SPECIFICATIONS FOR NEPTUNE RETAINING WALL / SLOPE SYSTEM ( rev. 2003 )
Facing units shall be Neptune modules as manufactured by, or under license from, Hercules Mfg., Inc. The units shall be
(___product type ___). The Neptune modules shall be identified from the face by an indention or depression at the top center of
the face in accordance with the drawings. Neptune modules are designed to be installed with an average side to side spacing
between modules of 8” for the Neptune Standard and Mega. The modules shall be designed to interlock when installed
according to the specifications so as to form a flexible, stable and plantable structure. Neptune modules shall have a divided
trough and protruding cross bars or “ears” extending from each side wall in accordance with the drawings. Neptune modules are
designed to be installed side-to-side so that the “ears” overlap one behind the other. The modules allow for variable setback
between 70° and 45° from horizontal as allowed within the context of each style and shown on the construction drawings and
system specifications. Each Neptune module shall have a solid bottom fill-receiving trough, which is open and unbounded at the
rear, allowing fill within the modules trough to be completely compacted and in contact with the retained mass. Color shall be
chosen by the owner. Neptune modules shall be made of concrete meeting the requirements of ASTM C 1372-97. Compressive
strength shall be a minimum 4000 psi @ 28 days with a maximum 5% absorption.
The Standard unit shall be 19” wide x 18” deep with a 8” course height, 165 lbs unit wt. and 1.5 sf coverage per unit.
The Mega unit shall be 19” wide x 24” deep with a 8” course height, 200 lbs unit wt. and 1.5 sf coverage per unit.
The backfill material shall be compacted (rock or soil) in accordance with these requirements (__ properties__)
The reinforcement shall be (_product code_) geogrid or woven geosynthetic as indicated on the plans.
The geotextile filter fabric shall be Mirafi 140N or Amoco 4547.
The drainage composite shall be Multiflow tubing as shown on the construction drawings
The leveling pad shall be constructed of compacted crushed rock similar to 1” minus, unless otherwise specified on the plans.
Foundation soil shall be excavated as required for the leveling pad and the reinforced fill zone to the depths and locations shown
on the plan sheet or as directed by the site engineer. The exposed foundation soil shall be observed by the on-site soils engineer
prior to construction to verify that the exposed material is suitable for a net design bearing pressure of (_per design__) psf and that
the base of the excavation is free of loose soil, uncompacted fill, water, or frozen material. Undercut any unsuitable soil. Undercut
areas shall be filled with crushed limestone and compacted to at least 95% of the material’s standard Proctor maximum dry density.
Construct the crushed rock or concrete leveling pad to the lines and grades shown on the plans.
Install the first course of units on the leveling pad. The units shall be placed on (__spacing as required __)” on-center spacing
and care must be taken to ensure that the “ears” are overlapped in order to protect the backfill. Install the next course in a running
bond stack. Pull unit forward to establish a ( angle required ) degree wall batter. Fill units, and spaces between units, with (
___soil or rock __). Backfill behind the units to the ends of the geogrids, and continue construction. Modules must be stacked and
completely backfilled before the next course is placed. No double stacking shall be allowed. Radius walls may require smaller or
larger spacing between units but the controlling factor is overlapped “ears”, not a running bond stack.
(Refer to published “Installation Guidelines” booklet for additional information )
The reinforcement shall be cut to design lengths and placed between the blocks at the elevations shown on the plans. The
reinforcements primary strength direction will be directed perpendicular to the wall face (into the fill.) Reinforcement placed outside
a plus or minus 4” zone of the placement design elevation will not be accepted. The geogrid shall be placed horizontally and lay
flat on the reinforced fill area. Reinforcement shall be placed on the modules so that it extends within 1” of the rear face of the
lower Neptune unit. Slack in the geogrid shall be removed prior to placing additional backfill. Construction equipment shall not be
operated directly on the reinforcement material.
Wall backfill material shall be placed in maximum 8” loose lifts and compacted to at least 95% of the material’s maximum dry
density as determined by the standard Proctor method. Backfill shall be placed, spread and compacted in such a manner that
minimizes wrinkles and movement of the reinforcement. Field density testing shall be conducted by a qualified soils technician to
verify that at least the minimum degree of compaction is being obtained.
The finished grade above the structure should include a drain swale and must be sloped in such a manner to drain all
water away from the wall.
12901 St. Charles Rock Road, Bridgeton, Mo., 63044 / 314-291-3200, 314-291-0265 fax
The modules are covered by one or more of the following patents: 5,277,012 5,658,098 D360,475 D340,996 D362,077
D347,285 D372,106 Other patents pending.