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HomeMy WebLinkAboutStudy Session - Holmby Park Remediation and Closure Strategy (sT-P i/3 UTeb `,6 y /j0 !Ei`T y/L�/5-y LeiT j CD c% mac, /Y/ T i NG 9 i � eo /yJ HOLMBY PARK Remediation and Closure Strategy September 20, 1999 Site Locatio L Peek WelHield ' - Tn�tmngard�. � ...,.- 0- _ O • West 0 WelHield O Cape Ann • a Residential .. IE •cove Development r W." WelHield S-f��y Secs, o•� i A y p , �r I M o� iS k � •'�` �� vr{ , i'4`Y , r �,f�" �' Ott CL (n :W77 �• "�:' '�< � '�,�.,aa£x. �...�' � �r 4 � NV :. •,w' #,`,�.�N.r^41t:10 s rer s"'+.��, .�x;��g r�w`L/a��^^: J ,, field ^ M y':�,)t , (D F MIX INi'O�r joS�'� 4s w , 4y9p emu , �I7 V �,o y rare'' T� k°H ,i:� �k'��' �. a"'� � Vie^ v'a rsi aa�•a,� �� "iy� 4 •m�.�; �,ON� s � f� ����II III' �°�'"" *�"z,+Y�rs, ' '��, ,�- r a �,q�,'� z � o � Pi I I II af, t�n`�' "�'a,,� Yc.; r�' -�' 1 � I� " I y ' }'G'��i'���i"✓+� fi�a. f y N 1 �E 9n FL aY _ 1 ME I Remedfatil by'So11 Uapor Extractfon 'mil cs w s 1 t' s FID Concentrations In Soil Gas Deep Wells--Cove Area Screen Depths:50.70 fed + 7/11/97 � t + Well � a r ti '3 sr r S ' + Concentration in parts-per million vapor >10.000 P-M 5.0w,10,000 1.000-5,000 500-1,000 100-500 10 ,100 3 FID Concentrations in Soil Gas Deep Wells—Cove Area Screen Depths:50-70 fed 117199 + Well 1 >� N - - ¢- .- . t Concentration in parts-per-Wbon vapor >10,000 FM 5,000-10,000 1,000-5,o00 M 50o-1,00o 100-500 <100 Reporting Closure. Plan J va„r Ambient LL rs7rr�.rr108n Canpacted�F.il( �r 1 Gravel Capped wells - Air flow between soil for future VIES and gravel � � _ �"IEwI Coet'���lnatlon �` 4 Site Locatio Park „ "� WelKield , ♦•• 0 O i' Wes.:: 0 Welifield .: Cape Ann Residential Development :. .© • cove T^*Avi ti WelKield. .A.Ch-WLOC9w Ch.W ruLL.4. 1Ce u.un 1.A..0 i Risk Evaluation Study Prepared by ChemRisk.in 1998 using site-specific data Chemicals of Interest • Thiophenes • Mercaptans • Sulfides and Disulfides • Total.Petroleum Hydrocarbon (TPH) components — Benzene — Polynuclear Aromatic Hydrocarbons (PNAs) 5 Current Closure Plan • Contaminated Areas — Remediation to standards listed in risk evaluation — Engineering controls to include clean fill cover, vented gravel, and vapor wells for backup — Land use limited to open.space—no structures or subsurface utilities — Areas-to be held only as public land — Chevron will conduct monitoring and retain responsibility:for residual contamination • Uncontaminated Areas - Some held as.public.land for structures and utilities near contaminated areas Remainder for private property development Remedial Standards Potential exposure:pathways of concern — Direct contact with contaminated soils' -,Vapor inhalation Clean-up values frorn risk:evaluation' Media Cleaiwrp Level Reduced Sulfur Conpounds ' Thioplienes Soil Vapor :_,: olalSuNur Mercapfans 100 ppbv DisulCdes ' Suifdes Benzene. Sod Vapor 7 ppbv Carcinogenic Pdynuciear Aro nafic Hydrocat ons Sal 1 ppm Noorardnogenic Polynudaar Aromatic Flydrocarbons Sal .. 55"ppm: Lead Sal `230 pprn`. Arsenic Shc 10 pprn Benzene Shc 1 ppm TOTAL TPH Soil 500pprn 6 rADey.elopment ,Op inns II Cosu� -Plan «� W J tiZ.D li- y�s -.ram r .rT�2 i r��,:a ; ¢•t_�'+:s'e6 r: Planning Issues • Development on Site Not Needed to Meet Affordable..Housing Requirements • Cape Ann Could Be Completed Without the Park • No Further Residential Development: Could Proceed in the Designated Area Without Completion of Soil Remediation and Construction of the Park Planning Issues • Per the Development Agreement, a 4 Acre Park Must Be Completed • Current Development Agreement Requires'-Dedicated Park - Current Proposal for Perpetual Easement Requires Legal Review HOLMBY PARK Remeiation and. Closure .Strategy September 20.91999 8