Presto GEOBLOCK^® Porous Pavement System

PP-Product Presentation
For comprehensive information on the Geoblock^® Porous Pavement System, please click on the web site link listed above.

Presto’s Geoblock^® Porous Pavement System is a series of interlocking, polyethylene paving units designed to provide superior load support and turf protection for emergency and utility access lanes, auxiliary parking, golf cart pathways, trails, and other high-use application areas. The Geoblock^® system provides vehicular and pedestrian load support while protecting the grass from the harmful effects of traffic.

Working with the Environment
In many cities, current storm water management systems are pushed beyond their capacities by run-off from traditional hard surfaces. With over 87% open area at the surface, the Geoblock system offers a permeable solution. The Geoblock design allows water to percolate into the ground through drain holes in the bottom of the units, decreasing storm water run-off and allowing natural groundwater replenishment. Under rainfall simulation of 64 mm/hour (2.5 inches), the run-off coefficient for the Geoblock system is 1.5%.

The Geoblock units are manufactured from up to 100% recycled polyethylene and are inert to common chemicals, will not absorb moisture and are unaffected by freeze-thaw cycles.

ISO-Certified Quality
Presto’s commitment to quality begins with manufacturing and continues through final installation. The quality management system for the sale, design and manufacture of the Geoblock® system is certified to ISO 9001:2009 and materials are specifically engineered in accordance with established geosynthetic industry guidelines.

The Geoblock^® System Advantage

• Fully Engineered System - Designed to provide long-term success; successful installations since early 1980’s.
• Permeable Design - 87% open surface; allows rain to percolate into the ground rather than contribute to storm water runoff.
• Interlocking Unit Design - Maximizes load distribution capability.
• Protects the crown of the grass; prevents soil compaction when properly installed.
• Reduces the amount of site preparation and subgrade improvement.
• Easily Installed - Ordinary tools used to cut units – does not require special fasteners or connection devices.

While some talk about strength per square foot, the structural integrity of the Geoblock system is built in. The system features a four-sided tabular, interlocking block design that provides superior load-bearing performance and performance and layout design and construction flexibility. The recommended staggered placement (bricklayer’s pattern) of the individual Geoblock units further increases the system’s load distribution capabilities and maximizes the number of adjacent units used to effectively spread concentrated wheel loads over the largest possible area.
UA-Uses, Applications
From fire access lanes to hiking trails, parking areas to golf cart paths, the Geoblock system improves both the usefulness and aesthetics of an outdoor environment.

• Emergency and utility access lanes
• Auxiliary parking areas
• Pedestrian walkways, trails and wheelchair access ways
• Approaches to monuments, statues and fountains
• Golf cart path shoulders and aprons
• Driveways, driveway shoulders and medians

Earn USGBC LEED™ credits for reducing site disturbance, storm water runoff and heat island effects, and for recycled content.

Both the Geoblock unit and the base support soil work together to support the imposed loading, while the Geoblock unit and the topsoil contribute to the vegetative support. Other components may include a geosynthetic separation / reinforcement layer, sub-drain components, and topsoil additives, which enhance vegetative growth.

Geoblock® Material Specification

Geoblock^® System Usage Guideline

Recommended Topsoil:
Suitable topsoil should be pulverized prior to filling the Geoblock cells and contain sufficient organic content to support vegetative growth. Topsoil such as sandy loam is recommended. Clay and clay loam materials are considered unacceptable.

Recommended Engineered Base: Vegetated Systems
A recommended ‘engineered base’ consisting of clear-stone / crushed rock having an AASHTO #5 designation blended with topsoil will promote vegetative growth and provide required structural support. The aggregate portion shall have particles ranging in size from 9.5 to 25 mm (0.375 to 1.0 in) with a D₅₀ of 13 mm (0.5 in). The percentage void-space when compacted shall be at least 30%. Topsoil, equal to but not greater than the aggregate void percentage, shall be added and blended prior to placement. The mixture shall be compacted to a density that will provide a minimum California Bearing Ratio of 7%. Under some conditions, a geotextile separation layer may be required between the natural ground and the ‘engineered base’.

AI-Assembly, Installation
The Geoblock system is designed for easy installation, requiring less site preparation, less subgrade improvement, less excavation and less granular backfill than other porous pavement systems. The Geoblock system installs easily around obstructions and contours, and can be cut with ordinary hand or power tools. The four-sided tabular, interlocking design saves installation time and money by eliminating the need for special tools, staples, cleats and rings.  The Geoblock system’s easy-to-handle size minimizes the quantity of blocks required on a given job, reducing installation costs and labor.

Installation Guidelines
Subgrade Preparation
Excavate the area, allowing for the Geoblock unit thickness and the ‘engineered base’ depth (where ‘engineered base’ is required). When working with in-situ soils that have poor permeability, provide adequate drainage from the excavated area if the area has the potential to collect water. The in-situ soil should be relatively dry and free from any standing water. Finish-grade the surface of the in-situ soil specifically when the Geoblock unit is to be installed without an ‘engineered base’. Level and clear the area of large objects such as rocks, pieces of wood, etc. to enable the Geoblock units to interlock properly and remain stationary after installation.

Geosynthetic Separation Layer
If required, the geosynthetic layer shall be rolled out over the prepared subgrade along the alignment of the reinforced surface. The geosynthetic shall be pulled taut to ensure that there are no folds. Geosynthetic layer overlaps, if required, shall be according to plans.

Sub-Drainage Component
If required, install the specified sub-drain and outlet according to construction drawings. Ensure that a proper slope is maintained throughout the drainage system and that the outlet is free from any obstructions preventing free drainage.

Base Preparation
The strength of the porous pavement system is determined, in part, by the support provided by a stable ‘engineered base’. Refer to the Geoblock Usage Guideline for engineered base thickness recommendations. The health of the vegetation, however, requires that the ‘engineered base’ be loose to facilitate root penetration. Start with an aggregate relatively free from fines and with a void space of 30% or greater.

The engineered base material is spread over the prepared base and compacted to a density that will produce a CBR of 7%.

Unit Installation

Orientation & Laying Pattern of Units
Place the Geoblock units with the round hole to the ground. When the application is an access lane, stagger the units to produce the bricklayer pattern. The pattern is positioned such that the long direction of the unit is perpendicular to the primary direction of traffic. When the application is a large area with random traffic flow, stagger the units to produce the herringbone pattern. This pattern reduces straight seams to one and a half block lengths.

The staggered pattern is developed by using half Geoblock units made by field cutting a full unit. Cut the units with a hand or power saw to custom fit both contours and/or around obstructions. These final seam patterns assure maximum load transfer and support. Other laying patterns are generally not recommended.

Positioning of Units
Place the first row of Geoblock units against a stationary edge when available. If the units are placed between two perpendicular or near-perpendicular stationary edges (i.e. two parallel concrete curbs), allow for potential thermal expansion of the Geoblock units by keeping the units away from the stationary edge. A compensation of 1.375 in (34 mm) could be applied for each 10 ft (3 m) increment of length. When the installation day(s) is optional, install the Geoblock units on cooler cloudy days as opposed to hot sunny days. This will minimize the temperature gain and resulting thermal expansion of the units when exposed to full sunlight for several hours.

Slide the units together so that the interlocking tab joint is fully engaged. Units should be placed such that corners and seams do not protrude above the desired surface elevation. The Geoblock units can be fixed in-place to prevent the units from shifting during installation with optional wood or metal stakes, or, by placing thread-forming tapping screws or nails through the perimeter interlocking tabs. This may be needed if 1) trafficking / turning of heavier construction vehicles causes movement of the units during the installation process or 2) large temperature changes occur during the installation process.

Note that plastic has a relatively high rate of thermal expansion. Joint separation and rejoining of separated units should be considered normal construction practice. Once a healthy turf is developed, the root system will provide all necessary anchoring of the system.

Unit Infilling
Infill the Geoblock units with the specified topsoil infill. Infilling should take place immediately after the units are installed to minimize the potential of joint separation caused by thermal expansion/contraction.
If the Geoblock units are to remain unfilled, contact Presto for recommendations.

Infill Procedures for Vegetated Systems

Infill the Geoblock units with a suitable topsoil. Use spreading methods that will leave the cell infill uncompacted. Overfilling the cells is not recommended since vehicular loading will cause undesirable compaction of the topsoil. For application of the vegetation, see Finishing Procedures for Seeding and Sod Application.

Spread the infill material uniformly over the units to a level even with the top of the cell wall.

Finishing Procedures
Seeding
Follow good seeding, fertilizing, and watering procedures for turf establishment based on regional practices. An increase in watering frequency may be necessary when free draining base materials are used. Use of a free draining base is generally not recommended.

Sod Application
Sod can be used for areas where immediate use is desired. Young sod that is free from netting materials is recommended. Mature sod with a more developed root system and sod with netting may be difficult to press/cut into the Geoblock cells.

When sod is used:
1) Sweep out the topsoil from the Geoblock unit to allow room to seat the sod. Enough topsoil must be removed so that the crown of the sod is recessed slightly below the top of the cell after pressing the sod in place. If too much topsoil is removed, the bottom of the sod will not make contact with the topsoil after it is pressed into the cell. Avoid removing too much topsoil.

2) Press the sod into the partially emptied cells using a roller or other suitable equipment.

3) Use recommended watering procedures to ensure healthy sod growth.

Delineation
With vegetated systems, once healthy turf has been established, the Geoblock cell wall structure will have minimal visibility when good turf-maintenance practices are followed.

If used for an emergency access lane, delineation may be desirable to create greater visibility. Delineation methods can include the following: in-ground or above-ground curbing, shrubbery or vegetation, perimeter lighting or delineation markers, or other suitable systems.

Maintenance
If required, snow removal should be done using one of the following basic procedures:

• Keep a metal-edged plow blade a minimum of 25 mm (1.0 in) above the surface during plowing operations, or
• Use a plow blade with a flexible rubber edge, or
• Use a plow blade with skids on the lower outside corners so that the plow blade does not come in direct contact with the porous pavement system.

When deeper ground freeze occurs, the system functions as a typical hard pavement surface. If a sharp metal plow-blade comes in direct contact with the surface during plowing, any portion of the Geoblock system that protrudes above the normal surface level could be removed by the blade.

TS-Technical Support
Presto Geosystems and its authorized distributors offer assistance in determining the ideal Geoblock system for your specific application. In addition, the following information is available for use by design professionals and contractors:

• Design Guidelines
• Material and CSI-Formatted Specifications
• CSI Format Specification
• Installation Guidelines
• Case Histories
• Technical Overview
• Test Documentation

PRESTO^®, GEOSYSTEMS^®, GEOWEB^®, ATRA^® and SPECMaker^® are registered trademarks of Presto Products Company.  LEED™ is a trademark of the US Green Building Council. © 1998-2004
This information has been prepared for the benefit of customers interested in the Geoweb cellular confinement system. It was reviewed carefully prior to publication.  Presto Products Company assumes no liability for its accuracy or completeness. Final determination of the suitability of any information or material for the use contemplated, or for its manner of use, is the sole responsibility of the user.