(Commentary: This guide specification is set up for a post-bid design solicitation to solicit Soil Screw Retention® Wall System designs where the Owner has selected a soil nail wall as the preferred wall type for the given wall location(s). It can be modified as appropriate to also serve as a pre-bid design solicitation and/or for a solicitation where alternate wall types are allowed by the Owner, with the Contractor allowed to select and submit a design for the wall type which the Contractor feels is most cost-effective.)

1.0 DESCRIPTION. This work consists of designing and constructing permanent SOIL SCREW® Retention Wall System(s) at the locations shown on the "Layout Drawings." The Contractor shall furnish all labor, plans, drawings, design calculations, or other materials and equipment required to design and construct the wall(s) in accordance with this Specification and the _____ Standard Specifications. (Commentary: If walls are temporary rather than permanent, revise above wording.)

Where the imperative mood is used within this Specification for conciseness, "the Contractor shall" is implied.

1.1 Contractor's Experience Requirements. The Contractor shall be experienced in the construction of permanent soil nail retaining walls and have successfully constructed at least 3 projects in the last 3 years involving construction of permanent soil nail retaining walls totaling at least 10,000 square feet of wall face area and at least 500 permanent soil nails. A brief description of each project with the Owner's name and current phone number shall be included.

A Registered Professional Engineer employed by the soil nailing Contractor and having experience in the construction of at least 3 completed permanent soil nail retaining wall projects over the past 3 years, shall supervise the work. The Contractor shall not use consultants or manufacturer's representatives to satisfy the supervising Engineer requirements of this section.

The soil nail wall shall be designed by a Registered Professional Engineer with experience in the design of at least 3 successfully completed permanent soil nail retaining wall projects over the past 3 years. The wall designer may be either an employee of the Contractor or a separate Consultant designer meeting the stated experience requirements.

At least 45 calendar days before the planned start of wall excavation, the Contractor shall submit the experience qualifications and details for the referenced design and construction projects, including a brief project description with the owner's name and current phone number. Upon receipt of the experience qualifications submittal, the Engineer will have 15 calendar days to approve or reject the proposed soil nailing Contractor and Designer.

1.2 Pre-Approval List

The following soil nailing design-build specialty Contractors are pre-approved:

1. Contractor Name
Mailing Address
Contact Name
Phone Number

2. Contractor Name
Mailing Address
Contact Name
Phone Number

3. Contractor Name
Mailing Address
Contact Name
Phone Number

1.3 Available Information. Available information developed by the Owner, or by the Owner's duly-authorized representative include the following items:

1. "Layout Drawings" prepared by __________, dated __________.The "Layout Drawings" include the approved preliminary plans, profile and typical cross sections for the proposed SOIL SCREW^® Retention Wall System locations. (Commentary-Specifier: Refer to Chapter 8 of the FHWA "Manual for Design and Construction Monitoring of Soil Nail Walls," Report No. FHWA-SA-96-069 for detailed guidance on conceptual plan information to provide on the Design-Build "Layout Drawings.")

2. Geotechnical Report No. ___, titled ______, dated ______, included in the bid documents, contains the results of test pits, exploratory borings and other site investigation data obtained in the vicinity of the proposed wall locations.

1.4 Soil Nail Wall Design Requirements. Design the soil nail walls using the "CHANCE Soil Nail Wall Design Manual Using the SOIL SCREW® Retention Wall System," 1997. The required partial safety factors, allowable strength factors and minimum global stability soil factors of safety shall be in accord with the manual, unless specified otherwise. Estimated soil design shear strength parameters, slope and external surcharge loads, type of wall facing and facing architectural requirements, soil nail corrosion protection requirements, known utility locations, easements, and rights-of-way will be as shown on the "Layout Drawings" or specified herein. Structural design of any individual wall elements not covered in the manual shall be by the service load or load factor design methods in conformance with Article 3.22 and other appropriate articles of the 15th Edition of the AASHTO Standard Specifications for Highway Bridges including current interim specifications. The seismic design acceleration coefficient is _______g.

1.5 Soil Nail Wall Design Submittals. At least 30 calendar days before the planned start of wall excavation, submit complete design calculations and working drawings to the Engineer for review and approval. Include all details, dimensions, quantities, ground profiles, and cross-sections necessary to construct the wall. Verify the limits of the wall and ground survey data before preparing drawings.

1.5.1 Design Calculations. Design calculations shall include, but not be limited to, the following items:

(1) A written summary report which describes the overall soil nail wall design.

(2) Applicable code requirements and design references.

(3) Soil Nail wall critical design cross-section(s) geometry including soil strata and location, magnitude, and direction of design slope or external surcharge loads and piezometric levels.

(4) Design criteria including soil shear strength (friction angle and cohesion), unit weights, and screw anchor pullout resistance.

(5) Design calculation sheets with the project number, wall location, designation, date of preparation, initials of designer and checker, and page number at the top of each page. Provide an index page with the design calculations.

(6) Design notes including an explanation of any symbols and computer programs used in the design.

(7) Soil Nail wall final design cross-section(s) geometry including soil strata and location, magnitude, and direction of slope or external surcharge loads and piezometric levels with critical slip surface shown along with minimum calculated global stability soil factor of safety for SLD design, and required nail lengths and strengths for each nail row.

(8) Structural design calculations for wall facing(s) and nail head/facing connections including consideration of facing flexural and punching shear strength, headed studs tensile strength, upper cantilever, minimum reinforcement ratio, cover and splice requirements.

(9) Other design calculations.

1.5.2 Working Drawings. Working drawings shall include, but not be limited to, the following items:

(1) A plan view of the wall(s) identifying:

(a) A reference baseline and elevation datum.

(b) The offset from the construction centerline or baseline to the face of the wall at its base at all changes in horizontal alignment.

(c) Beginning and end of wall stations.

(d) Right-of-way and permanent or temporary construction easement limits, location of all known active and abandoned existing utilities, adjacent structures or other potential interference. The centerline of any drainage structure or drainage pipe behind, passing through, or passing under the wall.

(e) Limit of longest nails.

(f) Subsurface exploration locations shown on a plan view of the proposed wall alignment with appropriate reference baselines to fix the locations of the explorations relative to the wall.

(2) An elevation view of the wall(s) identifying:

(a) The elevation at the top of the wall, at all horizontal and vertical break points, and at least every 30 feet along the wall.

(b) Elevations at the wall base and the top of leveling pads for casting CIP facing (if applicable).

(c) Beginning and end of wall stations.

(d) The distance along the face of the wall to all steps in the wall base.

(e) Nail locations and elevations; vertical and horizontal nail spacing; and the location of wall drainage elements and permanent facing expansion/contraction joints (if applicable) along the wall length.

(f) Existing and finish grade profiles both behind and in front of the wall.

(3) Design parameters and applicable codes.

(4) General notes for constructing the wall including construction sequencing or other special construction requirements.

(5) Horizontal and vertical curve data affecting the wall and wall control points. Match lines or other details to relate wall stationing to centerline stationing.

(6) A listing of the summary of quantities on the elevation drawing of each wall showing estimated square feet of wall face areas and other pay items.

(7) Wall typical section including staged excavation lift elevations, wall and excavation face batter, nail spacing and inclination, nail bar sizes, and corrosion protection details.

(8) A typical detail of production and test nails defining the nail length, inclination, and test nail configuration.

(9) Details, dimensions, and schedules for all nails, reinforcing steel, wire mesh, bearing plates, headed studs, etc., and/or attachment devices for shotcrete, cast-in-place or prefabricated facings.

(10) Dimensions and schedules of all reinforcing steel including reinforcing bar bending details.

(11) Details and dimensions for wall appurtenances such as barriers, coping, drainage gutters, fences, etc.

(12) Details for constructing walls around drainage facilities.

(13) Details for terminating walls and adjacent slope construction.

(14) Facing finishes, color and architectural treatment requirements (if applicable) for permanent wall facing elements.

The drawings and calculations shall be signed and sealed by the Contractor's Professional Engineer and by the Consultant designer's Professional Engineer (if applicable), previously approved by the Owner's Engineer. If the soil nail Contractor uses a Consultant designer subcontractor to prepare the design, the soil nail Contractor shall still have overall contract responsibility for both the design and the construction.

Submit three sets of the wall drawings with the initial submission. One set will be returned with any indicated corrections. The Engineer will approve or reject the Contractor's submittals within 15 calendar days after receipt of a complete submission. If revisions are necessary, make the necessary corrections and resubmit three revised sets. When the drawings are approved, furnish five sets and a Mylar sepia set of the drawings. The Contractor will not be allowed to begin wall construction or incorporate materials into the work until the submittal requirements are satisfied and found acceptable to the Engineer. Changes or deviations from the approved submittals must be resubmitted for approval. No adjustments in contract time will be allowed due to incomplete submittals.

Revise the drawings when plan dimensions are revised due to field conditions or for other reasons. Within 30 days after completion of the work, submit as-built drawings to the Engineer. Provide revised design calculations signed by the approved Registered Professional Engineer for all design changes made during the construction of the wall.

2.0 MATERIALS AND 3.0 CONSTRUCTION REQUIREMENTS. Construct the wall according to the approved drawings and the appropriate Sections in the Standard Specifications as applicable. Materials and construction requirements will be as set forth in the Permanent Soil Nail and Wall Excavation and Temporary Shotcrete Facing and Wall Drainage Specifications. All portions of these Specifications will apply except for Measurement and Payment, which will be as set forth below.

(Commentary: This solicitation is written assuming the Owner Agency will still provide construction inspection of the design-build construction. If not the case, and more responsibility for construction inspection and testing is to be placed on the Contractor, then the referenced construction specifications should be modified accordingly.)

4.0 METHOD OF MEASUREMENT. The unit of measurement for soil nailed walls will be lump sum for each wall listed on the bid schedule. When plan dimension changes are authorized during construction to account for field conditions, the lump sum price of the wall will be adjusted by applying a calculated per square foot cost adjustment factor to the added or decreased wall front face area resulting from the change. The adjustment factor will be determined by dividing the lump sum price bid for each wall by its original shotcrete facing front face area shown on the original approved working drawings. If the actual quantity increases or decreases by more than ____ percent from the original plan quantity, as authorized by the Engineer, the contract price will be adjusted per subsection _________ of the Standard Specifications.

5.0 BASIS OF PAYMENT. Payment will be full compensation for all labor, equipment, materials, tests, and incidentals necessary to acceptably design and construct the SOIL SCREW™ Retention Wall System, including the wall drainage network and the temporary shotcrete construction facing or permanent shotcrete facing (if applicable).

Pay Item	Measurement Unit
Soil Nail Retaining Wall No. 1	Lump Sum
Soil Nail Retaining Wall No. 2 Lump Sum	Lump Sum

If required, permanent CIP facings or CIP drainage gutters will be measured and paid for separately per Lump Sum in accordance with Section _______ of the Standard Specifications or CIP Facing special provision.