. Western

Australia Geological Survey, Hydrogeology Report 1995/9.

BADDOCK, L.J., 1995b. Coramup – Bandy Creek, Esperance groundwater investigation.

Western Australia Geological Survey, Hydrogeology Report 1995/13.

CHALMER, P 2017. Siting of Landfills, Best Practice Environmental Management EPA

Victoria 2015

DEPARTMENT OF PARKS AND WILDLIFE (2017) Letter to Mathew Scott (Shire of

Esperance) Re. Review of Hydrogeological Report for the proposed waste

management facility – Lot 12 Kirwan Road – 30 June 2017;

EMTAG 2017a. Summary hydrogeological investigation comments Merivale Rubbish Tip –

dated 24 June 2017;

EMTAG 2017b) Merivale Rubbish Tip, New Information;

JOHNSON, S.L. and BADDOCK, L.J., 1998. Hydrogeology of the Esperance – Mondrain

Island 1:250 000 sheet, Western Australia. Water and Rivers Commission,

Hydrogeological Map Explanatory Notes Series, Report HM 2, 24 p.

KRUSEMAN, G.P. and DE RIDDER, N.A., 1990. Analysis and evaluation of pumping test

data, second edition. International Institute for Land Reclamation and Improvement,

The Netherlands, 1994.

NATIONAL UNIFORM DRILLERS LICENCING COMMITTEE 2011. The minimum

construction requirements for water bores in Australia. Version 3

SHIRE OF ESPERANCE 2017a. Letter to Greg Mair (Dept of Parks and Wildlife) Re. Review

of Hydrogeological Report for the proposed waste management facility – Lot 12

Kirwan Road – dated July 2017.

STANDARDS ASSOCIATION OF AUSTRALIA (1993) Australian Standard for Geotechnical

Site Investigations. AS 1726-1993 ISBN 0 7262 7878 5

TALIS CONSULTANTS 2017b. Esperance Waste Management Facility – EPA Referral –

Phase 1 Hydrogeological Investigation. CMS17230 – dated Jun 2017

TALIS CONSULTANTS 2017c. Esperance Waste Management Facility – EPA Referral –

Phase 1 Hydrogeological Risk Assessment. 19.1c – dated Jun 2017


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TALIS CONSULTANTS 2017d. Esperance Waste Management Facility – EPA Referral –

Supporting Document – Phase 2. CMS17230 – dated 20 Oct 2017

TALIS CONSULTANTS 2018a. Esperance Waste Management Facility – EPA Referral –

Phase 2 Hydrogeological Risk Assessment. V1a – dated Mar 2018

TALIS CONSULTANTS 2018b. Esperance Waste Management Facility – Response to EPA

Request for further information TW17082 – dated 22 Jan 2018