Questions and Answers Set 4

July 8, 2015 Set 4 TO: All Potential Respondents

RFB 1414 River Tower Shoreline Restoration and Water Quality Improvement Project

FROM: Anita Hoover, Procurement Specialist 3 SUBJECT: Response to Questions QUESTION 1: On plan sheets 3, 4 and 5 in the notes on all three plan sheets it states,

“Deltalok material to be installed as designed by Natural Capital Solutions or approved equal”. I have looked and I have had vendors look and we cannot find any information on Natural Capital Solutions or a supplier for the Deltalok bags.

In the Response to Questions, Set 2. The response to question 11 is: “Envirolock is not an approved equivalent at this time”.

Can the supplier of the Deltalok bags be provided or can the name of an approved equal product be provided?

ANSWER: DeltaLok is now Terra-Gen in the United States. Erosion Management

Systems (EMS) is the regional representative and all questions related to DeltaLok and the Terra-Gen System are to be directed to Thomas Goebel, Natural Capital Solutions, LLC at 4608 N. Hale Avenue, Tampa, FL 33614, 727-458-4524, fax 813-443-5632.

The Terra-Gen System produced by EMS is an approved equivalent to

DeltaLok. Attached is the Engineer’s Manual for Terra-Gen.

Terra-Gen Engineer’s Manual

Engineers Design Manual

Engineer’s Design Manual - 3

Introduction

The Terra-Gen Erosion Control and Restoration System is a unique patented system that can construct

permanent structures with a vegetated face without using concrete rebar or other armored materials. The Terra-

Gen System is also the only earth retention system that does not use concrete or steel.

Terra-Gen amplifies the power of interconnecting sand/soil bags by leveraging upon existing industry practices

and standards. For example, the Terra-Gen System works with MSE (Mechanically Stabilized Earth) principles

that have been used in earth stabilization projects throughout the world for over 25 years. Another example of

how the Terra-Gen System works with existing industry know-how is illustrated through the Terra-Gen GTX line of

sand/soil bags. This line of bags is made from non-woven geotextile, a common material known for its soil

filtration, water permeability, root friendliness and strength.

Before construction begins, standard design guidelines and engineering requirements must be reviewed. Will

the retaining wall be a ‘critical’ structure requiring engineering documentation or will it be a ‘non-critical’ structure

falling within basic design and construction methods? The following conditions will require a full engineering

study:

The wall height, including terraces, exceeds 3’-6’ (depending on jurisdictions)

The wall will be built on unstable soils, such as clays or organic materials

The wall will encounter hydrostatic loading or erosion from wave action, drainage or site runoff

The wall will encounter loading conditions resulting from slopes or structures behind or above the wall

The wall will use geo-grid soil reinforcement or other mechanical stabilization devices

Product Name

Terra-Gen Erosion Control and Restoration System

Manufacturer

Erosion Management Solutions, LLC.

147 Keating Drive Belle Chasse, LA 70037

Tel: (504) 433-8142 Fax: (504) 433-3103 Email: [email protected]


Height: 1.6 in (50.800 mm)

Length: 12 in (304.80 mm)

Width: 3.5 in (88.900 mm)

# Spikes: 4 with capacity for 4 more

Weight: 0.13 lbs (59 grams)

Product Description The Terra-Gen System is a patented system used to create attractive vegetated earth slopes and walls for a

variety of purposes including environmental walls, erosion control, vegetated retained slopes, stream bank

stabilization and retaining walls.

Terra-Gen standard connector units are made from high strength polypropylene. The standard units are used to

interlock Terra-Gen GTX bags, thereby increasing the shear strength of the structure, enabling the creation of tall,

steep, and eco-friendly earth walls. The units are resistant to damage before, during, and after construction in all

climates. They are recyclable and reusable.

Spikes (for bag interconnection and for geogrid connection) are molded into the Terra-Gen connector units. As

sand/soil bag wall courses are installed, Terra-Gen standard units are positioned such that their spikes interlock

the Terra-Gen GTX bags. At all levels where geogrid is required, Terra-Gen standard units are used to also

connect the geogrid to the wall face.

Specifications

Terra-Gen Standard Connector Unit

Raw material: 100% polypropylene

100% recyclable

Provides a positive connection between the sand/soil bags, effectively interconnecting each and every sand/soil

bag into one solid unit. Terra-Gen GTX Bags

Terra-Gen GTX bags provide the ideal planter block for permanent vegetation.

These bags are water permeable, provide filtration and are root friendly.

Product Name Size Approx. Facing

Area/Bag (sq ft)* Approx. Facing

Area/Bag(sq m)*

Terra-Gen GTX-W 15 in x 35 in 1 sq ft. 0.10

* Facing area per bag will vary depending upon quantity of bag fill

The Terra-Gen GTX-W are manufactured from non-woven geotextile. These bags have the following characteristics:

Physical Hydraulic

Raw Material 100% Polypropylene Raw Material 100% Polypropylene

Grab Tensile Strength 90 lb (0.40 kN) Apparent Opening Size 70 U.S. Sieve (0.212

mm)

Trapezoidal Tear 40 lb (0.178 kN) Permittivity 2.2 1/sec

Mullen Burst 190 psi (1309 kPa) Flow Rate 150 gpm/sf

(6095 1/min/sq m)

UV Resistance 70% @ 500hrs


Terra-Gen GTX bags can be manufactured using alternate geotextile characteristics based on site specific needs.

Minimal project quantities apply.

To maximize wall uniformity and efficiency care should be taken to fill the bags completely and consistently. A

variety of bag filling machines are available for this purpose. Please note that the amount of wall facing covered

by the Terra-Gen GTX bags varies from job to job because of different fill materials, different quantities, and different closing techniques.

Geogrid

Geogrid is a commonly used component for engineered walls and will be specified by the project engineer.

The Terra-Gen System has been designed to work with all brands of geogrid.

When installing geogrid, ensure that it is flat when it is placed onto the backfill. This can be achieved by rolling out

the geogrid, and then pinning it into position (straight back, with flat surface) at the back of the backfill zone. By

placing backfill from the back of the backfill zone to the front of the backfill zone, the weight of the backfill will help

keep the geogrid straight and flat.

Wall Installation

The following topics cover the specific installation instructions for installing a Terra-Gen system.

Tools Required

Safety protection

Shovels

Tape Measures

Compactor

Broom

Site levels

Wheelbarrow

String line

Handheld stitching machine (Optional)

Bag filling machine (Optional).

Excavate Site

The project site may need to be excavated, and should be done so to the lines and grades shown on the con-

struction drawings. During excavation, care should be taken not to disturb additional foundation material.

The foundation must be adequately compacted to minimize wall settlement. The excavated area must be large

enough to accommodate the sand/soil bag embedment, and the required geogrid lengths.

Construct an embedment trench as specified in the engineering documentation, as required.

Take care to place the excavated materials in a convenient location if site materials will be used to fill the bags.

Reasonably Level Base

No footings are required. Only a reasonably level and compacted base is required. Note that a drainage zone

behind the wall face is not required because the wall face is water permeable. The permeability of the wall face

reduces hydrostatic pressure and helps maintain vibrant vegetation by providing hydration to the root zone.

Fill and Close Bag

We recommend filling the bags right at the job site, to minimize transportation and handling costs. Depending on

the job size, a variety of bag filling methods are available, which will work well with the Terra-Gen GTX bags.

To achieve optimum coverage ensure bags are completely filled.


Depending upon the application, suitable bag fill materials include:

Site soils

Top soils

Crushed stone

Blend of above materials

There are also a variety of techniques to close the bags, including:

Zip tie/Cable tie (Zap Strap)

Fold over technique

Industrial handheld sewing machine

Initial Base Course

Once the surface has been reasonably leveled, place filled bags to create the base course. Level the bags front to

rear and side-to-side.

After the base course units have been properly positioned, place and compact soil backfill behind and in front of

the bags to prevent shifting. Install the entire length of the base course before starting succeeding courses, if pos-

sible.

Interlock Base Course & Succeeding Courses

Place Terra-Gen standard units on top of the bags toward the edges so that each standard unit spans two bags

(see diagram on next page). Stagger succeeding courses of bags so that each standard unit pierces the middle

underside of the Terra-Gen GTX bag above it.

Engage interlocking feature by walking along each course of Terra-Gen GTX bags. This practice is recommended

to ensure good contact between the units and the bags.

Place Succeeding Courses

Succeeding courses will be set upon previous courses so that each top sand/soil bag will be placed over two bot-

tom sand/soil bags with one Terra-Gen standard unit sandwiched between the upper and lower courses. This will

create a running bond face pattern. Continue placing sand/soil bags, drainage aggregate and reinforced backfill.

The weight from the top courses will drive the standard units into the sand/soil bags, forming a positive connection

between the sand/soil. 1 Place base course of Terra-Gen GTX

Bags

2 Place a Terra-Gen standard unit such that

it spans the two Terra-Gen GTX bags

3 Place the second course of the Terra-Gen GTX bags

4 Repeat for the entire wall with same pattern


Walking along the courses of Terra-Gen GTX bags, or tamping the tops of the Terra-Gen GTX bags will help

ensure that the Terra-Gen GTX bags are securely interlocked.

Compacting the Backfill for Engineered Walls

Proper compaction of backfill is critical to the stability of engineered or mechanically stabilized earth walls. Poorly

compacted soil puts extra pressure on the wall, especially when loose backfill gets wet. Geogrid reinforcement

does not work if the soil around it is not properly compacted. The backfill soils should be compacted to a minimum

95% Standard Proctor. Both the type of material and the compaction equipment need to be considered when ad-

dressing this issue.

Consult an engineer for specific recommendations and use the following basic guidelines as illustrated on the fol-

lowing page for engineered walls.

a. Backfill material must have the proper moisture content for optimum performance when compacting.

b. Organic or heavy clay material should not be used. These materials hold excessive moisture and will not

compact properly.

c. Walk behind mechanical compaction equipment may be used to compact soils.

d. Ride-on mechanical compaction equipment should be operated no closer than within 3 feet (1 meter) of

the wall face.

e. Avoid over-compacting soils next to the wall face in an uncontrolled manner.

f. Qualified personnel should perform all soil testing. Soil tests should be taken no closer than three feet

from the back surface of the Terra-Gen GTX bags.

The proper thickness of material placed in a single lift is dependent on the type of soils and compaction equip-

ment being used. Most inorganic site soils, which are easily influenced by moisture levels, must be placed in

smaller lifts and will require greater compaction effort.

For your reference Terra-Gen has available standard engineering drawings for engineered walls depicting typical

installations to assist design professionals in specific applications. Install Geogrid for Engineered Walls

Geogrid is used to reinforce retained soil fill. Site, soil, wall loading, and seismic conditions all influence the design

of geogrid reinforcement.

Geogrid reinforcement is placed at wall elevations as shown on the construction drawings. At courses where the

construction drawings indicate that geogrid is required, use Terra-Gen engineered units. The Terra-Gen

engineered units not only interconnect the bags, but also provide a mechanical connection for the geogrid. To

connect the geogrid to the Terra-Gen engineered units, simply fit the geogrid over the hooks and pull taut.

Once the geogrid is anchored, lay the required length horizontally and ensure the highest strength direction is

perpendicular to the wall face.

When installing geogrid, ensure that it is flat when it is placed onto the backfill. This can be achieved by rolling out

the geogrid, and then pinning it into position (straight back, with flat surface) at the back of the backfill zone. By

placing backfill from the back of the backfill zone to the front of the backfill zone, the weight of the backfill will help

keep the geog rid straight and flat.

Build the next wall course to further drive the Terra-Gen engineered units into the bags and help anchor the

geogrid to the wall, then place and compact backfill on top of the geogrid.

Geogrids are usually stronger in one direction than the other, so it is very important to place them in the correct

direction. The strongest direction of the grid must be perpendicular to the wall face. Follow the geogrid manu-

facturer’s directions to ensure the geogrid is properly oriented. Also note, the geogrid type, length, and spacing

varies from different manufacturers and different specifications. Reference to installation guidelines for geogrid

product is recommended.


Repeat

Repeat steps 5-8 until all courses have been placed.

Capping/ Top of Wall

For the final row of taller walls, rotate the bags 90 degrees such that they extend further into the backfill to provide

an effective capping solution if required. Another capping method is to build a self-standing wall at the top as per

the Design Drawings.

Facing Options

Terra-Gen GTX bags are designed to accommodate any desired vegetation; roots can penetrate the Terra-Gen GTX bags without damage. Once established the roots help to increase the strength of the wall.

Vegetation Choice

1. Grasses/Turf

2. Bushes

3. Willow, Alder, Dogwood cuttings

4. Riparian Plants/Native Species

5. Wild Flowers

6. Vines, etc.

Methods of Achieving Vegetated Wall Face

1. Hydroseeding

2. Live Staking

3. Brush Layering

4. Seed Scattering

5. Plugs

Vegetation Selection

When selecting appropriate vegetation species, consider the following points:

1. Maintenance free cover crops can eliminate the need for trimming

2. Drought tolerant species may be recommended for more arid climates

3. Freeze tolerant species may be recommended for colder climates

Local vegetation experts should always be consulted


Design Method Earth Pressures

Active pressure SRW’s yield slightly Coulomb’s or Rankine

Tied back wedge

Tiers Most complex designs

Create steep slopes

Setback 2:1

Closer spacing surcharges External Overturning Stepping Six inch increments

Stability Sliding Bearing

Global

Walls Make top steps symmetrical Returns for steep steps

Stepped base affects grid

Internal Pullout Adjoining Posts behind wall preferred

Stability Over-stress Sliding

Structures Allow for movement Units cannot cantilever

Facial Stability Connection

Shear

Overturning at top

Design Limits Grid length Grid spacing

Shoreline Requires more drainage Scour protection Foundation concerns Rapid draw down

Rules of Thumb Embedment for Engineered Walls

At least one-tenth the height of the wall should be buried below the final grade in front of the wall when grade is

level. Embedment depth increases for special conditions. Tiers

The lateral distance between the tiered walls should be at least twice the height of the lower wall. If horizontal

spacing must be closer than this, the lower wall(s) should be designed and reinforced to withstand additional load

from the upper walls.

Maximum Height Without Geogrid

In best site and soil conditions, we recommend a maximum of 4-6 feet, though this does depend on specific juris-

diction requirements.

Geogrid Lengths

Lengths for level backfill walls are generally 0.6 to 0.7 times the wall height. Lengths increase with increased

slopes and increased wall loads.

Maximum Geogrid Spacing

Vertical spacing between geogrid layers should not exceed 2 feet in general.


Questions and Answers Question 1: How high can Terra-Gen walls be built without the use of geogrid?

Terra-Gen walls can be constructed between 2’ and 6’ high without geogrid depending on soil conditions,

amount of batter used, and surcharge on top of the wall. Typically, under good soil conditions, we recommend

geogrid be used for walls exceeding 4’ in height.

Question 2: Are concrete footings necessary?

No. The Terra-Gen GTX bags are soft and can adapt to imperfections in the base. Therefore a leveled

surface is usually sufficient unless the design engineer requires further sub-base.

Question 3: How high can I build a Terra-Gen wall?

It can be built as high as you need to. Terra-Gen walls can be built as high as any concrete modular block wall

because it is based on the same MSE principles. Terraces are often incorporated into tall walls.

Question 4: How many Terra-Gen GTX bags should be buried at the base?

Typically the ratio is 1:10 (one course should be buried for every 10 courses above the surface). In most

cases, other than where the grade slopes away from the wall at the base, 3 to 4 units are the maximum to be

buried on tall walls. More than that does not create an added benefit. For extreme ground water conditions

and in frost conditions we recommend filling the sand/soil bags with crushed stone.

Question 5: Should construction be started at one end of the wall or is it acceptable to start in the

middle?

Construction of the wall should begin at your lowest point whenever possible. Question 6: How do I finish the top of the wall off (capping)?

For the final row of taller walls, rotate the bags 90 degrees such that they extend further into the backfill to

provide an effective capping solution if required. Another capping method is to build a self-standing wall at the

top as per the Design Drawings.

Question 7: How high can Terra-Gen GTX bags be stacked before placing the backfill?

We recommend placing and compacting backfill every two courses at least. This aids in keeping the wall

straight and helps ensure good compaction.

Question 8: What type of material should be used for backfill?

Granular materials such as rock and sand are best if available. These types of materials compact fairly easily

and will not hold excessive moisture. Terra-Gen walls can be built with silty material and lean clays, but these

types of soils require more compaction and care should be taken not to place these materials when they are

wet. High clay soils that shrink and swell rapidly as well as organic soils should be avoided.

Question 9: How often do I need to compact the fill soils?

We recommend placing and compacting fill every two courses at least to avoid putting unnecessary pressure

on the wall. Thick lifts of soil require more compaction effort and create a greater force at the back of the wall,

generally 8 inch (20 cm) lifts is the recommended maximum. Consult with a geotechnical engineer for further

compaction criteria based on specific site soil.


External Stability Failures

BEARING OVERTURNING GLOBAL

Internal Stability Failures

PULLOUT INTERNAL SLIDING BREAKAGE Facial Stability Failures

SHEAR STRENGTH CONNECTION STRENGTH Basic Reinforcing Design Methodology for the Engineer

To properly stabilize a segmental retaining wall system the reinforced soil mass must be designed large enough to

resist loads from outside the wall system (external stability) and must contain enough soil reinforcement to keep

the soil mass together (internal stability).

For external stability, the reinforced soil mass must have sufficient width to resist sliding, overturning, and bearing

failure. For internal stability, soil reinforcement must have sufficient strength and layers to resist tensile overstress

(breakage) and sufficient length to resist pullout from stable soil.

Various wedges of soil which could move forward, away from stable soil, are analyzed to ensure that soil rein-

forcement layers have sufficient anchorage to hold these wedges in place.

External soil loads are calculated by traditional earth pressure theories used for design of any retaining walls. In-

ternal forces on geosynthetic soil reinforcement are calculated using two soil properties – internal angle of friction

and soil unit weight.

Accurate knowledge of these properties is needed for proper wall design. Generally, the cohesion of any fine-

grained soils is conservatively ignored to simplify design.

Passive resistance against sliding, provided by soil in front of wall bases, is also conservatively ignored.


Applications

The Terra-Gen System has a wide variety of applications including: Environmental Applications

Erosion Control

Steep Slope Stabilization

Storm water & Drainage

Fisheries Sensitive Creeks and Streams

Trail Enhancement

Culvert Headwalls

Riverbank Protection & Remediation

Slope and Slip Repairs

Open Pit Mining Restoration

Infrastructure Applications

Retaining Walls

Highway Walls

Bridge Abutments

Levees/Dikes & Berms

Noise and Roadside Barriers

Military & Emergency Applications

Flood Protection

Ammunition Storage Points (ASP’s)

Blast Walls/Bunkers

Commercial & Residential Applications

Garden Walls

Landscaping

Golf Courses

Advantages

The Terra-Gen System offers many advantages including:

Lightweight components

Easy to transport, store and handle

Variety of natural wall faces are possible

Modular construction ensures long term performance, soil containment keeps fines intact

Minimal site preparation; builds faster than other systems, resists settlement activity and hydrostatic pressure, no sagging, bulging, cracking or staining…graffiti proof

No footing or leveling pad required


Maintenance

The Terra-Gen System does not require any maintenance if appropriate seeds are selected for the wall face. Proper engineering design, installation and site preparation will ensure a maintenance free wall.

Technical Services

Terra-Gen System distributors are trained and knowledgeable of the product and installation, and can answer most questions. Please contact us if additional detail and information are required.

Documents

Questions and Answers Set 4