and groins were designed to protect the fill. The project has been a success; 

 the beach is effectively stable, and the rate of replenishment during the 

 first 5 years after completion of the project in October 1977 was only 

 approximately 35 percent of the predicted. 



Structures and beach fill 



348. As shown in Figure 39, the project consists of three rubble -mound 

 detached breakwaters and two groins that contain a sandy beach created by a 

 fill. Since the project was designed in American customary units, those units 

 were selected in the modeling and are used in the following discussion. The 

 length of the beach, defined by the distance between groins, is 1,250 ft, and 

 the nominal distance from the revetment at the park to the breakwaters is 



500 ft. The breakwaters are 250 ft long and separated by 160-ft gaps. Water 

 depth at the breakwaters is about 10 to 13 ft, depending on lake level. The 

 breakwaters have a crest height of 6 ft above the long-term average lake 

 level. The western groin, made of concrete, is 164 ft long, and the eastern, 

 composite concrete and rubble -mound groin is 360 ft long and is intended to 

 prevent sand from leaving the project. Except for a small groin compartment 

 on the west side of the project, the neighboring shore is almost devoid of a 

 subaqueous beach. 



349. The initial beachfill volume was 110,000 cu yd and had a +8-ft 

 berm elevation. After placement of the fill, the beach near the west groin 

 eroded, and this area was replenished with 6,000 cu yd in July 1980 and 

 another 3,000 cu yd in September 1981. However, the overall fill was surpris- 

 ingly stable and even experienced a slight volume gain of about 3,000 cu yd 

 per year (excluding the two extra fills) over the 5-year monitoring program. 

 In design of the project, the annual loss was predicted to be 5,000 cu yd, 

 representing 5 percent of the initial fill volume. The project has clearly 

 satisfied the two design criteria of protecting the park and providing a 

 recreational beach facility. Aerial photographs indicate that the project has 

 minimal impact on the neighboring shore. 



153 



