a. Corps of Engineers. Bottom surveys in .Bolinas Lagoon were made between 26 July, 

 and 8 August 1939 and in October 1956. Five ranges along the bay side of Stinson Beach 

 spit were surveyed in March and August, 1971. Depths and elevations in all of these surveys 

 were referred to local MLLW. At the time of these surveys, MLLW was listed by the 

 USC&GS as being 2.07 feet below the 1929 sea-level datum (SLD). On 6 May 1965, the 

 USC&GS revised these values such that now MLLW in Bolinas Lagoon is listed as being 

 1.9 feet below the 1929 SLD. The five Corps of Engineer ranges were resurveyed (on the 

 beach face only) by the State Lands Division, 34 March, and 3 April 1969. The Corps' 

 bench marks, previously established in their 1961 surveys, were used for the vertical control; 

 mean lower low water was assumed as 2.07 feet below the 1929 USC&GS sea-level datum. 



b. Bolinas Harbor District. In 1968 and 1969, the Harbor District contracted with 

 R. M. Towill Corp. of San Francisco to conduct the five bottom surveys offshore in Bolinas 

 Bay as previously mentioned. Surveys of Bolinas Lagoon were also made by R. M. Towill 

 Corp. from aerial photographs taken at low tide on 16 May 1968. All of the above surveys 

 give soundings below the 1929 USC&GS sea-level datum. 



c. U.S. Geological Survey. In August and September 1967 profiles of the bottom of 

 Bolinas Lagoon were surveyed along 26 referenced ranges to document the location and 

 configuration of channels. Elevations and depths were referred to the 1929 USC&GS 

 sea-level datum. 



d. State Lands Division. From 1948 to 1968, the State Lands Division determined the 

 alinement of mean high tide for a distance of about 500 feet along the beach face on 

 Stinson Beach Spit. Mean high tide was assumed to be 3.8 feet above the mean lower low 

 water for Bolinas Lagoon (Table 3) or 1.9 feet above the 1929 sea-level datum. 



10. Tidal Prism. O'Brien (1967) established a unique relationship between the minimum 

 flow cross section of a tidal inlet and tidal prism (the volume of water that flows into and 

 out of the lagoon during a tidal cycle). From the R. M. Towill bottom surveys of Bolinas 

 Lagoon, the USGS (J. R. Ritter, 9 July 1971, private communication), prepared a contour 

 map of the lagoon and calculated the volume of water in the lagoon at several tide stages as 

 follows: 



Tide Stage 



Volume 



(MSL Datum) 





(feet) 



(million cu ft) 



-6 



0.0 



-4 



3.0 







79.2 



+2 



161.0 



+4 



257.0 



+6 



360.0 



From a plot of these data the tidal prism between MLW (+0.8 MLLW) and MHW (+3.8 

 MLLW) was determined to be 109 million cubic feet. 



14 



