Posts Categorized: Design Specification

Choosing the Right Geocell

Written By: Bryan Wedin P.E., Chief Design Engineer, Presto Geosystems Not all geocells are created equal. While most manufacturers can provide similar-looking written specifications, you need assurances that the material delivered for your project is of the high quality that you expect. Important factors in the success of your geocell project include: Quality The geocell material is proven, strong, and will last Require only the highest quality virgin High Density Polyethylene (HDPE) resin Low quality or recycled resin can lead to weak and/or inconsistent seam strength, putting the success of your project at risk. Non-HDPE materials cannot match the nearly 40 years of in-ground experience of HDPE geocells and plastic alloy proprietary blends can mask cheap stiff filler materials. ISO Certification Important, but the manufacturer sets the testing protocol for the certification. Require a Certificate of Analysis (COA) for the material that is shipped to your project. An ISO certification that does not require continuous testing is lacking. Integral Components The complete solution includes proper components Non-corrosive, high-strength panel connection method (ATRA® Keys vs. weak staples or zip ties) Anchors that provide secure connections to the geocell (ATRA® stakes vs. J-hooks) Load Transfer Devices for tendon applications that are non-corrosive and… Read more »

The day-after disappointment of substitute materials.

by: William G.  Handlos, P.  E. Most everybody can relate a story of disappointment at Christmas time as a child. You’ve asked Santa for a specific toy or boot or piece of sporting equipment and you visualize what it will be like to open that gift. Then the moment comes and you open up the package and feel the initial excitement as you realize you’re actually going to get what you asked for. Then as the wrapping paper is pulled away from the box… you get a sinking feeling. How could this happen? Your list was clear. You supplied details… Specifications… Related exactly what you wanted. But this wasn’t the real thing. When poor substitutes arrive at a job site, the disappointment can be just as real. But, the stakes are higher. Reputations are at stake and sometimes property damage or public safety can be compromised when poor look-alike products are allowed on the job. This morning, with the Yuletide just days away, I witnessed the collision of Christmas with the disappointment of a poor substitute product collide in an email string in which I was included. First, overnight I received along with hundreds of other recipients the following email… Read more »

A Simple Question

Written by: William G. Handlos, P.E. How long does it take to install? It is a question we hear every day. When it comes to cost and installation rates for geosynthetic construction products, there are no simple answers to what seems like simple questions. In fact, beware of those who try to simplify determination of installation costs for their products with quick answers or charts and tables to determine construction rates. Experienced project managers and site supervisors of the crews charged with installation are in the best position to estimate productivity rates. They know best their crew’s capability and the characteristics of the site involved. The variables that need to be considered include: Crew size, talent, work ethic and workday length Temperature, precipitation and length of day (sunlight) Experience with product class Size of the project Site Access Site Conditions (see weather) Crew The optimum crew size is important. Too small and you may lose the benefits of assembly line productivity. Too large and you will find that you fall over each other and pay for extra “inspectors”. All crews are not created equally. The familiarity with tools and techniques vary greatly as does the work ethic both between crews and… Read more »

The Dangers of Breaking Specs and Bid Shopping

Written by William G. Handlos, P.E. Specifying Engineers and Architects work tirelessly to build plans and specifications that capture the essence of their vision as they work to write the guiding documents for their project. They make decisions about product types, grades, and take great pains to build into their documents citations of certifications and standards to assure only quality materials are allowed on the site. Yet, when challenged to accept “or equal” substitutions, it seems that all the standards of care can sometimes be lost and substandard materials seem to too easily find their way onto the site. The reason for this lapse is often a result of the timing of the hand-off between the design team and the project management team occurring just as the contractor award occurs. Contractors are concerned about leaving too much money on the table (the difference in value between the winning and the second bid). Just moments after the bid opening or notice of award, bid shopping commences. Bid shopping on publicly-funded projects is disallowed by legislation in some localities, but even when formally disallowed, informally it occurs widely. With the economic power of the project award and with the pressure of the potential… Read more »