1 Introduction 



Work Unit Objective and Monitoring Approach 



The objective of the Periodic Inspections work unit in the Monitoring Completed 

 Navigation Projects (MCNP) research program is to periodically monitor selected 

 coastal navigation structures to gain an understanding of the long-term structural 

 response of unique structures to their environment. These periodic data sets are 

 used to improve knowledge in design, construction, and maintenance of both exist- 

 ing and proposed future coastal navigation projects. These data also will help avoid 

 repeating past design mistakes that have resulted in structure failure and/or high 

 maintenance costs. Past projects monitored under the MCNP program, and/or 

 structures with unique design features that may have application at other sites, are 

 considered for inclusion in the periodic inspections monitoring program. Selected 

 sites are presented as candidates for development of a periodic monitoring plan. 

 Those sites receiving favorable response during MCNP program review are 

 inspected and a monitoring plan is developed and presented for approval. Once the 

 monitoring plan for a site is approved by the field review group and funds are pro- 

 vided, monitoring of the site is initiated. Normally, base conditions are established 

 and documented in the initial effort. The site then is reinspected on a periodic basis 

 (frequency of surveys is based on a balance of need and funding for each monitoring 

 site) to obtain long-term structural performance data. 



Relatively low-cost remote sensing tools and techniques, with limited ground 

 truthing surveys, are the primary inspection tools used in the monitoring efforts. 

 Most periodic inspections consist of capturing above- water conditions of the struc- 

 ture at periodic intervals using high-resolution aerial photography. Periodic aerial 

 photographs are compared visually to gauge the degree of in-depth analysis required 

 to quantify structural changes (primarily armor unit movement). Data analysis 

 involves using photogrammetric techniques developed for and successfully applied 

 at other coastal sites. At sites where local wave data are being gathered by other 

 projects and/or agencies and these data can be acquired at a relatively low cost, 

 wave data are correlated with structural changes. In areas where these data are not 

 available, general observations and/or documentation of major storms occurring in 

 the locality are presented along with the monitoring data. Ground surveys are 

 limited to the level needed to establish the accuracy of the photogrammetric 

 techniques. 



Chapter 1 Introduction 



