NJ Stormwater BMP
The _________ __________ and _____________________ __________
_____________ impact the computations to establish the existing groundwater
recharge and existing runoff conditions necessary to evaluate compliance with the
recharge and quantity control criteria of the Stormwater Management Rules. correct
answers soil type, hydrologic soil group (HSG)
Where HSG information from a published or online NRCS Soil Survey is either
unavailable or inconsistent with conditions in the field, Option 1 allows runoff
computations for pre- and post-developed drainage area conditions to be based upon
_______________ HSGs. correct answers default
On those areas of the development parcel for which the HSG is either unknown or
inaccurate with respect to field conditions, a minimum of _____ soil profile pit and _____
soil borings shall be conducted within each soil mapping unit of _______ acre or more
and less than ______ acres shown on the NRCS Web Soil Survey. correct answers 1,
4, 0.5, 2
Soil profile pits and soil borings performed for the purpose of determining HSG shall
extend to the depth of the __________________ ___________ _______________
_______________ or the deeper of ______ feet below existing grade or ______ feet
below proposed grade correct answers seasonal high water table, 6, 4
Generally, a minimum of _____ soil profile pits shall be excavated within the infiltration
area of any proposed infiltration BMP to determine the suitability and distribution of soil
types present at location of the BMP. Placement of the test pits shall be such that it
provides adequate characterization of the infiltration area. For BMP infiltration areas
larger than ______________ square feet in area, a minimum of _____ additional soil
profile pit shall be conducted for each additional area of _____________ square feet.
The total number of required soil profile pits shall be placed generally equidistant from
each other so as to provide adequate characterization of the infiltration area. correct
answers 2, 10000, 1, 10000
A linear BMP is defined as BMP with the following characteristics: correct answers -
possesses a minimum infiltration area length to width ratio of 4 to 1
-is limited to a maximum infiltration area bottom width of 25 feet and a maximum
infiltration area top width of 40 feet
For linear infiltration BMPs, a minimum of _____ soil profile pit shall be conducted within
each soil mapping unit for the first ________ linear feet. Where the distance exceeds
500 feet within the same mapping unit, soil boring shall be conducted for every
,________ feet and a soil profile pit shall be conducted for every __________ feet.
correct answers 1, 500, 500, 200
Soil explorations include what? correct answers soil profiles pits and soil borings
Soil explorations (soil profile pits and soil borings) shall extend to a minimum depth of
_____ feet below the lowest elevation of the basin bottom or to a depth that is at least
_____ times the maximum potential water depth in the proposed BMP, whichever is
greater. correct answers 8, 2
What type of tests may be performed on the most hydraulically restrictive soil horizons
or substrata at depths greater than those identified above (instead of soil profile pits and
soil borings)? correct answers permeability tests
As land development increases, runoff discharges to surface waterbodies more quickly
and for a longer period of time. Because of this change in volume, rate and duration,
surface waterbodies may be unable to convey the increased flow downstream, which
may lead to flooding or nearby areas. In addition, increased flow rates and velocities in
waterbodies may lead to erosion of stream channels and increased pollution entering
waterbodies. To reduce the potential negative effects of land development on flow rates
leaving the site, the New Jersey Stormwater Management rules (NJAC 7:8) establish
design and performance standards for runoff quantity. This design and performance
standard can be met by meeting one of three options: correct answers 1. Demonstrate
through hydrologic and hydraulic analysis that for stormwater leaving the site, post-
construction runoff hydrographs for the 2-, 10-, and 100-year storm events do not
exceed, at any point in time, the pre-construction runoff hydrographs for the same storm
events.
2. Demonstrate through hydrologic and hydraulic analysis that there is no increase, as
compared to the pre-construction condition, in the peak runoff rates of stormwater
leaving the site for the 2-, 10-, and 100-year storm events and that the increased
volume or change in timing of stormwater runoff will not increase flood damage at or
downstream of the site. This analysis shall include the analysis of impacts of existing
land uses and projected land uses assuming full development under existing zoning and
land use ordinances in the drainage area.
3. Design stormwater management measures so that the post-construction peak runoff
rates for the 2-, 10-, and 100-year storm events are 50, 75, and 80 percent,
respectively, of the pre-construction peak runoff rates. The percentages apply only to
the post-construction stormwater runoff that is attributable to the portion of the site on
which the proposed development or project is to be constructed.
.Groundwater recharge is defined as the amount of water from precipitation that
infiltrates into the ground and is not evapotranspired. Therefore, not all runoff that
infiltrates into the soil is recharged; only that portion that infiltrates past the root zone will
recharge the groundwater table. Groundwater is an important water resource; it is an
, important source of potable water, and it is crucial for surface waterbody baseflow
particularly during dry conditions when it may be the sole source of water feeding
streams or ponds. When soil is compacted or covered by impervious surfaces, less
precipitation is able to infiltrate, resulting in less groundwater recharge. To reduce the
negative effects of land development on goundwater recharge, the New Jersey
Stormwater Management rules at NJAC 7:8 establish design and performance
standards requiring recharge on major developments. This design and performance
standard ca correct answers 1. Demonstrate through hydrologic and hydraulic analysis
that the site and its stormwater management measures maintain 100 percent of the
average annual pre-construction groundwater recharge volume for the site.
2. Demonstrate through hydrologic and hydraulic analysis that the increase of
stormwater runoff volume from pre-construction to post-construction for the two-year
storm is infiltrated.
Annually, approximately 90% of the storm events in New Jersey are 1.25 inches or less;
on an undeveloped site, there is very little runoff during these small, frequent storm
events. The runoff that does come off the site has had significant time to interact with
the vegetation and flow into and through depressions on site, which allows for some
pollutant treatment through filtration and settling. On a developed site where vegetation
has been removed, topography has been made more uniform, and runoff is collected
and conveyed through a system of pipes, runoff has little time to lose any of its pollutant
load resulting in direct discharge into waterbodies. Additionally, the types of surfaces
common on developed land often consists of impervious surfaces and lawns, which
accumulate a variety of pollutants, including metals, suspended solids, hydrocarbons,
pathogens, and nutrients. To reduce the negative effects of land correct answers total
suspended solids (TSS) and nutrients
Sediments consist mainly of what? correct answers soil particles that are eroded or
deposited as a result of natural processes and human activites
Total suspended solids include sediment and other pollutants that can be removed from
water through __________________. One of the most significant sources of TSS is
_________________. correct answers filtration, sediment
High concentrations of suspended solids in streams and lakes may cause increased
___________________, which can significantly impact surface water ecology; these
impacts include reduction of light penetration, clogging of gills, smothering of benthic
communities, alteration of substrate, and filling in channels and ponds. Additionally,
TSS may also include toxins and metals, further impacting the aquatic ecosystem.
correct answers turbidity
________________________ and ____________________ are nutrients used by
plants during photosynthesis. In excessive amounts, these nutrients over-stimulate plant
growth in the aquatic environment, resulting in dense algal blooms. When the algae die,
microorganisms break down the organic matter, consuming large amounts of oxygen in
