Attention: Quinten Cloete - CESNET Paterson WWTW...Alexandria formations on which the Site is situated) is a unique intergranular aquifer, where water seeps rapidly through the highly

Ground Floor, Bay Suites

1a Humewood Rd,

Humerail

Port Elizabeth, 6001

P O Box 21842

Port Elizabeth 6000

South Africa

T: +27 (0) 41 509 4800

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E: [email protected]

www.srk.co.za

15 June 2015 490362 Paterson Waste Water Treatment Works Hydrogeological Investigation

Partners AH Bracken, MJ Braune, JM Brown, CD Dalgliesh, JR Dixon, DM Duthe, BM Engelsman, R Gardiner,

GC Howell, WC Joughin, DA Kilian, PR Labrum, B Liber, DJ Mahlangu, RRW McNeill, HAC Meintjes, JA Middleton,

MJ Morris, GP Nel, VS Reddy, M Ristic, PE Schmidt, PJ Shepherd, MJ Sim, VM Simposya, AA Smithen,

HFJ Theart, KM Uderstadt, AT van Zyl, DJ Venter, ML Wertz, MD Wanless, A Wood

Directors AJ Barrett, JR Dixon, PR Labrum, V Maharaj, DJ Mahlangu, VS Reddy, PE Schmidt, PJ Shepherd

Associate Partners R Armstrong, N Brien, L Coetser, M Hinsch, AH Kirsten, Dr LH Kirsten, S Kisten, JA Lake,

V Maharaj, SA McDonald, RD O’Brien, T Shepherd, JJ Slabbert, D Visser

Consultants AC Burger, BSC(Hons); JAC Cowan, PrSciNat, BSc(Hons); JH de Beer, PrSci Nat, MSc;

T Hart, MA, TTHD; GA Jones, PrEng, PhD; TR Stacey, PrEng, DSc; OKH Steffen, PrEng, PhD;

PJ Terbrugge, PrSciNat, MSc; DW Warwick, PrSciNat, BSc(Hons)

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Element Consulting Engineers PO Box 19429 Tecoma 5214

Attention: Quinten Cloete

Hydrogeological Investigation for the Upgrading of the Waste Water Treatment Works at

Paterson, Eastern Cape

1. Introduction

SRK Consulting South Africa (PTY) Ltd (SRK) was appointed by Element Consulting Engineers (ECE, the

Client) to conduct a hydrogeological investigation at the existing Waste Water Treatment Works (WWTW) of

Paterson in the Eastern Cape.

ECE was appointed by Sundays River Valley Municipality for the required services pertaining to the

upgrading of the Paterson Wastewater Treatment Works (PWWTW). The planned area in which the

upgrade is to take place is referred to as the Site (outlined in red in Figure 1 and Figure 2). The existing

PWWTW oxidation pond system will be upgraded to an oxidation ponds system with a screen, de-grit

system, 2 x anaerobic ponds, 6 x facultative ponds, 1 x maturations pond and an irrigation pump station.

The final effluent will be used for irrigation of an open field. Certain specialist investigations, such as this

groundwater investigation, forms a part of the environmental impact assessment (EIA) process to obtain

authorisation from the Eastern Cape Department of Economic Development, Environmental Affairs and

Tourism (DEDEAT) for the development. A groundwater specialist study is required as a part of the process

to investigate the potential of the development to influence the groundwater.

SRK followed the methodology described below in their hydrogeological investigation (quoted from the SRK

document “Proposal: Specialist Assessments for the Proposed Expansion of the Paterson Wastewater

Treatment Works, Eastern Cape Province”, dated 16 April 2015):

“Conduct a desktop assessment of the geology and hydrogeology within a radius of approximately 1 km

of the site. This will include an assessment of the geological, hydrogeological and topographical maps;

and the National Groundwater Archives (NGA) – a database of the Department of Water and Sanitation

(DWS);

http://www.srk.co.za/

SRK Consulting Page 2

KRUR/NELG 490362_Paterson WWTW Hydrogeological Investigation_Jun2015 Apr 2015

Undertake a hydrocensus of boreholes within a 1 km radius of the site. The hydrocensus will be limited

to identifying existing boreholes within a 1 km radius of the site, and recording any available information

of this borehole, including its position, depth, water level, water pH and conductivity;

Describe the potential impact of the WWTW on the hydrogeological features in general, particularly

during the operational phase; and

Recommend appropriate mitigatory measures, if available, to reduce the impact of the proposed

development upon the groundwater quality of the area.”

2. Results

The findings of the hydrogeological investigation are summarised in the sections below.

2.1 Desktop Study

2.1.1 Geology

According to the 1:250 000 geological map of Port Elizabeth (3324) by the Council for Geoscience, the Site

is underlain by Quaternary aeolian (windblown) sand. The aeolian sand overlies the Nanaga Formation,

which in turn overlies the Alexandria Formation, both of the Algoa Group. Refer to Figure 1 for a map with

the geology of the Site.

The explanation booklet “The Geology of the Port Elizabeth-Uitenhage Area” by F.G le Roux of the Council

for Geoscience (2000) describes the geological formations (in order from the youngest to the oldest) as

follows:

Quaternary aeolian sand occurs in the vicinity of Paterson, where sand, derived from the Nanaga

Formation to the south, has accumulated at the foot of the Suurberg range.

The Nanaga Formation comprises semi-consolidated to well-consolidated calcareous sandstone and

sandy limestones. Surficial calcrete of up to 3 m thick or a red soil commonly caps this formation. The

thickness of the Nanaga Formation is governed by surface relief and is often up to 150 m thick. The

formation forms smooth, rounded hills within undulating ridges, trending subparallel to the present

shoreline.

The Alexandria Formation comprises alternating layers of calcareous sandstone, conglomerate and

coquinite and is about 10 m thick. A conglomerate is often present at the base. The clasts consist

mainly of Cape Supergroup quartzites and sandstones.

No faults, folding or other structures have been mapped for the area.

2.1.2 Hydrogeology

According to booklet “An Explanation of the 1:500 000 General Hydrogeological Map of Port Elizabeth 3324”

by P.S. Meyer of the Department of Water Affairs (1998), the Algoa Group aquifer (including the Nanaga and

Alexandria formations on which the Site is situated) is a unique intergranular aquifer, where water seeps

rapidly through the highly porous material until it comes into contact with the underlying impervious pre-Algoa

Group rocks. From here it moves towards the sea within the conglomerate (where present) or the sandy

material; and often emerges as springs at the coast. Borehole yield analyses revealed that less than 60% of

boreholes yield less than 0.5 L/s, implying that 40% of boreholes yield more than 0.5 L/s. The groundwater

quality is generally potable, with electrical conductivity (EC, a measure of salinity) measuring < 300 mS/m

(the limit for drinking water according to the SANS241:2014 Standard is 170 mS/m). Sodium, calcium and

chloride often exceed the maximum recommended limits.

The booklet does not specifically describe aeolian sands, but describes coastal sands (aeolian sands

situated at the coast) and alluvium. These are essentially the same as aeolian sands, except for method

deposition and location. According to the booklet, yields may vary between 0.1 and 15 L/s. Groundwater

quality is described as generally potable (EC measuring < 300 mS/m), providing that the boreholes do not

extend through the sand and into underlying formations of poorer water quality. Water may exceed the

maximum recommended limits for sodium, total alkalinity and chloride.


KRUR/NELG 490362_Paterson WWTW Hydrogeological Investigation_Jun2015 Jun 2015

Figure 1: General Geology of the Site

2.1.3 National Groundwater Archive (NGA)

The NGA was queried for the Site and a surrounding 1 km radius. Four boreholes are listed within this area

and their available information is given in Table 1 below.

Table 1: NGA Borehole Information

Borehole ID Latitude Longitude Water Level

(m bgl) Discharge Rate (L/s)

Depth (m bgl)

Surface Geology

3325BD00060 -33.44128 25.97676 39.6 0.42 155.5 Aeolian sand

EC/P10/147 -33.43577 25.98469 5.2 N/A N/A Aeolian sand

EC/P10/148 -33.43577 25.98469 N/A N/A N/A Aeolian sand

EC/P10/146 -33.43577 25.98477 4.9 N/A N/A Aeolian sand

N/A: Not Available



Figure 2: NGA and Hydrocensus Boreholes

2.1.4 Site Drainage and Shallow Groundwater Movement

Envisaged drainage directions were drawn on a contour map of the Site and surrounding area (Figure 3) to

indicate the direction in which surface water and shallow groundwater would flow. From the Site, water will

move in an east southeastern direction towards the Boesmans River.



Figure 3: Drainage Directions Around the Site

2.2 Hydrocensus and Site Visit

A hydrocensus was conducted within a radius of approximately 1 km of the Site. Two boreholes were

located within a 1 km radius, and one was located just west of the 1 km radius, at Afgri Animal Feeds. The

borehole located closest to the Site is situated approximately 150 m to the northwest of the northern

boundary of the Site. According to a municipal official, these are the abandoned municipal production

boreholes. The municipality reportedly receives its water from boreholes that are situated approximately

8 km from the town. The municipal official also stated that there are a number of people in the town itself

that uses borehole water for personal use. According to a town resident, who had been involved during the

drilling of a borehole, one would intersect groundwater “anywhere” in the area immediately around the town.

This would be true for the sandy aquifer of the Quaternary aeolian sands of the area. He also reported that

they drilled through sand and clay layers, and that no bedrock was intersected in their borehole up to a depth



of 25 m bgl. The farms to the east of the Site could not be accessed during the hydrocensus, due to the

gates being locked.

Refer to Table 3 and Figure 2 for information on the hydrocensus.

The Site is situated in a catchment area and by looking at the available contour information; surface water

will drain from the west, northwest and southwest towards the Site. Currently the liners of the ponds at the

Site have lifted, most likely due to the flow of water under the liners. The ponds appear to overflow and leak,

forming various wetlands around the Site.

Photographs are given in Table 2 below. No rock outcropping was visible on the Site and surrounding area.

A landfill is situated immediately to the west of the WWTW.

Table 2: Photographs of Boreholes

Afgri Borehole Old Municipal Borehole 1

Old Municipal Borehole 2

Lifting liners in pond



Table 3: Hydrocensus Information

Borehole Other ID Latitude Longitude Depth (m bgl)

Water level (m bgl)

EC (mS/m)

pH Comment

Afgri Borehole

None -33.43600 25.97263 25 N/A 82 7.3

Borehole was in use during visit. Owner reported their pump can deliver ~840 L/h. Water used for boiler, showers etc. Water reported to be high in metals, is purified with reverse osmosis.


EC/P10/146 or EC/P10147

-33.43578 25.98472 N/A 3.02 N/A N/A Borehole open and abandoned. Depth measuring device detected an obstacle in borehole at ~12 m bgl.


EC/P10/148 -33.43578 25.98470 N/A N/A N/A N/A Borehole collapsed at ~3 m bgl.

2.3 Shallow Soils

During the Site visit, a number of shallow auger holes were made (up to 1 m bgl) to study the shallow soils

surrounding the Site. The soil mainly consisted of sand, with occasional horizons of clayey sand (refer to

Table 4. Shallow groundwater was intersected in all augered holes from approximately 0.5 m bgl.

Table 4: Soils Encountered

Grey brown sand in the auger

Clayey sand rolled into a sausage shape

2.4 Potential Risks & Mitigation

2.4.1 Potential Risks

Considering the “source - pathway – receptor” concept, the following can be concluded for the planned

development of the WWTW:

Potential sources of contamination / potential impacts:

Irrigation water in the form of treated effluent; and

Spillage or leakage of insufficiently treated / contained effluent.

Pathways:

Soil and groundwater

Receptors:

Groundwater as a natural resource and groundwater users (current and future). The Boesmans

River is situated approximately 5 km down gradient to the east of the Site. Currently there are no

known groundwater users within a 1 km radius of the Site. The two boreholes located to the north of

the Site are not in use.



Risk is considered to be present when a complete link between the source, pathway and receptor is formed.

Potential sources of contamination are expected to occur mostly under upset conditions where the designed

water treatment / containment systems do not function as planned.

The summary version of the document “A Protocol to Manage the Potential of Groundwater Contamination

from on Site Sanitation” (Mar 2003) (referred to as the Groundwater Protocol) by the former Department of

Water Affairs and Forestry (now known as the Department of Water and Sanitation), is used as a guideline

document to evaluate the scenario at the Site. According to the Groundwater Protocol, risk levels are based

on the following three factors:

the vulnerability of the underground water resources (aquifers);

the contamination load from the particular sanitation system; and

the current and/or future water use from the aquifer.

Although the planned ponds do not fall under sanitation, the same risk factors apply.

2.4.2 Assessment of Risks

Vulnerability of the Aquifer

The Site is situated on unconsolidated aeolian sand of unknown thickness. The sands create an unconfined

aquifer1 where water can freely move through the pore spaces between sand grains. The groundwater level

2

within these sands will be equal to the water table within the sandy aquifer, since it is unconfined.

The vulnerability of the aquifer is related to the distance that the contaminant must flow to reach the water

table3; the degree of natural degradation of the pollutants and also how easily it can flow through the soil and

rock layers above the water table (unsaturated zone4). The depth of the water table (and water level)

surrounding the Site is considered to be shallow, since it was measured at 3.02 m bgl in one of the boreholes

(approximately 150 m northwest of the Site). However, immediately under the Site in the wetland area,

groundwater was intersected at approximately 0.5 m bgl in the augered holes. Therefore it seems that

currently the water leaking from the WWTW and the water table under the Site is interconnected. According

to the Groundwater Protocol, an aquifer is classified as having a high vulnerability when the potential

pollution source has to move between 2 and 5 m to get to the water table. The potential pollution sources

(the WWTW and the irrigation water) will be situated anywhere between surface level and approximately 3 m

bgl. The definition of an aquifer with a high vulnerability is that it is vulnerable to many pollutants except

those highly absorbed, filtered and/or readily transformed.

Below the aeolian sand aquifer, is the Algoa Group intergranular aquifer, which is seen as a unique aquifer

where water seeps rapidly through the highly porous material until it comes into contact with the underlying

impervious pre-Algoa Group rocks.

Assessment of Contaminant Load from Pollution Sources; and the Ability of the Soils to Reduce the

Contaminant Load in the Unsaturated Zone

According to the Groundwater Protocol, the aeolian sands and clayey sands encountered at the Site have

the ability to be a good to very good barrier to contaminants (like bacteria and viruses), and the rate of flow

through it can vary from very slow (<10 mm/day) in clays to medium (0.1 – 10 m/day) in fine sands.

However, the unsaturated zone at the Site is currently very narrow to non-existing due to the leaking /

overflowing ponds. Should the problem with overflowing ponds be solved during the upgrade, the water

1 Unconfined aquifer: A groundwater aquifer is said to be unconfined when its upper surface (water table) is open to the atmosphere

through permeable material. As opposed to a confined aquifer, the water table in an unconfined aquifer system has no overlying impervious rock layer to separate it from the atmosphere. 2 Groundwater level: The depth to groundwater, as water measured in a borehole. This is likely not the water table, since there is often

a pressure component for groundwater boreholes which raises the water level above the bottom of the casing. This level may or may not reflect the water table. 3 Water table: The surface below which fissures and pores in the strata are saturated with water.

4 Unsaturated zone: The area extending from the top of the soil to the water table.



level may still be high, since the Site is situated in a drainage / catchment area and it was measured at about

3 m bgl in the nearby borehole. The water level in the unconfined san aquifer will also be influenced by

rainfall, and will be higher during periods of higher rainfall and lower during periods of lower rainfall.

The contamination load from the ponds is expected to be high initially as it enters the anaerobic ponds, but

will reduce as the effluent is treated and moves towards the maturation ponds. Once the final effluent leaves

the maturation ponds to be discharged, it should comply with the Standards mentioned in the National Water

Act (Section 39), irrigation with wastewater.

Current and Future Use of the Aquifer

Currently there are no registered groundwater users within a 1 km radius of the Site. The sandy aquifer is

currently being used by residents and businesses of the town, proving that it is exploitable. The sandy

aquifer as well as the underlying Algoa Group aquifer is seen as a groundwater carrier that could be used for

water supply in the future.

Conceptual Hydrogeological Model

In order to gain a better understanding of the underground setting, a hydrogeological conceptual model was

created (Figure 4:). The water level (which will be equal to the water table in this unconfined sand aquifer) is

shown under normal conditions, where the WWTW is not leaking or overflowing onto the aeolian sand (blue

dashed line). The water level is also shown (green dotted line) as it is currently perceived to be, with the

overflowing WWTW elevating the water table to surface level. It is important to note that the water table will

be higher (closer to the surface) during periods of higher rainfall; and will be lower during periods of drought.

Figure 4: Conceptual Hydrogeological Model

2.4.3 Mitigation of Potential Risks

The aeolian sand aquifer and the underlying Algoa Group aquifer are seen as exploitable aquifers from a

groundwater perspective; and its groundwater is currently being used. However, there are currently no

known or registered groundwater users within a 1 km radius of the WWTW. Water levels are considered

high (shallower than 5 m bgl) and the sand aquifer is unconfined. The aquifer may be further exploited in the

future.

Risk 1 – Pollution from WWTW

Potential pollutants from the ponds include bacteria (e.g. E.coli), nitrogen and ammonia. There should be no

seepage from the ponds into the underlying sands. It is recommended that a lining system must be installed

in order to prevent seepage into the sands.



Risk 2 Elevation of Water Table and Pollution from Irrigated Water

Wastewater is to be treated and reclaimed, and used for irrigation nearby the WTWW. The wastewater must

adhere to the requirements from the DWS and must not impact the natural groundwater quality negatively.

Currently the groundwater is believed to be potable and could be used in the future. The potential impacts on

the groundwater are as follows:

DWS standard for irrigation with wastewater does not take into account that discharge will take place

almost directly into the groundwater, since the water table is high and will become higher with irrigation.

If the irrigated water is not treated to drinking standards, the potential impact thereof on the existing

groundwater quality should be scientifically determined; as well as the effectiveness of attenuation of

bacteria over time and distance.

The water table will be raised where irrigation occurs. The natural groundwater level is therefore

changed.

It is recommended that irrigation should take place in the areas to the south of the Site, which is up-gradient

of the existing water logged soils. In this area the unsaturated zone should be “thicker”; and the movement

of the irrigated water through the unsaturated zone will allow for the attenuation of bacteria.

It is also recommended that the reclaimed effluent should be regularly tested (quarterly, or as specified by

the DWS or Department of Environmental Affairs) before it is irrigated to ensure that it complies with the

standards for irrigation with wastewater as per the National Water Act, Section 39, of up to 2000 m3/day. It is

also recommended that monitoring boreholes should be installed up-gradient and down-gradient of the Site

in order to detect potential pollutants entering the groundwater from the WWTW or irrigation water. The

monitoring boreholes should be drilled in such a way that the section of the aquifer that will most likely be

polluted first is adequately penetrated. This is the aeolian sand aquifer. However, it is recommended that

the Nanaga and Alexandria formations should also be drilled through, if they are intersected within the first

50 m of the borehole. If not, then the boreholes can be stopped at 50 m bgl. Approximate positions for

boreholes for a monitoring network is given in Figure 5 below.

Figure 5: Approximate Positions for Monitoring Boreholes



3. Conclusions and Recommendations

The Site and surrounding area is underlain by Quaternary aeolian sand, which overlies the Nanaga

Formation and the Alexandria Formation of the Algoa Group. The aeolian sand (immediately underlying the

Site, unknown thickness) is an unconfined aquifer where the water table and water level (in boreholes) is

expected to be equal. This type of aquifer can produce varying yields, ranging between 0.1 and 15 L/s and

is generally potable from an aesthetic perspective (taste etc.). The National Groundwater Archive revealed

information on four existing boreholes, of which two could be located during the hydrocensus. These were

found unused and abandoned. Access could not be gained to the farming properties during the

hydrocensus, therefore it is possible that all existing boreholes have not been recorded within a 1 km radius

of the Site. It was established during the hydrocensus that the sandy aeolian aquifer is being exploited by

the town residents and businesses.

The surface water and shallow groundwater drainage from the Site is in an east southeastern direction

towards the Boesmans River, situated approximately 5 km east of the Site. The Site is situated in a

catchment area to where surface water and shallow groundwater will drain from the north, west and south of

the Site.

A number of auger holes were dug, and it revealed the presence of sand and clayey sand. The clayey sand

does not seem to be laterally persistent, and may be linked to the wetlands only.

The water level / water table in the aeolian sand aquifer is high in this area, measured at approximately

3 m bgl in a borehole; and at approximately 0.5 m bgl in augered holes around the Site in the wetland areas.

The water table will vary with recharge, being higher during periods of high rainfall and lower during periods

of drought.

Potential risks are leakages or spillages from the WWTW as well as irrigation with reclaimed effluent.

Because of the high water table, potential pollutants can enter the groundwater relatively easily. Although

sand does have the property to attenuate bacteria and viruses over time and distance, there is insufficient

thickness of the unsaturated zone for the attenuation processes underneath the Site and in the immediate

vicinity. The following mitigation measures are recommended:

It is recommended that a lining system must be installed in order to prevent seepage into the sands.

There should be no seepage from the ponds into the underlying sands.

The quality of irrigated wastewater should comply with the National Water Act’s standards for irrigation

with wastewater and water quality monitoring should occur.

Because of the high water, irrigation with wastewater is not considered ideal. It is recommended that

irrigation should take place in the areas to the south of the Site, which is up-gradient of the existing water

logged soils. In this area the unsaturated zone should be “thicker”; and the movement of the irrigated

water through the unsaturated zone will allow for the attenuation of bacteria. A groundwater monitoring

system could be implemented to reveal the impact on groundwater quality and groundwater table.

It is recommended that monitoring boreholes should be installed up-gradient and down-gradient of the

Site in order to detect potential changes in the groundwater quality and to act accordingly. .

Yours faithfully,

Riona Kruger (Pr. Sci. Nat.) Gert Nel (Pr. Sci. Nat.)

Senior Geologist Principal Hydrogeologist

SRK Consulting

Documents

Attention: Quinten Cloete - CESNET Paterson WWTW...Alexandria formations on which the Site is situated) is a unique intergranular aquifer, where water seeps rapidly through the highly