State of Oregon 

Department of 

Environmental 

Quality 

NATIONAL POLLUTANT DISCHARGE 

ELIMINATION SYSTEM 

WASTE DISCHARGE PERMIT 

EVALUATION AND FACT SHEET 

April 2015 

Oregon Department of Environmental Quality 

Western Region 

4026 Pah-view Industrial Dr. Salem OR 97302 

Permittee: 

Existing Permit 

Information: 

Source Contact: 

Source Location: 

LLID 

Receiving Stream 

Proposed Action: 

Source Category 

Permit Writer: 

Cascade Pacific Pulp, LLC 

30480 American Dr, PO Box 400 

Halsey, OR 97348 

File Number: 36335 

Permit Number: 101114 

Expiration Date: November 30,2015 

EPA Reference Number: OR000107-4 

Lisa Scott 

(541)369-1752 

30480 American Dr 

Halsey, OR 97348 

1227618456580-147.4-D 

Willamette River 

Permit Modification 

Application Number: 959349 

Date Received: December 22, 2014 

NPDES Major- Industrial 

Steve Schnurbusch (503)378-8306 

Senior Water Quality Permitting Specialist 
Summary 

Cascade Pacific Pulp (CPP) shares an outfall with neighboring Georgia Pacific Halsey Mill (GP). 

CPP owns the outfall and is planning to relocate the outfall about 1300 feet downstream from the 

existing outfall location. They are moving the outfall because a large gravel bar has formed 

immediately upstream from the current location and is preventing the effluent from rapidly 

mixing with the river. 

The new outfall is being moved to a deeper location in the river with higher stream velocities. 

The outfall will consist of a 100-foot multiport diffuser with 20 equally spaced diffusers. The 

combination of the new location with the diffuser design will promote rapid mixing of the 

effluent with the river. 

DEQ is proposing to modify the permit to incorporate the location of the new outfall. The permit 

modification is limited to two changes: 

1. The location of the outfall will change from river mile 147.7 to river mile 147.4. 

2. The length of the zone of initial dilution (ZID) will be reduced from 22 feet to 15 feet 

and the mixing zone length will be reduced from 300 feet to 40 feet. 

No other changes are being made to the permit. Comments regarding this permit modification 

are limited to the two changes listed above. 

Discussion 

The Cascade Pacific Pulp mill is located just west of the town of Halsey. It sits adjacent to the 

Georgia Pacific Halsey mill. It is an integrated Kraft process pulp mill that produces bleached 

and unbleached pulp for sale. The facility consists of a pulp mill, chlorine dioxide generator, 

power and recovery, recausticizing process, water treatment and wastewater treatment. Pulp is 

produced from Douglas fir wood chips. The wastewater generated during the pulp production 

process is treated by primary clarification followed by biological treatment in two large aerated 

stabilization basins. The effluent is combined with neighboring GP Halsey and currently is 

discharged to the Willamette River at river mile 147.7 through CPP's outfall. 

CPP is requesting their permit be modified to reflect changes to their outfall location. CPP is 

proposing to move it downstream because of a gravel bar that has formed upstream of the 

existing outfall. Figure 1 shows an aerial photo of the river with the location and size of the 

gravel bar in 2006 compared to 2014. The gravel bar has increased in size and is now preventing 

the river from rapidly mixing with the effluent during low river flow conditions. The existing 

diffuser is a 104.5-foot multi-port diffuser with 19 operating ports. 

PAGE 2 
•

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-:«: a> -^- ,71 

Figure I: 2006 Aerial Photo and 2014 Aerial Photo (source: Google Earth) 

CPP hired a consultant to perform a mixing zone study with the primary objective of finding a 

new outfall location to promote better mixing. Stream depth and velocity measurements were 

taken at various transects downstream of the existing outfall. This data is illustrated graphically 

in Figure 2. The figure clearly shows the low stream velocity at the existing diffuser location. 

The field study also indicated the river current at the existing location was swirling and eddylike. Figure 2 indicates four alternate sites for the outfall. CPP chose site D to locate their new 

outfall (river mile 147.4). Site D was chosen because the river is deeper, experiences higher 

stream velocities and is well downstream 

from the influence of the gravel bar. 

The proposed diffuser is similar in length to 

the existing one. It is 100 feet long with 20 

duckbill ports equally spaced along the 

diffuser line. The ports are pointed 

downstream in a "fanned" orientation to 

optimize mixing (see Figure 3). The 

combined discharge of GP and CPP through 

the proposed diffuser was modeled using the 

mixing zone software CORMIX v9.0. The 

model predicts rapid mixing of the effluent 

immediately downstream of the diffuser. 

Because of the rapid mixing, DEQ is 

proposing to reduce the length of the ZID 

and the size of the mixing zone. The length 

is being reduced so that the dilution at the 

regulatory boundary (e.g. ZID) matches what 

was achieved with the existing diffuser as 

determined during the previous permit 

renewal. The existing diffuser achieved a 

dilution of about 47 at the ZID (22 feet 

downstream). The proposed diffuser 

achieves a dilution of 47 at a distance of 15 

ID»5WYJimMI5l.l5iIte3Q1 

Pratond.ORiWMSUSA A 

Citj v S*atiAiii_ti^i»1 t j rfcTuKoiO ^HWH) 

Figure 2; Bathymetry Field Study Data (Source: MixZon) 

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Unidirectional Perpendicular Fanned-Out Design 

{Hoi to Scale] 

Plan 

View 

Ua (m/sl 

Side 

View 

Figure 3: Diffuser Orientation 

feet downstream. DEQ is proposing to reduce the 

ZID from 22 feet to 15 feet. The existing diffuser 

achieved a dilution of about 85 at the edge of the 

300 foot mixing zone. The proposed diffuser 

achieves the same dilution at a distance of 40 feet 

downstream. DEQ is proposing to reduce the 

mixing zone distance from 300 feet to 40 feet. This 

greatly reduces the size of mixing zone and the area 

potentially impacted by the discharge. Moving the 

outfall downstream also prevents elevated effluent 

concentrations from occurring at the mouth of the 

slough just upstream from the existing outfall. 

Native fish have been documented in this slough as 

it provides good habitat for them. Moving the 

outfall downstream will ensure this critical habitat is 

not impacted by the discharge. Table 1 below lists 

dilution values for the various critical flow scenarios 

that are achieved by the diffuser. 

Table 1: Dilution Values 

*. 1*» 

U ' l 

\cute 

bronic 

I luman Health-

>n carcinogen 

I

I uman Health -

carcinogen 

ZID 

Mixing Zone 

Mixing Zone 

47 

85 

94 

Mixing Zone 193 

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