Federal Register / Vol. 56. No. 157 / Wednesday. August 14. 1991 / Proposed Rules 40477 



Otherwise, retvim to the applicable step 

 of the onsite determination method 

 being used. 



Step 4. Determine whether or not 

 hydric soils previously occurred: 



(1) Describe the type of alteration. 

 Examine the area and describe the type 

 of alteration that occurred. Look for 

 evidence of: 



(A) Deposition of dredged or fill 

 material — In many cases the presence of 

 fill material vfiU be obvious. If so. it will 

 be necessary to dig a hole to reach the 

 original soil (sometimes several feet 

 deep). Fill material wrill usually be a 

 different color or texture than the 

 original soil (except when fill material 

 has been obtained from similar areas 

 onsite). Look for decomposing 

 vegetation between soil layers and the 

 presence of buried organic or hydric 

 mineral soil layers. In rare cases, 

 excessive deposition of sediments may 

 be due to catastrophic conditions, e.g., 

 mud slides and volcanic eruptions. 

 Floodplain environments are subjected 

 to periodic sedimentation, but this is a 

 more normal occiurence and does not 

 constitute a significant disturbance for 

 purposes of this manual. 



(B) Presence of nonwoody debris at 

 the surface — ^This can only be applied in 

 areas where the original soils do not 

 contain rocks. Nonwoody debris 

 includes items such as rocks, bricks, and 

 concrete fragments. 



(C) Subsurface plowing — Has the area 

 recently been plowed below the A- 

 horizon or to depths of greater than 10 

 inches? 



(D) Removal of surface layers — Has 

 the surface soil layer been removed by 

 scraping or natural landslides? Look for 

 bare soil surfaces v^rith exposed plant 

 roots or scrape scars on the surface. 



(E) Presence of manmade structures — 

 Are buildings, dams, levees, roads, or 

 parking lots present? 



(2) Determine the approximate date 

 when the alteration occurred, if 

 necessary. Check aerial photographs, 

 examine building permits, consult v\nth 

 local individuals, and review other 

 possible sources of information. 



(3) Describe the effects on soils. 

 Consider the foUov/ing: 



(A) Has the soil been buried? If so. 

 record the depth of fill material and 

 determine whether the original soil was 

 left intact or disturbed. 



Note: The presence of a typical sequence of 

 soil horizon* or layers in the buried soil is an 

 indication that the soil is still intact; check 

 description in the soil survey report. 



(B) Has the soil been mixed at a depth 

 below the A-horizon or greater than 12 

 inches? If so. it will be necessary to 



examine the soil at a depth immediately 

 below the plow layer or disturbed zone. 



(C) Has the soil been sufficiently 

 altered to change the soil phase? 

 Describe these changes. If a hydric soil 

 has been drained to some extent, refer 

 to Step 5 below to determine whether 

 soil is effectively drained or is still 

 hydria 



(4) Characterize the soils that 

 previously existed at the disturbed site. 

 Obtain all possible evidence that may 

 be used to characterize soils that 

 previously occurred on the area. 

 Consider the following potential sources 

 of information. 



(A) Soil surveys — In many cases, 

 recent soil surveys are available. If so, 

 determine the soils that were mapped 

 for the area. If all soils are hydric soils, 

 it is presumed that the entire area had 

 hydric soils prior to alteration. Consult 

 aerial photos to refine hydric 

 boimdaries, especially for soil map units 

 with hydric soU inclusions. 



(B) Buried soils — When fill material 

 has been placed over the original soil 

 without physically disturbing the soil, 

 examine and characterize the buried 

 soils. Dig a hole through the fill material 

 imtil the original soil is encountered. 

 Determine the point at which the 

 original soil material begins. Remove 18 

 inches of the original soil from the hole 

 and follow standard procedures for 

 determining whether the hydric soil 

 criterion is met (Note: When the fill 

 material is a thick layer, it might be 

 necessary to use a backhoe or posthole 

 digger to excavate the soil pit.) If USGS 

 topographic maps indicate distinct 

 variation in the area's topography, this 

 procedure must be applied in each 

 portion of the area that originally had a 

 different surface elevation. 



(C) Deeply plowed soils or removed 

 surface layers — If soil surface layers are 

 removed, redistributed or deeply plowed 

 (excluding normal plowing), vegetation 

 will not be present, so review existing 

 information (e.g., soil surveys, wetland 

 maps, and aerial photos), identify a 

 nearby reference site that is similar to 

 disturbed area prior to its alteration, 

 evaluate for indicators of hydropytic 

 vegetation, hydric soils, and wetland 

 hydrology and make weUand or 

 nonwetiand determination, as 

 appropriate. 



(5) Determine whether hydric soils 

 were present at the project area prior to 

 alteration. Examine the available data 

 and determine whether evidence of 

 hydric soils were formerly present If no 

 evidence of hydric soils is found, the 

 original soils Eire considered nonhydric 

 soils. If evidence of hydric soils is found, 

 the hydric soil criterion has been met 

 Continue to Step 5 if hydrology also was 



altered. Otherwise, record decision and 

 return to the applicable step of the 

 onsite determination method being used. 



Step 5. Determine whether weUand 

 hydrology existed prior to alteration and 

 whether weUand hydrology still exists 

 (i.e.. is the area effectively drained?). To 

 determine whether wetland hydrology 

 still occurs, proceed to Step 6. To 

 determine whether wetiand hydrology 

 existed prior to the alteration: 



(1) Describe the type of alteration. 

 Examine the area and describe the type 

 of alteration that occurred. Look for 

 evidence of: 



(A) Dams — Has recent construction of 

 a dam or some nattiral event (e.g., 

 beaver activity or landslide) caused the 

 area to become increasingly wetter or 

 drier? 



Note: This activity could have occurred at 

 a considerable distance from the site in 

 question, so be aware of and consider the 

 impacts of major dams In the watershed 

 al>ove the project area. 



(B) Levees, dikes, and similar 

 structures — Have levees or dikes been 

 recenUy constructed that prevent the 

 area from periodic overbank flooding? 



(C) Ditches or drain tiles — Have 

 ditches or drain tiles been recently 

 constructed causing the area to drain 

 more rapidly? 



(D) Channelization — Have feeder 

 streams recently been channelized 

 sufficientiy to alter the frequency and/or 

 duration of inundation? 



(E) Filling of channels and/or 

 depressions (land-leveling) — Have 

 natural chaumels or depressions been 

 recently filled? 



(F) Diversion of water — Has an 

 upstream drainage pattern been altered 

 that results in water being diverted from 

 the area? 



(G) Groimdwater withdrawal — Has 

 prolonged and intensive pimiping of 

 groundwater for irrigation or other 

 purposes significantiy lowered the water 

 table and/or altered drainage patterns? 



(2) Determine the approximate date 

 when the alteration occurred, if 

 necessary. Check aerial photographs, 

 consult v^th local individuals, and 

 review other possible sources of 

 information. 



(3) Describe the effects of the 

 alteration on the area's hydrology. 

 Consider the following and generally 

 describe how the observed alteration 

 affected the project area: 



(A) Is the area more frequently or less 

 frequenUy inundated than prior to 

 alteration? To what degree and why? 



(B) Is the duration of inundation and 

 soil saturation different than prior to 



