Addendum 01 to Baseline Monitoring SOW - Sept 2020_0002.docx

Addendum to Statement of Work

Red Devil Mine - Alaska Baseline Monitoring

Site conditions at Red Devil Mine have changed since the original Scope of Work (SOW) was generated for baseline monitoring. This addendum documents those changes by listing the text excerpted from the original SOW, followed by the revised text. Only those sections of the SOW listed in this addendum have been modified. All other elements of the initial SOW remain unchanged.

C.1 Task 1 –Planning Initial SOW:

5. Purchase three new bladder pumps to be installed in monitoring wells MW06, MW16 and MW17. The work plan shall be modified to describe new pump installation (see Task 2, bullet 2).

6. Modify the work plan to describe how three existing bladder pumps shall be moved to different monitoring wells (see Task 2, bullet 3) Revision:

All bladder pumps have been installed in assigned wells. Steps 5 and 6 are eliminated from this SOW.

Note: The Red Devil Mine Administrative Record includes an addendum to the 2019 work plan that applies to fall sampling performed in 2020. The contractor shall prepare an addendum to the 2019 work plan that reflects activities to be completed as part of 2021 baseline monitoring.

C.2. Task 2 – Field Data Collection Initial SOW:

Field data collection will be performed in two different sampling events; one in late May or early June and second in September. The spring event will be conducted shortly after spring breakup when surface runoff and water table elevation is at or near the annual maximum. The fall event will be conducted during early fall when stream flow is typically approaching a minimum prior to freeze up and water table elevations begin seasonal decline.

Revision:

Monitoring procedures covering depth to water measurement, groundwater sampling and surface water sampling shall be performed using methods previously developed and documented in the 2019 Baseline Monitoring Work Plan.

Field data collection will be performed in two different sampling events; one in late May or early June and second in September. The spring event will be conducted shortly after spring breakup when surface runoff and water table elevation is at or near the annual maximum. The fall event will be conducted during early fall when stream flow is typically approaching a minimum prior to freeze up and water table elevations begin seasonal decline.

Initial SOW:

2. During the spring 2021 event, install new bladder pumps in monitoring wells MW06, MW16 and MW17 (see Task 1, bullet 5).

3. Remove the bladder pumps for wells MW01 and MW31 and discard the tubing. Decontaminate the pumps and install in wells MW32 and MW55 using new discharge tubing (See Task 1, bullet 6).

Revision:

All bladder pumps have been installed in assigned wells. Steps 2 and 3 are eliminated from this SOW.

Initial SOW:

4. Collect depth to static water level measurements on all monitoring wells listed in Table 1, including those wells that are not scheduled for sampling collection. Depth to water measurements are to be completed for all wells within a 24 hour period during both the spring and fall sampling events.

Revision:

4. Depth to static water level measurements shall be measured at all monitoring wells listed in Table 1, including those wells that are not scheduled for sampling collection. Depth to water measurements are to be completed for all wells within a 24 hour period during both the spring and fall sampling events. In addition, data shall be downloaded during the same 24 hour period from transducers installed in the monitoring wells designed as such in Table 1. Seven (7) wells contain Solinst Model 3001 Levelogger® Edge data logger/transducer units. One (1) monitoring well contains a Solinst Model 3001 Barologger® Edge. An optical reader cable and Levellogger software are needed for data download. A user guide is available on the Solinst web site.

Note: The version of Table below has been modified and reflects the current requirements of this SOW.

Table 1 Baseline Groundwater Monitoring Well Summary Base Scope of Work

MW03

MW04

MW06

MW07

MW08

MW11

MW12

MW13

MW16

MW17

MW18

MW19

MW20

MW21

MW22

MW23

MW24

MW25

MW30

MW31

MW32

MW33

MW34

MW35

MW36

MW39

MW48

MW55

Notes:

1. Groundwater samples shall be collected from monitoring wells highlighted in yellow

2. Northing and easting are provided as Alaska State Plane coordinates.

3. Monitoring wells MW14 and MW15 have been decommissioned.

4. Monitoring wells containing dedicated bladder pumps are indicated and are to be sampled according to methods previously developed for Red Devil Mine baseline monitoring and documented in the 2019 Baseline Monitoring Work Plan.

5. Wells highlighted in yellow but don’t contain bladder pumps shall be sampled using a peristaltic pump according to methods previously developed for Red Devil Mine baseline monitoring and documented in the 2019 Baseline Monitoring Work Plan.