dcr cleanfill resource consent application … · establishing a final quantum of stream...

Winstones DCR consent application ecology conference statement 2013

DCR CLEANFILL RESOURCE CONSENT APPLICATION

STATEMENT OF AGREED MATTERS BETWEEN

TECHNICAL EXPERTS: AQUATIC ECOLOGY OFFSET

The undersigned have followed a process of discussions as a group: Dr Ian Boothroyd, Dr Graham Ussher, Mr Dean Miller and Mr Keith Hamill.

INTRODUCTION 1. This joint signed statement is provided voluntarily to assist the resource consent panel hearing the application by Winstone Aggregates for

resource consent for a replacement for the Dry Creek Cleanfill site. 2. Our purpose was that the experts seek to reach agreement with the other expert witness(es) on matters within their field of expertise, and to

provide explanation for where agreement could not be made. 3. Provide a written statement prior to the resource consent hearing that includes:

• the matters on which the expert witnesses agree; • the matters on which the experts do not agree, and the reasons for their disagreement.

4. The statement relates to the conferencing topic of Aquatic Ecology Offset. 5. A conferencing meeting was held on 12 July 2013 and followed up with a conference call on 15 July 2013.

6. Participants were:

• Dr Ian Boothroyd (IB) (on behalf of Winstones and GWRC) • Dr Graham Ussher (GU) (on behalf of Winstones) • Mr Dean Miller (DM) (on behalf of Winstones) • Mr Keith Hamill (KH) (on behalf of GWRC)


Statement Agreed Disagreement Explanation Stream Length The quantity of permanent stream lost to the proposed DCR development is 952 m.

All

The quantity of intermittent stream lost to the proposed DCR development is 706 m.

All

Offset for loss of Intermittent Streams Based on length of intermittent stream the SEV principles (where SEV is <1) require a default 1:1 ECR (i.e., 706 m of restored intermittent stream for the loss of 706 m).

All KH considers that the SEV principle provides a precautionary approach to loss of intermittent stream. IB considers that the SEV approach is precautionary but any compensation outcome can be influenced by the conditions of the site and the proposed overall mitigation.

The DCR multiplier (based on condition of intermittent stream) returns an ECR of 0.6 (i.e., 440 m of restored intermittent stream for the loss of 706 m).

All GU considers that as a minimum length of restored intermittent stream 440 m achieves an equitable offset for the loss of condition (quality) of 706 m of intermittent stream but more than 440 m would be necessary if it was deemed desirable to meet parity in length as well as condition for the loss of condition and extent of 706 m of intermittent streams.


KH has the opinion that when ECR is <1 a more precautionary approach is used because of uncertainty about whether the ecological outcomes will actually be achieved. This is particularly the case with the method used by MWH to assess the extent and condition of intermittent streams, which was reasonably coarse. IB and DM agree that the method used by MWH to assess the extent and condition of intermittent streams was reasonably coarse but was nevertheless acceptable for the DCR site.

Irrespective of the application of an SEV or DCR multiplier the issue is how to define full ecological replacement (i.e., no net loss). The two components of full ecological replacement are extent and condition but accepted approaches allow trades between the two to achieve no net loss. The requirement is the acceptable loss of stream length so long as there is parity in stream condition.

All IB considers that whilst parity of stream condition and length is important other factors may influence the overall ‘ecological replacement’.

Irrespective of the application of an SEV or DCR multiplier the outcome is to provide guidance regarding a quantum of compensation that might meet a no net loss requirement and other factors may be considered in establishing a final quantum of stream restoration as compensation for any loss of permanent or intermittent streams.

All

The offset for the loss of 706 m of intermittent streams lies between 440 and 706 m (as per statement above).

All Stock exclusion is the most significant ecological benefit to intermittent streams (and seepages).


A length of no less than 550 m of restoration of intermittent stream (which may be made up from 100 m as permanent stream) is acceptable contingent on the fencing, stock exclusion and invasive weed management within the entire area encompassing the DCR Offset site. This agreement is also contingent on the DCR offset area being protected in perpetuity (e.g., via covenant or lease conditions) which requires the exclusion of stock as a primary requirement.

We note that the available intermittent stream for restoration within the DCR offset area amounts to some 449 m. We agree that, in this case, topping up with some adjacent permanent stream is acceptable to achieve the offset requirements. Additional permanent stream used for this purpose should not be included in the offset for the loss permanent streams.

Offset for loss of Permanent Streams The benefit of stream restoration (e.g., riparian planting and stream fencing) prior to impacts can be reflected in a ‘discount’ rate within offset calculations. If a single multiplier is used over the total length lost over all stages of construction and operations then a multiplier of 1.2 for the ECR calculations is acceptable so long as the planned staging of the DCR construction and operations is in accordance with the planned loss of the permanent streams.

GU, DM, IB

KH prefers a multiplier of 1.5 where planting is not ahead of impact (e.g., Stages 1 and 2) and a multiplier of 1.2 beyond that.

We note that overall the ECR methodology and the DCR methodology converge to the same or very similar multiplier (of approximately 1.2) when applied to replacement of steam length.

If SEV approach is used it is preferable to apply it to the stages of development, with adjustments to the multiplier used on the ECR according to when the offset planting occurs at each stage, i.e., a multiplier of 1.5 where planting is not ahead of impact (Stages 1 and 2) and a multiplier of 1.2 beyond that (accounting for risk but not time delays).

KH IB considers that either approach is acceptable providing that the offset outcome is acceptable and reasonable. A table of indicative ECR-derived stream offset lengths is provided as Appendix 1 to this conferencing statement.


The offset for the loss of 952 m of permanent streams lies between 1,510 m and 1,675 m of permanent stream length within the proposed DCR offset site (assuming an average stream width of at least 1.45 m).

All Calculations of the respective offset stream lengths are provided in Appendices 1 and 2 attached to this statement.

Current versus Potential Condition The ECR is calculated based on the difference between the impacted score and the potential SEV score for the loss of stream and the difference between the current and potential SEV for the offset stream. The ECR does not use the existing condition of the impacted stream (lost stream).

All Assumptions: • Allows offsetting to be targeted to

anticipated effects on the future predicted baseline.

• It assumes that the existing landuse may remain and a purposeful change to management of the streams occurs that includes improvements to the stream to the full extent possible.

• Stream loss means no opportunity to realise future potential.

• Allows offset to be targeted to anticipated effects on the predicted future baseline.

The DCR offset model is calculated based on difference between the impacted stream SEV score (post-impact) and the existing (current) condition SEV score for the lost stream and the difference between the current and potential SEV for the mitigation stream.

All Assumptions: • Allows offset to be targeted to

actual effects on the current baseline. It assumes a steady baseline state over 35 years – i.e., an equal chance that the waterways may degrade further or improve without DCR going ahead, under plausible scenarios that exist for the site under the current District Plan rules.


Both the ECR and the DCR offset model provide guidance for compensation for the loss of permanent streams at the DCR site. The DCR offset model offers guidance that is based on the current condition of the permanent stream to be lost. The ECR offers guidance that is based on the anticipated future potential condition of the permanent stream to be lost.

All A table of indicative ECR-derived stream offset lengths is provided as Appendix 1 to this conferencing statement. A table of DCR offset model-derived stream offset lengths is provided as Appendix 2 to this conferencing statement.

Seepages Our preference is for the DCR offset area to be fully fenced to include all seepage areas, intermittent streams and permanent streams as one entity.

All Our preference includes full fencing, stock exclusion and protection (e.g., covenant) of the entire DCR offset area.

Fish Passage in piped T1 during Construction and Operations During the construction and operational phases of the cleanfill it is desirable to retain the capability for fish passage between the upstream habitats and downstream reaches of Tributary 1.

All

It is unlikely for fish passage to occur without specific fish passage friendly design features within the pipe under the proposed cleanfill and at the entrance and exits to the pipe under the proposed cleanfill. Alternatively a trap and transfer methodology could be applied.

All

Some of the offset calculations are contingent on the inclusion of fish passage through the T1 piped stream section.

All Important because it is one of the assumptions used in calculating the offset.

The SEV scores used for offset calculations assume fish passage would be available (as a partial or intermittent barrier to fish passage).

All


Final Stream Diversion It is desirable for a permanent open stream channel (final stream diversion) to be established between the upper reaches and lower reaches of T1.

All

It is desirable for the final stream diversion to include improved instream habitat, riparian planting and hydrological connectivity between existing upstream habitat and Pauatahanui Stream; and to provide for fish passage.

All

It is preferable to have an indicative design and management plan for the final stream diversion that caters for (but not limited to):

1. Fish passage (climbing species) 2. Diverse instream habitats 3. Fenced and planted for riparian cover

All

Discount Rates A discount rate is a way of valuing current condition over future condition with respect to losses or gains in stream condition. A high discount rate provides an incentive to minimise time lags between impact and offset (i.e., a high discount rate means that compensation occurring further into the future will require a greater length of stream planted than if it is realised earlier).

All

The DCR model uses the discount rate to address time lags only and the risk of not achieving the expected outcome is address by other ways (e.g., conservative assumptions in the calculation and robust supporting conditions). There are a range of risk free discount rates used in the literature (about 0.7-4.2 in NZ), the most appropriate to use is debatable and dependent on the specific application. Using a low discount rate requires more certainty that risk of not achieving the desired outcome is very low, or that uncertainty is addressed by other means if not included in the discount rate.

All KH considers that 0.8% is too low a discount rate. GU considers that 0.8% is appropriate, and has separated uncertainty and risk from the discount rate and he considers that he has addressed them separately and appropriately in the offset design for DCR.

19 July 2013


Appendix 1: Offset calculated per stage of development at the proposed DCR development using ECR methodology.

Permanent streams Stage Length lost

(m) Area lost (m2) (based

average stream width at the impact reach of 0.915m)

ECR Offset area required (m2)

Offset length (m) (based on an average stream width at the mitigation stream of 1.45m)

1 25 22.9 3.17 72.5 50.0 2 384 351.4 3.17 1113.8 768.1 3 66 60.4 2.5 151.0 104.1 4 477 436.5 2.5 1091.1 752.5

Total 952 871 2428.4 1674.8


Appendix 2: Summary of offset anticipated to achieve at least a no-net-loss of ecological values for the proposed DCR development. Grey shaded cells represent offset model outputs for losses and gains. To achieve no-net-loss of values, shaded cells across rows should add to be equal to or greater than zero (modified from Table 3 of the T&T offset technical report; Appendix 10 of the Resource Consent Application). Permanent stream offsets have been calculated on the basis of length and area separately to illustrate two ways of communicating the same offset result i.e. 1,510 m stream length which equates to (for this project) 2,200 m2 of stream area.

Ecological type Loss within DCR footprint Gain from offset over a 35-year period Replacement ratio (multiplier)

Area/ Length removed (ha/ m) (a)

Habitat Hectares units removed

Area/ Length replaced (ha/ m) (b)

Habitat Hectares units replaced

(b/a)

Permanent streams (by length)

952 m

-0.036 HH 1,510 m

0.036 HH X 1.6

Permanent streams (by area)

871 m2 -0.036 HH 2,190 m2 0.036 HH X 2.5

Intermittent streams 706 m -205.5 Hm 440 m 206.1 Hm X 0.6

dcr cleanfill resource consent application … · establishing a final quantum of stream...

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