 |
MYSTIC RIVER WATERSHED association
20 ACADEMY STreet, suite 203
ARLINGTON, MA 02476 |
December 16, 2003
Belmont Planning Board
Belmont MA
Dear Planning Board
members:
The Mystic River Watershed
Association (MyRWA) is very concerned about impacts of developing the Belmont
Uplands site on water quality and flooding in the Alewife area. As you know,
the proposed development is located adjacent to Little River and immediately
upstream of Alewife Brook, which are areas of special concern to us because of their
important role in water quality, flooding and future recreational use issues
within the watershed. We are also concerned about the impacts of developing
the site on the high-quality wildlife habitat and open space values of the
Belmont Uplands site. These values have been well documented by other commenters,
however, and will not be addressed in this letter.
This letter provides an
overview of current water quality and flooding problems in the Alewife, and
describes why we believe that the proposed O’Neill development is unacceptable
given these problems. We hope that this information will help the Planning
Board in its efforts to assess the environmental impacts of this project.
We are aware that the proponent has made a request to the
Belmont Selectmen for a rezoning of the proposed site, to allow a change from a
commercial to a residential project. The proponent has provided a plan
illustrating the relative layout of the proposed residential development.
Specific plans and details (including existing and proposed contours, storm
water management design, etc.) have not yet been submitted, however. Our
comments in this letter are therefore based on the limited information
available regarding the residential development, as well as our review of the
proponent’s analysis of the commercial development performed during the MEPA
process.
The remainder of this
letter first presents some overall observations. We then discuss water quality
issues, describe flooding issues, and finally present our recommendations
regarding Belmont’s decisions about this site.
General Observations
In general, the effects of development on
water quantity and water quality are well documented: development changes the
hydrologic regime of the land. The hydrologic regime includes the volumes,
duration, rates, frequency, and routing of both stormwater and groundwater.
Development also increases pollutant loading to receiving waters. Once a site
is developed, it is virtually impossible to replicate pre-development
hydrologic site conditions. The impacts of development can only be mitigated,
typically by constructing Best Management Practices (BMPs) to control the peak
rate and water quality of the discharge. It is important to keep this general
point in mind, given that the O’Neill property is one of few undeveloped
parcels within the Alewife area of the Mystic River Watershed. Once this
property is developed, the existing hydrologic regime is forever changed.
The poor water quality and flooding problems that plague the
Alewife area now are the result of many poor land use planning decisions in the
past. These decisions have not taken adequate account of the flat topography
of the area and the poor condition of much of the sewer infrastructure. Each
decision about development can be portrayed as a minor contributor to the
overall problems, and our fragmented town-by-town and site-by-site decision
process has encouraged this shortsighted approach. The cumulative effects have
been dramatic, however. It is clear that the area’s wastewater infrastructure
and capacity to control flooding are already inadequate, and the affected
municipalities are just now beginning to deal with the high costs of past
development decisions.
Ideally, no new development would be allowed until these
capacity problems have been addressed. Belmont should meet its growth and
revenue goals by encouraging redevelopment of previously developed sites that
would reduce runoff and improve water quality. Any development of an
undeveloped site should be viewed with great skepticism, and should be held to
the highest possible standards. Given what we now know about the area’s water
quality and flooding problems, it is inexcusable to require only that a new
development on valuable open space meet the minimal standards that would apply
to any development. While MyRWA recommends that the Belmont Uplands site not
be developed, we also suggest, should the development go forward, that Belmont
apply much higher standards for mitigation of environmental impacts, as
described below.
Water Quality
Current conditions:
MyRWA’s Mystic Monitoring Network (MMN) has been collecting
water quality data in the Alewife subwatershed since 2000. Our data show
significant problems with water quality in the Winn Brook, Little River and the
entire Alewife subwatershed, especially due to high levels of bacteria
contamination and especially in wet weather. The following is a summary of MMN
data for this area:
|
Results of MMN Bacteria Monitoring in the Alewife
Area
|
Location
|
# of Samples
|
Fecal Coliform Levels (cfu/100 ml)
|
Geometric Mean (cfu/100 ml)
|
% Violating MA Standard for Secondary Contact
(>1,000 cfu/100 ml)
|
|
Winn's Brook Discharge to
Little Pond
|
26
|
10-17,300
|
864
|
42.3%
|
|
|
3
|
152-9.636
|
1,162
|
66.7%
|
|
Belmont Drain to NW Corner
of Little Pond
|
3
|
2,900->200,000
|
39,155
|
100.0%
|
|
Mass Highway drain between
Oliver Rd, Lake St
|
1
|
5,300
|
-
|
100.0%
|
|
East of Acorn Park Drive’s
West End
|
1
|
910
|
-
|
0.0%
|
|
Outflow from 'Martignetti
Marsh'
|
1
|
2,700
|
-
|
100.0%
|
|
Source: Mystic River
Watershed Association, Mystic Monitoring Network – samples from July 2000
through March 2003.
|
A variety of factors contribute to the poor water quality of
the Alewife subwatershed. These include infiltration/inflow (I&I)
(extraneous clean water discharged to the sewer system), illegal connections,
Combined Sewer Overflows, and overland stormwater runoff. The proponent states
that there is adequate sewer capacity to handle wastewater from the project
during dry weather. Our monitoring data suggest that this is not true – the
condition of the sewer system is currently not adequate to prevent bacteria
contamination of Little River and Alewife Brook.
Impact of development on water quality:
Stormwater runoff in urban areas contributes a number of pollutants
to adjacent waterbodies. For example, the following data from New York State
provides estimates of typical pollutants in runoff, including Total Suspended
Solids, phosphorus and nitrogen, bacteria, copper, lead and zinc.
Constituent
|
TSS
Mg/L
|
TP
Mg/L
|
TN
Mg/L
|
F. Coli.1000 col./mL
|
Cu
Ug/L
|
Pb
Ug/L
|
Zn
Ug/L
|
|
Residential Roof
|
19
|
0.11
|
1.5
|
0.26
|
20
|
21
|
312
|
|
C/R Parking
|
27
|
0.15
|
1.9
|
1.8
|
51
|
28
|
139
|
|
Residential Street
|
172
|
0.55
|
1.4
|
37
|
25
|
51
|
173
|
|
Lawns
|
602
|
2.1
|
9.1
|
24
|
17
|
17
|
50
|
|
Landscaping
|
37
|
-
|
-
|
94
|
94
|
29
|
263
|
|
Driveway
|
173
|
0.56
|
2.1
|
17
|
17
|
-
|
107
|
Source: New York State
Stormwater Management Design Manual. Appendix A
The Massachusetts Stormwater Policy addresses TSS removal
from impervious surfaces, but does not address the substantial TSS releases
from lawns. Moreover, under Massachusetts policy, roof water is considered
clean and can be directly infiltrated. Roof runoff often contains elevated
levels of nutrients and heavy metals, however, and roof runoff must be treated
in New York.
The most recent fall conference of the Massachusetts
Association of Conservation Commissioners emphasized the importance of
protecting areas that buffer wetlands to prevent this contamination. A variety
of site-specific factors affect the removal of particulates (TSS, sediments,
toxic organics, metals and pathogens) and soluble nutrients from runoff. For
example, removal is greater with vegetative cover and less with impervious
surfaces and compacted soils, and removal is less with steeper slopes (as
characterize the Belmont Uplands site.)1 The less vegetative cover
and the steeper the slope, the wider the buffer area must be to protect
wetlands from pollutants in urban runoff.
In addition to stormwater pollutants, the proposed
residential development is expected to generate more wastewater than the
proposed commercial development, amounting to 38,500 gpd. As described above,
this wastewater will be discharged to a sewer system that is not adequately
containing contaminants.
The developer’s analysis:
MyRWA questions a number of assumptions made in the
proponent’s design of the proposed stormwater system, as described in the next
section on flooding. The uncertainties in the analysis of flooding impacts
also apply to the analysis of stormwater quality. More work is needed to
ensure that pollutants in stormwater runoff do not adversely affect the quality
of Little River and Alewife Brook.
The developer’s analysis of environmental impacts does not
consider the fact that the existing wastewater infrastructure is in poor condition.
Decisions about new connections to the existing system are premature, given the
need for further work by Cambridge, Belmont and MWRA to identify the sources of
bacteria contamination in Little River and Alewife Brook.
Implications and recommendations:
The Phase II stormwater requirements and EPA’s 308
enforcement actions against Belmont and neighboring communities are requiring
substantial work to locate and correct problems with sewers and stormwater
runoff that are causing high bacteria levels. The cost of these efforts to
Belmont can be expected to grow in the future. In MyRWA’s view, it makes
little sense for Belmont to obtain revenues for the town by allowing
developments that worsen its wastewater management challenges.
Ideally, there should be a moratorium on adding new
wastewater discharges to an already-overburdened system. At a minimum, any new
developments should be required to retain the maximum amount of stormwater
on-site and to fund very substantial improvements in the sewer systems. The
review of impacts should recognize that both Belmont and Cambridge must
undertake intensive infiltration and intrusion removal from their sewage
conveyance systems, as well as an aggressive program to identify (though smoke
tests, cameras, or dye tests) and remove illegal connections of sewage pipes to
stormwater infrastructure, before any new sewer connections are allowed in this
area.
We are aware that the developer has agreed, as part of a
Memorandum of Understanding with Belmont, to provide $115,000 in funding for I&I
removal. This amount is likely to fall well short of what would be required to
make a reasonable dent in Belmont’s sewer improvement challenges. We recommend
that the developer be required to achieve a specific level of level of
mitigation, whatever that might cost. The mitigation should be at least 4-to-1
and preferably 10-to-1.
·
The Department of
Environmental Protection has been routinely requiring proponents proposing to
add significant new wastewater flow to assist in the I/I reduction effort to
ensure that the additional wastewater flows are offset by the removal of
I/I. Currently, DEP is typically using a minimum 4:1 ratio for I/I
removal to new wastewater flow added.
- A 10-to-1 mitigation ratio is being required for developments
in Woburn.
It is also important to note that I/I removal is an on-going
process, with a continuing need to investigate and address sources of I/I.
MyRWA is concerned that a one-time effort to reduce I/I by a certain amount is
not sufficient to ensure that the wastewater impacts of the proposed
development will not overburden the capacity of an already-inadequate system.
In addition to considering ways to reduce wastewater impacts, the proponent
should commit to a continuing effort over the life of the project to provide I/I
mitigation. Such a commitment might be expressed as a given amount of funding
each year that would allow Belmont to keep I/I below current levels by the
amount implied by a 10-to-1 mitigation requirement.
Flooding
Current conditions:
Current efforts by the Tricommunity Flooding Workgroup to
understand the causes of flooding, along with research by Steve Kaiser and
other area residents, show that:
- Flooding in the Alewife subwatershed is a serious problem
and is apparently becoming worse.
- The dramatic reduction in available open space in the
Alewife area over time is a major contributor to this situation.
- Current flood levels are not well documented, and there is
evidence the 100-year floodplain is understated.
- The standard 100-year storm assumptions are out-of-date.
While more work is needed to develop solutions to the severe
flooding problems, it is already evident that any additional contribution to
stormwater flows cannot be tolerated in this region.
Impact of development:
The proposed project will eliminate a forest stand of mature
trees. Several thousand gallons per acre of water are used by plants each day,
thereby drying the soil and making more room in the "soil sponge" to
hold floodwater. During the growing season, the resulting loss of
evapotranspiration will increase soil and water temperatures and decrease
on-site water infiltration.
Recent research indicates that the mere act of disturbing
soil can increase runoff potential, and that this is not typically accounted
for in pre-/post-development site hydrologic modeling. Soil compaction occurs
when heavy pressure on the soil (from trucks and construction equipment)
reduces pore space and closely packs particles in the soil. This reduces water
and air storage in the soil, which increases runoff. Results of a study in
Ocean County, New Jersey2,
showed that some soils that were classified as hydrologic soil groups “A and B”
(well drained soils) actually had the infiltrative properties of “C and D” (poorly
drained soils) when located in subdivisions and other cleared areas. Soils at
the Uplands site are classified as hydrologic soil group “B” in the proponents
FEIR.
The substitution of impervious surface for trees and
compaction of the soils at the Uplands site will inevitably increase total
runoff. Under the state Stormwater Policy, developers are required to prevent
increases in peak runoff. This is often accomplished by retaining stormwater
to allow infiltration and delay runoff to surface waters. Depending on the
rate of infiltration and evaporation, the BMPs used may or may not reduce
overall runoff, however.
The Alewife area already experiences flooding at relatively
common rainfall levels. A stormwater management system that prevents an increase
in peak flow but does not actually reduce total runoff could simply increase
the duration of the peak at existing levels – levels that already cause serious
flooding. Avoiding an increase in peak runoff is not an adequate standard in
an area that already suffers from widespread flooding. Any project in this
area should be required to substantially reduce total runoff with a high
degree of certainty.
Developer’s analysis:
The developer’s analysis of flooding impacts is inadequate
to ensure that flooding will not be worsened by the proposed project. The
proponent has provided only a basic analysis of flooding impacts, which
includes a number of assumptions that MyRWA questions. Moreover, the proposed
stormwater system is designed only to meet the minimal standards for
mitigation, despite the vulnerability of the area to flooding.
MyRWA commented on the use of infiltration as a BMP at the
site during its review of the MEPA DEIR. We feel our concerns were not
adequately addressed in the FEIR and would continue to be a concern with the
residential plan.
The commercial development includes the construction of an
underground infiltration/detention basin. The performance of this basin
depends heavily on the groundwater elevation below the vault and the
surrounding soil conditions.
During a storm, the infiltration basin will fill up with
stormwater, which will infiltrate into the soil to the groundwater table.
Typically, the infiltration rate from the system is greater than the capacity
of the soils to convey the water (hydraulic conductivity), and a groundwater
“mound” forms underneath the system. This generally is not a problem, as long
as the mound does not intersect the bottom of the infiltration system and is
able to dissipate before the next storm. When the mound intersects the
infiltration system, however, the infiltration capacity is significantly
reduced, and any volume of water that exceeds the storage capacity of the
system is routed through an overflow to a surface outfall.
According to the proponent, observed seasonal high
groundwater elevations were about 3.7 feet below the bottom of the infiltration
basin. The current separation guideline in Massachusetts is 2-feet. It should
be noted, however, that other jurisdictions recommend greater separation
distances. For example, the State of New York recommends a 3-foot separation,
and the EPA recommends 4-feet. The serious flooding conditions that already
plague this area suggest that more conservative standards be applied to this development.
Even if the design separation distance were adequate, the
proponent has not adequately evaluated the ability of the subsurface soils to
convey the infiltrated stormwater. MyRWA recommended that the proponent
perform a mounding analysis as part of the FEIR, but this comment was not
addressed. As part of the Town’s Peer Review, the consultant-reviewer has also
recommended that soil test pits be performed by a Certified Soil Evaluator to
determine soil and groundwater information specific to the areas designated for
use a treatment swales, detention basins and infiltration basins.
Another problem concerns the assumptions about rainfall
levels. Currently, the Massachusetts DEP requires the use of rainfall data
published in the National Weather Bureau’s Technical Paper-40 (TP-40). Recent
research indicates that the precipitation amounts for various frequency storms
are greater than those reported in TP-40. The document was published in 1961,
and therefore does not reflect the last 40 years of precipitation data. A more
recent study of precipitation patterns was published by the Cornell University
Northeast Regional Climate Center in 1993, in “Atlas of Precipitation Extremes
for the Northeastern United States and Southeastern Canada.” In eastern
Massachusetts, the more recent Cornell Study precipitation values show up to a
29 percent increase in rainfall amounts for each frequency. In general, the
greatest disparity between values occurs with the more extreme storms, which
are those most likely to cause flooding. Although the use of TP-40 is
specified by the Massachusetts Wetlands Protection Act, more stringent design
storms may be used under a local bylaw or ordinance. For example, the Town of
Holliston requires the use of the Cornell data in hydrologic and hydraulic calculations3.
Implications and recommendations:
The on-going work of the Tricommunity Flooding Workgroup is
likely to show that Belmont, Arlington and Cambridge will have to take a wide
variety of measures to reduce flooding in the Alewife area – there are not
likely to be any quick fixes. Any development with the potential to worsen the
flooding problem should therefore be required to meet a very high standard for
mitigation of potential runoff. The proposed development does not provide
adequate assurance that even the most basic mitigation standards (no increase
in peak flow) will be met.
The developer should be required to conduct a more accurate
infiltration and runoff analysis before any approvals are given for the
project, because such an analysis may show that the current stormwater
management plans are inadequate. Providing for more stormwater retention might
dramatically affect the design of the project, and no approvals should be given
until this issue is adequately addressed. Promising to look more carefully at
assumptions about seasonal high groundwater levels and soil infiltration rates
at a later date, in the detailed design phase, is not sufficient. These
parameters are too important to the basic feasibility of a project in this
location to be dealt with as an afterthought. Belmont should require an
analysis of infiltration, peak runoff, and duration of high runoff levels under
more realistic assumptions about precipitation levels and compacted soil
infiltration rates.
Given the serious flooding issues in this area, the
developer should also be required to achieve a much higher level of stormwater
control than is specified in the Stormwater Management Policy for a typical
site. For example, Cambridge typically requires for developments outside the
100 year flood plain that there be no more peak runoff from the 25-year storm
post-construction than would occur during the 2-year storm pre-construction.
The Boston Water and Sewer Commission requires that the maximum amount of
stormwater feasible be retained on-site. Proponents must fully investigate
keeping stormwater on-site before BWSC will even consider discharges to their
stormwater system. Belmont should require similar, more aggressive standards
for stormwater management in this flood-prone area.
Conclusion
In summary, MyRWA recommends against any development of the
Belmont Uplands site, for reasons presented in this letter as well as to avoid
loss of a valuable wildlife habitat and open space resource. Should the
development go forward, we strongly urge Belmont to require much higher
standards for mitigation of its adverse environmental impacts. This would
require exploring ways to reduce the size of the
project or to relocate the project in a less-sensitive area, as well as to
improve the design of the stormwater and wastewater systems.
Thank you for the opportunity to comment on this important
issue. Please feel free to contact me or our President Fred Paulsen with any
questions or comments.
Sincerely,
Nancy Hammett
Executive Director
cc Belmont Conservation Commission
PHONE: 781-316-3438 • FAX:
781-641-2103 • WEBSITE: WWW.MYSTICRIVER.ORG
