periods less than 12 seconds (12 seconds is equal to the annual mean plus one 

 standard deviation wave period). Errors of this magnitude are generally 

 tolerable for most engineering applications, although it is worthwhile to know 

 the error bounds for some design considerations. When investigating coastal 

 phenomena involving very long period swells of 15 seconds or greater these 

 corrections will produce significant increases in the magnitudes of the wave 

 parameters and it is recommended that the corrections be used. 



Tide Gages 



37. Water level data from the FRF pier are presented in this report. A 

 NOAA/NOS control station, located at the seaward end of the research pier, 

 consisted of a Leupold-Stevens gage manufactured by Leupold and Stevens, Inc., 

 Beaverton, Oregon. The Leupold-Stevens analog-to-digital recorder was a 

 float-activated, negator-spring, counterpoised instrument that mechanically 

 converts the vertical motion of a float into a coded, punched paper tape 

 record. The below-deck installation at pier station 19+60 (see Figure 2) 

 consisted of a 30.5-cm-diameter stilling well with a 2.5-cm orifice and a 



21 .6-cm-diameter float. 



38. The FRF tide gage was checked daily by a tide gage tender at the 

 FRF for correctness of time, proper operation of the punch mechanism, and ac- 

 curacy of water level information obtained. The accuracy was determined by 

 comparing the gage level reading to a level read from a reference electric 

 tape gage. Once a week, a heavy metal rod was lowered down the stilling well 

 and through the orifice to ensure free flow of water into the well. During 

 the summer months, when biological growth was most severe, divers inspected 

 and cleaned the orifice opening as required. 



39. Quarterly, a NOAA/NOS tide "party," which consisted of NOS person- 

 nel familiar with the installation and equipment, performed a tide station in- 

 spection and review. The tide gage was surveyed in from existing NOS control 

 positions and the equipment checked and adjusted as needed; and NOS and FRF 

 personnel reviewed procedures for tending the gage and handling the data. Any 

 specific comments on the previous months of data were discussed to ensure data 

 accuracy. 



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