, Materials and methods Samples  Set of 28 pipes from 5 major manufacturers, with triplicates from each pipe  6 diameter sizes (½” – 2”) Reference data  Slope k (mm/h 1/2 ) of the line from the moving front test using pure toluene (Fig.2 and 3) Instruments  Foss NIRsystems ® 6500 (Foss-NIRsystems, Silver Spring, MD) (Fig.4)  Labspec ® Pro Model A (Analytical Spectral Devices, Inc., Boulder, CO) (Fig.5) L. Esteve Agelet 1 C. R. Hurburgh 1 Jr. F. Mao 2 and J. A. Gaunt 2 Department of Agricultural and Biosystems Engineering 1 Department of Civil, Construction and Environmental Engineering 2 Iowa State University Methods  6 scans per sample, 18 scans per pipe type  Spectral data were analyzed without treatment, and with First and Second Svitsky-Golay derivatives  Calibration by Partial Least Squares (PLS) with one-out cross validation  Software: The Unscrambler ® v.9.5 (Camo AS, Trondheim, Norway) Results  The models from both instruments showed a strong relationship between spectral data and permeation performance  The moving front test is an adequate method to get reference data (SEL=0.001 mm)  The best PLS calibration models with raw spectral data for pipe sizes from 0.5 to 1.25” gave (Fig.6): - r 2 =0.94 and RPD=4.27 for Foss instrument - r 2 =0.90 and RPD=2.72 for ASD instrument  The models including the largest samples (1.5 and 2”) were less accurate (Fig.7): - r 2 =0.92 and RPD=2.93 for Foss instrument - r 2 =0.90 and RPD=1.90 for ASD instrument Fig 6. PLS validation models for pipe sizes from 0.5 to 1.25”. Foss (left) and ASD (Right) instruments. Conclusions  PVC pipe permeation performance can be predicted using spectral data from the NIR region.  Larger pipe models did not give as accurate results as models including pipes of sizes from 0.5 to 1.25”.  Models from Foss 6500 were more accurate.  Treatment of spectral data with derivatives gave poorer results. Acknowledgements Iowa State University gratefully acknowledges that the Awwa Research Foundation is the joint owner of the technical information upon which this manuscript is based. Iowa State University thanks the Foundation for its financial, technical, and administrative assistance in funding and managing the project through which this information was discovered. The comments and views detailed herein may not necessarily reflect the views of the Awwa Research Foundation, its officers, directors, affiliates, or agents. The findings described here are preliminary in nature and are subject to revision. A final project report will be published by AwwaRF. References Holsen, T. M., Park, J. K., Jenkins, David, and R. E. Selleck (1991) Contamination of potable water by permeation of plastic pipe. Journal AWWA, vol. 83 (8), Prediction of PVC pipes performance under permeation conditions Introduction  Permeation of PVC mains have been already reported in United States usually where spills of fuel derived solvents have occurred (Holsen et al., 1991)  Risk of drinking water contamination Objective Develop NIR calibrations for predicting susceptibility of PVC pipes to permeation by organic solvents  Permeation is the flux of contaminants (solvents, gas or liquid) through solid, non- metallic and porous materials Fig.1. Permeation scheme Fig.2. Image from the moving front in the pipe wall Fig.4. Foss NIRsystem 6500 Fig.5. Labspec Pro A Fig.3. Representation moving front length (mm) vs. time 1/2 (h 1/2 ) Fig 7. PLS validation models for pipe sizes from 0.5 to 2”. Foss (left) and ASD (Right) instruments. © 2006 Iowa State University and AwwaRF Various pathways of diffuse reflectance