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Home My WebLink AboutCT 00-02; Calavera Hills Stockpile; Tentative Map (CT) (4)r l [ r L [ r l Geotechnical• Geologic • Environmental .. .. .. .. • .. ... .. ... -... .. ... IIIII -.. .. REVISED MITIGATIVE RECOMMENDATIONS FOR REMOVAL AND PLACEMENT OF TOXAPHENE AFFECTED SOIL DURING GRADING ROBERTSON RANCH, PARCEL 1 CITY OF CARLSBAD, SAN DIEGO COUNTY CALIFORNIA 92008, DEH FILE NO. H02725-001 FOR COUNTY OF SAN DIEGO DEPARTMENT OF ENVIRONMENTAL HEALTH LAND AND WATER QUALITY DIVISION SITE ASSESSMENT AND MITIGATION PROGRAM P.O. BOX 12961 SAN DIEGO, CALIFORNIA 92112-9261 W.O. E3098·3-SC OCTOBER 28, 2002 .. .. ... --- .. .. .. Geotechnical • Geologic • Environmental 5741 Palmer Way • Carlsbad, California 92008 • (760) 438-3155 • FAX (760) 931-0915 October 28, 2002 County of San Diego Department of Environmental Health Land and Water Quality Division Site Assessment and Mitigation Program P.O. Box 12961 . San Diego, California 92112-9261 Attention: Mr. Ewan Moffat, M.S.D-561 W.O. E3098-3-SC Subject: Revised Mitigative Recommendations for Removal and Placement of Toxaphene Affected Soil During Grading, Robertson Ranch, Parcel1, City of Carlsbad, San Diego County, California 92008, APN 168-050-47, DEH File No. H02725-Q01 Dear Mr. Moffat: Based upon comments and recommendations made by Mr. Ewan Moffat of the County of San Diego Department of Environmental Health (DEH), GeoSoils, Inc. (GSI), has prepared this revised report for mitigative recommendations for the removal and subsequent placement of toxaphene af(ected soil during grading on the subject property in the City of Carlsbad, California. These recommendations are based upon our knowledge of the property (GSI; 2002e, 2001c), our previous agricultural chemical residue surveys (GSI; 2002a, 2002c, 2001 b), and conversations with Mr. Ewan Moffat of the (DEH). The purpose of this revised report is to provide mitigative recommendations during remedial grading for the estimated limits of removal and for the location of burial of impacted earth materials at locations and depths which will effectively eliminate Mure human contact, as well as eliminate potential impacts to surface water and groundwater. Based upon our information provided in the referenced Phase I Environmental Site Assessment (ESA) report on historical land use (GSI, 2001c), the subject property was utilized for agricultural purposes from at least 1928 to the present. Based upon our previous chemical testing of near surface soils onsite (GSI; 2002a, 2002c, 2001 b), detectable concentrations of restricted agricultural residues exist within Parcel 1 of Robertson Ranch. Concentrations of toxaphene above the Preliminary Remedial Goal (PRG) of 0.44 milligrams/kilogram were encountered in locations which are actively cultivated or were in the past and several localized areas. Generally, the toxaphene was encountered within the upper %to 1 foot of soil. GSI {2002a) recommended the following: .. • -11 It is our understanding that if a "Closure Letter" is needed, a· final report of the excavation, removal, and burial of the affected soils onsite will be required by the DEH for review. The • final report would include a sample and burial location map and laboratory test results . • -... --- - • -.. • .. • " • ,.. ... LIMITATIONS GSI has performed the services for this project in accordance with the terms of a contract between GSI and Client and in accordance with current professional standards for investigations of this type. The conclusions presented in this report are based on the information collected during the study, the present understanding of the site conditions, and professional judgment. Please note, subsurface and hazardous waste/toxic substance conditions may vary from those provided in historical documents reviewed by GSI. The interpretations and recommendations of GSI are based solely on such information and/or information supplied by Client. Findings of this assessment based on data provided by others carries no warranty, expressed or implied, as a result of the usage of such data. It is possible that future assessments may reveal additional data or variations of the current data which may require the current conclusions and recommendations to be reevaluated . As a result, GSI makes no warranty, either express or implied, as to its findings, opinions, recommendations, specifications, or professional advice except that they were promulgated after being prepared in accordance with generally accepted standards of care and diligence normally practiced by recognized consulting firms performing services of a similar nature. The information in this report is relevant to the date of the site work and should not be relied on to represent conditions at any later date. Facts, conditions, and acceptable risk factors change with time, a,ccordingly, this report should be viewed within this context . County of San Diego Robertson Ranch, Parcel1, Carlsbad Ale:e:\wp7\env\e3000\e3098-3.nnf GeoSoils, Inc • W.O. E3098-3-SC October 28, 2002 Page4 II II II II II II It f I E L E v A T I 0 N 120 80 (IN FEET) 40 X EXISTING GRADE Qal -------- I J f 1 f J I I I I II II II II II Proposed location of toxaphene affected soil Qal BEDROCK (Claystone -paleosol) 120 80 E L E v A T I 0 N (IN FEET) 40 N44E At Station 111 • 60 College Boulevard LEGEND af Artificial fill Qal Quaternary alluvium --Approximate location of geologic contact ¥ -Groundwater B-4 Approximate location of exploratory geotechnical boring by GSI, April 2000 LOS ANGELES CO. RNERSIOE CO. ORANGE CO. SAN DIEGO CO. CROSS SECTION X -X' figure 1 .0. E3098-3-SC DATE 10/02 SCALE 1":40' --• -.. • -.. -.. • .. • .. .. .. ... .. ,. .. • Surficial soils with concentrations of toxaphene greater than the PRG criteria shall be placed within street areas only, and should be placed below 5 feet of subgrade to mitigate the potential for human contact. Soils requiring remediation should not be placed in canyon bottoms or below subdrains, where there is potential contact with groundwater. Affected soils should be buried within the property boundary only, and placed so as not to adversely affect surface water. Recommended depths of removal at the four locations with elevated toxaphene are 2 feet near ACRS-7 and 1 foot below existing grade for the eastern portion of the property and near RS-15 and RS-24 . Based upon review of chemical laboratory results from our previous pesticide surveys (GSI; 2002a, 2002c, and 2001 b), GSI recommends that the limits of removals for the four locations are as presented on Plate 1, with the addition of two areas around ACRS-5 and ACRS-6 (removals of 1 foot below existing grade). Calculations for remedial soil removal indicate approximately 46,000 cubic yards recommended for removal. Based upon a review of our previous geotechnical evaluation of the subject site (GSI, 2002e), groundwater was encountered in exploratory borings in the location of the proposed College Boulevard at depths ranging from 9 feet below ground surface (bgs) to 14 feet bgs. Alluvium in this area consists of clayey sand and was encountered to a depth of 45 feet bgs in the central alluvial valley and approximately 25 feet bgs on either flank of the alluvial valley. Paleosol soils were encountered beneath the alluvium. Partial geotechnical removals within valley areas are anticipated to be on the order of 5 to 6 feet, or to depths where saturated alluvial deposits are encountered . GSI reviewed grading plans for College Boulevard, dated December 27, 2001, by O'Day Consultants, Sheets 23 and 24. Between station numbers 1 06+Qg and 112+:n!, fill depths ranging from 30 feet to 35 feet in thickness are proposed for the construction of College Boulevard. It is our understanding that toxaphene affected soil must be placed 10 feet below subgrade (to allow fQr the proposed 8-foot deep sewer and storm drain pipes) and at least 1 o feet above groundwater (to allow for a possible 5-foot raise in groundwater during heavy rainfall years). Preliminary calculations indicate that there is sufficient area within the site boundary to bury all affected soil. A cross section presenting proposed grade, proposed underground utilities, existing ground surface, groundwater, proposed location of proposed placement of toxaphene affected soil, and geology at station 111 +§2 College Boulevard is shown on Figure 1, and the approximate location of the cross section is shown on Plate 1. Removals and burial should be monitored by a representative of this office. Random sampling should be conducted in at least 18 locations after removal of the affected soil onsite to evaluate that all affected earth materials have been removed and buried. If concentrations of restricted pesticides are detected above the PRG criteria in samples collected at the removal depth, additional removal would occur until residue concentrations of earth materials are below PRG criteria. County of San Diego Robertson Ranch, Parcel 1, Carlsbad File:e:\wp 7\enV\e3000\e3098-3.rmf GeoSoils, Jne . W.O. E3098-3-SC October 28, 2002 Page2 -.. .. .. • .. • • .. -• -------.... --.. -• • 1111 • • .. .. 1 II The opportunity to be of services is appreciated. If you shoUld have any questions, please do not hesitate to contact the undersigned at (760) 438-3155. Respectfully submitted, ·· _,.-~~-;~·--. .. / GeoSoils, Inc. /~.::.<. . _;,~ l.. Goci .. ·\f ,' , · /;:·/~S ?'~\'f.;, bley <{: x .• REA6400""lJ Director of Enviro eti1lit~RAi~ Reviewed by: REA-1 6400 DG/JPF/jh Attachments: Appendix -References Plate 1 -Agricultural Chemical Residue Survey Sample Location Map Distribution: County of San Diego (2) Addressee (3) McMillin Companies, Attention: Mr. Don Mitchell (1) Job Site Trailer, Attention: Mr. Tom LaMarca Robertson Ranch, Parcel1, Carlsbad File:e:\wp7\env\e3000\e3098-3.rmf GeoSoils, lne. W.O. E3098-3-SC October 28, 2002 PageS -.. - ---.. -.. -.. - ... .. .. -.. - ... .. .. 1111 ... .. .. ... .... APPENDIX REFERENCES - --.. ... .. ... • .. • - APPENDIX REFERENCES County of San Diego, Department of Agricultural, Weights & Measures, 2001, Request for public information number 01-RP0051, dated October 2 . County of San Diego, Department of Environmental Health, 2002, Voluntary assistance program, DEH Number H02725-001, Robertson Ranch, Parcel 1, El Camino Real at Calavera Drive, Carlsbad, dated January 4 . GeoSoils, Inc., 2002a, Agricultural chemical residue survey to delineate limits of soil removal, Robertson Ranch, parcel1, city of Carlsbad, San Diego County, California, 92008, DEH file no. H02725-001, W.O. E3098-3-SC, dated June 28 . __ , 2002b, Sampling for toxaphene, Robertson Ranch, Parcel1, city of Carlsbad, San Diego County, California 92008, DEH file no. H02725-001, W.O. E3098-3-SC, dated May24. 111 __ , 2002c, Detailed agricultural chemical residue survey, Robertson Ranch, Parcel1, city of Carlsbad, San Diego County, California 92008, DEH file no. H02725-001, • W.O. E3098-3-SC, dated April 26 . .. .. .. .. .. • -.. .. -• • • -• -- __ , 2002d, Work plan for detailed chemical residue survey, Robertson Ranch Parcel1, city of Carlsbad, San Diego County, California 92008, DEH File No. H02725-001, W.O. E3098-3-SC, dated February 25 . __ , 2002e, Geotechnical evaluation of the Robertson Ranch property, city of Carlsbad, San Diego County, California, W.O. 3098-A1-SC, dated January 29 . __ , 2001 a, Request for assistance, Robertson Ranch -Parcel 1, a portion of APN's 168- 040-30, 168-050-17 and 208-010-32, city of Carlsbad, County of San Diego, California, W.O. E3098-2-SC, dated December 6 . __ , 2001 b, Umited agricultural chemical residue survey, Robertson Ranch-Parcel 1, city of Carlsbad, San Diego County, California 92008, W.O. E3098-2-SC, dated December 4 . __ , 2001 c, Phase I environmental site assessment, Robertson Ranch -Parcel 1 , city of Carlsbad, San Diego County, California 92008, W.O. E3098-1-SC, dated August 6 . Smucker, Stanford J., United States Environmental Protection Agency (USEPA}, Region IX, Region 9 Preliminary Remediation Goals · (PRGs} Table 2000 Update, dated November 1. GeoSoils, Ine. ·~--~ ... ~-----~~r········· -··-·---~--~----------~·---~--·--.. _, ---..... >-·-·--·~~-~··,.. .. -,..,.,; .. •~··_,-~-........-.::. _ __.._ lOS MlGElES CQ AIV<.OR~!OE CC Of'\ANGE. CO SAN DIEGO CO _ .. _., .. ,,_,n --~"""""....--•·norro•~-;;;-""'-~--•--------t ·-AGRICULTURAL CHEMICAL RESIDUE SURVEY SAMPLE LOCATION MAP P!ate 1 --·-···---- USf)lfN,'>' P!t? .-:vf,)J..,Jt.~:..R't 1r~: ?R:J !JI[X.f(A!.,{ !I'! I,V;_,'I_I!r;•/(_.L NO. ,J7J[!J7 5, ,~A.i!.:) ~~ ;;IL 'll LL I .. OCATIONS ARE APPROXiM.I\TE I ACRS-10 RS-24 RS-28 ' / xr---'x· LEGEND Approximate location of previous agricultural chemical residue soil samp1e collected by GSI, September 2001 Approx1rnate location of agricultural chemical residue s01l sample collected by GSI, April 2002 Aiiproximate location of agricultural chemical residue soil sample collected by GSI, June 2002 Approximate limit of soil removal Approximate location of cross section x -x· O'Day Coosu:tan\s, inc. -~------------------- •t'r.PCf..P ~Jr n #PAt., Y, /31• ,r.NO ----~~------~- -----------~----------------------------.. ·--------»·--·----·-----------.. ·-----.. ----...... --·- ~· ...... --~----~---~---~----··- BASt 1~/ilP TOP06~!?AP/1/C SOURCE: ~-'---·-- 5;1/•, :cr ~ 4/, ' ,HY / I,'.-4 •,,-,Pl..fr5 ~ •'c V".Jt ';,''2}-:6t7 t lL r~ ~ 'fl~lw1 , .J/-d '/,/. Y 08 'd.~ ' "L 64 " "• '999 l-VR ROBE.RTSO/il Ri1/VCfl ASSESSOR'S PARCEL NU&/BfRS> --- ~y;g (,'U-)2 ~~--------------·--- .VOTES: p fl978J r S££ RECORD OF SL:rift.:Y ------ A"-10 'OT [/"![' A/JJL/.5 'Y,1)/T ?!.AT rJR ''ROPtRTY UV£ JA ·,.: 2 ::..'[ ~:[·TRA ,'[ P! ..!.,V F~JR .,r'U? r•:_.t.,~ A.' Ct-.:Yt~T AVO Pl?·?f-'0.·,1_:__'"! Df':A,'\'4,";1 4VU •. 'h, .DfS W CAVi'dJ/•.r .;:c . ..,:• ~~~ ' C~'Jt~{-,[ fOI__lL[V-41?0 p ' --j / ' 1 1,,_/_~ ~ . '·" ,(;~--(' -------··- • I /' ·- J I ' I ·: / / ( -o ' . .' '/d ')'", '}/;". . ' '/ / / .. ' .. I ___.J i ) ·-- / -1 .. r" .. l' } t Proposed location of toxaphene affected soil -- ' ' ' .L ' \ '· '· I " ' r \ -. ) J ACRS-10 -' . • '· ' ,. ,_ -,. .. ' . - ! UNDEVELOPED LAND RS-17 ,, Fertilize~ Mixing Tanks --/ ,. .. / . / --' -/ -/ ' \ I .. ·' -;...._ --., '-'( ·, '-' ... .. RS-19 Drainage Area ~ "AOr'C/ r .. 11 1 t.-L ~- I I I ' .. LiMITS OF RESI'oUE SURVEY RS-20 ,_, Drainage Area ... \ , . RS-21 ... \ !!) Sprayer. '"'-' Equipment' -. I ·' ' Storage I I ,, ' / _ .. -· >-' -------------_-------------·--------------------...... _..-.,. __ ___ ------~---~-------'~~-,-.,-..,.,...,,.,..-•. c--·-··-. ...,., ··, ....... , t·... .. .. ·----·-····-----.. -" ... ---·-·" ; ' ,, I ., ' •;. -· '· " • ,, . ' {·'' • ' •• ' ) I f . ' I •• --:'-I I • i ,._, I .. . "// I I• ' 1 .. " .. " ' . . ,.l ,_ '' J: i . • JC) RS-25 RS-16 .- ,. ~~~· 1 ,. I l.l) ; Flower Processing 'Area I --~~ • .. / , .. 614!).' <1 ,_ .. I I / .. .. ,_ ,·'1' / 1 --• • RS-27".t.~ I RS-14 --- . ' / ~.)~C PJ~'~ur , ~~rl SIJT\~ 1 :10 \ ~· ~ln< CJ tc,.loO D:.'~::t(l /tJ0-9.31-77\Jl; t~'• ~l-0-931-&Sim '· - -_, " ·- -·. ; , .. :;· / / . .' .. C'H E"'~ ttn>''i} .,..,,,,...,· ll '•o<:e~~ <;1 5u• -tey.r.o; -------~----- ' l\ '---.--· ';' ~. I '~ I ' '-_. -· I r~--· I §) RS-11 , -. "• t ( ~ ,, ~, . / • ~' ,:_ll d ' .. I • .. I. .. I \ ~ \ \ ' j i . j ' • . .. /·" "' • ... 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