CDA Paper

CANADIAN DAM ASSOCIATION
ASSOCIATION CANADIENNE DES BARRAGES
CDA 2016 Annual Conference
Congrès annuel 2016 de l’ACB
Halifax, NS, Canada
2016 Oct 15-20
Technical Developments in Fish Exclusion & Guidance,
Debris Barrier & Demarcation Systems
Andrew Peters, Pacific Netting Products, Kingston, WA, USA
ABSTRACT
This presentation will review the developments in materials and technology that have led to successful installations
of fish guidance and collection systems, temperature and algae control curtains, and debris control systems at high
head dams, run of the river facilities, and pumped storage facilities at sites in the US Northwest, as well across the
USA and Canada. The implications of these developments will affect methodology of regulatory compliance for
communities affected by fish passage barriers around the world. We will discuss different designs, various
components and the planning, materials, engineering, operations, and maintenance considerations that all successful
projects require. To illustrate and illuminate, we will provide an introduction to PGE, North Fork Clackamas,
Clackamas, Oregon, USA.
Objective and Value: This presentation will be of interest to researchers, educators, practitioners, biologists,
engineers, tribes, and regulators who are interested in methods to collect, protect, or restore migratory fishes and
aquatic species and those who desire to better understand downstream passage solutions or prevent impingement and
entrainment of species at facilities and comply with regulations.
RÉSUMÉ
Cette présentation porte sur l’évolution des matériaux et des techniques qui ont permis d’installer avec succès des
systèmes de guidage et de collecte de poissons, des écrans de régulation de la température et de lutte contre les
algues ainsi que des systèmes de contrôle des débris à même les barrages de haute chute, les centrales au fil de l’eau
et les installations d’accumulation par pompage de sites aménagés dans le nord-ouest des États-Unis et dans d’autres
régions du Canada et des États-Unis. Les répercussions de ces avancées auront une incidence sur la méthode
employée par les collectivités touchées par des obstacles au passage des poissons à l’échelle mondiale pour se
conformer à la réglementation. On y aborde différentes conceptions et divers éléments de même que les facteurs
nécessaires à la réussite des projets (planification, matériaux, ingénierie, exploitation et entretien). Les projets
suivants serviront à illustrer et à étayer ces questions : PGE, North Fork Clackamas, Clackamas, Oregon, États-Unis.
Objectif et utilité : Cette présentation s’adresse aux chercheurs, aux enseignants, aux praticiens, aux biologistes, aux
ingénieurs, aux collectivités autochtones et aux organismes de réglementation qui souhaitent en apprendre plus sur
les méthodes de cueillette, de protection et de rétablissement des poissons migrateurs et des espèces aquatiques et
avoir une meilleure compréhension des solutions de passe en aval ou des moyens de prévenir l’empiètement et
l’entraînement des espèces aux installations et de respecter la réglementation.

CDA 2016 Annual Conference, Halifax, NS, Canada Page 2 of 11
HISTORY
Sixty years after German chemist Hans von Pechmann noted a precipitate while working with a form of
methane in ether, Karl Ziegler and Erhard Holzkamp invented high-density polyethylene (HDPE). The
process included the use of catalysts and low pressure, which is the basis for the formulation of many
varieties of polyethylene compounds. Phillips introduced HDPE in 1954. Company marketing executives
were wildly optimistic, expecting that the product would be a big hit. But produced in only one grade, it
was unsuitable for some applications. It was the introduction of the immensely popular hula hoop that
caused demand to soar and help pave the way for more practical uses. In 1955, HDPE was produced as
pipe (Gabriel 1998). For his successful invention of HDPE, Ziegler was awarded the 1963 Nobel Prize for
Chemistry. Today these products are used in commercial and industrial applications, including most
recently, for containment, guidance and collection of debris, and floatation of fish guidance systems,
demarcation and security at dams around the world.
To better understand the recent developments, it’s important to understand a bit of the chemistry and
manufacturing process. Polyethylene is a polyolefin produced by polymerizing the olefin, ethylene. A
polyolefin is any of a class of polymers produced from a simple olefin (also called an alkene).
Polymerization is the process of joining the monomers to build up larger molecules. Polyethylene, the
most popular plastic in the world, is the polymer you see most in daily life. This is the polymer in grocery
bags, shampoo bottles, children's toys, and even bulletproof vests (AWWA 2005).
Polyolefins are high molecular weight hydrocarbons. When ethylene is polymerized the result is relatively
straight polymer chains. As a group of materials, the polyolefins, generally possess low water absorption,
moderate to low gas permeability, good toughness and flexibility at low temperatures, and a relatively
low heat resistance (AWWA 2005). A molecule of polyethylene is nothing more than a long chain of
carbon atoms, with two hydrogen atoms attached to each carbon atom. It might be easiest to draw as in
the picture below, (although the chain of carbon atoms being many thousands of atoms long) (Polymer
Science Learning Center 2016).
Figure 1: Chain of Carbon Atoms (Polymer Science Learning Center, 2016)
TYPES OF POLYETHYLENES
Different kinds of polyethylenes are formed as a result of the varying degree of branching in their
molecular structure. HDPE plastics form flexible but tough products and possess excellent resistance to
many chemicals (AWWA 2005). Below are brief descriptions on how polyethylenes differ from each
other.
Linear Low Density Polyethylene: (LLDPE) contains a significant number of short branches in its
molecular structure. Because it has shorter and more branches, its chains are able to slide against each
other upon elongation, without becoming entangled like LPDE (which has long branching chains that
would get caught on each other). This gives LLDPE higher tensile strength and higher impact and
puncture resistance than LDPE. It has a density of 0.91-0.94 g/cm3.

Branched or Low Density Polyethylene is cheaper and easier to make than other types. LDPE (Low
Density Polyethylene) has the most excessive branching. This causes the low density to have a less
compact molecular structure, which is what makes it less dense. It has a density of 0.910-0.925 g/cm3.
MDPE (Medium Density Polyethylene) has a little less branching then the HDPE. It is less notch-
sensitive then HDPE and has better stress cracking resistance. It has a density range of 0.926 - 0.940
g/cm3.
Linear or High Density Polyethylene: (HDPE) has minimal branching of its polymer chains, much
stronger than branched polyethylene. Because it is denser (0.941-0.965 g/cm3), it is more rigid and less
permeable then the LDPE. Much of this paper will be referring to products built of HDPE and different
methods of molding and construction.
UHMWPE (Ultra High Molecular Weight Polyethylene) has extremely long chains, with molecular
weight numbering in the millions (usually between 2 to 6 million). In general, HDPE molecules have
between 700 and 1,800 monomer units per molecule, whereas UHMWPE molecules tend to have 100,000
to 250,000 monomers each. The chains of UHMW align in the same direction. The bonds between the
chains are not very strong, however, because they are so long, there are more bonds holding it together
then polyethylene with shorter chains. These long chains give UHMWPE incredibly high tensile strength.
The longer chains serve to transfer load more effectively to the polymer backbone by strengthening
intermolecular interactions. This causes the material to be very tough and gives it the highest impact
strength of the polyethylenes. It has a density of 0.928-0.941 g/cm3. (US Plastics Corp, 2016) Fiber built
of this material can be extremely beneficial in building flexible screens or barriers (nets) that can be used
for fish guidance or collection. See Table 1 for a comparison of PE Properties.
Table 1: Comparison of PE Properties
Property As Density Increases
As Molecular Weight
Increases
As Molecular Weight
Distribution Broadens
Tensile Increases Increases
Stiffness Increases Increases slightly Decreases
Impact strength Decreases Increases Decreases
Low temperature brittleness Increases Decreases Decreases
Abrasion Increases Increases
Hardness Increases Increases slightly
Softening Point Increases Increases Increases
Stress crack resistance Decreases Increases Increases
Permeability Decreases Increases slightly
Chemical resistance Increases Increases
Melt strength Increases Increases Increases

THERMOPLASTICS AND THERMOSETTING
Plastics material can be classified in two groups, thermoplastics and thermosetting plastics.
Thermosetting plastics can be heated only once. Once heated the material will soften and flow under
pressure. The chemical reactions in this process cause the material to harden and set. Once set, material
will not soften again by applying heat and pressure.
HDPE is a thermoplastic. When heated to a sufficient high temperature it will be softer and flow under
pressure. On cooling it will harden. Repetition of this process a number of times is possible until the
degradation of the material takes place.
While there are many plastic molding processes and techniques to form useful debris and flotation
products, we will discusses only two techniques in this paper, rotational molding and plastic extrusion.
ROTATIONAL MOLDING PLASTICS
Rotational molding or rotomolding is an extremely popular process for producing items that are usually
hollow, including flotation products. Molds for rotational molding are normally split negative molds with
built-up mechanical locking.
In rotational molding a ﬁne powder of plastic is fed into a cold metallic mold, which, after being closed, is
rotated around both the equatorial and polar axes. Then the mold is heated to a temperature above the
melting point of the polymer. The tumbling action in rotational molding somewhat ensures that the
powder is regularly brought in contact with the forming polymer shell. After the melted powder has
covered the entire inner surface of the mold the whole aggregate is cooled at room temperature. The
cooling is carefully controlled to avoid the product shrinking or warping. The mold is opened and the
product is removed.
The process is a single-surface molding process, which means the mold can only affect the quality of one
surface of the molded part. The free (inner) surface cannot have a thickness (or texture) as if it was
formed between two metal surfaces in a mold. As a result, wall thickness tolerance is never as good as
two-surface processes such as extrusion molding. In addition, the need for rapid heat transfer and
minimum weight to facilitate rotation calls for relatively thin walls, which are possible in view of the low
pressure involved. So in rotational molding it is common to specify a minimum wall thickness rather than
a nominal wall thickness. For general purpose, run-of-the-mill parts such as tanks and outdoor toys, the
wall thickness variation in rotomolded parts is typically ±20%. For certain products, such as medical
facemasks and optical parts, a variation of ±10% can be achieved. (Crawford 2003).
Another variable in close tolerances is consistency in molding conditions, particularly the point at which
the plastic part separates from the mold wall. In normal rotomolding, this release point can occur early or
late during cooling, in a fairly random fashion. Part release depends on interactions of variables such as
the amount of release agent on the mold, the cooling rate, the smoothness of the rotational speeds, the
design and shape of the mold, etc. If the plastic part separates from the mold wall, then the air gap
between the plastic and the mold means that the molder has lost control of the cooling rate of the plastic.
This leads to inconsistencies and shrinkage in different areas of the molding, which leads to warpage.
Warpage is a complex process depending on mold size, material from which the mold is constructed,
cooling mode, and presence or absence of release agent. (Crawford 2003).

EXTRUSION OF THERMOPLASTICS
Extrusion plays a prominent part on the plastics industry. Extrusion, unlike molding, is a continuous
process, and can be adapted to produce a wide variety of finished or semi-finished products, including
pipe. This technique is particularly useful when thermal and mechanical means are required to obtain a
uniformly processed product in a continuous operation, such as HDPE (Mamalis 2010). Essentially, it is
not much different from squeezing toothpaste out of the tube. Anything that is long with a consistent
cross section is probably made by extrusion. Common examples are spaghetti, candy canes, chewing
gums, drinking straws, plumbing pipes, door insulation seals, optical fibers, and steel or aluminum I-
beams.
For the plastic extrusion process, plastic pellets or powder (dry blends) are fed into a heated cylinder,
(changing from a solid to a vicious liquid), where rotating screws homogenize it and squeeze it through a
die to give a finished or semi-ﬁnished product. The die is designed to produce the desired shape of the end
product. Extruding can produce soft or rigid items, which can be compact or cellular in form. The formed
material, or extrudate, is cooled and drawn away from the die exit at a controlled rate through a take-off
puller. The take-off puller is a key component that guides the material being exited from the die through
the sizer at a continuous rate, in order to maintain and control the size of the extrusion. This type of
plastic extrusion, a “steady-state process,” converts a thermoplastic raw material to a finished or near-
finished annular product. During the manufacturing process, the plastic pellets or powder may be mixed
with colorants before the process begins, and also may be compounded with other materials, such as
ultraviolet (UV) inhibitors, additives (Mamalis 2010).
In rotational molding the operating pressures are relatively low, allowing molds to be made from less
expensive materials. As a result, lower density resins are used to create full molecular bonding. The
higher pressures that can be created in the extrusion process allow much higher density resins to be used.
It’s this difference in density, the result of both the materials and manufacturing process, that will have an
effect on the suitability of a product for a particular application.
BENEFITS TO DAM SAFETY, FISH PASSAGE, MAINTENANCE AND OPERATIONS
Log booms have been used for years to protect facilities from debris, ice, and waterborne traffic. Trees,
often plentiful, were inexpensive and easily replaced. Constructed in a daisy chain method, the strength of
log boom systems was limited by the chain, wire rope and fittings and attachment methods used, as well
as the strength of the log. However, over time, log booms become waterlogged, and during their life they
will attract a variety of biological growth. With exposure to the environment when the pool is lowered, a
log boom’s life, no matter how it is constructed, will be significantly decreased due to rot and
decomposition.
More recently, barriers for fish guidance and collection systems, as well as facility protection, visibility
and demarcation have been built using colorful, foam-filled plastic floats, strung on a wire like a necklace
(Figure 2). These floats are often fabricated with rotational molding, the casting process described earlier.
The safe working loads of booms built in this fashion depend largely on the strength of the float
connection materials, wire rope, chain, and shackles. Inexpensive, lightweight and easy to install, these
types of floats are similar to those that protect swimmers from boat traffic. When used in heavy debris
applications, the combination of thin wall construction, excessive amounts of moving hardware, lack of
continuity in the boom surface (gaps between floats), and a lack of UV protection can result in limited life
span and costly deployments.

Figure 2: Cowlitz River Debris, PNP Photo
Extruded, high-density polyethylene debris booms have recently been introduced for debris, demarcation
and security in rivers, lakes and ocean environments. One of the benefits of this material is the ability to
conduct a risk analysis in order to size a boom for a particular site. The material is commercially
available, built to standards that have been developed by other industries. Primary among these standards
is ASTM D3350, which is a comprehensive classification standard that delineates seven key properties
associated with piping performance. Ranges of performance for each of these properties are defined
within this standard as well. The material is rugged, flexible, and durable, with outstanding chemical and
environmental stress crack resistance. It is resistant to corrosion with high impact strength and ﬂexibility,
and the standards and construction techniques allow investigation and understanding of each of these
properties. As a non-conductor of electricity, these booms are immune to the electrochemical-based
corrosion process that is induced by electrolytes such as salts, acids and bases, nor are they vulnerable to
biological attack with their non-stick surface that results in low friction factors and exceptional resistance
to fouling.
Operators concerned with containment, guidance and collection of debris, and floatation of fish guidance
systems, demarcation, and security at dams around the world benefit from rigorous industry standards for
HDPE. In addition to those briefly mentioned earlier, other benefits to the industry will include:
Buoyancy: Because HDPE’s density is about 96% of that for fresh water, and about 94% of that for sea
water, these booms float even when full of water.
Ductility (strainability): Because of its relatively high strain capacity, HDPE piping can safely adjust to
variable external forces generated by wave and current action. High strain capacity also allows the HDPE
piping to safely shift or bend to accommodate itself to altered bedding that can result by the under
scouring that may sometimes occur with strong wave and current actions
Corrosion Resistance: Corrosion is one of the costly problems associated with metal debris booms,
connections or attachments to plastic booms. Decomposition is one of costly problems associated with
wooden debris booms. Corrosion can occur both inside outside a pipe, and may require costly cathodic
protection or coatings to try and extend the service life. Unlike other materials, HDPE will not rust, rot or
corrode. This means an extended service life and long term cost savings.

Resistance to Biological Growth: Biological attack may be described as the degradation of the piping
material caused by the action of organisms such as bacteria, fungi, insects, or rodents. HDPE has no
nutritional value. It is considered inert in that it will neither support nor deter the growth or propagation of
micro- or macro-organisms.
Weathering: Over time, ultraviolet (UV) radiation and oxygen may induce degradation in plastics that can
adversely affect their physical and mechanical properties. To prevent this, various types of stabilizers and
additives are compounded into a polymer to give it protection from these phenomena. The primary UV
stabilizer used in HDPE debris booms is carbon black, which is the most effective additive capable of
inhibiting UV induced reactions. Carbon black is extremely stable when exposed to the outdoor elements
for long periods of time and is relatively inexpensive compared to some of the more exotic colorant
systems used in rotomolded products. The result is a piping system of uniform color that does not chalk,
scale, or generate dust in response to extended periods of outdoor exposure. Studies conducted by Bell
Laboratories on the stability of carbon black containing PE used in wire and cable application have shown
that these materials can sustain exposure to the elements over periods of 30 years (AWWA 2005).
Fatigue Resistance and Flexibility: Extruded HDPE pipe is flexible and ductile, not rigid. It has
outstanding resistance to fatigue. High levels of strain can be safely tolerated since the associated initial
stresses in the pipe wall relax and redistribute as the pipe system becomes increasingly stable while
settlement and compaction take place. PE pipe can be field bent to a radius of about 30 times the nominal
pipe diameter or less depending on wall thickness (12” PE pipe, for example, can be cold formed in the
field to a 32-foot radius). With ﬂexibility and good stress crack resistance, PE can be used in many
forms. It functions at temperatures from –54 to +50 °C in low-pressure applications and to 93 °C in non-
internal pressure applications. Where metal pipe ruptures when freezing water expands, flexible HDPE
will not.
Fracture Mechanics: Fracture mechanics refers to the study of crack growth originating from flaws that
may exist within a material or structure. Flaws may be the result of inhomogeneities within a material,
manufacturing inconsistencies, gouges, and scrapes that result from the handling or mishandling of the
finished product or any other number of sources. The fracture resistance of a given structure or material
will depend on the level of stress applied to it, the presence and size of any flaws in it, and the inherent
resistance of the material to crack initiation and growth. Extensive research conducted on gas pipe
indicates that modern PE resins designed for pressure piping applications are extremely resistant to slow
crack growth. The requirements of ANSI/AWWA C906 ensure that water pipe produced in accordance
with this standard will demonstrate comparable levels of resistance to slow crack growth provided that the
pipe system is designed, installed, and operated in accordance with industry standards (AWWA 2005).
Extended Service Life: In many applications, extruded HDPE is the material of choice for both pressure
and non-pressure applications for gas and water distribution systems. Pipe applications require the
product to be installed in the ground for lifetimes sometimes in excess of 100 years. It has a track record
of reliability and durability in service, and cost-effective, long maintenance-free lifetime and low whole-
life costs.
Leak-Free Joints: HDPE piping systems can be joined with leak-free fusion jointing systems. Fusion
involves the heating of two HDPE surfaces then bringing them together to form a permanent, monolithic,
leak-free system. The fusion process for HDPE is proven and has been used by the natural gas industry
for over 40 years. Approximately 95% of all gas distribution piping in the United States is polyethylene
pipe joined by heat fusion. (AWWA 2005)
Eco-Friendly: In addition to its outstanding physical characteristics, HDPE is recognized for its minimal
impact on the environment:

• It takes less energy to manufacture HDPE than non-plastic pipes.
• HDPE is lightweight, resistant to site handling, and can be more cost effective to transport than
metal pipes.
• HDPE does not emit potentially hazardous levels of toxins into the air during production, during
fusion or into the ground or water during use.
• HDPE pipe can be recycled back into non-pressure piping applications.
RECENT APPLICATIONS OF HDPE AND UHMWPE
Proprietary designs using extruded HDPE materials and UHMWPE fibers were recently used at Portland
General Electric’s Clackamas River Hydro Project, Near Portland Oregon (Figure 3). This 54 MW facility
with a hydraulic head of 42 m contains a reservoir that is over 4.5 km long and 225 m wide in the forebay
that typically fluctuates < + .6 m. The facility was required to update their fish passage operations and
installed a floating surface collector (Figure 4) designed by R2 Resources and downstream guidance and
exclusion nets built of 6.35 mm square mesh Dyneema® fibers (UHWMPE) and a proprietary HDPE
Multi-Function Boom™ built by Pacific Netting Products (PNP).
Figure 3: Clackamas River, Figure 4: FSC with Guide Net,
Courtesy of Nick Ackerman, PGE Courtesy of Nick Ackerman, PGE
The spillway exclusion net, 100 m x 32 m deep, limits spillway passage of fish. It is built of 6.35 mm
Dyneema® fibers and fitted with pneumatic floats to drop the net (allowing flow) with spill reaches 10
kcfs. (Figure 4).
The guidance nets attached to FSC are 23 m deep, 152 m long, and were built with 6.35 mm , knotless
Dyneema® square mesh. The top 5 m of the net was covered with a non-permeable 5-ply, 60 mil
Hypalon® fabric to assist with flows. With a design life for 10 years, this flexible barrier is deployed year
round, supported by a float system of .45 m and .6 m hard shell, foam filled, PE floats, supported by 25.4
mm cable, and 762 mm x 6 m foam-filled steel floats. To allow maintenance and operations staff access,
the barrier is fitted with an in-line boat gate that operates at loads up to 7 kip (Figure 5).

Figure 5: North Fork Installation, PNP image
The floating surface collector, barrier and collector nets were the first stage of this project. During initial
operators, several dump truck loads of debris were removed weekly from the FSC. To prevent debris
from interfering with fish passage operations, a Multi-Function Booms™ with a debris curtain, flanged
end fittings to reduce connection hardware, and a debris splashguard was supplied. Access within
restricted areas was provided by means of a manually operated boat gate. To allow ease of shipping,
configuration, and installation, booms were provided in approximately 15 m sections. The booms were
anchored to the shore by embedment anchors, and a mid-barrier spar buoy was supplied to insure correct
orientation for debris guidance by natural river currents. Total length of boom was about 400 m.
TWO KEY COMPONENTS
1) Boom Sections
There were two key components of the Multi-Function Boom: the boom sections, and the debris guidance
and prevention system. Boom sections were of two types, the first of which were non-grounding sections,
15 m long, .6 m diameter, built with a high density polyethylene and designed for a SWL of 34,019 kg at
a 2:1 safety margin. The sections were built with flanged ends and bolted together on site (Figure 6).
The other type of boom section is the grounding section. To allow maximum water surface contact as
pool fluctuation occurs, and to assist with exclusion of debris near shore anchors during these periods of
fluctuation, the shore end sections of the Multi-Function Boom were shorter and joined together with
heavy duty, shackle connections that will allow the boom to contour to the site shoreline topography.
They are approximately 8 m long, and also .6 m diameter, built of the same material. Externally mounted
hot dipped galvanized A36 padeye, designed and rated to match Multi-Function Boom breaking strengths,
were used with load rated shackle to connect these sections.
These shackles (easily inspected by O and M staff) are the only moving part on the entire boom, other
than those on the boat gate. There are no connections of any sort below water line which require
inspection or maintenance; no wire rope, chain or cables holding booms together that wear and break, and
no fittings or attachments where logs or debris can build, snag or become impinged (Figure 7).

Figure 6: Flanged Connection, Figure 7: Connections, Grounding Section
Non-Grounding Section
Because of the material used and process followed, industry standards based on the physical properties of
the combined effect of the three fundamental polymer properties (density, molecular weight, and
molecular weight distribution) can be met. Each section of boom material is built with PE4710 per ASTM
F714 with cell classification 445574C (black) as per ASTM D3350 and PPI-TR4. Each is provided with
Type 1, closed-cell, expanded polystyrene foam logs, conforming to ASTM C578, and sized to fit the I.D.
of the pipe. Attachments are built from HDPE Sheet Material that will comply with ASTM D3350 class
445474C /PE4710 and PE80. The components in the debris boom sections were joined together by fusion
welding, performed by operators with a current Federal Code Title #49, section 192.283, 192.285, and
192.287 certification.
All fusion operators were familiar with full surface butt fusion of polyethylene pipe using heater plates,
and other methods of full surface fusion of polyethylene products. Extrusion welding was not allowed
except in areas of gussets, or where full surface welding was not possible.
2) Debris Skirt
To improve debris collection, a continuous length, heavy duty, 4-ply poly nylon, high quality debris skirt
with a rubber SBR cover compound was attached to the keel of the boom and a continuous small debris
splash guard was fitted to the top of the boom. The skirt is 14.2 mm thick, offers exceptional resistance to
impact, tearing, and abrasion and a 10:1 ratio of working tension vs. break strength with less than 2%
stretch at full working tension The debris skirt was weighted with galvanized chain in areas where the
skirt may be in contact with the sea bed, (Figure 8) or with weight bars of in all other areas (Figure 9).
The skirt weight was twenty pounds per lineal foot. Skirt depth was 1.2 meters below the keel and the
keel is approximately 10 cm below the waterline of the Multi-Function Boom. The skirt was attached the
boom keel with 12 mm structural hex bolts and galvanized clamp plate, providing 100 percent connection
strength. The splash guard is a welded fitting to the length of boom. This system was designed to provide
the best possible debris guidance and collection, to prevent debris from passing under or over the boom
and to assist in the guidance of the debris to a particular location on shore for easy removal.

Figure 8: Debris Guidance Skirt, Figure 9: Debris Guidance Skirt,
Grounding Section Non-Grounding Section
CONCLUSION
The use of HDPE extruded material for debris and demarcation, and the use of UHMWPE for fish
guidance and collection as discussed in this paper can allow operators better control over their
investments in operations, safety and environmental compliance. The guidance and exclusion nets at the
PGE North Fork site, built of the UHMWPE fiber, and the debris booms to protect the dam facilities,
have resulted in record downstream migrant counts from the period of 1958 – 2015 which summarized
briefly include:
• September 2015: Record count of Chinook juveniles (3x previous record)
• October 2015: Record count of coho juveniles
• November 2015: Record count of coho juveniles (4x previous record)
• November 2015: Record count of steelhead juveniles
• November 2015: Record count of lamprey macropthalmia
These results, combined with knowledge and understanding of the benefits of the materials, including
their strength, longevity and lifetime cost, should give dam operators comfort in the ever-increasing
pressures of risk management and environmental compliance.
REFERENCES
AWWA (American Water Works Association) Manual M55. 2005. Engineering Properties of Polyethylene.
Crawford, R.J. and M. P. Kearns, 2003. Practical Guide to Rotational Moulding, 2nd
Edition, Shawbury,
Shrewsbury, Shropshire, SY4 4NR, UK.
Gabriel, Lester H. 1998. The Complete Corrugated Polyethylene Pipe Design Manual and Installation Guide.
University of California, 1998.
Mamalis, A. G., K. N. Spentzas, G. Kouzilos, I. Theodorakopoulos, and N. G. Pantelelis, 2010. On The High-
Density Polyethylene Extrusion: Numerical, Analytical And Experimental Modeling. Advances in Polymer
Technology, John Wiley & Sons, Ltd. Vol.29: pp 173-184.
Polymer Science Learning Center. Internet accessed August 1, 2016. http://pslc.ws/macrog/pe.htm
US Plastics Corp. Internet accessed August 1, 2016.
http://www.usplastic.com/knowledgebase/article.aspx?contentkey=508

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