ARCHIVED REPORTS_XR0012407 - Laserfiche WebLink

Home Browse Search

FORWARD - Vibe following is a chronological description of the City of Stockton's bench mark elevationand datum story: ORIGINAL CITY OF STOCKTON DATUM The original City of Stock-ton(COS) datum was an assumed elevation of 100 feet at an unknown bench ' mark in the general vicinity of McCleod Lake This v.as probably done to avoid negative elevations in those areas below sea level. 1982 CITYWIDE CONVERSION TO NGVD29 In 1982 the City hired R.W SIEGFRIED(RWS)&ASSOC to determine the elevations for the control monuments, Bench Marks 1 thru 34,established to PHASE I of the COS horizontal control survey, as shown ' on Record of Survey Book 28 Page 58 The elevations were established by a Second Order level circuit and utilized the National Geodetic Vertical Datum of 1929 (NGVD29) The official adjustment of 1967 listed the elevation of 12.966 for U.S Coast & Geodetic Survey (USC&GS) Bench Mark "C104I"(COS "D",see U S ' survey monument descriptions on page 23,Permanent Identification (PID)JS 1385) and was used as the initial bench mark to determine all subsequent elevations A conversion from the onginal COS datum to the NGVD29 ' was them determined by comparing the elevations of U S PID HS0393(ongmally COS bench mark"G")at City Hall near McCleod Lake as follows Original COS Datum Bench Mark Elevation= 98.41 ' NGVD29 Datum COS 1982 Elevation= 12 09 Conversion= 86.32 NOTE: See Appendix A for additional elevation and datum comparisons. Is FEBRUARY 1984 ADDITIONS In January and February 1984,elevations were determined by RWS for Bench Marks 35 through 46,as ' shown on Record of Survey Book 28 page 119. A second order level circuit was nin from COS Bench Mark "D" to Bench Marks 16 and "F",utilizing the NGVD29 Datum elevations as established above. In January of 1984,a report of the Vertical Control Survey for the East Stockton Sarutary Sewer Protect ' (ESSSP) was published This report was prepared by George S Nolte and Associates The report lists those bench marks used to establish their Datum as well as those new bench marks which were established In February of 1984 ties were made between the NGVD29 Daturas as established above and the ESSSP Datum. ' The results are as follows ' CIRCUIT NGVD29_DATUM ESSSP_DATUM DIFFER1110E C.O S:B M "F"to ESSSP T B M 170(BM No 86) 20 860 20 574 +286 C.O S.-B M. "26"to U S.0&G S 0-833(BM No L) 14 693 14 327 +360 ' C.O S -B M. "28"to ESSSP T B M 203 (BM No 99) 12 402 12 087 +315 Average difference between the 1982 Stockton/NGVD29 Datum and the ESSSP Datum is+0 322. 0 32 feet was added to all of the bench marks listed in the ESSSP report. In tum, these adjusted bench marks are ' included herein as Bench Marks 47 through I IS and "J" through"M". JUNE 1984 ADDITIONS ' In April and May 1984,elevations were determined by RWS for Bench Marks 116 through 134,as shown n Record of Survey Book 28 Page 138 A second order level circuit was run from and tied back to Bench Mark ' 31. , t