Ohio VAP Leach-Based Soil Values (LBSVs)

What Are Leach-Based Soil Values?

Leach-Based Soil Values (LBSVs) are the maximum concentrations of contaminants that can remain in soil such that leaching into groundwater will not cause exceedances of the Unrestricted Potable Use Standards (UPUS). They are established under OAC 3745-300-09 (Risk Assessment Rule) and OAC 3745-300-10 (Ground Water Rule).

LBSVs are frequently the most restrictive soil standard at a VAP site - significantly lower than the direct-contact GDCSS values. For example, the residential direct-contact soil standard for benzene is 28 mg/kg, but the LBSV for benzene in Soil Type I is 0.017 mg/kg - over 1,600 times lower. If you’re only screening soil results against direct-contact standards, you’re missing the pathway most likely to fail.

Source: All values on this page are from the Ohio EPA Voluntary Action Program Derived Leach-Based Soil Values Technical Guidance Document, October 2008, Revision 3. This remains the current Ohio EPA guidance as of the February 2025 VAP rule update. However, since LBSVs are back-calculated from UPUS values, CPs should verify that the underlying UPUS for each chemical has not changed since the 2008 derivation. Where UPUS values have changed, property-specific leach-based values should be derived per OAC 3745-300-09.

Organic Chemical LBSVs (Table I)

The organic LBSVs were derived using the RISKPRO SESOIL vadose zone model. Values vary by three soil types defined by saturated vertical hydraulic conductivity (Kv) of the vadose zone. These values assume a dilution factor of 1.0 (no dilution).

Vadose Zone Soil Types

The soil type classification is based on the saturated vertical hydraulic conductivity (Kv) of the vadose zone and the general geological setting:

Soil Type I - Clean Sand and Gravel Kv: 10⁻³ to 10⁻⁴ cm/s. Recharge: ~8-14 in/yr. Depth to groundwater >5 ft. Typical settings: glacial outwash, buried valley aquifers, beach ridges, coarse alluvial deposits, fill material.

Soil Type II - Silty Sand Kv: 10⁻⁴ to 10⁻⁵ cm/s. Recharge: ~4-8 in/yr. Depth to groundwater >5 ft. Typical settings: interbedded sand/gravel with silts and clays, poorly-graded sands, some buried valley aquifers, glacial end moraine deposits.

Soil Type III - Till/Clay Kv: <10⁻⁵ cm/s. Recharge: <4 in/yr. Depth to groundwater >5 ft. Typical settings: glacial till, lacustrine sediments, flood plain deposits, thick colluvial deposits.

Most sites in Ohio’s glaciated western half will classify as Soil Type II or III. Buried valley aquifer sites in the Great Miami, Mad, and Scioto river valleys are often Soil Type I.

When You Cannot Use These Values

The generic organic LBSVs from Table I cannot be applied when any of these conditions exist:

• Depth to groundwater is less than 5 feet (excluding seasonal high water table)
• Vadose zone Kv exceeds 10⁻³ cm/s
• Thin soils (≤5 feet) overlie consolidated bedrock with significant infiltration

In these cases, property-specific fate and transport modeling is required per OAC 3745-300-09.

Dilution Factors for Organics

The Table I values assume no dilution (DF = 1.0). If site conditions allow, CPs can apply Ohio EPA’s generic dilution factors to produce less restrictive LBSVs. The dilution factor depends on soil type, aquifer hydraulic conductivity, and source area size.

Soil Type I Dilution Factors:

Aquifer K (cm/s)	<0.5 acre	0.5-1 acre	1-5 acres	5-10 acres
≥10⁻¹	15	10	5.3	4.0
10⁻² to 10⁻¹	2.3	2.0	1.4	1.3
10⁻³ to 10⁻²	1.1	1.1	1.0	1.0

Soil Type II Dilution Factors:

Aquifer K (cm/s)	<0.5 acre	0.5-1 acre	1-5 acres	5-10 acres
≥10⁻¹	22	16	7.6	5.7
10⁻² to 10⁻¹	3.1	2.5	1.7	1.5
10⁻³ to 10⁻²	1.2	1.1	1.1	1.0

Soil Type III Dilution Factors:

Aquifer K (cm/s)	<0.5 acre	0.5-1 acre	1-5 acres	5-10 acres
≥10⁻¹	68	49	22	16
10⁻² to 10⁻¹	7.7	5.8	3.1	2.5
10⁻³ to 10⁻²	1.7	1.5	1.2	1.1

To apply a dilution factor, multiply the Table I LBSV by the applicable DF. For example, benzene in Soil Type II with an aquifer K ≥10⁻¹ cm/s and source area <0.5 acre: 0.009 x 22 = 0.198 mg/kg - still far below the 28 mg/kg direct-contact standard.

Dilution factors require that upgradient groundwater is unimpacted, source area is <10 acres, and aquifer K exceeds 10⁻³ cm/s. If these conditions aren’t met, use DF = 1.0 or derive property-specific DFs using the Summers model (described in Section 6 of the guidance document).

Dilution factors apply only to organic LBSVs (Table I). The inorganic values already include a built-in dilution-attenuation factor.

Inorganic Chemical LBSVs (Table II)

The inorganic LBSVs were derived using the EPA soil/water partitioning equation. Unlike organics, they do not vary by soil type - instead, they vary by source area size, with a built-in dilution-attenuation factor of 10 for larger sources and 20 for smaller sources.

These values apply only when soil pH is between 5 and 9 and the soil has ≥10% fines.

Metal	Source ≥½ acre (mg/kg)	Source <½ acre (mg/kg)
Antimony	3.6	7.2
Arsenic	3	6
Barium	56,000	110,000
Beryllium	57	114
Cadmium	21	42
Chromium (as Cr VI)	56	113
Lead	89	178
Mercury	12	23
Nickel	182	363
Selenium	2.15	4.3
Silver	3,120	6,240
Thallium	1.5	3.0
Vanadium	130	65
Zinc	44,000	88,000

Note: Chromium values assume all chromium is hexavalent - the most conservative assumption.

Practical Notes for Consultants

LBSVs vs. Direct-Contact Standards - Know Which Governs

When screening soil data at a VAP site, you must compare results against both the GDCSS (direct contact) and the LBSV (leaching). The lower value governs. For most VOCs and chlorinated solvents, the LBSV will be orders of magnitude lower than the GDCSS. Here are a few comparisons:

Chemical	Residential GDCSS (mg/kg)	LBSV Soil Type I (mg/kg)	Which Governs?
Benzene	28	0.017	LBSV (1,647x lower)
TCE	10	0.036	LBSV (278x lower)
Vinyl Chloride	1.3	0.009	LBSV (144x lower)
PCE	170	0.15	LBSV (1,133x lower)
Toluene	820	6.8	LBSV (121x lower)
Total Xylenes	260	156	LBSV (1.7x lower)
Arsenic	14	3 (≥½ acre)	LBSV (4.7x lower)
Lead	200	89 (≥½ acre)	LBSV (2.2x lower)

The leaching pathway governs for nearly every chemical. The only scenario where direct contact might be more restrictive is for chemicals with very high Kd values (strong sorption) and low toxicity via direct contact.

Soil Type Determination Is Critical

The soil type classification directly affects which LBSV applies. At a site with mixed lithology (common in Ohio), the most permeable material in the vadose zone typically controls the classification. Don’t average - use the most conservative (most permeable) soil type present in the vertical profile between the contamination and the water table.

If you’re unsure of the soil type, default to Soil Type I (most restrictive for most chemicals). Getting it wrong in the non-conservative direction is an audit finding.

When the LBSV Doesn’t Exist for Your Chemical

Table I only covers 18 organic chemicals. If your site has contaminants not on this list (which is common - SVOCs, pesticides, many chlorinated compounds are absent), you need to derive property-specific leach-based values using SESOIL or another approved fate and transport model, or use the soil/water partitioning approach referenced in OAC 3745-300-09.

Non-Potable Groundwater Changes Everything

If groundwater at your site is classified as non-potable (RNPUS), the leaching pathway to a drinking water receptor is incomplete. This can eliminate the need to meet LBSVs entirely for the drinking water ingestion pathway, though you may still need to address leaching relative to vapor intrusion or ecological exposure standards.

Related Resources

• Ohio VAP Program Overview - How LBSVs fit into the overall VAP framework
• Ohio VAP Soil Standards - VOCs - Direct-contact soil standards for comparison
• Ohio VAP Soil Standards - Metals - Direct-contact metals standards for comparison
• Ohio VAP Groundwater Standards - VOCs - The UPUS values that LBSVs are designed to protect
• Ohio Vapor Intrusion Evaluation Guide - The other pathway that often drives cleanup
• Ohio EPA LBSV Guidance Document (PDF) - Full source document with appendix and technical support